title: Finding certain positions in a room?

text:
# Question
Title: Finding certain positions in a room?
I have LEGO NXT and a square room of 100x100cm. I would like to use the center of the room always as my starting point(the black box). The green box is going to be my park area. Circles can be the randomly placed obstacles on my way. Red is the walls of the room. Objectives:

* When starting no matter where the robot is, it should return to the center, afterwards it should be able to park into the green box when requested.
* In its returning center/home progress there can be obstacles on the way, I should try to overcome these obstacles and park successfully. The obstacles don't have to be circular, they can be square as well.
* If there is an obstacle in the park/center area I should give an error not possible to park or abort the parking...

Worst-case scenarios: Robot starting from the corner and obstacles on the way to park. I'm using for the time being the color sensor and ultrasonic sensor, I can also add a gyro sensor but haven't made yet deep search about it. I also have an RFID sensor but I think only with 2 transponders it won't help much.

My first challenge is without any obstacles for starters would be identifying the center to the robot, and it knows where it has to come from a random position. Any tips?

# Answer
> 2 votes
There are a few different but related problems here.

* **Position** Your robot should be able to know where it is in the room. This can be achieved in a few ways:
    + Using the ultrasonic sensor as a sonar, rotating it around and storing the readouts, then calculating based on the known map of the room (if the layout is fixed and known in advance).
    + Tracking the movements and calculating from the last known position. This method depends on how accurate are the starting data and the measurement of the movement. This also loses accuracy over time.
    + Placing unique markers along the floor or the wall that the robot can read. I don't know how could this be accomplished using LEGO pieces, but I wouldn't say it's impossible to do. However, you could mark the two important locations (the green box and the center) to have an easy way to tell if you're at them.
* **Orientation** Your robot should also know which direction is it facing. Most of the above methods offer a way to calculate this, but you could also use a compass sensor.
* **Knowledge of the environment** Your robot should know if there is an obstacle in its way. The random obstacles are by definition impossible to know in advance, so you'll need to detect them somehow.
    + You could use the aforementioned ultrasonic sonar if the obstacles provide a good enough acho.
    + If the obstacles are made of a suitable material, you could try to use a color sensor to see if there is one in front of the robot
    + In theory, you could try to measure the resistance of the motors when you try to drive into an obstacle but this might prove impossible, depending on the capabilities of the hardware and software you are using. This method also makes it impossible to use the incremental location method.

Given these problems in my opinion your best bet would be a simpler, more brute force approach. Outlined in highly abstract pseudocode below:

```
going to the green target box:
while not in target area
  while not at wall
    if obstacle is in front of me: get around
    else: move forward
  end while // now you're at the wall
  move forward along the wall
end while // now you're at the target

going to the center: // assuming you're at the green box
turn towards the center
while not at center:
  if obstacle is in front of me: get around
  else: move forward
  if moved more than the journey should have taken: announce that you're stuck
end while // now you're at the center or lost

```

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Tags: nxt, mindstorms, sensor-ultrasonic
---


# Question
Title: Is it possible to add block to the on-brick "NXT Program" menu?
I have an NXT 2.0 (8547) set.

Is it possible to add some custom blocks to the NXT progranm submenu on the brick itself (like the existing "forward 5", "turn left", ...) so that I can add and use some simple steps there without the use of a PC?

Rationale: I'm playing around with the block with my small daughter (3), and adding in the PC to do something isn't very small-children friendly :-)

# Answer
> 3 votes
There is a piece of software called ICON (archived copy) which runs on the NXT and allows you to create programs on the NXT with many more commands than the built-in NXT programmer.

---
Tags: nxt, mindstorms, nxt-g
---


title: Name of trunk-like objects

text:
# Question
Title: Name of trunk-like objects
What's the name of the black curved elements in the header/banner of https://www.flickr.com/groups/lego\_arboretum/?

The full picture along with some others of the same diorama can be seen here: https://www.flickr.com/photos/mark-of-falworth/sets/72157638713690815

In addition, does anyone know whether there is an instruction guide for these trees?

# Answer
I *think* the piece you're referring to is Dinosaur Tail / Neck Middle Section with Pin.
> 4 votes

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Tags: piece-information, instructions, part-identification
---


title: What is included in set #7155?

text:
# Question
Title: What is included in set #7155?
I found an open box LEGO #7155 at a local Goodwill.

The funny thing is that there are 3 unopened bags in the box, 3 booklets (instructions, and 2 other small booklets along with 4 large pieces that are not in bags.

The set looks to be complete, but my question is this. Is this how this set came in the box? Are the 4 pieces (2 large beige oval for front of ship and 2 - 2x16 brown pieces) supposed to be loose in the box.

Everything looks pretty much untouched and brand new other than the fact that the box is open and Goodwill can't help themselves with writing on boxes.

# Answer
> 4 votes
It is very common for Lego to pack larger parts like Plate 2 x 16 not in a seperate bag, for sets this size.

If I look at the inventory of set 7155, and compare this with sets I built over the years, I think 3 bags for the parts could be correct:

* bag with minifig parts and small parts like 1x1's and 1x2's;
* bag with large size parts like the 4x8 plates;
* bag with remaining parts.

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Tags: sets
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# Question
Title: How quickly do new molds reach PAB on the Lego website?
A few months ago, I asked Lego customer service if the 1x2 jumper plates on the Lego PAB site would be the new mould (with stud holders) or the old mould (with pegs). I received no reply, not even to say that they didn't know.

If anyone has ordered 1x2 jumpers or 2x2 round tiles recently, did you receive the new moulds or the old ones?

How long does it take for the new moulds to hit the Pick a Brick bins?

# Answer
I suspect that is unanswerable except in very vague terms like "some time after the new molds get put into production" and "it will be a LONG time before the old ones go away completely".
> 2 votes

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Tags: piece-information
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# Question
Title: Is the Lego 8884 IR Receiver compatible with earlier IR Speed Remotes e.g. from set 7897?
I'm thinking of buying the new Train power function, e.g. 8884 IR Receiver, 88000 Battery Box, and 8879 IR Speed Remote. However I already have the set 7897, is the Speed Remote from this set compatible with 8884 IR Receiver ? Does anyone know ? I think the train motor is compatible by the way, correct me if I'm wrong.

# Answer
> 4 votes
I think RC devices are not compatible with PF devices due using different IR protocols.

For instance, see this forum thread for more explanation. Also this cool site.

Summarizing,

* RC and PF can use the same rails
* RC and PF cannot use the same remote controllers
* RC and PF uses different engines:

+ RC places it in bogie (as 9v do)
    + PF places it in body

# Answer
> 1 votes
You can only control PF IR receivers with the PF remote controls. These are the normal (8885) or the speed control (8879). With the speed remote control you can also choose different speeds. And yes, the train motor from 7897 is compatible with power functions, as long as you use a extension wire (acts like adapter from the old 9V-system to PF, 8886 or 8871).

You could also use a trick by controling a motor via the receiver from 7897, wich controls the PF remote control. But that´s a bit tricky, and I haven\`t found a way yet where you can actually control the speed stepwise :/

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Tags: trains, compatibility, city
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# Question
Title: Can I re-use my LEGO Store Pick a Brick cup?
I was wondering if anyone went into a LEGO store with their old Pick a Brick cup and got a discount for re-using it, or do you have to buy a new cup?

# Answer
Yes, you can. Or at least I've been able to reuse mine in the past. I believe it was $0.50 off for the big cup and $0.25 for the small cup.
> 13 votes

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Tags: shopping, pick-a-brick, lego-store
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# Question
Title: Virtual LEGO / Technics / Mindstorms simulation environments
I know that there are quite a few LEGO CADs floating around, but are there any physically correct simulation environments for models built with LEGO / Technic / Mindstorms parts, that would, for example, allow me to:

* simulate how far would a particular moving part would move / rotate / etc, until it collides with other part
* simulate gear links (ideally, with tolerances / precision / friction of plastic gears)
* get estimates of speeds / torques exerted by specific motors
* get estimates of battery power drain

So far I've found Robot Virtual Worlds, but it doesn't seem to allow construction of arbitrary environments and, what's more important, seem to simulate only a few preset robots. Also it seems to be pretty crude in terms of physics simulated. Anything else exists?

# Answer
Recently I met with TeamSim. Its possibilities are impressing:

* you can make own robot via LDD and export it to the program
* you cam make own mat (FLL, WRO, sumo mats are already available)
* you can program a robot via NXT-G

I have no chance to investigate this program in detail, but I think it's what you want.
> 7 votes

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Tags: technic, mindstorms, cad
---


# Question
Title: What are the bricks in this picture/video?
Can someone please identify the pieces in this picture? I'd like to acquire these, but I'm not a LEGO enthusiast, so I don't really have an idea where to start.

For reference, the picture was taken from this video.

# Answer
These are all fairly common parts that shouldn't be hard to find. It looks like they are a cheese slope (50746), a 1x1 tile (3070), and a 1x1 round plate (4073).

These parts are common enough that they are available in many sets, or you can purchase them separately from LEGO Pick-a-brick. If you're looking for a more affordable secondary market, you could also check out Bricklink.
> 4 votes

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Tags: piece-information, part-identification
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# Question
Title: How can the "Bar Holder with Clip" part be used?
I'm wondering whether the "bar holder" end of this element (http://www.bricklink.com/catalogItem.asp?P=11090) can be used as a stud. In other words, would it have enough clutch power to hold e.g. a 1x1 plate? And what about a 1x1 brick?

The reason for asking this question is that I'm looking for an element with a clip on one side and a stud on the other side. Sort of like this element (http://www.bricklink.com/catalogItem.asp?P=2555) but with a stud at the bottom. Any suggestions?

# Answer
One possible solution might be to use one of the new 1x1 round plates with open studs and a Bar with Clip
> 8 votes

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Tags: building, piece-usage
---


# Question
Title: How can you remove a minifig from its key chain?
My sister has a LEGO minifigure attached to a key chain, but she wants to remove it from the key chain, how can she do this?

# Answer
There is also a third method, using a cheap and readily available soldering-iron. The benefit is that it is a much faster and more reliable method than trying to pull the pin out by sheer force, which may or may not work depending on how strong you are. With a soldering-iron the pin just pulls out within a couple of seconds, no force required. See tutorial and video here: http://thebrickblogger.com/2011/01/lego-keychain-removal/
> 2 votes

# Answer
Most of the key chain minifigures are standard minifigs that have a large pin with a ring on top running through the top of their head into their torso.

