# Question
Title: Help identify this 70s or 80s lego space set
I bought some bags of LEGO bricks which appear to contain a 1970's space set in it. I want to find instructions to put it all back together.

# Answer
> 4 votes
The brick with the space logo is from either set 452/894 or set 6901. The buggy is technic set 1972. Information from Bricklink search.

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Tags: set-identification, space
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# Question
Title: Is it possible to use a LEGO NXT ultrasonic sensor for a LEGO train crossing?
I was looking at LEGO NXT components, and I found the ultrasonic sensor. I was wondering that if I put off to the side of the track, the nose of my train would activate the sensor, thus operating the servo and closing the gate?... I have already prepared my crossing with a gate attached to a 12 stud axle. At the end of the axle pointing away from the track, a servo would move the axle at about 45 degrees. Is this possible or are there any alternatives that would work better? I'm not sure if my idea has been attempted before with Power Functions tracks. Also note that I am using a 32x32 base plate. I am hoping that I won't have to use a Mindstorms control panel (I'm not entirely sure what they're called) because they are so expensive.

# Answer
As you suspected, you cannot use the Ultrasonic sensor without an "Intelligent Brick" (EV3 or NXT). MINDSTROMS would be a great way to automate your train if you are willing to make the investment.

For more ideas on how to use LEGO MINDSTORMS with LEGO trains, check out Sioux.NET.
> 1 votes

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Tags: nxt, trains, sensor-ultrasonic
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# Question
Title: NXT shuts down USB on Mac after connecting motors
After successfully connecting our NXT to my Macbook Air and upgrading firmware to 1.31 we built our first robot. We plugged in the motors to ports A, B & C and now we get an Error stating that USB ports have been shut down because a device is drawing too much power. I have tried Reseting NXT and now it is stuck in "clicking mode" I have tried two different computers and three different cables. I also plugged in in through a USB hub all with the same result. I have restarted, Shutdown and restarted, Unplugged and restarted, Reset P-Ram.

# Answer
The clicking mode means that you need to reload the firmware on the NXT (under the Tools menu in the NXT software).

If you still get the overcurrent shutdown using different cables and different computers, then the conclusion has to be that there is something wrong with the NXT itself. The USB port should be drawing little to no current at all since the NXT has its own power source.

It would also be worth contacting LEGO support if you do indeed have a defective NXT.
> 1 votes

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Tags: mindstorms, nxt, motor
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title: where can I find simple Lego ideas

text:
# Question
Title: where can I find simple Lego ideas
I have just acquired a bunch of bricks and specialized bricks. Where could I get a lot of ideas?

Anything to do with a city would be good. I have already tried the LEGO club.

# Answer
> 1 votes
That's a pretty vague question, but here are some general resources on city building:

Rebrickable has a large selection of MOCs. Browse through it and see if you can find something fun there.

You can look through all of the official City sets. Brickset is a good place for that.

Twinlug has a fun Micropolis standard you can use to build a large layout together with other fans.

When you get serious, you might want to get into the modular buildings \- it has become a pretty common standard to build for as well.

Hopefully that gives you a start.

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Tags: ideas
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title: Strain Gauge on LEGO Bridge

text:
# Question
Title: Strain Gauge on LEGO Bridge
I had an idea to teach my son (almost 4) about bridges and large structures from an engineering point of view. I thought that it would be cool to build a large bridge and put a strain gauge on it. One of those foil like strain gauges. Then I would drive some heavy LEGO cars filled w/ pennies over it and we could watch the resistance change on the strain gauge.

My question is, would it be possible to get some meaningful results out of this? I see a number of problems.

1) I've never used a strain gauge before, and I'm wondering if the pulling apart of the bridge due to the various forces is an appropriate use case for a real strain gauge. The deformations would get rather large quickly since we're working with bricks and could possibly render the strain gauge useless.

2) The introduction of the strain gauge itself, glued onto bricks radically would change the way that the forces are distributed. The strain gauge now acts as a physical support holding two bricks together.

# Answer
> 2 votes
Lego bricks can withstand a fairly high pressure before they deform, but Lego creations tend to deform more easily at the various connection points. Therefore it's possible to build a relatively easily deformed bridge using long pieces, such as technic beams. You could build a bridge that deforms easily and then show how it flexes under the various weights.

As for using a real strain gauge, that might be overkill, but if your bridge is fairly bendy you could probably compensate for whatever structural rigidity you'll get from the guage itself. Also I'd go with putting the gauge on a separate, flexible piece (such as paper or plastic) and just pin it to the bridge using normal lego parts. Presumably you don't need super-accurate measurements for this demo?

Lego also has some springs and shock absorbers which can possibly be used to help with your design. Either use them to make the bridge flexible, or use the compression of the shock absorber as your measurement of how deformed the bridge is.

# Answer
> 1 votes
I have designed some special measuring tooling for my previous employer that uses strain gauges, but is is not always that easy. You need for sure:

* an amplifier,
* glue them on the construction in the correct orientation
* 2 strain gauges on both sides for temperture compesation
* a way to calibrate the measuring device or construction

this resulted for us that we most of the time we were using commercial available tooling like load cells and only make our own if commercial was not an option.

I don't know what will happen if you glue them over the joint between 2 brick, but the measurement will not correct. These strain gauges have a liniear behavior when glued to a surface. When we had a strain gauge that was not correctly glued or got loose we noticed that in the measurents.

I thing I was wondering about, for who are you planning to do these measurement, your 4 year old son, or for your self. I think if its for your son, that he is to young to fully understand this, for the effort you need to get it working.

If its for your son, I would just let the brigde break, when the load is to high. If you want to visualize the behavior you can also use 1 of the bridge construction games that are available for example on Steam. These show with colors the stresses in the different beams.

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Tags: durability
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title: How make robot turning going straight?

text:
# Question
Title: How make robot turning going straight?
I have been struggling with this function for a while.

I want my robot to turn left until it detects black then turn right until it hits black again. Then, I will divide the angle in half and call rotateTo to make the robot move that angle. I don't know why it is not working the way I want it to.

The reason I do that is because after I turn left or right it is not exactly 90 degrees. That is why I want to make sure it is facing the right direction before it continues moving. Here is the code:

```
int numberTurn = 0;
int numLeft = 0;
int numRight = 0;
RegulatedMotor Left = Motor.A;
RegulatedMotor Right = Motor.C;
while(color_id!=7){
    moveForward(300, 50);
    color_id = color_test.getColorID();
}
while(color_id==7){
    moveForward(300, 50);
    color_id = color_test.getColorID();
}
color_id = color_test.getColorID();
Left.resetTachoCount();
Right.resetTachoCount();
while(color_id!=7){
    Left.rotate(100,true);
    Right.rotate(-100,true);
    color_id = color_test.getColorID();
}
Right.stop(true);
Left.stop(true);
numLeft += Left.getTachoCount();
while(color_id==7){
    Left.rotate(-100,true);
    Right.rotate(100,true);
    color_id = color_test.getColorID();
}
Right.stop(true);
Left.stop(true);
numRight += Left.getTachoCount();
while(color_id!=7){
    Left.rotate(-100,true);
    Right.rotate(100,true);
    color_id = color_test.getColorID();
}
Right.stop(true);
Left.stop(true);
numRight += Left.getTachoCount();
numberTurn = (numRight-numLeft)/2;
Left.rotateTo(-numberTurn,true);
Right.rotateTo(numberTurn,true);
while(Left.isMoving()){
}

```

Left and Right is motor. For color\_id, 7 is black Anyone have any ideas why it doesn't work?

# Answer
The main problems I see are the following:

1. The value in the numRight variable is wrong for two reason: The 'right' sensor is not reseted at the proper time and you read the 'left' sensor value instead of the 'right'.
2. The angle calculation is faulty
3. The half rotation is performed in the wrong direction

Here are my code comments:

```
//Move forward until you find black
[...]

//Move forward until you are not on black anymore
[...]

//Reset the rotation sensors
[...]
//   WARNING: The right sensor is reset for no reason
Right.resetTachoCount();

//Turn left until you find black
[...]

//Get the left rotation sensor data
[...]

//Turn right until you are not on black anymore
[...]

//Get the right rotation sensor data
//   ERROR: This action should not be done until you have turned all the way to the right
//   ERROR: At this stage the right sensor should be reseted
//   Note: ...and the 'left' data was put in the 'right' variable
numRight += Left.getTachoCount();

//Turn right until you find black
[...]

//Get the right rotation sensor data
//   ERROR: This data should come from right.getTachoCount();
numRight += Left.getTachoCount();

//Calculate the half angle
//   ERROR: The calculation should be: numberTurn = ((numRight + numLeft) / 2 ) / 2;
//   Explaination: By adding the two rotations and then dividing by 2 you get the average of the two.
//                 The result is then divided by 2 again to get the half angle.
numberTurn = (numRight-numLeft)/2;
//Rotate back (should be to the left) to half the angle
//   ERROR: Rotation is performed to the right when it shoud be to the left
Left.rotateTo(-numberTurn,true);
Right.rotateTo(numberTurn,true);

```

**Recommendation**: When dealing with multi steps processes like this one, add the steps one by one while re-testing each time. The test should validate that the previous steps are still working and that the added step is working as planned.
> 2 votes

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Tags: programming, monobrick
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# Question
Title: Will they ever make LEGO The Amazing Spider-man 2 sets?
I realized that they released an exclusive minifigure of The Amazing Spider-Man 2 in the San Diego Comic Con but I am still wondering if they will ever make LEGO set(s) based on the movie.

# Answer
> 1 votes
It depends on licensing as well. Note that they have made sets for Ultimate Spiderman. The X-Men designs all follow their comic counterparts. Loki, Thor etc follow their Movie style counterparts.

This suggests that they have the license for the comic and animated styles, but Fox and Sony retain the rights for the movie looks of the characters.

# Answer
> 0 votes
That depends. First of all, the movie needs to leave theaters. Seeing how LEGO has not made an Amazing Spider Man 1 set, it is fairly un-likely they will do sets for the sequel.

# Answer
> -1 votes
Actually yes the will Because in 2014 October Sony has SIGNED lego tasm to Lego They made a electro Polybag that was given out But thats all i know but yeah They will make some because they have Rights to

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Tags: minifigures, collectable-minifigures
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title: How to Make a Lego Claw Arm?

text:
# Question
Title: How to Make a Lego Claw Arm?
I am trying to build a lego claw arm to pick up stuff that is out of my reach and I need some ideas on how to design it. I would like a mechanism to be able to open and close the claw from the opposite end of the arm.

I'm not looking for an arm design which can extend. I would also like ideas about fixed-length arms. Also, I have many, many different TECHNIC pieces. Designs can be very complex and they can use large numbers of pieces.

# Answer
> 13 votes
If you're after a simple collapsible solution to reach those items just out of reach, you can start with the following setup:

You can extend this for quite some way, and use longer bricks or beams throughout if you wish.

To finish it off, I'd use a couple of longer bricks with some additional plates on the end to act as fingers, and add some handles (via axles) at the bottom. If you use longer bricks at the ends then the middle pin would need to be offset from the centre to keep it smooth.

# Answer
> 9 votes
I built a similar model to Zhaph's claw arm but with beams and a basic claw attachment:

**360° Animation, Demonstration Video**

I had a few problems operating the claw when I built it again with real bricks. If you collapse the beams too far, it can be difficult to open them again. When you try to pick up items with your tool, you also have to anticipate just how far the tool extends (try and possition the claw as close to the object as possible, the beams will push the object into the claws).

# Answer
> 3 votes
If you don't need the arm to be extendable then you might get some ideas from the various Technic sets that feature cranes or claws, like the 8868, 8479, 8436, 8110 or 9397.

These offer multiple alternatives, as in pneumatical or purely gear-driven solutions, can be scaled up with appropriate supports and mounted on your own arm designs.

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Tags: technic, design
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title: Can I pitch an idea to LEGO?

text:
# Question
Title: Can I pitch an idea to LEGO?
How would I contact LEGO about an idea for some kits to be built and sold? I have designs for simple kits that I have built for my son that I think would be very popular.

# Answer
> 19 votes
LEGO doesn't directly take product ideas from fans.

However, there is a website called LEGO Ideas where you can post creations that may potentially get turned into official LEGO kits.

The process is as follows:

1. **Submit your idea to LEGO Ideas.** Take some time to get good pictures, and write a good description, or your idea will probably not make it off the ground.
2. **Get votes for your idea.** The way LEGO Ideas works is that ideas that can get 10,000 supporters (votes) in a year will get put into a review process. The best way to get votes is to share your idea. Tell your friends, and spread it on Facebook or other social media.
3. **Go through the review process.** Once you reach 10,000 supporters, your idea goes to the LEGO review board. The review board will look at your idea, and decide if it is worth creating as an official set. Things like size, cost, part complexity, new parts, and licensing will all be factored in to the review. Be away that only about 1 in 10 ideas that reach the review board are approved by the review board.
4. **Buy your new LEGO product.** Once the review board green-lights your idea, it will be turned into an official LEGO product! The products are often, but not always, limited edition kits, so get them while they last - as the creator you are given complimentary 5 sets and 1% of net sales.

Hopefully, this will give you some background on the LEGO Ideas process if you want to pursue that route to get your idea turned into an official LEGO kit.

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Tags: lego-group, ideas
---


title: How to start with technic?

text:
# Question
Title: How to start with technic?
I have bought myself the technic set 9393 Tractor. I really like the model and I want to dig deeper into the Lego technic universe. I am not focused in building pre-designed models (although I enjoy it, and it would be a plus), but I want to have a decent set of technic parts, such that I can build models on my own. So what is the best way to get a basic set of bricks:

* Buying some sets and take the parts from the sets? (rather buy a big set, or several small ones?)
* Buying used parts as bulk?
* Are there non-model technic sets, similar to the traditional Lego, for which they have door sets, wheels sets etc. ?

I know this question might be a bit broad. So let me add that I am not necessarily want to build motorized models right away. Also, I do not plan to build *huge* models, more in the size of the 9393 model.

# Answer
> 11 votes
Here are the two things that I would recommend:

1. Get yourself a big set if you have the budget for it. These will have a large variety of pieces and once you've built the models from the instructions you'll have a good understanding of a lot of different building techniques.
2. Watch eBay or similar sites for large lots of Technic parts by the pound. These can be a little hit or miss, but the price per piece is far lower than most other ways of buying parts. Keep in mind that prices tend to be higher around the holidays.

There used to parts packs for Technic like what you are describing, but I believe they were removed now that pretty much everything is available from Pick-A-Brick. You can also get any parts that you want from bricklink.com, and if you don't mind used parts, this can be a pretty affordable option.

# Answer
> 7 votes
I have to say I did the opposite and bought loads of small kits first and then larger kits later, however I did do a lot of research on the net and there are plenty of good books for reference material on individual mechanisms on Amazon (without having to buy lots of useless pieces for only specific functions on one kit only – can be quite expensive option). Ebay can fill up on specialised hard to get pieces and in a variety of colours too- although one has to wade through most of the junk available to find what one needs and it also depends on what you want to build? Bulk buying is a good use of this method – pick a brick can be expensive but the quality of the new bricks are without question.

Pinching plans of Technic kits from LEGO directly or from other fansites, is a good idea (with permission) to expand your knowledge of all the possibilities out there, too. Finally, I find that technical manuals from real machines are really good for inspiration like those cutaways from plane books are really useful or car repair books etc – so do your research first and ask around – lots out there...

# Answer
> 6 votes
Coming to this late, as I am in the same kind of boat.

Options might be different in 2014 due to newer options for models.

I'm trying to find a nice few sets that can cover me for building almost anything else. Using rebrickable, adding models to a set and then looking at other Technic models (both official and MOC) will give you an idea of what sort of bits you want next. Also gives you suggestions on models to buy to up your % match.

8043 seems like a good set, but has 4 piddly M motors, which I guess is okay on top but on its own is a little lame, also the price for this retired model has gone INSANE.

So far I have gone with these three...

42030 Volvo L305F Wheel Loader

Got it for £131 new, has 2 remotes, various sized motors (including steering servo), actuators, bucket and some rather large wheels.

42009 Mobile Crane

Seems to be the largest model you can get for a good price (£105), has the most pieces in any Technic model so far (although apparently half of these are just pins!) but this brings another motor and battery box (sadly just 1, but still), diffs, a bunch of wheels and obviously lots of pieces.

I already own a few small (9391, 42001) and a mid sized model (80690, buckets, wheels small LA)

42028 Bulldozer

Recently bought this for £25 as a present, really good price, just been looking at how much track is to buy on its own and its not much less than this. Although its ~14 short of building the 8043 (and I'm guessing short of a lot of MOCs) but its a start, at least you get extra parts. Could buy 2!

Hopefully they, obviously large will be a good start.

Ideally what I personally want next is:

* A proportional remote, the train sets include these + the "smaller" battery box that a lot of people use, although the big designers often have the rechargeable boxes, the 6xAAA are drop in replacements (mostly, assuming they haven't made use of the reversal pin). Im not sure I will do this though as I don't think the lad will like me gutting a train (and I don't want to stretch to two!)
* Pneumatic kit, no sets seem to have a lot in them. ile9os on ebay has a VERY nice "pro" set. I wish they had more than 1 mini-pump in the collection, sadly to get 3 (to make a total of 4) from bricklink the price goes up when you have someone that has a quantity you want (bricklink is kind of a pain for that).
* Steering kit, there are a few different types so looking at smaller models for these.
* Springs, I'm keeping an eye out on deals of smaller Technic non motorised sets for these.
* Wheels, but I'm going to resist buying them on their own though as you can easily get these on smaller models, and will eventually be overrun with them (as I am with non-Technic LEGO since I decided to buy a batch lot and later on... I have too many!)
* More clutch gear, the above has some in but would like more, the crane has a lot in because it has one motor for all the functions. Service truck seems to be another and has some pneumatic kit - personally don't like that model though and I'm not sure about the price (still watching)

42005 seems to be good for steering ball joint(x2) small springs(x4) "steering arms"(x4) steering rack(x2) knobwheel(x2). All that would cost you around £20.45 on ebay at a quick glance, and has sold as low as £23 on amazon (currently £33, I'm going to hold out for sub-£27) and it has 327 parts. You can see why people buy and part out to sell.

btw for the likes of Amazon, get onto camelcamelcamel and set a LOT of "crazy" price alerts and sit on them for a long time.

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Tags: technic, shopping
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# Question
Title: What are the largest LEGO® Power train sets available commercially [Oct 2014]
What set(s) are the largest by number of pieces? These sets could be retired or existing.

I am also curious what set(s) have the most rails pieces included.

# Answer
> 7 votes
Right now, the largest commercially available train is the Lego City Cargo Train, Set 60052. It comes in at about 887 pieces. There are 30 rail pieces in this kit. Extra rail pieces are also commercially available through Lego. The 7898-1 cargo train would come in second as far as piece count. Same amount of track as the 60052.

# Answer
> 6 votes
Apart from those mentioned by Joe, there are several larger sets in the Advanced Models category. They are not powered out of the box, but can be motorized.

These are:

Also, if you need more rails, check out the dedicated rail packages:

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Tags: sets, trains, power-functions
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# Question
Title: How to locate objects, and move towards them, without pre-programming the path
So I need to find objects in an enclosed area, I have access to the standard set of NXT sensors, i.e. ultrasonic/light.

However, the ultrasonic sensors seem to be very unreliable and erratic, in regards to finding objects accurately.

I cannot pre-program the path to the objects, so I'm trying to work out how is the best way to go about locating these objects? The objects are small, and on the floor.

I was thinking a sort of swivel motion at the start, to find any objects using the ultrasonic, and then just moving a small distance at a time, then swivelling again etc. Are there any other better ideas?

Also, there is a wall enclosing the area, would there be a way of programming the NXT to avoid it?

I'll be programming the NXT in NXC. Can't afford LIDAR :(

# Answer
If the ultrasonic cannot echo-locate the objects because they're too small, even with the sensor suspended very close to the floor, I suggest using a very sensitive feeler out front. It can be sticking forward like a jousting lance, and your robot can swivel back & forth while traveling to scan.

The trick to making it very sensitive is to: (1) make it pivot at its base on the front of the robot with a smooth pin, (2) make it long and lightweight (use long axles), (3) mount two opposed touch sensors as close to the pivot point as possible, and (4) pre-load the touch sensors such that minimal travel is necessary to trigger each one.

The same techniques can be applied with a large diameter roller out front (like a steam roller) to detect any bumps on the floor (if the objects are kind of flat).
> 6 votes

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Tags: mindstorms, nxt, software, nxc, pathfinding
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# Question
Title: What advanced railroad features are possible with the Lego PF train sets?
I recently got my first train set, the Constitution Chase, and it has sparked my imagination for building train layouts. My 3-year-old son has a small collection of wooden trains and we enjoy building tracks together. His tracks include cross-overs, switches, and bridges, and I know there is a wide range of products in that family that we could pour money into: elevated tracks, etc. However, now that the Lego train has invaded our home, I feel that we'd be better served building Lego layouts.

I've seen from shop.lego.com that there are straight, curved, flexible, and switch tracks available for purchase now. However, there doesn't seem to be any of the following currently for sale:

* cross-overs (there was a 9V crossover at one point)
* bridges (presumably, we just build whatever bridges we need, whatever way we want)
* sloping track
* double switches (There was one for sale a few years back, but it's extremely expensive now)

So, given the rather limited track selection, but the otherwise infinite flexibility of Lego, is it possible to build what's missing? Can cross-overs or double-switches be built from parts? Can PF trains climb sloping tracks, or go down inclines (and how do we make the track incline properly)? Is there an easy way to achieve a figure-8 track layout?