There are two main ways to deal with it:

1. Cut it off.

This is straightforward. You can use a large pair of linemen's pliers or something similar to make the cut. You could also use a hacksaw of some kind. The main disadvantage of this method is that the head will still be permanently attached.
2. Pull it out.

Pulling it out is a little trickier. One method is to put something through the ring (such as a paperclip) and then pull hard to try to remove the pin. The pin is ribbed, so this could be difficult. This can be made easier by heating the pin first (perhaps with a soldering iron as TheBrickBlogger suggests) in order to slightly melt the plastic surrounding it.
> 0 votes

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Tags: minifigures
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# Question
Title: Repairing Lego minifigure torso cracks/damage
I have a ton of Lego minifigures that I really put through their paces throughout my childhood (fighting pirates, exploring space... basic stuff really). A number of them are damaged on the torso. Starting at the base on the left and right sides of the torso there are cracks that extend upwards toward the minifigure's "armpit". The cracks cause the legs to be loosely attached to the torso (and hence fall out sometimes).

Is there a way to repair damage (probably not) or hide it and prevent further cracks from creeping up the torso?

# Answer
> 10 votes
one thing that worked for me is to use a very small needle-nose plier or a tweezer to hold the torso from inside while pushing the crack apart (very carefully). now you can use a toothpick or a needle get a bit of superglue in the crack to fix it.

note that this just works for bigger cracks like the ones going up to the armpits.

# Answer
> 5 votes
I had this trouble when I was a nipper. My dad owned a model shop so I used the same glue that you use on Airfix type kits ("Polystyrene cement") - you can get this from model shops. Use a cocktail stick to smear a bit inside the figure, above where the top nobules of the legs will go so it won't interfere. Don't use too much because it kind of melts the plastic, almost like welding it.

Because of this it'll dry and hold the crack shut, but because you're not holding the crack open when you apply, you won't see the glue, it'll be like a patch on the inside.

Be sure to test on a scrap bit of lego 1st to see how it affects the plastic. Add too much and it'll turn your figure into a shapeless blob. also note it takes maybe 20 mins to dry

# Answer
> 4 votes
There is at least one *possible* way to hide the damage to a cracked torso and brace it at the same time. Wrapping the outside of a cracked minifig torso with a decal and/or a piece of transparent tape can increase the snugness of the pelvis/torso fit as well as reduce the rate of future cracking.

**There is a downside.** If you do this without taking due care, your minifigs will look shoddy. Sometimes it's better to use a cracked stock minifig in the background of a model rather than having a poorly repaired minifig stick out like a sore thumb in the middle of an otherwise stellar project.

# Answer
> 2 votes
What I have found that works, most of the time, is DURO super glue. Extreme safety must be exercised as it is super glue and can cause skin to bond and burn as well as prove poisonous via inhalation. I would recommend using wet(with water) latex cleaning gloves as the water seems to prevent the gloves from sticking to themselves or each other to handle the glue, and then using a nail or something thin to apply it to the crack. However, it can cause the piece's colour to rub off, so be careful. One should always test the cracks(dependent on piece, e.g. putting legs into a torso). and look for more(with magnified glass (glasses, monocles, loupes, magnifying glasses, etc.) before returning it to use. The glue must be left to dry for at least 8 hours(maybe more), even though it will initially appear dry. Still, it seems to work. The torso I had from Rodney Rathbone had a bad crack on the left side, and some DURO seems to have done the job.

# Answer
> 1 votes
I used option 2 and I couldn't fit the needle. So if you can't get a bottle of gorilla glue and stick the tooth pick. First take out the legs and the where the crack is. Then you stick the toothpick into the gorilla glue and apply on the inside crack and outside crack. Make sure you get the cracks bottom where it transitions from inside to outside

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Tags: minifigures, repair
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title: Simple optical switch?

text:
# Question
Title: Simple optical switch?
I have built a conveyor belt for my son out of Lego Technic. Now, I would like to add a simple optical switch, so that the belt stops when an object arrives at the end of the belt... However, I am not sure about which part I should use for that.

# Answer
> 6 votes
I'm assuming from your question that you are currently using Power Functions parts to control your conveyor. In order to achieve the sort of electrical automation that you are talking about, you'll need something like LEGO Mindstorms. The current line is called EV3. You'll need at minimum the Intelligent Brick, a light sensor, a motor, and a few cables. You can also buy the complete EV3 kit.

If that seems too pricey for you, you could try searching for used NXT (previous version), or even RCX (first version) Mindstorms kits.

Once you have the Mindstorms parts that you need, you'll just need to program the brick to do what you want using software on your computer.

# Answer
> 1 votes
I'm not aware of an official LEGO Power Functions optical switch but considering that PF is based on simple electric components it could probably be hacked together at the cost of sacrificing an official PF power cable for the connectors. I have no reliable information about the exact voltages, currents and possible signals used in the PF system but I'm pretty sure these can be acquired easily from the net. After finding out these you'll only need an off-the-shelf optical gate sensor, some wires, the necessary resistors, a cut PF cable and some soldering to produce a component that you described above.

It could also teach your son about basic principles of electronics and DIY, meanwhile awakening his curiosity to stepping out of the predetermined boundaries and hacking things (in the positive meaning) to achieve what he needs.

---
Tags: technic
---


title: Types of instruction manuals

text:
# Question
Title: Types of instruction manuals
I noticed there are 4 different types of instruction manuals (at least for large sets):

* **Type I**: Similar piece colors are not very distinguishable (especially Dark Gray and Black). Some building steps could be clearer (for example, adding arrows or changing the point of view). Similar-looking pieces are sorted in the same bag. Bags are not numbered.
* **Type II**: Same as **Type I** but with numbered bags.
* **Type III**: The piece colors are a lot closer to the actual pieces and are easily recognizable (Black has even a white outline). All building steps are better described. Pieces are better sorted in the bags. Bags are numbered.
* **Type IV**: Same as **Type III** but with the pieces to be added in a given step outlined in yellow or red.

One could think of a type to be an improvement over the previous one, and when a new type is released, the old one wouldn't be used anymore. But that's not the case.

Here are some sets with their corresponding type:

* **Mobile Crane** (8421) released on **24-Oct-07** is of **Type II**.
* **Death Star** (10188) released on **21-Jun-08** is of **Type I**.
* **Pet Shop** (10218) released on **12-May-11** is of **Type II**.
* **Town Hall** (10224) released on **03-Mar-12** is of **Type IV**.
* **Palace Cinema** (10232) released on **01-Mar-13** is of **Type III**.
* **Mobile Crane MK II** (42009) released on **27-Jul-13** is of **Type II**.
* **Maersk Line Triple-E** (10241) released on **01-Jan-14** is of **Type IV**.
* **Parisian Restaurant** (10243) released on **01-Jan-14** is of **Type III**.

Do you know why the manual types are not in strict chronological order?

# Answer
> 2 votes
I remember that in the 80's black technic parts where always hard to recognize in the instructions, in those years you had to count the studs yourself. Over the years black became a little lighter in colour to a dark grey. This was also shown on one of the first pages of the instructions.

This stays OK until the introduction of dark grey parts. At that point LEGO struggled again with colours in the instruction. This was around 2008. In the year later this was solved by making black darker again. This current colour scheme is used in for example 42009. So this set is not a type II but another type. Also LEGO nowdays try to keep the same parts both in black and dark grey to a minimum per set.

Until now I never noticed that LEGO uses two different ways to show black parts. With and without a white outline. And also on the PDF's instruction it look like the shade of black is different. I don't know the reason for this and if the white outline is only used for non technic sets.

Numbered bags are used through the whole line of sets. And make the building a little easier by reducing the number of parts to look through while finding the part needed.

The coloured outline on the build steps are used at least from 2000. These are often used in larger models like 3723-1: LEGO Mini-Figure, where it can be hard to see where a part go. Often because of the uniform colour of a model.

# Answer
> 1 votes
I would hypothesize that, perhaps, it's not a matter of one style being the "official" current style at a given time so much as there are probably multiple individuals or teams that write the manuals for assembling the models, each of whom have a slightly different writing and illustration style.

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Tags: instructions
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title: My Blocks with return parameter

text:
# Question
Title: My Blocks with return parameter
I have the retail EV3 kit and have created a function with in and out numeric parameters.

While using the \[in\] params seem quite straight forward, it seems that I can only set the \[out\] param once. Dragging a second wire from a constant or variable will not connect when I place them.

**Can I only set an \[out\] param once?**

**Does setting the \[out\] param act like the "return" keyword?**

I have had a look around, but there is very little help on the EV3 My Blocks at present.

Bad, but simple example:

Please note that this is a simplification of the problem, and in this case I could set x to -1 or have another case in the sensor switch to set x to -1. I am trying to explorer the limitations of EV3 My Blocks out parameters.

# Answer
> 2 votes
> Can I only set an \[out\] param once?

Yes. You cannot tell it to be 2 different values at the same time. This applies to any block, not just the output block.

> Does setting the \[out\] param act like the "return" keyword?

Not really. The return keyword in most (if not all) programming languages causes the function to exit, which is not the case here. It just allows you to assign the output value (or values - you can have more than one output parameter).

# Answer
> 0 votes
I think this is as close as you'll get (other than the constant being set to 99 instead of -1). You end up with 2 output parameters instead of one. If you really want only one output, you'll need some logic to determine which to output.

# Answer
> 0 votes
I don't think I showed a great example. Using David Lechner's advice I changed the code to be more like the below:

I use x to store my return value, and when loop 02 is finished, x is copied to the output param.

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Tags: ev3, programming, ev3-g
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# Question
Title: Which Lego Police set or sets do I have?
We were given a big bag of Lego pieces. When sorting through them my son found a bunch of police pieces but we can't figure out which set or sets they belong to. I've tried looking up a few individual pieces but that hasn't helped and I can't seem to find the right set or sets by looking at googled images. Any help would be greatly appreciated.

# Answer
Most of the parts are of set 7288. I see at least the following:

* Window / door with the gates
* Big wall parts with stickers.
* Cop minifig & white shirt criminal
* Computerdesk and front of the truck
* Red front of the small car

I also see parts of 7279:

* Gray shirted criminal
* Part of the ATM terminal
* Parts of the little car (lights and front with sticker)
* Maybe the dog, it's hard to see the print of the head on the photo.