Bonus points for solutions that stick to System pieces instead of Technic pieces, since I have more System than Technic. I am, however, willing to buy parts as needed (except that double-switch, yikes it's expensive).

# Answer
> 14 votes
## Track Features

You can do most things that you can do with traditional model railroads using LEGO trains. This includes cross track, bridges, switches, and inclines.

### Cross track

As far as I know, this was never released for either RC or PF trains. As you noted, there was a cross track part for the 9V trains. If you aren't aware, 9V, RC, and PF track is mechanically compatible, the only difference is that 9V track has metal rails. If you don't mind the look of metal rails on your cross track when the rest of your track is plastic, the 9V crossing should work fine.

### Bridges

You are correct that there aren't dedicated train bridges. You are left to build whatever you like.

You can make anything from a simple bridge that just holds up the track like this one based on the Unofficial LEGO Technic Builder's Guide (source):

Or you can create something elaborate like this bridge from the 2006 NMRA show:

### Sloping Track

LEGO does not produce sloping track for the common train gauge. There is sloping track for the 4-stud gauge, but I doubt you will have much use for it. Aside from the tiny gauge, it is also too steep to climb for normal trains. Here's what it looks like:

Monorails did use sloped track, so if you don't mind mixing those into your layout, they could be an easy option. Here's an example of elevated track from 6399:

You can also build your own inclines, but keep in mind that it takes quite a bit of space. You can't do much more than 2 plates of incline per track section for most trains.

### Switches

Each era of trains has had switches, so this is not an issue.

### Double switches

Other than the one you mentioned, I don't think this has ever been released before. It seems like it would be pretty difficult to build custom track from parts, and this would very challenging to build.

## Example layouts

Sets often come with example layouts including which track pieces that you need. Here's one example from an old 12V set:

Here's a similar example from a 9V set:

I'll just leave you with this cool 12V layout video.

# Answer
> 8 votes
You can create crossover tracks out of LEGO elements much like I did in this video.

https://www.youtube.com/watch?v=\_i6OWkxXtuo

I got all the parts for around 4€

Also you can create your own slopes will standard LEGO tracks. You can watch then in action in this video https://www.youtube.com/watch?v=LMWF465KWfY and read about how to create them yourself at The Technic Gear.

My advice is just take a sheet and think and draw before start building.

# Answer
> 7 votes
The crossover hasn't been done in RC track, but a 9V crossing will work just fine, as PF and RC track are physically compatible (the only difference being the lack of conducting metal on PF track, which is a problem only when using 9V motors).

LEGO never produced specific bridges, which makes sense since everyone builds his own. The closest thing would be Heavy hauler, which contains ready-made bridge elements - but that's the upper decoration only, you'd still need to build a sturdy structure under it.

Another reason why LEGO probably never made any is that they'd also need to take sloping into account, and it would mean a set containing way too much track. The Duplo and monorail slopes can be very steep because the trains use gears on a rack, but a regular LEGO train will need a way more gentle slope. Some people recommend no more than 1 plate every track piece; 1 brick is really pushing it (depending on your train), and more is certainly not a good idea. Even with 1 brick every track piece, you'll only get 8 bricks higher every meter. Not a problem if you've got the bricks and track, but it makes sense that LEGO wouldn't produce a full slopes/bridge set.

Sloping by itself isn't required either, as the slope has to be gentle, the existing track will easily accommodate the connections. There you'll certainly need to limit the slope change to no more than one plate per track part. For example, if you really want to have a slope of 1 brick per track, you'll need to start with 1 plate, then only 1 brick (+2 plates) and 2 bricks (+3 plates). Same thing at the top, so if you go to 10 bricks for example, the heights of your pillars will be: ...0, 0, 0, 1 plate, 1 brick, 2 bricks, 3, 4, 5, 6, 7, 8, 9, 9 bricks and 2 plates, 10 bricks, 10, 10, ... Yup, it's long. Note that if you don't care about that, the flex-track piece is very flexible in that regards too.

When LEGO introduced RC track, one of their arguments was that they would be able to do much more fun stuff with track, which they immediately demonstrated with the double-crossover switch, and later with the flex-track, but unfortunately they haven't really followed suit on that topic. Probably trains aren't such a big market for LEGO (that's the reason they stopped 9V to start with).

And you didn't read this from me, but RC track is easier to mod than 9V track...

As for what's possible, keep in mind there are some existing software for track planning. Even LEGO has a basic online one, but for serious stuff you'd probably better use Alban Nanty's BlueBrick. There's also Train Depot Track Designer which hasn't been updated in a long time but may still prove easier to use.

# Answer
> 2 votes
Here is a new cross track available from Bastens http://www.bastens.com/cross-train-track-lego-compatible.html which is more stable than building one from scratch.

Cheers!

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Tags: trains, power-functions
---


title: Fixing poorly applied stickers

text:
# Question
Title: Fixing poorly applied stickers
Does anyone have any tricks to removing a sticker and reapplying, after a significant period of time? I recently purchased a lot of sets from 2000-2010 range, and the stickers look like they were applied by my 4-year old, while blindfolded...

I'm dealing with sets like Town Plan, and Joker's Ice Cream Surprise, so purchasing new stickers is not an option, and unfortunately stickers really make the sets in these two instances. I'm hoping someone has experience with using a glue or something else to repair the adhesion.

# Answer
Unfortunately older stickers are difficult to remove and reapply because the sticky part of the paper tend to rip off and leave a residue on the LEGO element itself. But the fact of the matter is that applying that taking off and re-applying even a new sticker is a challenge and it will almost always be visibly damaged at least a little bit.

Your best bet is just to get new stickers. You can find pretty much any sticker-sheet LEGO ever released all the way back from the beginning, and many times in new condition. In fact several Bricklink stores specialize in selling old stickers.

Just go to Bricklink, type in the set number and look at the inventory listing. The sticker sheet will be included there. Then see which seller have it at what prices and choose the one you like the most.

Here is the general listing of all LEGO stickers: http://www.bricklink.com/catalogList.asp?catType=P&catString=160
> 3 votes

# Answer
To remove stickers, I use lighter fluid. However, it can damage plastics, and I've never used it on LEGO bricks before, so please test it first.

Apply the lighter fluid to the sticker, and use a sharp metal object (like an X-Acto Knife) to slowly pry the sticker from the brick. You will probably have to regularly apply the lighter fluid as new parts of the sticker are exposed.

Once removed, set the sticker grahpics-side down a piece of newspaper or other disposable surface. To restore the stickiness, spray the back side with spray glue or spray adhesive, available in most craft stores. Now, immediately reapply to your bricks.

**CAUTION:** chemicals like lighter fluid, Goo Gone, spray adhesive, etc. can damage both the stickers and the plastic bricks. Test this process with an unimportant brick first.
> 2 votes

---
Tags: repair, stickers, glue
---


# Question
Title: Any way to create a gear+chain, like for a bike?
I would like to create a LEGO bike. I can imagine how most of it would work, but i'm stuck at the chain.

I need a way for the turning pedals (at one spot) to cause the wheel (in the back) to spin with them. A design like the classic bike chain would be nice, but something else that does the job would also work.

It would be best if a solution uses standard pieces, but i do have a few special pieces.

# Answer
> 5 votes
It looks like LEGO sells chain and sprockets, don't know if you'd have them lying around though.

You could also try using pulleys instead. If you don't have any of the actual pulleys, take the tread off of two wheels and stretch a rubber band across, that should work too.

# Answer
> 4 votes
The Technic Riding Cycle theme features several bikes that may be of inspiration. One particular set Moto Cross Bike (42007) uses several 3711: Technic, Link Chain parts to make a chain.

Based on Bricklink prices for the last six months, 39 chain pieces (the amount shown in the set above) would cost £4.29 (Aprox. $6.91 or €1.26).

Pulleys and rubber bands are generally more commonly found in sets but they don't tend to provide as much traction as a gear and chain.

---
Tags: building, gears, wheel
---


# Question
Title: Lego EV3 doesn't respond to direct command
I tried to execute command (via bt) play tone:

```
play_tone = '\x0F\x00\x00\x00\x80\x00\x00\x94\x01\x81\x02\x82\xE8\x03\x82\xE8\x03'
# send commands to EV3 via bluetooth
with open('/dev/tty.EV3-SerialPort', 'w', 0) as bt:
    bt.write(play_tone)

```

or start program “Demo” on EV3 brick

```
run_demo = '\x30\x00\x00\x00\x80\x08\x00\xC0\x08\x82\x01\x00\x84\x2E\x2E\x2F\x70\x72\x6A\x73\x2F\x42\x72\x6B\x50\x72\x6F\x67\x5F\x53\x41\x56\x45\x2F\x44\x65\x6D\x6F\x2E\x72\x70\x66\x00\x60\x64\x03\x01\x60\x64\x00'

```

but nothing happens. No error in python script. Wireless connection status (EV3 brick display) show connected during script execution.

OS X 10.9.4, Python 2.7.5, EV3

# Answer
Both of your examples are working for me. In the Bluetooth settings on the EV3, make sure "iPhone/iPad/iPod" is *not* checked.
> 1 votes

---
Tags: ev3
---


# Question
Title: What are these bricks with filled interior and holes/tubes going through?
I recently bought at haul and found a bunch of these regular sized bricks. Can anyone identify the for me?

They are 2x4 bricks, but with holes in the side of the bricks:

From: https://i.stack.imgur.com/Atc7p.jpg

It says Lego on the stud, but no part numbers are to be found anywhere, so I guess they are old.

Any help is appreciated.

# Answer
> 9 votes
They were used until 1990 for trains, the holes are there to stick in the wheels.

This is the part: http://www.bricklink.com/catalogItem.asp?P=7049b And these (for example) were the wheels: http://www.bricklink.com/catalogItem.asp?P=wheel2a

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


title: Gearing down a PF XL

text:
# Question
Title: Gearing down a PF XL
I'm looking for the best way to gear down a Power Function XL.

I need to achieve a very slow output RPM (less than 1-2 RPM). I've tried a 625:1 gear (trough 40:8 gear). Can someone link to a well done gearbox like that? Moreover, how I can make an axle more resistant at high torque (I've tried with brick round 2x2).

# Answer
The XL motor runs at approximately 220 RPM. Therefore, the following gearbox from the ELEC 201 class LEGO Design module from Rice should be sufficient:
> 4 votes

# Answer
You can use a worm gear for a compact, high ratio gearbox. By putting a worm gear on the motor shaft and using it to drive a 24 tooth gear you can achieve a 24:1 reduction.