Then remains the stick of dynamite, the minifig in front of the red car parts, the second dog and bigger white bricks, that are not of these 2 police sets.

Maybe you can take a look for yourself on Brickset.com. The remaining set(s) are probably from around 2011, as these 2 are. Maybe look for a kind of plane / helicopter, because of the slope pieces.
> 7 votes

# Answer
At least the mobile police post 7288; the label on the piece identifies it.
Look for pieced used as license plates; license plates on Lego cars often contain the set number. In fact, any number printed or stickered on a piece is likely to be the set number. The dog doesn't have to be from a police set; he also appears in at least one firefighter set.
> 3 votes

# Answer
The white two-legged assembly with the blue light that's just above the left dog looks to be part of the robot dog from Space Police set 8399.

Additionally, the minifig near the red car front appears to be from the World Racers theme and the one just under it that's missing its head looks like Johnny Thunder from the Adventurers theme.
> 1 votes

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Tags: city, set-identification
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title: Pneumatic pistons getting sticky

text:
# Question
Title: Pneumatic pistons getting sticky
My sons "9641 Pneumatics Add on Set" now suffers from stiction.

How can this be fixed? Can it be cleaned? Is there a recommended lubricant?

# Answer
In this discussion at LUGNET the conclusion seems to be that you could use dry graphite if you are comfortable with graphite powder everywhere. Else you should try lithium grease or canola oil.

There is also a serious warning about using hydrocarbon oils that could damage the rubber seals inside pistons and the rubber air tubes.

One poster also noted that stiff pneumatic cylinders can be unstuck by moving them by hand for a while. This definitely does worth a shot before trying to add any kind of "foreign" material such as oil.
> 4 votes

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Tags: cleaning, pneumatic
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# Question
Title: Third-party blocks with a smiling face or an umbrella with 2 dots on each side
I bought a bunch of duplos from the thrift store and inside there was not Just duplos but also mega bloks. I was able to separate most of them but there are a few that I just cannot tell which is which. They have a logo in the middle of the stack but its a picture rather than a word. I'm trying to find anything online but am having no luck. The logo almost looks like a smiling face or an umbrella with 2 dots on each side.

# Answer
> 4 votes
After some searching, I have finally come up with the brand.

I too purchased a lot of bricks and found these odd ones in the mix, they are Tandem bricks, and there isn't too much information out there on them.

# Answer
> 2 votes
All Duplo and LEGO bricks have the LEGO logo (the logo is just the word LEGO) on the brick somewhere, usually on a stud. Megabloks always have blank studs and slightly offset colors compared to LEGO or Duplo bricks.

# Answer
> 1 votes
Although the logo on the "umbrella-bricks" you have are not Megablock, they are not Duplo either. Duplo always have the LEGO logo somewhere, and the studs are hollow. The hollow studs make them compatible with standard Lego bricks that are at least size 2x2, since the cylinder inside the Lego brick fits perfectly inside the hollow Duplo stud. See the locomotive on this image where it has some 2x4 Lego bricks on Duplo bricks:

Also see this answer on another post for more details on Duplo piece information.

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Tags: 3rd-party, duplo
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title: Scan objects while moving?

text:
# Question
Title: Scan objects while moving?
I'm using leJOS with an NXT robot. I want to scan the distances of objects from my robot. While rotating the Ultrasonic sensor from right to left, I would like to find out which object is closest to me.

`Motor.A.isRotating()` seemed to me as a good idea, but later I found out that leJOS hasn't implemented it yet. They are suggesting using `isMoving()` instead. So I tried this:

```
 while(!Button.ESCAPE.isDown())
   {
    Motor.A.rotateTo( 40);
    while(Motor.A.isMoving())
    {
     value = sonic.getDistance();
     LCD.clear();
     LCD.drawString("Distance: ", 0, 2);
     LCD.drawInt(value, 0, 3);
     LCD.refresh();
     Thread.sleep(100);
    }
    Thread.sleep(100);

    Motor.A.rotateTo( -40);
    while(Motor.A.isMoving())
     {
      value = sonic.getDistance();
      LCD.clear();
      LCD.drawString("Distance: ", 0, 2);
      LCD.drawInt(value, 0, 3);
      LCD.refresh();
      Thread.sleep(100);
     }
      Thread.sleep(100);
   }

```

I'm open to suggestions and tips! Thank you!

# Answer
> 0 votes
I'm not a leJOS expert, but from looking at the docs, I don't think that the rotateTo method works the way that you are expecting:

> public void rotateTo(int limitAngle)
>
> Rotate to the target angle. **Do not return until the move is complete.**

So here's what your code is actually doing:

```
Motor.A.rotateTo(40); // Rotate to 40 and return when rotation is finished
while(Motor.A.isMoving()) { // The motor won't be moving
    // Execution never gets here
}

```

The rotateTo method takes an optional `immediateReturn` parameter that allows it to return without waiting for movement to complete:

> immediateReturn - if true do not wait for the move to complete

Replace your calls to rotateTo(angle) with rotateTo(angle, true), and you should be on the right track. Something like this should be more effective:

```
Motor.A.rotateTo(40, true); // Begin rotating to 40 and return immediately
while(Motor.A.isMoving()) { // The motor will be rotating for a time
    // Execution should loop here until the motor stops
}

```

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Tags: nxt, mindstorms, motor, sensor-ultrasonic
---


title: Return a robot to its start position?

text:
# Question
Title: Return a robot to its start position?
I have a LEGO NXT robot, and after some movements I would like it to return back where it started. After some research, it looks like my best option is to revert the motors. To decode their movements but I couldn't find any examples for it, could someone give me a hand? I'm using leJOS for programming.

# Answer
You can read the tacho count and rotate a negative amount of degrees. Or you may want to use the Navigation class and create a path while you move, then you just need to follow the path back.

But unless the robot is perfectly calibrated it will fail miserably. I explain it all here http://thetechnicgear.com/2014/06/howto-calibrate-differential-drive-robot/
> 2 votes

# Answer
Are you programming your robot to move? If so, then you could just keep a running log in your code of how far did each of the motors turn. Based on this log you could replay the whole log backwards to return to the starting point (with the approppriate precision of course). If your robot is moving due to external forces (e.g. someone is pushing it) then you can only rely on the decoding that you mentioned above.

For code references see these resources:
> 0 votes

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Tags: mindstorms, nxt, motor, pathfinding
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# Question
Title: Are there any LEGO elements not being produced because of mechanical problem with the mould?
I am referring element number 702 4x4 corner brick, and possibly other elements that have not been in sets in a considerable amount of time.

# Answer
> 2 votes
I've been wondering the reasons why a number of pieces are no longer available and it appears the decision to reduce the overall amount of different pieces is simply a cost based one.

From a Q/A with someone from the Lego Company: "...the piece count has been reduced drastically and there's a move back to roots in Lego, not only for creativity but to save money. Lego went from 12,000 different pieces to 6,800 in the last few years-a number that includes the color variations."

snippet was from here: http://lego.gizmodo.com/5019797/everything-you-always-wanted-to-know-about-lego

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Tags: piece-information
---


title: Holonomic robots using Mindstorms

text:
# Question
Title: Holonomic robots using Mindstorms
I just got some Rotacaster wheels and want to try building a 3 wheeled Mindstorms omnibot (holonomic robot) and I'm looking for a practical (easy) discussion about writing a driving program. I've found some theoretical papers but need something a little easier to implement. Has anyone here built one and what advice can you give?

# Answer
> 2 votes
Here is an article that may be useful:

http://botbench.com/blog/2014/05/11/omniwheel-article-in-dt-practice/

# Answer
> 3 votes
I got also the wheels and found it really interesting... so I wrote an article were I explain all the maths and show you how to build one yourself ( instruction attached ) http://thetechnicgear.com/2014/04/howto-build-3-wheels-holonomic-robot-using-lego/

The code is for EV3 software and I will surely rewrite it for leJOS ( despite there is a class that already does the work ) on the following weeks.

# Answer
> 2 votes
There is an excellent model at Hitechnic, complete with building instructions and example programs. It's for NXT, but shouldn't be very hard to adapt to EV3.

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Tags: mindstorms, programming
---


title: NXT or EV3 gyro sensor

text:
# Question
Title: NXT or EV3 gyro sensor
Do NXTs or EV3s have gyro sensors or built-in gyro sensors? How can I know the direction of the robot?

# Answer
LEGO doesn't make a gyro sensor for NXT, but Hitechnic sells a **gyro third party product** and Mindsensors has a **combo gyro/accelerometer/compass (IMU)**. Both can be used with EV3, and LEGO also has a **gyro sensor**, included in the **Education kit**
> 4 votes

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Tags: mindstorms, nxt, ev3
---


# Question
Title: Why do official LEGO PDF instruction books have such poor quality?
More often than not, my boys are working from PDF instructions downloaded at the LEGO site. The quality of those PDFs is poor. I'm sure you've experienced the jagged, pixelated lines and the bricks so dark you have to figure out the size through a process of deduction.

I'm familiar with the sites that offer user submitted scans, and occasionally we find what we need at one of them, but why is it even necessary? Is it a case of LEGO wanting to leave some motivation to pick up the actual sets with the actual instruction booklet? Is it something far less calculated than that, maybe just a legacy process for generating the PDFs that needs to be updated?

I'd be grateful for any insight!

# Answer
> 4 votes
Mσᶎ' comment has dealt with the technical reasons quite eloquently, and I'd guess Mσᶎ' analysis is likely correct.

However, I suggest that we can dig a little deeper to guess why the process hasn't been fixed.

Disclaimer: the following is pure speculation. I don't work for TLG (I wish!) and have no special knowledge or insight into the company or its policies.

**A Revealing Question**

In my mind, the important question is why the instructions are published as PDFs at all? Whilst LEGO is a passion for the fans, it is also a business. The PDF instructions are provided as a free service to TLG customers: they receive no direct financial benefit from the publication of their instruction books.

So, why do they bother? Presumably for indirect business benefits. Things like:

* The hope that customers will buy bricks / sets to make up sets they don't own
* Easier to deal with customer enquiries regarding lost instructions
* Customer good will

**Costs and Benefits**

Assuming this is the case, we can speculate that TLG have not invested in better PDF instructions because they don't consider the additional benefits will be covered by the cost of improving the quality.

* Do many people really purchase bricks based on these instructions? I doubt it.
* The poor quality PDF instructions are probably good enough for customer enquiry purposes, or at least TLG may perceive that it is.
* TLG may perceive that customers in general don't care about the instructions quality - the few of us who do may not provide sufficient incentive to improve things.

The bottom line is that these instructions are provided on a goodwill basis. Unless TLG receive incentive to improve them, they probably won't.

**A Call to Action**

So, if you really care about the instructions, what can you do?

I suggest that it might be worth contacting TLG's customer services. If they get enough complaints, they may consider making improvements. Alternatively, they may consider it worthwhile providing a paid service for obtaining better quality copies of instructions.

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Tags: instructions, lego-group
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# Question
Title: What is the best way to make a staircase?
I have built a Bat Cave from some bookcases and lego base plates. ( http://alice-yarns.co.uk/blog/2013/11/17/the-batcave-part-i/ ) I want to add staircases for the characters to move between each of the three shelves. But what is the best way of doing this?

I wondered about making it purely from lego bricks but I can't see how this could be stable.

# Answer
Seeing the size of your project you'd certainly need lots of bricks if you wanted it to be built entirely out of LEGO.

Check out the 3rd and 4th models in this video: https://www.youtube.com/watch?v=SRP8HcEaRpQ

Or if you'd prefer to have spiral staircases and have lots of turnplates you could try building one according to this video: https://www.youtube.com/watch?v=U4sA9abH8so or this answer: What is the best-practice for circular lego staircase construction?

But I think Batman would rather have a lift than a staircase :)
> 2 votes

# Answer
Building a staircase out of bricks is easy enough, but uses a lot of brick pieces, as zovits already answered. If you want to achieve something faster, with fewer pieces, you could look into the spiral-staircase-piece

or the regular staircase piece.

The spiral staircase piece combines with some plate+pin pieces (bottom, top) and some posts. You can connect as many posts together as you want using a pin.

The advantage of using the spiral staircase is mainly the simplicity of it; it's not that versatile a piece, but it works for its purpose and does have a nice round edge. Plus the stairs can be rotated, which allows for a "hidden staircase" feature.

The advantage of using the regular staircase piece is that it is very sturdy and it takes up very little space. You can build a similar staircase using the inverted slope and some 1x4 plates but it isn't as strong (and it's slightly taller).
> 4 votes

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Tags: building
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# Question
Title: How can I tell if minifigures are custom-made or LEGO Originals?
I see that on Amazon you can find a lot of minifigures but I can't tell if they are cheap knock-offs or not.

# Answer
> 4 votes
If you can't hold them in your hand and inspect them closely for the usual LEGO production marks, as it would be the case with buying from Amazon, your best bet would be asking the seller and checking whether the individual parts exist as official LEGO pieces. A custom piece that doesn't appear in any official sets or catalogues clearly indicates a third-party make. Note however that the inverse is not true, if all parts of the figure can be found in official sets, they still could be custom-made. At this point it all comes down to the honesty (well-informedness?) of the seller and your trust in her/him.

# Answer
> 4 votes
Also, I would suspect that Amazon has a "buyer protection" that protects you in case you "get taken" by a fake or sub-par quality figure. If the product description says, "Lego..." then I'm sure you're protected in the event that the product that reaches your house isn't "Lego".

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Tags: minifigures, shopping, clone-brands
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# Question
Title: What element is this a piece of, and how can I repair it?
Yesterday, as I was putting away some Lego, I saw the following obviously broken piece.

I couldn't figure out what element this was a piece of, so I was all ready to ask it here, when I came across the other part.

So instead of a genuine question, I'll post it as a challenge. First one to find the element this is a part of, gets a bonus (which I'll set and award as soon as possible).

>

That leaves me with the question how to repair this, if possible.

# Answer
> 16 votes
It's difficult to tell exactly what part this fragment came from, but it looks like it is part of a broken Technic gear or pulley. It looks like it probably came from 3736:

Your fragment looks like it was probably once one half of the center axle hole of that part.

In terms of repair, I suppose you could try to glue this back together, but given that the part was likely bent as well as broken, this is unlikely to work well. Luckily, this part is common, abundant, and cheap, so it's trivial to replace via Bricklink if you are so inclined.

If this part broke under relatively normal conditions, you could also request a replacement via LEGO customer service. I've done this in the past for parts that have broken while building, and TLG has been happy to ship me replacements at no cost.

---
Tags: piece-information, part-identification, repair
---


title: How to restore minifig faces?

text:
# Question
Title: How to restore minifig faces?
Vintage minifig heads (from the 80s, 90s with the classic smiley) often lose their eyes and mouths after years of play. The paint wears off.

How do you best restore the heads?

# Answer
If you have a steady hand you can use hobby paint or a Sharpie, let it dry, then put on a clear-coat for protection. But those heads with the classic smiley faces are so cheap on BrickLink, you could just replace them. Here are the Catalog listings for the original Classic Smiley on BrickLink along with the dates of production:

Hollow stud original from 1978-2013: http://www.bricklink.com/catalogItem.asp?P=3626bp01

Solid stud from 1991: http://www.bricklink.com/catalogItem.asp?P=3626ap01

Stud recessed from 2009-2014: http://www.bricklink.com/catalogItem.asp?P=3626cp01
> 5 votes

---
Tags: minifigures, repair
---


title: LEGO Mindstorms NXT projects

text:
# Question
Title: LEGO Mindstorms NXT projects
I have a LEGO Mindstorms NXT set and since I bought it I almost never used it. Sometimes I think I could do something interesting with it, but I usually either feel like just copying a previous made project or stuck with no ideas of what to do. The obvious answer probably is

> "If you try some project of other people at some point you start connecting the dots and come up with your own ideas"

I would like to know if other people had this feeling in the past what they ended up doing.

As for background information: I have no experience with Technic sets, but have experience with computer science and math.

# Answer
I think your "obvious" answer is right. Given that you have a background in computer science and math, I'm certain you will be pleasantly surprised how fast you can go beyond connecting dots and come up with unique and innovative designs. I admit being in the same position, but with an EV3. It sat for almost six months before I really started working with it. Based on my experience, I encourage you to commit to doing a few small projects to understand the potential. Start small for some immediate gratification. Log some experience, and you will start seeing ways to hack this little device. This is a necessary step to doing something cool and innovative. You gotta commit to building!
> 3 votes

# Answer
If you just start trying to make a robot that does a perfect square path you will be surprised how hard stuff gets and how many things you can do... beyond all the imaginative design...

I have already written three posts on the subject and each time I have to kill new ideas so I can concentrate in what I have to do.

The first one is this http://thetechnicgear.com/2014/05/tutorial-using-motors-draw-square-mindstorms-ev3-lejos/ and as you can see it is a pretty basic robot.
> 2 votes

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Tags: nxt, mindstorms
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# Question
Title: Interfacing Mindstorms NXT 2.0 with webcam
I very recently started playing with Mindstorms and have used the sensors that was provided along with the NXT 2.0 set. I'm planning to work on something on the lines of image processing and I need a camera for this. Is there a way I can interface the NXT Brick with a webcam so that the Brick can send instructions to the webcam as to when to capture the image? Are there other better methods of using webcams and Mindstorms together?

Anything along those lines would be helpful. Any pointers to good reading materials would also be helpful.

# Answer
I would go and give a try to leJOS http://lejos.org/ if you can write Java.
> 1 votes

# Answer
IMHO your best bet is to use Mindsensors' NXTCam
> 0 votes

# Answer
If you could use a PC as intelligent robot brick, I would suggest you:

* standard web-cam
* OpenCV (for image processing)
* nxt-python
> 0 votes

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Tags: nxt, mindstorms
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# Question
Title: What elements do I need to create a smooth multi cheese slope ramp?
I love cheese slopes, but I am having issues when I try to produce a smooth gradient using several in succession. I end up with a gentle saw tooth effect at each junction. What combination of elements do I require to get the smooth appearance I'm trying to achieve?

# Answer
To create a smooth surface with cheese slopes they must be offset by one-half plate in height. There are several techniques to do this. Here is one using the common "headlight" brick. It has the advantage of being extendable to nearly any length.
> 15 votes

# Answer
This would be a way but other techniques may suit you as well.
> 10 votes

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Tags: building
---


# Question
Title: What's a good age to start getting into Mindstorms with my child?
What is a good age to start getting a child into LEGO Mindstorms? Also, how would you recommend introducing her?

I can't wait to start building robots with my daughter. She loves LEGO and the idea of robots, and I know she will have a blast. I know I will need to (and actually really want to) help her do everything.

I think I already know the answer (aka, now as she's almost 5), but I'm looking to see what suggestions others might have from their own experiences. Thanks!

# Answer
I started at age 9 and it was just right for me. Since Mindstorms now comes with a modified version of LabVIEW, I'd maybe wait until they can learn how to use the software.
> 4 votes

# Answer
I think there is a lot of variability in terms of what can be considered an appropriate age for a child to begin Mindstorm. For any given age, it is important that you scale the difficulty of any given activity to the child's knowledge, skills, and attention. Indeed, part of the learning process is providing a challenge, but with children essential they feel successful. As adults, we tend to focus on outcomes -- that is, the build in the final form. With children, give most of your attention to the process. That is how you will ultimately rope them in to become master builders. Good luck!
> 2 votes

# Answer
In order to have fun with Mindstorms you need to have a decent knowledge of maths and some physics ... but it is also a great incentive to learn these... I would say 9-11 does best. But it really depends of your child.
> 1 votes

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Tags: mindstorms
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# Question
Title: Is there a way to program the EV3 brick with NXC?
I tried to program the EV3 brick with NXC so i used BricxCC. The download of the program to the EV3 was successful but when i tried to start the program (which actually didn't show up on the program screen), there was a "FILE NAME ERROR". I use the Firmware V1.03H.

# Answer
> 2 votes
Not right now. RobotC support is already there ( although it isn't free ).

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Tags: software, ev3, nxc
---


title: Does NXC work with EV3?

text:
# Question
Title: Does NXC work with EV3?
Is it possible to create and run **NXC** programs on the **EV3** brick?

I installed BrixcCC, created a simple Hello World NXC program and selected "Download and Run" in the Compile menu.

The EV3 brick made a sound as if the program was downloaded; however, nothing happened on the EV3.

Very strange, but I was unable to find ANY good info on this subject on the web.

Would very much appreciate your help.

# Answer
> 0 votes
Not yet. You can try RobotC that's pretty similar.

---
Tags: mindstorms, ev3, compatibility, nxc
---


title: How to install NXT Firmware 1.28?

text:
# Question
Title: How to install NXT Firmware 1.28?
Lego is giving 1.31 from their website but I need 1.28, how can I install it?