For high torque applications you could use multiple parallel axles held together by gears or wheel hubs.
> 2 votes

---
Tags: building, power-functions, gears
---


# Question
Title: NXT brick not executing programs correctly
I have an issue that I am hoping someone might be able to resolve:

We're using Mindstorms in the classroom as part of a STEM program, and have one NXT brick that won't execute programs correctly. The program is a simple move/turn/move program and the program works on other bricks.

It will move forward and seems to attempt the turn but then just stops.

Working programs from other groups also don't execute correctly on this particular brick so we eliminated a programming error.

We have tried soft reset, hard reset, and updated the firmware all with no effect.

I'm hoping it doesn't mean we have one totally useless robot. Any help is appreciated!

# Answer
> 2 votes
There are a few options for the cause of the error. It could be at the microprocessor level, meaning that the execution of the program is wrong, or it could be at the motor driver port, meaning that the NXT tries to drive the motor attached to the specific port but can't due to some electrical failure.

The first option can be eliminated by using other forms of output (e.g. screen) instead or along with the motors, the second can be analyzed by swapping motor ports and testing them individually.

However, in any case you probably won't be able to repair it yourself, so you should contact Lego instead if the existence of the error is certain.

---
Tags: nxt, programming
---


# Question
Title: Where will the World First Lego League be held in 2015?
Every year First Lego League (FLL) is held in 3 different countries. I know that the world festival will be held in St. Louis, but where will the other two be?

Last year it was held in Germany and Canada.

# Answer
The FLL World Festival is going to be held in St. Louis, MO, USA, on April 22-25, 2015 (http://www.firstlegoleague.org/event/worldfestival). This is the only official championship event held by the FLL.

Before the World Festival, various qualifying events are held all over the world. You can learn more about those events by searching on this page: http://www3.usfirst.org/whats-going-on

Unofficially, FLL partners hold Open Championships around the world. These events generally take place in the United States (in addition to the official World Festival), Canada, Asia, and Europe. For more information, visit this Wikipedia page: http://en.wikipedia.org/wiki/FIRST\_Lego\_League\_Open\_Championships
> 3 votes

---
Tags: lego-group, fll
---


# Question
Title: What kind of design is comparable to these programming concepts?
I understand this may sound like a weird question, but bear with me here, OK?

I'm getting ready to teach some kids introductory computer programming. We're going to use Scratch, a drag-and-drop "brick-based" language designed by MIT.

Now, scripts in Scratch are comparable to LEGO structures. Each script needs a base, and pieces to build it up. So far, so good.

However, scripts can also contain **conditionals** and **loops**, both of which accept a sub-structure.

I would like to show my students a LEGO structure that is comparable to a Scratch script. How could i do something like conditionals and loops?

# Answer
A conditional can perhaps be represented by a door that can be blocked from the other side, or maybe two doors, of which only one is blocked via a sliding brick.

As for loops, I would represent them as conditionals with counters, by blocking a door with a set number of bricks and removing one brick per iteration. If you'd rather count upwards, then a fixed size hole can be filled with bricks gradually.

These analogies were made to the "minifig walking through a set of corridors - the program" analogy, but we could surely find solutions for axles and gears or even pneumatics if you were thinking along those lines.
> 2 votes

# Answer
Based on the image on the Scratch home page, I would simply wrap the substructure in a single color, which represents the loop.

For example:

```
 ______
|_Loop_|__
|__|__s1__|
|__|__s2__|
|__|__s3__|
|______|

```

If that makes sense.
> 1 votes

---
Tags: piece-usage
---


# Question
Title: How many ways can six 8-peg lego blocks of six different colors be combined?
I have seen the number quoted as \> 650 billion. The quote is from a Danish mathematician, Soren Ehlers. Intuitively, this does not seem correct to me. Any mathematicians/statisticians out there who can help either verify the huge number, or give me a correct number?

# Answer
> 5 votes
To expand on Zhaph's answer, I'm assuming that you have a fixed set of six colors, and each block is one color.

If that's the case, this is a simple combination problem on top of the orientation problem. Since there are six colors and six bricks, there are 6! ways to assign those six colors to the six bricks, or 720 ways.

Now, we apply this combination to our orientation, and get:

> 915,103,765 orientations x 720 color combination/orientation = 658,874,710,800 combinations

# Answer
> 2 votes
I'm not sure what the rules are around the colours, however from the LEGO Facts page:

> Take six eight-stud LEGO bricks (2x4) – how many ways can they be combined?
>
> With the aid of computers, the exact number of combinations has been calculated as 915,103,765!
>
> Just so you know, two eight-stud LEGO bricks can be combined in 24 different ways and three eight-stud LEGO bricks in 1,060 ways.

This is probably based on the work done here.

The colour combinations would therefore be higher than that - but you'd need to be avoiding duplicate combinations.

---
Tags: building
---


title: Communication between two Ev-3 bricks

text:
# Question
Title: Communication between two Ev-3 bricks
How the communication between two Ev-3 bricks is done over Bluetooth? What is the nature of data that can be communicated?

# Answer
> 2 votes
You can do it using EV3 Bluetooth blocks. You can send integers, string or boolean using different "mailboxes" so the receiver just need to use the Block to read from a particular mailbox to get the data.

Maybe I write a post where I detail all this more because LEGO documentation isn't helpful at all.

# Answer
> 2 votes
You can use the EV3 bluetooth blocks in the blue tab of the programming software.

One thing though: The two bricks have to have different names. Like "Kim" and "John".

Check the EV3 help too.

---
Tags: ev3, compatibility
---


# Question
Title: What adhesive can bond LEGO bricks to metal?
The Scouts are making some Christmas decorations using LEGO, and we need to stick them on to some metal stands. Could anyone please advise the best glues and process (e.g. sanding, etc.) to join bricks to metal. Many thanks.

# Answer
Have you considered screwing your decorations to the metal stand, using Technic brick holes to pass the screws? If done properly no harm is done to the bricks, and you will not fear a bad glue joint!
> 13 votes

# Answer
I'm always hesitant to recommend gluing LEGO as it is so much against the spirit of LEGO. Have you considered using the magnet bricks? They come in several regular LEGO brick sizes, and they stick to metal surfaces just fine.

If you must use glue, most glues will readily stick to the plastic, so that is no problem. What you need to check is what glues work well for metal. Personally I would go over to a home improvement store, hobby shop or craft store and ask, as there will be different glues available in different regions/countries.
> 5 votes

# Answer
Many thanks for all your help and ideas.

We have experimented with gorilla glue and a couple of others but settled on **two part Araldite Rapid**, which doesn't take long to set. As they are tree decorations that we are selling to raise funds to build a new building (our old one is rotting away!) they needed to be fairly robust.

Sorry that we are sticking Lego forever, but for every brick we sell we get real bricks in return for our new building!
> 3 votes

# Answer
Depending on how sturdy you need it, then a lot of glues will work. In other words, if this is just going to sit on a shelf, you really don't need tremendous adhesive power.

In this case, I would recommend something like JB Weld or Gorilla Glue. However, make sure you properly prepare both surfaces by roughing them up a bit and cleaning them.

If you need something stronger, I'd look at two-part epoxies that are used in automotive repair. These are specifically formulated to bond metal to plastic. Fusor 116 is one such product.

LEGO bricks are made from ABS, so any glue that will bind ABS to metal will work.
> 2 votes

---
Tags: glue
---


# Question
Title: How do I get the Mindstorm EV3 software to recognize an NXT brick via Bluetooth?
I'm trying to program my NXT brick via the EV3 software over a Bluetooth connection.

I can connect it via USB (although that too failed initially, but has since been resolved; not sure why) but I'd really like to do it via Bluetooth as I could with the NXT 2.1 software.

How do I get the EV3 software to recognize my NXT brick over Bluetooth?

Here is a copy of the connection area in the EV3 software showing that the NXT brick is available via USB but not Bluetooth:

And here is the same NXT brick available in the NXT 2.1 software:

# Answer
> 2 votes
Communicating with the NXT from the LEGO MINDSTORMS EV3 software is not supported.

From http://www.lego.com/en-us/mindstorms/support/faq/:

> 3.10 Is the LEGO® MINDSTORMS® EV3 Home Edition Software backward-compatible with NXT Hardware?
>
> Yes. You can program your NXT Intelligent Brick using the new LEGO MINDSTORMS EV3 Home Edition Software. However, not all Software features are supported by the NXT Intelligent Brick.

It does not explicitly mention Bluetooth, but it is one of features that is not supported.

References:

---
Tags: ev3, mindstorms, nxt, ev3-g, bluetooth
---


# Question
Title: Can Mindstorms EV3 communicate using protocol 802.15.4?
My aim is to make the robot communicate using **protocol 802.15.4** through a USB dongle 802.15.4 over 6LoWPAN.

The robot has to be able to get information from TelosB.

I wonder whether this possibility has already been tested and if it is possible to make it work and of course how?

# Answer
> 1 votes
This can be done using ev3dev.

https://github.com/ev3dev/ev3dev/issues/46

---
Tags: technic, mindstorms, ev3, programming
---


# Question
Title: Flash update breaks the Mindstoms NXT viewer
After udating to the lastest version of Flash on my Macbook Pro (OS X 10.7.4) The Mindstorms NXT software that comes in the box no longer displays the build instructions. It does load up, but the build instructions pages are blank.

Is this a known issue, and is there a fix available?

# Answer
This is fixed using the NXT software version available from http://www.lego.com/en-us/mindstorms/downloads/software/nxt-software/ instead of CD that came with the NXT set.
> 1 votes

---
Tags: nxt, mindstorms
---


# Question
Title: Lego EV3 - sending direct commands over RFCOMM Channel (Objective-C, Xcode)
I successfully open RFCOMM Channel to Lego EV3 brick with code:

```
IOBluetoothDevice *device = [IOBluetoothDevice deviceWithAddressString:@"xxxxxxxxxxxx"];
IOBluetoothRFCOMMChannel *rfCommChannel;
IOBluetoothSDPUUID *sppServiceUUID = [IOBluetoothSDPUUID uuid16:kBluetoothSDPUUID16ServiceClassSerialPort];

IOBluetoothSDPServiceRecord *sppServiceRecord = [device getServiceRecordForUUID:sppServiceUUID];

if ( sppServiceRecord == nil )
{
    NSLog( @"Error - no spp service in selected device." );
}

UInt8   rfcommChannelID;
if ( [sppServiceRecord getRFCOMMChannelID:&rfcommChannelID] != kIOReturnSuccess )
{
    NSLog( @"Error - no spp service in selected device." );
}

if ( ( [device openRFCOMMChannelAsync:&rfCommChannel withChannelID:rfcommChannelID delegate:d] != kIOReturnSuccess ) && ( rfCommChannel != nil ) )
{
    NSLog( @"Error - open sequence failed." );
}

```

Now I wish to send direct command:

```
unsigned char play_tone[] = {0x0F,0x00,0x00,0x00,0x80,0x00,0x00,0x94,0x01,0x81,0x02,0x82,0xE8,0x03,0x82,0xE8,0x03};

```

over RFCOMM Channel using class IOBluetoothRFCOMMChannel method:

```
- (IOReturn)writeSync:(void *)data length:(UInt16)length

```

I tried to do send it using different ways but none of them worked. How should I do it properly?

# Answer
> 3 votes
I have found solution. I create category NSString+NSStringHexToByte:

NSString+NSStringHexToBytes.h

```
#import <Foundation/Foundation.h>

@interface NSString (NSStringHexToBytes)
+ (NSData *)dataWithString:(NSString *)string;
@end

```

NSString+NSStringHexToBytes.m

```
#import "NSString+NSStringHexToBytes.h"

@implementation NSString (NSStringHexToBytes)

+ (NSData *)dataWithString:(NSString *)string
{
    string = [string stringByReplacingOccurrencesOfString:@"0x" withString:@""];

    NSCharacterSet *notAllowedCharacters = [[NSCharacterSet characterSetWithCharactersInString:@"abcdefABCDEF1234567890"] invertedSet];
    string = [[string componentsSeparatedByCharactersInSet:notAllowedCharacters] componentsJoinedByString:@""];

    const char *cString = [string cStringUsingEncoding:NSASCIIStringEncoding];
    const char *idx = cString;
    unsigned char result[[string length] / 2];
    size_t count = 0;

    for(count = 0; count < sizeof(result)/sizeof(result[0]); count++)
    {
        sscanf(idx, "%2hhx", &result[count]);
        idx += 2 * sizeof(char);
    }

    return [[NSData alloc] initWithBytes:result length:sizeof(result)];
}

```

and now:

```
NSString* playTone= @"0f0000008000009401810282e80382e803";
NSData* data = [NSString dataWithString:playTone];
[self sendMessage:data toChannel:rfcommChannel];

```

where sendMessage is:

```
-(void)sendMessage:(NSData*)data toChannel:(IOBluetoothRFCOMMChannel*)rfcommChannel
{
    [rfcommChannel writeSync:(void*)data.bytes length:data.length];
}

```

---
Tags: ev3
---


title: Chinese Knockoffs?

text:
# Question
Title: Chinese Knockoffs?
I'm looking at the Lego Super Star Destroyer on eBay and I see that a number of people are selling it for ~$600 USD. From time to time there are bids that sell at ~$300 USD that claim to be sealed and brand new. These sets come from Hong Kong or China from a user that has a 0 feedback. This seems to me to be a bit fishy since the set is now discontinued and it should fetch higher than the original selling price of $400 USD.

If you search Lego minifigures from the superhero lines, you get Chinese users selling packs of five minifigures for far below the asking price again. I asked about this one in the past.

Has anyone else noticed this? Do we have a brick authenticity problem? mj

http://www.ebay.com/itm/LEGO-Star-Wars-Super-Star-Destroyer-Spaceship2-New-Building-Set-Battleship-/251594504283?pt=Building\_Toys\_US&hash=item3a9433785b

# Answer
> 6 votes
The SSD auction will be a scam and the minifigs are indeed knock-offs of which eBay is awash.

# Answer
> 5 votes
For sets currently available through LEGO.com or other online retailers, the cheaper sets may be authentic, but part of a scam known as drop shipping.

This type of scam works like this:

You order a remarkably cheap, new LEGO set from eBay or the like.

The seller uses your contact information and a stolen credit card to purchase a set directly from an authentic retailer.

You pay the illegitimate seller.

You receive a package directly from LEGO that has a packing slip with someone else's information on it.

The "seller" now has cash from the transaction without needing a PIN for the stolen card.

You now have a cheaper set that was obtained via illegal practices.

A 3rd person is a victim of credit card fraud.

LEGO products are unfortunately ideal for this type of fraud, as they are high value and high in demand.

---
Tags: star-wars
---


title: LEGO TECHNIC CyberMaster Software

text:
# Question
Title: LEGO TECHNIC CyberMaster Software
I come again to ask a favor. Can someone share the installation CD in English of LT 8482 CyberMaster or where can I download the software in English??

# Answer
About 10 mins on Google didn't turn up any place to download the software, but you can always buy a CD from one of the sellers on Bricklink:

http://www.bricklink.com/search.asp?itemID=43378

You might be able to get one of them to upload the CD
> 1 votes

---
Tags: mindstorms, technic, software
---


title: Unlimited engine option does not work

text:
# Question
Title: Unlimited engine option does not work
I work in a school and all my Lego NXT bricks have the same problem. Unlimited choice in the activation time engine does not work. The other functions (rotation, and second degree) are going well. So I can use my probes and so I am very limited in the tasks to be performed.

I've done these actions, but without success:

* Reset On my brick
* Update Bricks
* Update The program to version 1.31
* Contact My representative

# Answer
You need to ensure that your program has a way to stay alive (wait block, wait for sensor, etc...), otherwise as soon as the program ends all motors are stopped.
> 3 votes

---
Tags: motor
---


# Question
Title: Is it possible to create your own wheel?
After my other question, i pretty much have a bicycle design all planned. My problem now is with wheels.

None of my LEGO wheels are big enough to work on a bike. And, the biggest ones are all pretty fat.

I was wondering if it would be possible to simulate my own wheels, that i could then attach to a LEGO creation.

It doesn't have to be made out of only LEGOs; i'm open to other building toys and materials as well.

# Answer
> 7 votes
You can always brick-build a wheel. The curved slope pieces can closely approximate a circle.

For example, 12 4x1 curved slopes gives a circle with a radius of 160 LDUs (8 studs).

For more information on brick-built wheels, I suggest you refer to the "Brick Built LEGO Wheels Book":

http://www.ultimate-design.org/2014/05/unofficial-free-brick-built-lego-wheels.html

---
Tags: building, manufacturing, wheel
---


# Question
Title: How to Decipher Lego Building Instructions Filenames?
On the official site for downloading lego instructions, the filenames are often quite cryptic, and many sets have as many as six different files you can download and sometimes it's hard to tell which one you want. Can anyone enumerate what all those various part of the filename mean?

Examples 1:

```
Woody's Roundup! 7594

BI 3005/48 - - Download size: 5.71 Mb
BI 3005/48 - - Download size: 5.71 Mb
BI 3005/48 - 7594 V 110 2/2 - Download size: 5.94 Mb
BI 3005/60 - 7594 V 110 1/2 - Download size: 5.91 Mb
BI 3005/60 - 7594 V 140 1/2 - Download size: 5.91 Mb
BI 3005/60 - 7594 V 29 1/2 - Download size: 5.87 Mb
BI 3005/60 - 7594 V 39 1/2 - Download size: 5.87 Mb

```

Here's what I've figured out so far BI = building instructins 3005 = set number 48 or 60 = ?? 7594 = ?? V = version 110, 140, etc = ?? 29 = A4 paper 39 = US letter paper 1/2 and 2/2 = the booklet number

Example 2:

```
Batman™: Arkham Asylum Breakout 10937
 BI 3016/12-65G - Download size: 4.68 Mb
 BI 3016/12-65G - Download size: 4.68 Mb
 BI 3016/68+4*- - Download size: 12.79 Mb
 BI 3016/68+4*- - Download size: 12.79 Mb
 BI 3016/76+4*- - Download size: 15.96 Mb
 BI 3016/76+4*- - Download size: 15.96 Mb
 BI 3016/80+4/65+115g - Download size: 14.5 Mb
 BI 3016/80+4/65+115g - Download size: 14.5 Mb

```

Now this one's even crazier `68+4*` huh?? And it kind of looks like all the files are duplicated? Or is the second one possibly a newer or bugfixed version?

# Answer
After emailing back and forth with LEGO, I think I have an acceptable answer:

Example:

```
BI 3005/48 - 7594 V 110 2/2 - Download size: 5.94 Mb
^   ^   ^      ^   ^     ^                   ^
1   2   3      4   5     6                   7

```
1. Stands for `Building Instructions`
2. A number for internal usage by different LEGO teams.
    * You'll see that many different sets share this number, and all the numbers are fairly close (generally in the early 3000's). My guess is that it has something to do with whoever drafted and finalized the instruction manual.
3. This number shows the number of pages in the manual.
    * When the number is show `x+y`, that means `x` building pages, and `y` instructional pages (e.g. what to do with bricks, or what bags are needed).
4. This is the set number.
5. This number refers to the page format of the instruction manual.
    * V29 means ISO A4 paper format.
    * V39 means letter paper format.
    * Other Vs (like 110, 140, etc) are different file formats. LEGO said "those are the types of versions throughout our country that we ship to". I'm guessing that they are related to the official formats for the manuals that are included with the kits.
6. The booklet number: `x/y` means `x` booklet number out of `y` booklets.
7. The file size of the instruction in megabytes (not megabits, as it would seem to imply).
> 13 votes

---
Tags: instructions
---


# Question
Title: How do I make my logo/mascot into a custom LEGO model?
I operate an Indoor Playground & Cafe and would love to find out how to make my mascot/logo into a 4' custom LEGO sculpture. Any assistance appreciated!

A bit of looking indicates that LDD will generate instructions and parts list but I am not competent with this type of CAD software. Additionally, LEGO no longer 'makes my model'.

# Answer
> 4 votes
The cheapest way to go about doing this is to design it yourself, like you said, using one of the LEGO cad softwares (LEGO Digital Designer, LDraw, MLCAD, etc.). Then, buy the pieces and build it. However, that takes a lot of time, and unless you are experienced, may not turn out so good.

The easiest (but also likely expensive) way to do this is to hire a LEGO certified professional. The LEGO certified professionals are LEGO enthusiasts who have turned that passion into a business, and are officially recognized by LEGO for their work and skill.

http://aboutus.lego.com/en-us/lego-group/programs-and-visits/lego-certified-professionals

I would contact a certified professional and see how much they need to design and build your logo.

# Answer
> 1 votes
A big Scratch Cat was designed and creating in the following way, according to a Scratch Team member:

> The Lego company very generously helped us create a version of the Scratch cat made of Lego. My friend Duks and I made a 3D model using Rhino, and we sent it to Lego for fabrication. A few months later we got a big crate containing... this!

Source: http://scratch.mit.edu/projects/1017438/

This seems to be a successful mix of the two methods from Nick's answer.

---
Tags: design
---


# Question
Title: How can I connect the RCX 2.0 to an external power source?
I want to build an auto-feeder with the RCX 2.0 for my cat. The problem is, that I often had to exchange the batteries. Is there an adapter for the RCX to connect it to a power point?

# Answer
The older RCX 1.0 had a power plug inbuilt. However Philo has shown how to create one yourself in a fairly simple way: LEGO® 9V Technic Motors compared characteristics, scroll down to the section "Getting maximum mechanical power from RCX output" towards the bottom of the page.