# Answer
Heh, found it on my computer, click to download from Google Drive.
> 2 votes

# Answer
I believe the Enhanced Firmware included with BricxCC is based on v1.28. You can find a download for the firmware there and download it using NXT-G or you can install BricxCC and install it via the IDE.
> 0 votes

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Tags: mindstorms, nxt
---


# Question
Title: In LEGO mindstorms NXT programming: is it possible to download a file from a robot onto the computer?
I've lost the file for a project, but the robot still has it, and I'm wondering if it is possible to transfer the file onto my computer from the robot, and continue to work on it. How would you do this?

# Answer
Yes, you can download it back in computer. But you can't work on it anymore - it is already compiled (has `.rxe` extension). However you can download it on another NXT and continue to use there. You can edit and work only with `.rbt` files.

---

My LEGO MINDSTORMS NXT program doesn't work anymore for already two months... Some problems with flash player. So I can't provide any screenshots.
> 2 votes

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Tags: nxt, mindstorms
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title: EV3 Education Edition software license

text:
# Question
Title: EV3 Education Edition software license
I got a new EV3 education kit.

Can I install it on a several computers or does the license work on one computer only?

# Answer
That depends on which version of the Education Software you purchased:

* LEGO® MINDSTORMS® Education EV3 Software Single User
As the name implies, this is only allowed to be installed on a single computer: "The single license version of the EV3 Software allows you to install and run the software on one computer."
* LEGO® MINDSTORMS® Education EV3 Software Site Licence
This version allows you to install the software on a number of computers within a single location: "The site license version of the EV3 Software is necessary when installing on more than one computer. It allows you to install and run the software on all computers located at the address of the purchasing institution."

If you're planning on installing this on more than three computers the Site License is the way to go.

Note that the Home Edition is a separate download, and would have it's own licensing, but appears to be freely available, and installable on as many computers as you like - details of some of the differences can be found in this answer to "What is different between the EV3 Home and Educational sets?".

---

In response to Alex's comment:

Without seeing the full wording of the license, it's hard to advise you correctly, however:

1. Usually you can reinstall software on the same computer after an OS reinstall - depending on the validation mechanism you may need to contact Customer Services to get it reset, but I doubt this will be the case with this.
2. Again, this is typically supported by most software licenses - it's often things like transferring ownership that are expressly excluded.
> 4 votes

# Answer
If you purchased the education set through First Lego League, you are allowed to install on up to 10 computers.
> 0 votes

# Answer
According to the license agreement supplied with the software (using the activation code from the Software Single License) you may:

a. use the Software on one single computer;

b. use the Software on a second computer as long as the first and second computers are not used simultaneously;

c. copy the Software for back-up and archival purposes, provided any copy made must contain all of the original Software’s proprietary notices;

...

So: You may install on more than 1 computer, but not use the software on more than 1 computer simultaneously.

You can reinstall the software after OS re-installation, as long as you have a backup copy of the software. According to the licence document (with the activation code), you can download the software only once. This seems not to be the case at the moment, but might change in the future.

You can install on a second computer, without removing it from the first. You are not allowed to use it on both computers at the same time, however.
> 0 votes

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Tags: ev3, software, education
---


# Question
Title: What is this weird and specific technical part?
I found this part among some parts I bought. It looks like it serves a specific purpose.

What is it?

# Answer
This is an Technic Steering Arm and was used is the steering mechanism of all kind of technic car like 1972-1: Go-Kart

With the introduction of studless building it was replaced by Beam 3 M. W/4 Snaps.
> 10 votes

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Tags: technic, piece-information, part-identification
---


title: What can I do with this steering wheel?

text:
# Question
Title: What can I do with this steering wheel?
I found this steering wheel + "dashboard" combination among some parts I bought.

What is it, in what kind of models is it used, and can I do anything else with the "dashboard" (for lack of a better word)? It seems like a rather large and specific part, just to hold a steering wheel.

# Answer
> 4 votes
This steering wheel is from 4613-1: Turbo Chopper, as this is the only one with an orange version of this element.

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Tags: piece-information, set-identification
---


# Question
Title: Can't send multiple commands to EV3 using Python
I want to use Python to send commands to an EV3 brick. In C++ things work as expected - for instance, this starts the motor on port A and then stops it after a while:

```
#include <unistd.h>
#include <fcntl.h>

int main()
{

    // command to start motor on port A at speed 20
    char start_motor[] = "\x0C\x00\x00\x00\x80\x00\x00\xA4\x00\x01\x14\xA6\x00\x01";

    // command to stop motor on port A
    char stop_motor[] = "\x09\x00\x01\x00\x80\x00\x00\xA3\x00\x01\x00";

    // send commands to EV3 via bluetooth
    int bt = open("/dev/tty.EV3-SerialPort", O_RDWR);
    write(bt, start_motor, 14);
    usleep(500000);
    write(bt, stop_motor, 11);
    close(bt);
}

```

When I try the same thing in Python, however, only the first command is executed (the motor starts but it doesn't stop):

```
import time

# command to start motor on port A at speed 20
start_motor = '\x0C\x00\x00\x00\x80\x00\x00\xA4\x00\x01\x14\xA6\x00\x01' + '\n'

# command to stop motor on port A
stop_motor = '\x09\x00\x01\x00\x80\x00\x00\xA3\x00\x01\x00' + '\n'

# send commands to EV3 via bluetooth
with open('dev/tty.EV3-SerialPort', mode = 'w') as bt:
    bt.write(start_motor)
    time.sleep(5)
    bt.write(stop_motor)

```

I have also tried: suppressing the `\n`; using `os.open('dev/tty.EV3-SerialPort', os.O_RDWR)`; using `bt.flush()`; `using os.fsync(bt)`; using `bt = open(... (instead of with)`; and changing the mode and buffering arguments of the open method. Nothing worked.

Well, it does work if I close the tty and open it again, but this sounds inefficient:

```
# ...
with open('dev/tty.EV3-SerialPort', mode = 'w') as bt:
    bt.write(start_motor)
time.sleep(5)
with open('dev/tty.EV3-SerialPort', mode = 'w') as bt:
    bt.write(stop_motor)

```

So, what am I missing here?

(OS X 10.9.3, Python 2.7.6, EV3 \[31313\])

# Answer
> 4 votes
Works for me if you set buffering to 0 and get rid of the newlines.

```
import time

# command to start motor on port A at speed 20
start_motor = '\x0C\x00\x00\x00\x80\x00\x00\xA4\x00\x01\x14\xA6\x00\x01'

# command to stop motor on port A
stop_motor = '\x09\x00\x01\x00\x80\x00\x00\xA3\x00\x01\x00'

# send commands to EV3 via bluetooth
with open('/dev/tty.EV3-SerialPort', 'w', 0) as bt:
    bt.write(start_motor)
    time.sleep(5)
    bt.write(stop_motor)

```

---
Tags: ev3, programming, python
---


title: What exactly is this Lego train motor?

text:
# Question
Title: What exactly is this Lego train motor?
I bought this in the early 90s as a spare, since the type of Lego train was being phased out. Presumably the old 12V system. The original train was given away but I still have this. I want to sell it but need to know what it is. It has the numbers 49 5 on the bottom.

# Answer
> 7 votes
It appears to be Electric, Train Motor 12V Modern.

---
Tags: part-identification, trains
---


# Question
Title: How much do bricks cost at the LEGO Store?
I have never been to a LEGO Store, and I am hoping to go to one soon. I was wondering if anyone knew how much bricks cost at the LEGO Store? I want to buy some minifigs and some bricks. Do they sell the bricks by pound, or price per brick, or something else?

# Answer
> 8 votes
The most common way to buy bricks from LEGO stores is by filling up a PaB cup:

There are two sizes of cups and occasionally other containers that can be filled during certain promotions. The large cup is $15.99 USD and the small cup is $8.99 USD currently. This isn't advertized, but you can also buy bricks in the boxes that they are shipped to the store in. These are $100 USD.

LEGO stores also typically allow you to build your own custom Minifigs. These include legs, torso, head, headgear, and an accessory. These are currently 3 for $9.99 USD.

# Answer
> 4 votes
Pick-a-brick is a pretty cost effective to get bricks, in my experience. Prices will vary by your locale, of course, but I have one data point. For a 17 EUR PAB cup, I got around 100 EUR worth of bricks using BrickLink's average price. Since the average price is often above the median, and the median is not shown on the page, I instead recalculated using the price of the lowest lot with sufficient bricks (so if my cup contained 20 of part X I used the price of the cheapest X lot with \>= 20 qty) an still the value was around 42 EUR.

---
Tags: minifigures, shopping, lego-store, pick-a-brick
---


# Question
Title: Where can I purchase replacement stickers for a current set?
My stickers for set 60035 are damaged and need to be replaced. Where can I obtain replacements?

# Answer
> 5 votes
If the set is a recent release you can call LEGO's customer service and they will send you a replacement. If it is an older, discontinued set, you can find replacement stickers on BrickLink. Here are all the stickers listed: http://www.bricklink.com/catalogList.asp?catType=P&catString=160

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Tags: stickers
---


# Question
Title: Where or how do I get replacement stickers for my LEGO set?
I have a BMW Williams F1 LEGO set 8461 that I built when I got it several years ago. I unfortunately let it sit out on my shelf for a long time. The stickers have peeled and cracked and some have nearly disintegrated.

How or where do I get a new sheet of stickers so I can rebuild the model properly and then have it put in a case so I can help keep this from happening again?

---

UPDATE (put this here as it would not fit in the comments).

I got my response back from LEGO. The set is too old and they do not carry that set of stickers any more.

> Dear Scott,
>
> Thanks for getting in touch with us.
>
> We're sorry we no longer have the stickers you need. We try really hard to keep as many replacement LEGO® parts as we can, but sometimes we run out of pieces from old sets. A second hand toy expert or collector might be able to help, or you could even try searching at flea markets or second hand shops.
>
> Thank you again for contacting us. If you have any further questions, please feel free to reply to this email or call one of our friendly Customer Care Advisors at 1-800-835-4386 (from within the US or Canada) or 1-860-749-0706 (from outside the US or Canada). We are available Monday through Friday from 8AM - 10PM EST and Saturday through Sunday from 10AM to 6PM EST.
>
> Daniel
> LEGO Direct Consumer Services

# Answer
You can either buy them on BrickLink, or contact LEGO Customer Service directly. BrickLink might be the cheaper of the two options, but if LEGO has them in stock, they are guaranteed to be factory-new.
> 36 votes

# Answer
For older sets, you can buy replicas made by some Dutch fans. I've met them on a few occasions and have seen the stickers they make and quite frankly, the quality is excellent. As far as I can see they don't do Technic sets yet, but it can't hurt to ask.

Granted, they are not genuine, but for genuine LEGO sticker sheets you'll usually end up paying a fortune, and then they'll peel off anyway.

For genuine stickers, don't forget eBay or even Google.
> 17 votes

# Answer
For long-retired products, it may be possible to find scanned images of the stickers online.

Then use a high quality color printer to print new decals which you glue to the bricks.

The result is not perfect, but often good enough to fool an untrained eye.
> 6 votes

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Tags: shopping, stickers
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# Question
Title: How can I preserve opened Lego packages?
For some reason I keep my old Lego boxes (since the 1980s), and my son's old Lego packages. Because they are quite large, they take up a lot of space in my house, even if they are put one into another. I suppose I am not the only one (see this comment) who keeps them.

I actually don't know why I store them — maybe some psychological issue — but how can I *effectively* store old packages? And those of you who keep old boxes, do you ever display them, or browse them? Or do you just keep them?

# Answer
Well I used to keep mine as well. One thing I found very good was to take a razor or a box cutter and cut the front and backs off! this may seem obvious or defeat the purpose, but it made them easier to store. I would stack them all and slip them on a shelf or under my bed to keep them flat. This proved to be a very effective solution. Also, you could try to collapse them at the ends to have them take up less room as well.
> 3 votes

# Answer
When I was young my mother used the technique of cutting out the front and back and thus preserving the various ideas that the photographs of the set provided. She stuck the box bits into a large craft book and it was stored on the bookshelf; it was handy to get to and flip through. *Don't do this; don't go cutting the front and the back off.* Whilst most of the interesting information is only on the front and back, the economic value of the box is destroyed when you cut it up like this.

If you want to resell the LEGO as a set later, having the original box greatly increases the value of the set. The boxes for certain Technic sets can achieve values of $50 or $100 - just for the box.

**The best way to preserve a LEGO box without it taking its full volume is to use a box cutter to cut the glue that holds the flaps onto the sides. This preserves every visible surface of the box and allows you to reassemble/re-glue it at some point in the future.** Cut down like this the box takes up a fraction of its original size, and can be stored in an out-of-the-way place like an attic or on top of large shelving (be aware that a box cut down like this can be surprisingly large and unwieldy). Don't stack too many boxes atop each other like this - cardboard is both heavy and floppy, and searching through a substantial stack may require more strength/space than you have available.
> 2 votes

# Answer
Well there is two ways the easy way to throw them into a bucket or you can first separate them into groups either by size,color,set,etc. than put each group of separated LEGO bricks in some sort of container such as a bucket box or back. I think that a bucket is the best idea because it is more safe and can be put anywhere of size
> -4 votes

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Tags: storage, packaging
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title: Minifigures creator?

text:
# Question
Title: Minifigures creator?
Does a website to create custom minifigs exist?

For exemple, you choose your head (between all official LEGO releases), torso, legs, and hair, and then you can purchase it for the same price as you would if you were buying each of the pieces from a Bricklink seller.

I'm looking for a simple way to create yourself and your friend's avatars in LEGO.

# Answer
Minifig Generator might work for you.

Or maybe the ~~SigFig Creator.~~

Flash based, but also fun: Mini-Mizer.

Even better, suggested by rioforce: LEGO Universe Minifig Wizard

I'm sure there are more...

6 hours later... OH! you mean like an actual bit of molded plastic.

For that, probably your best bet is using one of the above to find some approximation and then hit up something like Bricklink to buy the proper parts.
> 6 votes

# Answer
If you are close to an official LEGO store they have stations to make your own minifigures. LEGO also has an online Pick-A-Brick store where you can buy parts individually. They have a decent selection of legs, heads and headgear, but the toros selection is quite limited. You can check it out here: http://shop.lego.com/en-US/Pick-A-Brick-11998. Other that that, BrickLink is your best option. Just make sure you create a Wanted List, so you can minimize the number of sellers you need to shop from.
> 4 votes

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Tags: minifigures
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# Question
Title: Tips on shipping large sets (super star destroyer, 2001 Discovery ship)
I have two large sets I'll need to sell when I move (SW super star destroyer, and 2001 discovery). They are both very long (5 feet?) and impractical to ship complete. Any tips for newbie in best way to pack them?

For example, should i minimize disassembly and only disassemble enough so it fits into the shipping box? And would bubble wrap be enough to protect the bricks?

(since i'll be selling them without manual or original box, I'd assume that buyer will be more experienced LEGO builder)

Thank you so much!

# Answer
> 6 votes
I would suggest that you first ask the buyer what they would like. For example I would definitely prefer to get the set fully disassembled as I would like to build it from scratch.

If the buyer doesn't care which way you ship it, fully disassembled is still the safest way. It will take up less room and also it is less likely that parts will be damaged or warped in shipping. You can pack loose parts in ziplock bags.

If the buyer would like the set partially disassembled you can take it apart in the most logical sections, then first wrap each section in cellophane wrapping (the kind used for food). Cellophane protects an assembled set the best because it "sticks" to LEGO leaving little or no gaps, so parts won't fall off. Once you have done that, use bubble wrap around the sections to protect them from bumps while shipping, then place them in the box or boxes.

Also, use FRAGILE stickers or stamps on the box. They do help. And make sure you buy full insurance to cover any loss or damage. Even if the buyer doesn't want to pay for it, it is worth it for your own peace of mind. Hope this helps some! ;)

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Tags: shopping, packaging, trading
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title: Dimensions of Mindstorms NXT pieces

text:
# Question
Title: Dimensions of Mindstorms NXT pieces
I don't have access to my NXT boxes at the moment (they're stuck behind a wardrobe that won't get moved for a week or so) and I'm working on this project where I need to know the dimensions of the NXT, motors and sensors in mm. I did a search but couldn't find anything on the net and was wondering if anybody knew what the dimensions (height, width, depth) of the NXT brick, motors, US sensor, color sensor (the one in NXT 2.0 that works as a lamp and light sensor also) and touch sensor? Thanks

# Answer
Just measured them myself. Some of the dimensions might be just a little bit off, but I hope this suffices:

**NXT:**

Length: 111 mm

Width: ~71.7 mm

Height: 40 mm (extra 8 mm if you have a rechargeable battery installed)

**Motor:**

Length: ~105 mm

Width: 40 mm

Height: ~45 mm

**Ultra-sonic Sensor:**

Length: 44 mm

Width: 44 mm

Height: 30 mm

**Generic Sensor:**

Length: 44 mm

Width: 22 mm

Height: 30 mm

If it's a touch sensor and the button is not pressed, then it's 47 mm long.

Again, some of these may be a bit off since some dimensions were difficult to properly measure with the ruler I was using due to the geometry of some of the pieces. If you want a more accurate and precise measurement, someone else might be better equipped to answer your question.
> 6 votes

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Tags: mindstorms, piece-information, size
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# Question
Title: Difference between LEGO Castle and LEGO Kingdoms
Can anyone explain what the difference is between LEGO Castle and LEGO Kingdoms. I don't understand why they are not in the same product group. Also LEGO Kingdoms is no longer listed on the lego.com website.

# Answer
> 11 votes
LEGO Kingdoms is a sub-theme of LEGO Castle. LEGO Castle is one of the oldest LEGO themes, and through the years it had various sub-themes like Knight's Kingdom, Fantasy Era, Dark Forest, etc.

The current LEGO Castle theme is simply called LEGO Castle without a sub-theme name and I think that is causing the confusion. The previous LEGO Castle theme released between 2010 and 2012 was called LEGO Kingdoms. The only set that is still available from LEGO Kingdoms is the #10223 LEGO Kingdoms Joust set.

At the online LEGO Shop you will see that the two themes are listed separately. The reason being that they are actually two sub-themes of LEGO Castle, even though the current one doesn't have an official sub-name. So to be clear, LEGO Castle is the theme, with two current sub-themes; LEGO Castle and LEGO Kingdoms.

LEGO has always listed sub-themes separately. For example when LEGO Kingdoms first came out there were still some LEGO Fantasy Era sets left from the previous years, and although they were both sub-themes of LEGO Castle they were kept in separate categories. The same thing is happening now, except this time one of the sub-themes have the same name as the main theme. I hope this is not too fonfusing...(c;

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Tags: lego-group
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# Question
Title: Where to order custom mini-figs in Europe
General question is are there any custom Lego minifig online stores in Europe like there are many in the US ?

In detail: My friends friend is getting married and she would like to surprise them with an original gift. She is looking for two specific LEGO minifigs, custom or not but from sellers in Europe because she needs those for next Wednesday. these are the minifigs she is looking for:

Star Wars Queen Amidala http://www.ebay.com/itm/LEGO-Custom-Star-Wars-Queen-Amidala-4-Handmaidens-Invasion-Dress-03dB-/170787423998?pt=Building\_Toys\_US&hash=item27c3b946fe

Mario http://images.sodahead.com/polls/001480721/3cea492bc51cc7ffd403f2deaf7cb328\_answer\_5\_xlarge.jpeg

They don't have to be these exact ones but those same characters.

# Answer
Your friend can get Queen Amidala at several shops based in Europe. Here are all the listings with the country of the shop: http://www.bricklink.com/catalogPG.asp?M=sw387. It might be also worth checking the eBay listings specific for their country.

As far as Mario, LEGO never made an official one, however this UK based store does carry some: http://www.customminifig.co.uk/super-mario-bro-custom-minifig/
> 3 votes

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Tags: minifigures, star-wars, customization
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# Question
Title: What is the difference between these hole shapes?
I purchased an assorted bag of LEGO Technic pieces. There are pieces with axle holes, but what puzzles me is that the holes are different from what I am familiar with.

1. There's a piece with an hourglass-shaped hole (center of photo). What is the purpose of this shape?
2. There's a piece with an hourglass-shaped hole, but with two thin tabs (left in photo). What is the purpose of this shape?

I'm familiar with the normal round hole, in which an axle can rotate freely, and the "plus" shaped hole, found in cogs etc., that grip an axle so the piece doesn't slide along the axle. But these two are new to me, and their purpose isn't obvious.