The idea is to create two fake batteries and draw a wire from each, creating a +9V and a ground from a separate source. You would need a voltage regulator though. **WARNING**: supplying incorrect voltage can destroy your RCX.

Image and technique by Philippe "Philo" Hurbain © 2000-2009, used in accordance to "You are free to use it for any purpose, just give me credit...".
> 10 votes

# Answer
If you'd rather not cut off the ends off two batteries and jury-rig in rods of hot melting glue to act as spacers, and instead have access to a 3D printer, take a look at http://www.thingiverse.com/thing:122810 :-)

---

As the contents of the linked page have been removed, here are the original files:

And of course the STL file from the archived version of the site.
> 2 votes

---
Tags: mindstorms, rcx
---


# Question
Title: How can I tell which LEGO minifigure I found?
I found a mini-figure on the the ground by a recycling bin. I want to figure out what set/collection he belongs to but can't find anything other than how to tell what you're getting in a blind bag.

He's normal size for a mini-fig, not a shorty or anything. He has a dark red pirate bandanna type hat with a "tail" hanging down his head. His head is grey or grey-green with green eyebrow and cheek markings and pointy looking bottom teeth made to look protruding from his mouth. His torso is a dark orange with a silver breastplate and brown straps on his back. Also there is a dark red belt. His arms are black and his hands are brown. His pants are red but not dark red like his hat.

He's a mean looking guy and doesn't seem to match Pirates of the Caribbean or Lord of the Rings/Hobbit but looks like he would fit in with those sets.

Any help would be greatly appreciated.

# Answer
The torso is from Lando Calrissian.

The rest of the parts are from Kithaba.

They both came in the 2012 Desert Skiff Star Wars set
> 14 votes

---
Tags: minifigure-identification
---


title: 9v and Power Functions Hybrid?

text:
# Question
Title: 9v and Power Functions Hybrid?
I am building a train layout and I am running some of my track through a tunnel. I would like to know if I could hook up a 9v train motor at the opposite end of my train. The front will use Power Functions for the motor. Will this work together in case my IR receiver loses communication to the controller and at the same time run at the same exact speed? Is there an alternative?

# Answer
> 3 votes
I'm not so sure using 9V will be usefull ?

My son has a PF cargo train in his room, when he turns it on, it goes, ok.

but even if my son goes downstair to get a cookie while he still has the PF emitter in his hand, then train still runs !

According to me, PF infrared link is used only when you wish to change speed setting, so if you don't plan to slow down your train in the tunnel, you are ok.

# Answer
> 2 votes
One option is to only use the 9V train motor, but power it most of the time with the PF battery back. This will require some customization of the motor, and probably some cutting/soldering of the wires, but this would work. (See: Can 10153 9V train motor be powered by the Power Functions Battery pack?)

Another solution is to add a second battery pack in parallel to the first, and only turn it one when the train is in the tunnel. You can mechanically (and automatically) turn it one when the train enters the tunnel, and then turn it off when the train leaves the tunnel. A small switch under the train (using something like two of these to make a switch that can be "flicked" on and off).

# Answer
> 1 votes
If you don't connect the two subsystems electrically, then it is quite possible to do so. The Power Functions motor will be on when it can get a signal and the 9V train motor will be on when the train runs over the metal rails. The metal rails will need to have external power attached, and you have to adjust the speed there separately. The mechanical resistance of the unpowered motor will probably have undesired effects though.

If you can't make a seamless transition from unpowered rails to powered ones, then you might look into building a more complicated setup where a PF remore receiver "sets" some kind of mechanical variable that controls the on-board motor output. This way even if you lose PF reception, the train will still run at the speed you set last.

If your train is longer than the tunnel, you could also install two PF receviers, one in the front and another in the rear. This way one of them will always be in range.

You could also consider using an SBrick. It controls PF units via Bluetooth, so no line-of-sight is required.

---
Tags: trains, power-functions, 9v
---


# Question
Title: Is the LEGO Midstorms EV3 software compatible with OS X Yosemite?
OS X Yosemite (10.10) was just released yesterday. I want to upgrade, but I am worried that the EV3 software will be incompatible.

What should I do?

A. Upgrade

B. Stay on OS X Mavericks (10.9)

# Answer
The educational software of mindstorms is not yet updated.(Version 1.1.0) If you download the free version of mindstorms (Version 1.1.1) you can connect via Bluetooth under Yosemite to your brick!
> 0 votes

# Answer
B. Stay with OS X Mavericks. I can confirm that bluetooth no longer works with Yosemite. Spent two hours trying to make it work, but in vain.
> 2 votes

# Answer
I have run the LEGO MINDSTORMS EV3 software successfully on Yosemite Beta for a couple weeks. The only problem I have had is that I cannot get Bluetooth to work. The bluetooth problem appears to be at the OS level rather than a software compatibility issue though.

Update:

I reported this to Apple via https://bugreport.apple.com. It was marked as a duplicate, so apparently Apple knows about it. Unfortunately, their bug reporting system is not very open and you can only see your own bugs. There is no other feed back on the status of getting it resolved. I would suggest that everyone that has the problem report the bug as well. This should let Apple know there is demand to get this fixed and hopefully they will make it a priority.
> 1 votes

---
Tags: ev3, compatibility
---


title: How to close color Sensor properly?

text:
# Question
Title: How to close color Sensor properly?
I want to get data from the color sensor with Bluetooth. I can get data but when the program terminates, the color sensor dose not close even though I call function `close()` on the color sensor. The following code is what I did with EV3 Bluetooth connection.

```
RemoteEV3 ev3 = new RemoteEV3("10.0.1.1");
ev3.setDefault();
Keys keys1 = ev3.getKeys();
color_sensor = new EV3ColorSensor(SensorPort.S2);

do{
  color_id = color_sensor.getColorID();
  System.out.println("Here is color id: "+color_id);
  Delay.msDelay();
  keys1.waitForAnyPress();
}while(keys.getButtons()!=Keys.ID_ESCAPE);

color_sensor.close();

```

And it throws the following exceptions:

```
Exception in thread "main" lejos.hardware.DeviceException: unable to open port
at lejos.internal.ev3.EV3Port.open(Unknown Source)
at lejos.hardware.motor.BaseRegulatedMotor.<init>(Unknown Source)
at lejos.hardware.motor.EV3LargeRegulatedMotor.<init>(Unknown Source)
at lejos.remote.ev3.RMIRemoteRegulatedMotor.<init>(Unknown Source)
at lejos.remote.ev3.RMIRemoteEV3.createRegulatedMotor(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:322)
at sun.rmi.transport.Transport$1.run(Transport.java:177)
at sun.rmi.transport.Transport$1.run(Transport.java:174)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:556)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:811)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:670)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source)
at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
at sun.rmi.server.UnicastRef.invoke(Unknown Source)
at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(Unknown Source)
at java.rmi.server.RemoteObjectInvocationHandler.invoke(Unknown Source)
at com.sun.proxy.$Proxy0.createRegulatedMotor(Unknown Source)
at lejos.remote.ev3.RemoteEV3.createRegulatedMotor(Unknown Source)
at test_bluetooth.Bluetooth.main(Bluetooth.java:186)

```

I am not sure that color sensor is really closed because when I run the program for the second time it yields the exception that it's unable to open the port of that color sensor. However, after I restart the brick, it works fine for the first time the program is run, then I need to restart again to use that color sensor port. Can anyone tell me how to properly close the color sensor?

# Answer
> 2 votes
Looking at the stack trace in the exception you've posted, the error seems to be coming from a call to `RemoteEV3.createRegulatedMotor`:

```
at lejos.remote.ev3.RemoteEV3.createRegulatedMotor(Unknown Source)
at test_bluetooth.Bluetooth.main(Bluetooth.java:186)

```

After that, it's just going through the motions to try and open a port on a remote device...

From looking at the LeJOS source, that method isn't called by the main `RemoteEV3` constructor when setting up the ports, so it is probably something you're calling in your main block.

Both Sensors and Motors need to be closed.

As a point of note, it's recommended that instead of connecting to the remote sensors directly as you're doing there, you instead use the `createSampleProvider` method:

```
RemoteEV3 ev3 = new RemoteEV3("10.0.1.1");
RMISampleProvider color_sensor = ev3.createSampleProvider("S2",
               "lejos.hardware.sensor.EV3ColorSensor", "Color ID");
float[] color_id= new float[1];
color_sensor.fetchSample(color_id,0);

```

It is apparently more efficient because instead of running the sensor driver on the PC and sending requests to the remote EV3 you're creating the sensor driver on the remote EV3 and sending the samples to the PC.

---
Tags: ev3, bluetooth, remote-control, sensor-colour, lejos
---


# Question
Title: EV3 RMIregulatedMotor Regulation Problems
I have problem with regulation of the motor when I control EV3 with Bluetooth. Here is the code:

```
RemoteEV3 ev3 = new RemoteEV3("10.0.1.1");
    ev3.setDefault();
    RMIRegulatedMotor leftMotor = ev3.createRegulatedMotor("A", 'L');
    RMIRegulatedMotor rightMotor = ev3.createRegulatedMotor("B", 'L');
    EV3ColorSensor color_sensor = new EV3ColorSensor(SensorPort.S2);
    int color_id = color_sensor.getColorID();
    while(color_id!=7){
        leftMotor.setSpeed(300);
        rightMotor.setSpeed(300);
        leftMotor.setAcceleration(1000);
        rightMotor.setAcceleration(1000);
        leftMotor.backward();
        rightMotor.backward();
        Delay.msDelay(500);
        leftMotor.stop(true);
        rightMotor.stop(true);
        color_id = color_sensor.getColorID();
    }
    System.out.println("Establishing connection. Please wait ...");
    if(leftMotor!=null) leftMotor.close();
    if(rightMotor!=null) rightMotor.close();
    if(color_sensor!=null) color_sensor.close();

```

The problem is that the EV3's motor not continuously moving. It is stop a bit and then continue moving, it is kinda lagging or problems with regulation of RMIRegulatedMotor. However, if I change from RMIRegulatedMotor to RegulatedMotor and compile it directly with the brick not Bluetoothm, there is no problem at all.

# Answer
Looking at your code, you're saying:

1. Set the motors to a speed of 300, acceleration of 1000
2. Run the motors backwards
3. Pause execution of your program for 500ms
4. Stop the motors
5. If you're not seeing colour id 7, go to 1.

Assuming that this was exactly the same code you had on the Brick, I'd guess the delays introduced by the communication will cause a stuttery motion that you might not notice when running it on the device.

If you pulled the following lines out of your `while` loop things would probably be smoother:

```
leftMotor.stop(true);
rightMotor.stop(true);

```
> 1 votes

---
Tags: ev3, programming, motor, remote-control, lejos
---


title: Index of the City sets by category

text:
# Question
Title: Index of the City sets by category
I'm running trough bricklink, peeron and brickowl, but I can't find a "good" (I mean 'fitting my idea') index to browse across city sets.