# Answer
> 9 votes
These are 3 different versions one the same shape / function that fit over axle.

* The right one is the oldest from the 80
* The left one came next
* The middle one came after that.
* To make it more confusing, lego is now back producing the right shape again

What I can remember had the original one a lot of clutch power and was hard to be removed.

Personal I think the left one had some problems with manufacturing, due to the small tabs.

I believe the middle one broke easily.

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Tags: technic, gears, shapes
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# Question
Title: Does longterm storage in a connected state harm the studs/tubes?
Does storing bricks in a connected state lessen their longevity?

# Answer
> 19 votes
After researching the question further via some local AFOL, the answer appears to be "No". The tube/stud system remains robust if stored in a connected state. Connectivity issues arise after the studs/tubes begin to wear down due to excessive usage or the elements become cracked. Simply storing a model intact does not lessen the life of the bricks. However, storing LEGO elements out of direct sunlight is recommended.

# Answer
> 12 votes
I have some standard Red 2 x 4 Bricks that have been stuck together in the same configuration since the early '90s, I just separated one and tested it compared to another Red 2 x 4 Brick from the same era, (and probably the same basic building set), but stored loose, and I could not discern any real difference in clutch power.

This is of course highly subjective and a very small sample size, but for at least this one brick 20+ years of being stuck to another brick has not had any noticeable effect on its clutch power.

I would think that other factors such as temperature, exposure to UV light and frequency of use will have a much larger effect on the clutch power of LEGO than being stored stuck to other LEGO elements.

An interesting and related point is discussed in another LEGO Answers question, 'Are transparent neon Lego bricks made from a different plastic than usual?', in which it is stated that elements made of polycarbonate should not be stock together as polycarbonate in contact with polycarbonate creates a very tight bond. (Transparent elements are usually made of polycarbonate, wheres other elements are usually made of ABS plastic post circa 1963\*).

Further reading:

<sub>\*Link shamelessly plagiarised from @Joubarc's answer.</sub>

# Answer
> 8 votes
I can tell you for a fact that removing the tire from some of the older wheel design has a pretty sizable chance of breaking them.

# Answer
> 6 votes
I had my childhood lego in a bucket for about 20 years. After opening it up again, I didn't notice any real damage. The older part molds for some pieces are more prone to breaking as they have thinner connections etc, but just because they were in storage does not seem to have affected anything.

# Answer
> 4 votes
Yes, but not very noticeably or quickly.

Keeping bricks assembled will always create stress on the bricks, and will gradually warp the plastic. However, the rate at which clutch power is affected, and to what degree is unclear, and depends on other conditions.

My most pronounced experience with this was a set (6085) that I purchased which had likely been assembled for 15-20 years. Although the elements were shipped disassembled, I had been informed that the model had stayed together, placed on a shelf, and had been dusted before shipping to me.

Although most elements assembled fine, without any discernible clutch loss, a few connections were slightly loose. Upon closer inspection, the loose connections were those where the "dust marks" lined up perfectly-- IE, those particular elements were assembled in that particular configuration for a long time. Rotating those same elements' connection points resulted in normal clutch power, but using the same orientation was looser.

Granted, there are other concerns which may have affected this particular example, such as humidity, UV exposure, ambient temperature, etc. I expect that fluctuations in these other conditions will likely expedite the degradation of clutch in assembled elements.

# Answer
> 2 votes
Having them connected may actually *increase* longevity, at least for parts of the brick. This shields out light and air pollution. I have several LEGO bricks that were connected for 30+ years, and the sides exposed to air (and Los Angeles air pollution) were significantly more yellowed than the sides that were connected.

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Tags: storage, durability
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# Question
Title: Is there a way to buy LEGO houses without minifigs?
Why are there so many LEGO Friends minifigs, but barely any houses? I have made about 10 families and I still only have one house.

# Answer
LEGO Friends are essentially the same as minifigs when it comes to building things like houses. The main difference is the colour palette. If you don't mind that your Friends live in houses that use primary colours instead of pastels, you can just buy any regular Lego house (the Creator line has many) and put Friends in there. Previous houses from the Creator line from 2007-2010 did not include any minifigures, but current houses typically do include some minifigs. Feel free to mix them with the Friends mini-dolls or keep them in storage or give them away if you want.

You can also download the instructions for any existing model and the recreate it using Friends-coloured bricks if you prefer to use those colours.

If you're curious about sets that might be available now that feature houses, Brickset allows you to search sets tagged "house" or sets containing the word "house" in the name. You can sort the list by year of release in descending order, to show you sets more likely to be available in stores.

Some houses that were for sale in 2014:

31012 Family House

7346 Seaside House

10228 Haunted House
> 12 votes

# Answer
The best way is to obtain loose bricks and make up your own houses!
> 5 votes

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Tags: friends
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title: What happened to Cuusoo set #6

text:
# Question
Title: What happened to Cuusoo set #6
Lego Cuusoo just announced set #7 Ghostbusters 30th anniversary. Cuusoo set #5 is the Curiousity Rover.

Why is there no set #6? What happened to it or did Lego announce it and then change their minds?

# Answer
Looks like LEGO switched up the numbering of the CUUSOO/Lego Idea sets. The Ghostbusters set is officially #006 as can be see on the Lego.com site and now that review units of the Exo-Suit have been released to several Lego related blog sites, it has the number #007 on it.

Official LEGO Shop listing of Ghostbusters set Click on the box image

Review of Exo Suit

Hi Res shot of Exo Suit box
> 5 votes

# Answer
The sixth LEGO CUUSOO set is the upcoming Exo Suit. See announcement here: http://blog.lego.cuusoo.com/2013/10/21/results-of-winter-spring-summer-lego-reviews/
> 7 votes

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Tags: set-numbering, ideas
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# Question
Title: How do they keep the outdoor models so clean at the various Legoland parks?
I've visited Legoland in California a few times and was always impressed with the lack of accumulated grime or bird "strikes" on the outdoor displays. How do the park employees accomplish this feat? What combination of tools and/or techniques do the Parks utilize to keep the models free from build up?

# Answer
I've been to Legoland Windsor (in the UK) on one of the days they were cleaning some of the boats, and it looked hard - all manual work, with a large toothbrush and plenty of elbow grease
> 4 votes

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Tags: cleaning, legoland
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# Question
Title: Can I build UCS Death Star by buying bricks separately?
I'd like to get the UCS Death Star, but it's too expensive :(

I got the build manual, and I see what bricks I need. I am thinking of buying them separately via Bricklink.

Has anyone tried doing that?

# Answer
There is a whole site dedicated to working out how you can build a particular model using parts from other sets - Rebrickable. A combination of that and Bricklink would be cheaper as you'd end up with fewer extra parts.

There's also a thread on EuroBricks where someone has done what you're doing and there are some useful tips (mostly about buying as much as you can from a small number of sellers to avoid huge postage costs). Brickset's "links" tab is handy for more information on the set.
> 6 votes

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Tags: sets, shopping
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title: Can EV3-G MyBlocks be recursive?

text:
# Question
Title: Can EV3-G MyBlocks be recursive?
Imagine I create a MyBlock called `function1` from a line of blocks. Can I call that block from within itself?

This is the program for the block `recursiveTest`.

Will this block function properly?

# Answer
> 2 votes
**No, EV3 MyBlocks cannot be recursive.** If a MyBlock contains a copy of itself, then the following error will be produced upon compiling:

For some reason, LEGO's programming software has become progressively less immediate about notifying you that this cannot be done. In EV3-G, it waits until compile to let you know that you can't do this. In NXT-G (the software for programming the NXT), trying to put a MyBlock in itself produces an error upon placing it. And in the Robotics Invention System 2.0 (the software for programming the RCX), it simply won't let go of the MyBlock you're dragging if you try and place it into itself.

If you want a programming language for the EV3 that supports recursion, I'd like to offer LeJOS EV3 (Java-based, free) and ROBOTC (C-based, costs money) as alternatives. They're both EV3-compatible, and support recursion.

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Tags: mindstorms, ev3, programming, ev3-g
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title: Help with identifying LEGO sets

text:
# Question
Title: Help with identifying LEGO sets
Our family (with very big hearts) gave us some LEGO they found. But... I do not know what sets they are from. I already identified 11 sets, but cannot find the last 4 (I think)

Could you please help?

1. Construction machines

2. Recycling truck

3. Girl car

4. Firetrucks

Please, do not pay attention to the state they are in. I still need to clean them. But I'm reluctant to dismantle them until I know what set they are on ( and have a manual to put them back together) .. yep, I'm a freak ;-)

Please, any hints are welcome.

# Answer
> 10 votes
I believe that this covers everything:

Construction vehicles:

Recycle Truck (6668)

Friends car (30103)

Fire vehicles:

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Tags: city, friends, set-identification
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# Question
Title: Pass sensor or motor port number as a parameter
I want to create a block for one light sensor or one motor separately. Is it possible to give the number of the port as a parameter to a sensor or motor block via data wire? In NXT-G it was possible.

# Answer
> 8 votes
Yes, it is possible to pass the port number as a parameter to a sensor or motor block via data wire. It's just that it's manually selected by default. To change this, go to the port of the sensor or motor block, and select the top-most option which has the plug icon on it:

It will then create a data port for which motor port you want to use:

The same principle applies with sensor blocks. The input for both sensor and motor blocks is read as number, and you can validly enter a number 1-4 to represent which port.

In the above example, a variable is created, and that variable is then passed to both the motor and sensor blocks. Since it was set as 1, it will move motor connected to port A, and wait until the touch sensor connected to port 1 has been touched.

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Tags: mindstorms, ev3, programming, ev3-g
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# Question
Title: Is the NXT forward compatible with EV3 sensors and motors?
Is it possible to use EV3 sensors and motors with the NXT intelligent brick? I've read that the EV3 is backward compatible with NXT motors and sensors, but does vice versa work as well? Is the NXT forward compatible with EV3 sensors and motors?

# Answer
Short answer: you can use EV3 motors with NXT, but you can't use EV3 sensors on NXT. NXT sensors and motors work with EV3.

Detailed answer: read Laurens Valk **paper**.
> 1 votes

# Answer
The NXT works fine with EV3 motors, and will read them as NXT motors. EV3 sensors, on the other hand, do not natively work with the NXT, with the exception of the touch sensor.