Is there a kind of list like

* vehicle
    + cars
    + trucks
    + planes
* buildings
    + houses
        - 7641
    + police station
    + ...

does anyone of you have knows a such index ?

note: my english is not fluent, so, here are some precisions: I'm looking for "houses" sets on ebay to complete my son's town streets. He has a lot of vehicles, but a few buildings

# Answer
> 6 votes
No, but Brickset now provides the facility to enable one to be made. See http://brickset.com/article/12960/tags-a-new-way-to-search-the-database

# Answer
> 1 votes
While there is no explicit "house" tag, I would recommend browsing in Brickset's City theme: http://brickset.com/sets/theme-City

You can refine the search based on year (include only recent, therefore easy to buy sets), tags (building, shop, ...) and subtheme (airport, construction, police, ...).

---
Tags: sets, theme
---


# Question
Title: Looking for a Basic Lego set with mostly large bricks
I am looking to buy my son his first set of LEGO bricks (because my mom will not give me my old ones!!!). Most of the 650ish piece sets I have looked at contain a large amount of 1x2, 2x2, etc. I am looking for a set that has more 2x4s, 2x6s or bigger than those with more smaller pieces. Can anyone recommend a good set? It does not need to be that big of a set either, but if I could find one that would be great!! I cannot wait to finally own my own LEGO bricks that don't actually belong to my parents!!!

# Answer
If you can get to a Lego shop, there is a Pick a Brick wall with mostly large bricks that you buy by the cupful for less per brick than you would pay in most sets.

These two sites:

http://www.brickbuildr.com/view/pab/

, and

http://wallofbricks.com/

show you the current(ish) contents of the Pick a Brick walls around the world, they are updated by fans so they might not be up to date.
> 2 votes

# Answer
There are always a range of bricks-only sets in production, the current one is called LEGO Basic Bricks Deluxe (Inventory). That is probably the closest you will get to what you want at this moment (November 2014).

With Christmas coming up, though, keep an eye out for a new brick set from a major retailer like Walmart. In the past there have been gems like LEGO 5512 XXL Brick Box.

Your best bet, however, is to go to Bricklink.com and find a store that sells ample quantities of used bricks in the colors and sizes you want.
> 1 votes

---
Tags: shopping
---


# Question
Title: Can anyone identify these Bionicle sets?
Can anyone identify these Lego pieces? They were given to us in a bin of toys, and we cannot identify them. We know they're Lego, and have a 2002 date on them.

# Answer
> 5 votes
Those appear to be Bionicle figures, a theme that was active from 2001 to 2009 (and making a comeback in 2015, I hear). The line focused on buildable "action figures" (aka "constraction figures").

See here: http://brickset.com/sets/theme-Bionicle

# Answer
> 3 votes
The yellow one is the Glatorian-era Mata Nui, the red one with the staff is a Toa Nuva-era Rahkshi (Turahk, to be specific), and the green spider-thing is a Toa Hordika-era Visorak (Keelerak) that has been placed upside-down.

The other four are Metru Nui Matoran, without their masks; the lighting makes it hard to tell what elements they correspond to, but the ice one appears to have the wrong head.

Turahk: http://brickset.com/sets/8592-1

Keelerak: http://brickset.com/sets/8746-1/Visorak-Keelerak

Can't post other links due to reputation; sorry about that.

---
Tags: set-identification, bionicle
---


# Question
Title: Please help me identifying these spaceship parts - big sloping ring
Which lego set do these parts belong, I have a full box of random pieces, and I wish to build something starting from this. Thanks

# Answer
> 7 votes
It's from a LEGO UFO set from the late 1990s. You can see all the sets in this theme here: http://www.bricklink.com/catalogList.asp?catType=S&catString=34.311. What you have is most likely the #6975 Alien Avenger: http://www.bricklink.com/catalogItem.asp?S=6975-1

---
Tags: set-identification
---


# Question
Title: Help identifying a black round piece with three rings
I'm on a personal project to document the brick list for building every one of Chris Deck's Star Wars miniatures (http://sw.deckdesigns.de/minis.htm), and I'm unable to find in the Lego catalogue or Bricklink a canister-like black piece with three different radius values. Look for the second step (3rd picture) in http://www.brickshelf.com/cgi-bin/gallery.cgi?f=93630.

Thanks!

# Answer
> 6 votes
I believe that the part you are looking for is 6221 (Peeron 424) :

This part was most commonly found in Technic sets and was often used as a spacer on longer pins or as a crank handle:

Here it is on Bricklink.

---
Tags: part-identification
---


# Question
Title: Are coloured bricks used by Set Designers recycled to make black bricks?
I heard on a podcast of the Adam Savage Project that the master builders (designers of 'sets' of LEGO) are allowed to use as many blocks as they need to design a certain set. All of the bricks they use to design the sets are then thrown together, melted down, and made into black bricks as it is cheaper than resorting and less time consuming. Due to the pieces being used they are not allowed to be resold... Is this true?

# Answer
**Short answer: No.**

**Long answer:** After searching around the web and finding nothing related to this subject, I fired an email towards LEGO Customer Service asking them this very question.

Today I have received this reply:

> Dear Adam,
>
> Thanks for getting in touch with us and sending us this question.
>
> I have investigated the case further with our LEGO® product specialist team and I received the following answer from them:
>
> No this is not true, the designers build the sets and then they have to get approved. If the set isn’t approved the bricks and sets stay out or on the designers desk, and the set is taken apart the bricks are used again. I hope this information will help to settle the debate.
>
> We want to make sure we're doing a good job for you, so you’ll always find the link to a four-question survey in our emails. Please tell us how we did today:
>
> LEGO Survey link
>
> Please let us know if you need anything else.
>
> Happy building!
>
> Ildikó LEGO® Service
> 4 votes

---
Tags: manufacturing, lego-group
---


# Question
Title: Trouble with Commander app: Using buttons to control motors
I'm having trouble with the Commander app for Android. I've put an EV3 into set 8448. I'm using one of the large motors for propulsion and a medium motor for rack and pinion steering. I don't have the remote (using the education set) so I'm trying to use my phone as a remote instead. I downloaded the Commander app.

I went into "create my own". I can use a slider to make the car go backwards and forwards, however, I tried to set up two buttons for steering, one button to make the medium motor go one way and another button to make it go the other way. Only one of the buttons works. It's only possible to make the medium motor go one way, not the other. How can I make it so the button controls can control the motor in either direction?

Any help would be greatly appreciated.

# Answer
> 1 votes
You cannot have more than one control per motor. If you have two controls, the signals are essentially sent to the EV3 at the same time, so only the second one will seem to work because it immediately changes whatever what sent by the first.

In your example, with 2 buttons, the buttons either command the motor to move or stop. If neither button is pressed, both are telling the motor to stop, so no problem. But if you press the first button, it tells the motor to turn, but the second button is telling the motor to stop. Since the EV3 got the message from the second button last, the motor stops and it appears that the first button does not work.

So, if you want to use the Commander app for this, you will need to use a different control that can turn the motor in either direction with just one control such as a slider or tilt.

---
Tags: ev3, commander
---


# Question
Title: Trying to get a modified traffic signal challenge worked out
The challenge is for a robot to go around the perimeter of a rectangular field and execute 90 degree turns when it gets within 4.5 inches of a wall. Simultaneously, if the bot encounters a red flag, it needs to stop until the flag color turns green. At that point, the arm holding the color sensor needs to dip to avoid the traffic signal, and once it is passed, continue on it's way.

I have tried running two threads, one where the bot encounters a flag (which I have constructed a switch for cases red and green), while the other is where it encounters a wall. I think these two threads need to be encased within an infinite loop, but I can't seem to make it so.

# Answer
You can use finite state machine. In this case you will have these 5 states:

1. RUN

Action: turn on the motors for moving straight

Transition to state TURN in case of event: ultrasonic sensor detects obstacle closer than 4.5 inch).

Transition to state WAIT in case of event: color sensor detects red color

2. WAIT

Action: stop motors

Transition to state CONTINUE in case of event: color sensor detects green

3. CONTINUE

Action: move forward a bit while avoiding the flag

Transition to state RUN immediately.

4. TURN

Action: Turn the robot 90 degrees right, increment the rotations

Transition to state STOP in case of event: rotations = 4

Transition to state RUN in case of event: rotations \< 4

5. STOP

Action: Interrupt the program.

Here is the code I've just scratched without a testing, let me know if it works:

You can enhance the state machine to check for the flag during rotations, too. :)

You can learn this robotics topic from the great book by Daniele Benedetelli - LEGO MINDSTORMS EV3 Laboratory.
> 1 votes

---
Tags: ev3, programming
---


# Question
Title: How to program light sensor to follow moving light using NXT
Cannot figure out how to simply program Lego Mindstorm NXT robot to follow another moving robot that has a bright LED light attached to it.

Currently my programme looks like this:

# Answer
> 2 votes
If I were you, I'd make it this way:

The leader robot has a very bright light shining backwards, but not in a tight beam, rather a wide cone, so it can be seen from the back easily.

The follower robot has the light sensor facing forward, with a cowl around and in front of the sensor in order to narrow its sensing angle. In other words, the sensor is modified in such a way that it only picks up anything if the light source is directly in front of it, not to the sides. This will help filtering out background "noises" (ambient light and other light sources).

Then the follower robot runs this pseudocode:

```
while true // enter stopping condition here if required
  while light is visible // current light value is over a threshold - experiment with this value
    go forward some amount
  // if light is not visible the while loop exits and we need to find the light
  store current light level to variable FRONT
  rotate 10 degrees to the right // experiment with various values, maybe less is enough, maybe more is needed
  store current light level to variable RIGHT
  if RIGHT < FRONT // the light probably moved to the left
    rotate 20 degrees to the left // twice the amount in the previous turn
  // else the light probably moved to the right, where we are currently headed
  // so there is no need to rotate further, just continue with the next iteration,
  // checking if we see the light now

```

This way the follower will go after the leader while it is headed in the right way, but when the follower loses the leader, it stops and turns around to look for the light.

This method however has a drawback. If the follower is slower than the leader, it will be left behind during the "stop and look around" phases, but if the follower is faster, it will run into the leader from the back.

You could remedy this by giving the leader a bumper on the back connected to a push button (pressure sensor), and program the leader to only move forward when something (probably the follower) has pushed into its back bumper.

Let me know if you need additional help.

---
Tags: nxt, programming
---


title: How can I wire up the LEGO 2838?

text:
# Question
Title: How can I wire up the LEGO 2838?
I would like to know how to hook up the LEGO 2838 9v motor. I understand that the Power Functions extension wire is compatible with the 9v system, but how on earth do I wire them up?