The reason for this is that, touch sensor notwithstanding, EV3 sensors use a hardware communication protocol called UART, which is not supported by the NXT. The NXT only supports analog and digital I2C. The EV3 touch sensor works with the NXT because it's an analog sensor, unlike the other EV3 sensors.

That being said, it is possible to make EV3 sensors work with the NXT via an EV3 sensor adapter:

An adapter is required for each sensor port used. Unfortunately, it's not currently supported in NXT-G; just in NXC and EV3-G.
> 0 votes

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Tags: nxt, mindstorms, ev3, compatibility
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# Question
Title: How can I find the analog output of a color sensor?
Could anyone provide me with an image of the voltage output of an NXT or EV3 colorsensor. I would like to have the analog output if it's possible, and not the digital output.

# Answer
Depends on what programming software you are using. The education versions of the NXT and EV3 software having data logging features that may be what you are looking for.

The education versions of NXT and EV3 programming software are available for purchase from www.education.lego.com
> 1 votes

# Answer
Making the assumption here that by analog, you mean something more fine-grained than just the 6 or 7 colors.

Both the NXT and EV3 color sensors have the capability of reading the individual color components. The value read is not a voltage, but just a "percent" of reflected light of each color.

For NXT-G, you can find a block here (the *Color Range Block*). (see comments)

For EV3-G you can find a block here. The EV3 block requires firmware version 1.06 (there is a bug that prevents it working in earlier versions).
> 0 votes

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Tags: mindstorms, nxt, ev3, programming
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title: Design of record-breaking builds

text:
# Question
Title: Design of record-breaking builds
This is more a theoretical than practical question...

If one wanted to build a 40-metre tower out of only Lego using the fewest pieces or cost, what design would be a good one, e.g. types of pieces and overall shape?

I've just read that some builders in Budapest broke the world record for the tallest Lego tower at 34.76 metres. It looks like a simple elongated pyramid.

The previous record holder used a cross-shaped cross-section.

BBC has also featured some research to calculate the maximum theoretical height.

# Answer
> 4 votes
If you could design using Technic Axle 32 as your primary member that would probably be cheapest. You can get 500 of them for under $1 each on BrickLink, and making an Eiffel Tower shape out of those could be fairly strong. You'd be using axles in compression which isn't ideal so you'd need to be careful about bending forces, but in terms of cost per metre of height that's about as good as you can get. 32 studs is about 25cm, so your 40 metre tower is about 160 axles high. Assuming four legs (because Lego makes rectangles easier than triangles) you'd need 480 axles for the legs, plus another hundred or so for bracing. If you could work out a way to use only 3 legs the structure would be lighter.

You'd use axle connectors to join them end to end and either Technic liftarms or string for bracing (compression and tension respectively). There are Technic link parts in a few lengths that are lighter than liftarms, like this 15-long one and the tension member at the bottom would be a baseplate (or several baseplates)

If you made it modular using a "platform" that was, say, 16 studs square you'd end up with extra internal legs but a very easy to build structure. Say you make a tower that's two metres tall (8 axles) and tapers from 32x32 to a point. Four of those next to each other would support another similar tower on top of all of them. And so on, but the inside towers will end up with 2,3 or 4 towers sitting on top of them. A better design would make set of four symmetrically located parts "unique" and thus use fewer total parts but at the cost of the whole model being significantly more complex. On the other hand, I think you'd be able to get more than 2m out of each stage of such a tower.

I might have a go at a short version of this tonight if I can find my collection of long axles and see how stable it is. Somewhere in the garage is about 20 of them, so I should be able to get a metre tall fairly quickly and easily... if I can find those axles.

An alternative part that would involve a lot of SNOT techniques would be single train rails. Or even the modern click-together rails. I can't think of a good design for those off the top of my head, though.

# Answer
> 4 votes
Just using bricks the cost argument becomes more important. Unfortunately large quantities of bricks really require that you deal with The Lego Group directly (and they're usually quite happy to deal). For rough price guides we can look at bricklink again. Sorting by quantity available from a single seller for some common parts (we don't care about price per metre if we can only get 20 of the part), cost per 2x4 brick volume in bold:

The bold figures give you a direct comparison, suggesting that 1x1 bricks are the same price as 2x2 bricks but more fiddly to work with and probably both heavier and weaker. Note that volume available increases with brick size for the most part.

So it looks as though your cheapest bet via BrickLink would be a containment wall of whatever larger bricks you could find with a core of 1x1 and 2x2 bricks. I suspect if you built a want list with the more common 1x1 bricks you could find one or two sellers who have lots of that size and do a deal "I'll buy all of them", because 1x1 bricks are a slow seller but you get a lot of them in the "bulk bricks" sets when sellers part them out.

Or just ask TLG for a couple of hundred kilogrammes of 1x1 or 2x2 bricks and see what you can get cheap. If you have media and charity tie-ins organised and some plans for the tower I suspect you'd get a better reception. I'd be tempted to add 2x3 or 1x3 bricks to tie things together, since compressive strength is not the limiting factor (see Ben's answer). If you're doing that it's probably better to model a few different bricks (or find the data online) so you can have an informed discussion about which bricks you want.

# Answer
> 2 votes
The key point that the team at The Open University calculated made was that while you could **in theory** build a tower about 3.5km high of bricks before the ones at the bottom would be crushed by the weight of the ones above - this was based on the load-bearing ability of a single 2x2 brick - they also stated that a 2x4 would fail sooner (less support on the sides I assume).

However, **in practice** this wouldn't be possible as:

> "There isn't a chance you could do it in reality," Johnston says. "Long before the brick fails, the tower would fail as a structure itself, by buckling. The other thing you have to remember is that we were very careful to load this equally down the middle, so that all four walls were loaded."
>
> A 3.5km tower would have to be built so straight that it was no more than 2mm off centre at the midway point

The 12m high (40ft) Christmas tree that was built in St Pancras was built around a metal frame for additional support and rigidity.

Note that the GWR is for "Interlocking Plastic Bricks" which would certainly rule out the use of string, and might also rule out the use of axles as they are not "bricks".

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Tags: records
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# Question
Title: Can't get EV3 to work with touch sensors
My FLL team just got a couple of EV3 sets and the kids were trying to program a simple switch that has the robot drive into a wall, back up, and turn right once the touch sensor in the front is pressed.

The pressed condition in the switch has a move tank going backwards followed by a turn. The unpressed condition has a move tank going forward.

The robot just goes forward and does not stop after it runs into the wall and the sensor is clearly pressed.

## We tried switching the bricks, the sensors, the cables, the ports and reinstalling the firmware. Nothing works. Help...

Thank you for the replies. I'm not sure I'm responding in the right spot but here is the screenshot:

Also, it's not a port number issue. In fact, when you check the ports on the software it shows that it's recognizing the sensor and its state on the correct port. And it does get pressed. We even tried pressing it manually just to make sure.

I just reinstalled all the software and firmware and now it's not even going through the switch! It just skips it and goes on to the last block. I think I'm out of my depth here...

# Answer
> 1 votes
Are you sure that the button is being completely pressed? A quick test would be to hold the robot and manually press the touch sensor. If the wheels start turning backwards, then there isn't anything wrong, you just need to make sure the button gets pressed completely.

If you're sure the button is being pressed, then it's probably a software problem. It seems like you have a conditional block, is it reading the same port that the sensor is connected to.

You could make a really simple program that has a forward tank movement inside a loop and make the exit condition for the loop be to exit when the button is pressed. If you put an end block after the loop, the robot will drive forward forever until the button is pressed.

Hopefully one of those options will help you fix the problem!

# Answer
> 1 votes
Code is works as the robot is behaving. The problem is that the first block is a sensor block, which is processed in the blink of an eye. The second block moves forward for 2 rotations at 50% power.

So long as only one sensor is being watched, a wait for block is sufficient. Here is an example:

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Tags: ev3
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# Question
Title: How can I build an (automatic) Mindstorms charging-station?
I'm thinking about buying LEGO Mindstorms and start programming robots. I'm a software engineer and LEGO fan since I was a child so this sounds like the perfect combination of my dearest hobbies.

But some questions come into my mind that I simply can't find out on the LEGO website:

* Is is possible to programmatically check the battery charge status?
* How is the NXT 2.0 block, where the power for all those motors and sensors come from, charged
* Is there a possibility to build some kind of charging station where my robot can drive in to get recharged?

The point of this is, I would love to have a robot that's driving around doing stuff, and when the batteries are almost empty (let's say \< 10%). it would drive to the recharging station on its own — and when it's full again (\> 95%), get out of the station again and continue doing other stuff.

# Answer
As a software engineer, you would probably be more at home in NXC, a C-like language compatible with the standard firmware. You can then use `BatteryLevel()`.

If you want to use the standard programming environment, use this custom block.
> 14 votes

# Answer
1. Yes, it is possible to check the battery level. I am a software engineer, too and i have already done that in different environments (leJOS, NXC).
2. It is not charged. It uses standard AA batteries. There is a really handy rechargable battery pack, though.
3. A recharging-station could probably be built with this, but it might be quite tricky to do. As far as I know, there are no "wireless" charging possibilities like those some mobile phones are using (using magnetic fields to transfer energy or something). You would need to drive the robot towards the plug, but i assume that that's possible.
> 10 votes

# Answer
For the recharing part, keep in mind noone said you must use AA batteries or the rechargeable pack. You can build your own charging adapter, which means you can also equip it with a different (more powerful?) battery of your own, and have charging contacts which are more easy to access for a recharging station. (Or use wireless charging if you know how).

This may require some electrical knowledge, but it will be easier to automate than trying to plug the charger in the rechargeable battery. That said, you can combine both, use the rechargable battery, and use a cut power supply cable to connect it to large recharger contact plates or something.
> 4 votes

# Answer
What you need is a Wireless Power Charger with a Voltage and current suitable for charging your Robot

here is a link to an instructable that will show you how to build a generic wireless charger. You will need to adapt it to your own needs. i.e. adjust the receiver voltage to charge the power pack

http://www.instructables.com/id/Wireless-Ipod-Charger/

With this circuit, you should be able to build a charging station that the BOT simply needs to get near to recharge itself. (a small pad with the transmitter in the base and a homing signal The robot can track)
> 2 votes

# Answer
Lego NXT vacuum cleaner project included charging station http://www.plastibots.com/index.php/2010/11/13/pulito-featuring-dflex/
> 1 votes

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Tags: nxt, building, automation
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