# Answer
> 4 votes
To wire 2838 motor, you have to use one PF extension cable, one end connected to PF power source (either battery box or IR receiver), the other end has a 9V compatible plug on bottom. Unfortunately, 2838 also has its connector on bottom, so you also need a 9V cable (such as this one) to connect them.

---
Tags: motor, power-functions, 9v
---


# Question
Title: Can additional MyBlock icons be added to the EV3 palette of icons available in the MyBlock builder?
I'm a big believer in using MyBlocks when using EV3. For FLL teams, every robot needs to move forward, backward, turn right, turn left, arm up, arm down. Even before a robot is built, those MyBlocks can be created. However, none of the icons on the available palette of icons seem suited to the task.

Is there a way to add icons to the palette?

The palette of icons for the parameters is much more useful, so for now, we'll ignore that palette.

# Answer
Go to the directory

* (for home edition) c:\Program Files (x86)\LEGO Software\LEGO MINDSTORMS EV3 Home Edition\Resources\MyBlocks\images\
* (for edu version) c:\Program Files (x86)\LEGO Software\LEGO MINDSTORMS Edu EV3\Resources\MyBlocks\images\

And create a group of 3 icons for each new icon:

* PolyGroup\_NNN\_NAME\_Diagram.png \[size 34x34\] - visible in the diagram
* PolyGroup\_NNN\_NAME\_Palette.png \[size 25x25\] - visible in the command palette
* PolyGroup\_NNN\_NAME\_Palette\_MouseOver.png \[size 25x25\] - visible in the command palette while moving the mouse over the icon

Where

* NNN is a next available number (98 icons already installed), so continue with 098
* NAME - use some name

Restart the SW and open MyBlock builder, you will find the added icon.

It will not work, if you open your code on another EV3 installation without your modifications.
> 2 votes

---
Tags: ev3, software, ev3-g
---


# Question
Title: Identifying Lego kits from unopened bags for library
I'm a librarian and we recently received one of the Junior Maker Lego kits that LEGO distributed to 15 libraries in each state. It's a wonderful kit and includes a lot of basic blocks along with many numbered bags that clearly go to sets. However, none of the set information is included, nor can I find it online. Some I know are from the Chima theme based on the minifigs. I'm happy to upload pics if you all wouldn't mind helping, but there's about 20 different ones. Is there an easier way to do it?

# Answer
If you really want to know, I would suggest identifying the most unusual part in a bag, then using that part, search for what sets it has appeared in recently. Each piece usually has a small number printed on it. Use this part number on bricklink, or peeron to search for the part, and then click the link that shows you what sets it has appeared in.

Alternatively, take a picture of the bag and post it to the AFOLs of Facebook group and you'll probably have an answer in 5 minutes or less.
> 1 votes

---
Tags: set-identification, juniors
---


# Question
Title: On what plane is 7292 Propellor Adventures based?
The set 7292, *Propeller Adventures*, features a twin engine airplane. It looks a bit like the de Havilland Mosquito, but not quite.

On what plane, if any, is it based?

# Answer
It looks like a pretty generic twin engin-ed WWII bomber. Maybe like this Mosquito bomber?
> 5 votes

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Tags: sets, vehicle, model-identification
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title: What is LUGBULK?

text:
# Question
Title: What is LUGBULK?
I have heard that LEGO have (or had) a programme called LUGBULK whereby clubs can purchase bulk lots of LEGO components direct fom LEGO.

Is that true? If so, is it economical and how can I get involved?

# Answer
The Brick Blogger describes in detail how the LUGBULKS system works.

> The LUGBULK program debuted in 2009 and still operates as a pilot program for LEGO. LEGO realizes that AFOLs are the ones that make communities aware of LEGO in a wide range of venues that LEGO does not have the time or resources to reach. Therefore, supplying these AFOLs with an affordable supply of bulk pieces seems like a really good idea.
>
> The logistics of this project are a nightmare though if you think about it. There is no way to offer this discount to every AFOL who wants cheap LEGO bricks. Therefore, the first organization level is that AFOLs must be part of a LEGO User Group (LUG). This LUG must then register every year if they want to participate.

I recommend visiting the original article for more infomation. In particular which LUG (LEGO user groups) are qualified to use LUGBULK.
> 16 votes

# Answer
Yes, it does exist and it is indeed a logistical nightmare, but at least it does exist.

From what I understand from the participation from the LUG I'm a member of, all participants must provide their data to LEGO and must agree not to resell parts they buy.

The participants don't buy things on their own; rather, the club is responsible to select elements it wants to buy and quantities. There are limits, but I don't know for sure which ones (I think max 80 different elements per order), so the club must find a way to make sure all its members get something they want.

The way my club chose to do it is to select some elements which are likely to please a lot of people (basic dark red bricks, for example), then they buy them with their own account and resell them to members.

The prices are somewhat cheaper than if you would call LEGO yourself (which works in certain countries, by the way) or if you used the online pick-a-brick, but I can't say by how much. And since the club as a whole is involved, it's sometimes frustrating for individuals.

As how to get involved, you will need to be a known club, in which case you're likely to already have contacts with LEGO, so use these to ask how the lugbulk works.

If you're a new club which is yet unknown from LEGO, by all means, try to make yourself known, this can bring many advantages other than the lugbulk.
> 11 votes

# Answer
LUGBULK does allow members to buy things at a reduced cost that is determined by LEGO's production pricing.

I know our LUG allows each member to pick a certain number of elements that we want and then vote on the remainder. That way, everyone is guaranteed a certain amount pieces they want. Plus we can choose from the rest of the line-up also.

But of course, you have to be a member of a LUG, hence the name LUGBULK. I'd recommend contacting your local LEGO store to see if they know any members of your local LUG (if there is one). Otherwise, you can always start your own. You do need a certain minimum of members to be able to order LUGBULK and there are monetary requirements to meet also.
> 4 votes

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Tags: shopping, terminology, lugbulk
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title: LEGO Technic part Numbers

text:
# Question
Title: LEGO Technic part Numbers
My daughter got the LEGO Technic - Service Truck set. When we looked at the instructions, we saw a different notation on parts.

eg: the beams (cross beam) it has number 5 in white circle. what does that 5 stand for. Other instructions in same book have the number 3 or 7 in white circle.

Can anybody advise what these numbers mean?

# Answer
Beams, axles, panels, and axles connectors usually have numbers next to them, to uniquely identifies the piece:

* for beams and axles, the number is the length (length in number of holes)
* for panels, it identifies the panel (and the panel mold contains the same number)
* for axle connectors, it identifies the angle (again, the same number is part of the mold, and visible on the piece)

Same pieces with different colors have the same number attached
> 8 votes

# Answer
These numbers indicate the length of the beam or axle shown.

For a beam, this number is the number of holes it has. For an axle you have to hold it next to a beam and than count the number of holes.
> 4 votes

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Tags: technic, instructions
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# Question
Title: Are NXT Light sensors compatible with EV3?
I would like to use the NXT light sensors with my EV3 brick. I don't have enough light sensors as I need 2 for each robot (per set) and it only comes with one. However, I have a lot of NXT sensors. Will the EV3 be able to use the NXT light snesor and is the NXT light sensor as accurate as the EV3 light sensor?

# Answer
NXT Color Sensors are supported directly by EV3-G, the EV3 software running on the PC or MAC. NXT **Light** Sensors are not.

To use **Light** sensors requires a bit of trickery. EV3-G has a Raw Sensor block that provides access to the Light sensor values. The raw sensor returns values from 0-1023, which is very different than the 0-100 of the NXT-G Light Sensor block.

Setting up the **Light** sensor to use ambient or reflected light is also solved with a bit of trickery. Use the Sound Sensor Block and toggle the dB setting.

Once that much is tested and working, create a set of MyBlocks to mimic existing Color Sensor blocks.
> 5 votes

# Answer
Raw sensor value works, but shows a level of dark, not of light :), meaning that higher values indicate lower light.

Ambient light works directly, but for reflected light you need to insert a EV3 Color Sensor block with Reflected Light mode to turn on the light in the NXT Sensor. After that, use raw values or the Sound sensor block.

The Sound sensor block is not included in the download version of the EV3 software (at least not in mine), you can download the necessary ev3b file from http://www.lego.com/en-us/mindstorms/downloads and then import it into your project.
> 2 votes

# Answer
The kids on the FLL team I coach created a video that explains how to use the NXT light sensors on an EV3. Hope it helps. http://youtu.be/I7Bqvk-uMLk?list=UU2r9xq9o39SbEX1cESNdIHA
> 1 votes

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Tags: mindstorms, nxt, ev3
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title: Part identification

text:
# Question
Title: Part identification
Can you help me identify which part numbers these parts are? I can't find them on Lego's site or on brickset.com:

**Edit:**

I've found the two dark grey bricks in the left photo, so that just leaves the yellow one, and the other two photos.

Thanks! Ben

# Answer
> 4 votes
I'd say the yellow part is listed on BrickSet as "Lamp Holder" or "Plate, Modified 1 x 1 with Clip Light - Thick Ring", 4081 on BrickLink, Peeron, etc.

The light grey piece is from the Flick Missiles, and is listed on Brickset as "3 M.Arch W.Knob And Shaft Ø¸3.2" or "Technic, Pin 1/2 with 2L Bar Extension (Flick Missile)", 61184.

The final piece is "Mini Fig. Back Palte W. Knob" or "Minifig, Neck Bracket with Back Stud", 42446

For completeness, the other two are:

"Angular Plate 1.5 Bot. 1X2 1/2" on Brickset or "Bracket 1 x 2 - 1 x 2 Inverted", 99780

The tile I couldn't find on Brickset other than in Rebrickable inventories where it's listed as "Tile 1 x 2 with Joystick and Vehicle Control Panel Pattern" (3069bpr0090) or on BrickLink as "Tile 1 x 2 with Vehicle Control Panel Pattern", 3069bpc1

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Tags: part-identification
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# Question
Title: Why is there no set with much RC Straight tracks?
after visiting many Lego events (brickmania, antwerpen, BE), I wish to expand my train layout much more than adding a box or two of 7499 ...

Why does Lego didn't released a set with, for example 24 straight track ( #53401 )

Even if 7499 contains flex rails, I don't like these, they are noisy.

Any tips for finding some ??

I can't imagine peoples who exposes layout in 5 meters by 8 meters with 4 tracks have bought a pallet of 7499 !

# Answer
According to Brickset there are 8-8 straight track pieces in all of these sets (including the sets with straight tracks without metal conductors):

The 60098: Heavy-Haul Train has 12, and both of 60336: Freight Train, 60198: Cargo Train have 16 straight pieces.

This seems to be the maximum amount, even the large complete train sets do not contain more than 16 straight tracks.

You might have more luck purchasing them piece by piece from other AFOLs, or see if there is a Pick-a-brick shop in your area.
> 3 votes

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Tags: trains, city
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