title: Software to help inventory set

text:
# Question
Title: Software to help inventory set
Are there any software applications to help check the inventory of a lego set?

Currently I load the set-up as a bricklink wanted list and then delete each part one by one until I have only the missing parts left. This works okay but can be a bit cumbersome when checking about a hundred sets.

# Answer
> 3 votes
I have had the same problem there are 2 ways you could do it.

**Way One is to use rebrickable**

1. Go to http://rebrickable.com/home Create an account.
2. Then go MYREBRICKABLE and select My Sets.
3. Then click Add set to this set list and search for the set you want. Now you can add all the sets you have.
4. IF you like you can go to the My Parts section and add any parts you might have bought.
5. Now if you want to find out how many red 2 x 2 bricks you have you can simply go to My Parts. Then tick the tick box where it says 'Set Parts' and click update. All your parts from your MY Sets and My Parts will now be shown below. You can see and example of this below.

**Way two is to use brickstock .**

1. So what I do is open brick stock.
2. Then Click Import and chose Bricklink Inventory.
3. Search for the set I want and then click ok. It then will create a file listing all the parts that make up the set(You will see a small hard hat icon at the top right as it download all the part images).
4. Do this for all your sets and combine the files and you will have one master file.

---
Tags: software, inventory
---


title: Chima Speedorz game -- how to play?

text:
# Question
Title: Chima Speedorz game -- how to play?
Lego Chima Speedorz sets include cryptic instructions on how to play the game, but I'm unable to fully understand them. I'm looking for a comprehensive answer or guide that details the game rules.

# Answer
I think this might help you, its a pretty nice writeup on how to play: http://thebrickblogger.com/2013/01/lego-legends-of-chima-speedorz-game/
> 2 votes

---
Tags: chima
---


# Question
Title: How to Download my orders from Bricklink
I know you can log in to Bricklink and download my orders as Excel or many other formats, but I am trying to do it programmatically. Does any one know how to do this though Powershell perhaps?

# Answer
Check the Bricklink API feature. I personally have not tried it, but it looks like it should have all the features you need, namely downloading the order list and orders themselves.
> 1 votes

---
Tags: bricklink
---


# Question
Title: I just purchased a used LEGO Studios set and had some extra pieces that don't belong
Can anyone tell me what set they might be from?

backside:

# Answer
It's tough to predict where such a small number of pieces came from, but some are likely from the Hydronauts theme, specifically Hydro Crystallisation Station (6199):

This set includes the chromed headgear with studs on the back as well as the printed tile that is already attached to the back of yours.

The minifig utensils are likely from Mobile Outpost (6520):

Here are links to the sets that these parts appear in if you'd like to explore this more:
> 3 votes

# Answer
The trans neon green helmet on the right of the first pic appears to be from any of the Aquazone, Aquaraiders I, Hydronauts, or possibly even Time Cruisers.

It's a start... :)
> 1 votes

---
Tags: piece-information
---


title: How to enter wifi-password on ev3dev?

text:
# Question
Title: How to enter wifi-password on ev3dev?
After successfully installing ev3dev and getting the USB connection working I now want to get my wifi-dongle working (or rather connecting). The dongle is successfully found and my LAN is displayed.

But as expected I need to type a password, this is the problem! How do I insert a password in the brickman interface?

# Answer
When the password dialog pops up, press ENTER (the middle button) to open an on screen keyboard.
> 2 votes

---
Tags: ev3dev, wi-fi
---


# Question
Title: How do I make use of the full SD-card after installing ev3dev
After writing the image to the 8G microSD-card, initial setup of network and installation of git (with apt-get) I could not install anything else since I was out of diskspace. This confused me. But `df -h` shows me that `/dev/mmcblk0` has a size of just under 1G. `/dev/mmcblk0p1` has a size of 40M.

So I got a card with roughly 7G unused and unaccessible. How do I get hold of it?

When I insert the card in my laptop (Ubuntu) it does no longer automount itself and when I try to get some info about it I get this with `parted` and `lsblk`:

```
$ sudo parted -l /dev/mmcblk0p1
Model: ATA HTS721080G9SA00 (scsi)
Disk /dev/sda: 80.0GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type      File system     Flags
 1      1049kB  76.8GB  76.8GB  primary   ext4            boot
 2      76.8GB  80.0GB  3219MB  extended
 5      76.8GB  80.0GB  3219MB  logical   linux-swap(v1)

Error: /dev/mmcblk0: unrecognised disk label

$ sudo lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda           8:0    0  74.5G  0 disk
├─sda1        8:1    0  71.5G  0 part /
├─sda2        8:2    0     1K  0 part
└─sda5        8:5    0     3G  0 part [SWAP]
sr0          11:0    1  1024M  0 rom
mmcblk0     179:0    0   7.4G  0 disk
└─mmcblk0p1 179:1    0   7.4G  0 part

```

What can I do:

* Could I resize the disk in the current installation?
* Could I do a new installation an during the installation procedure set the size of the final result?
* Could I create new partitions in the unpartitioned area and move the OS to that partition?

# Answer
If you install ev3dev with an image file dated 1 May, 2015 or later, it should automatically expand the root partition to fill the space available on the SD card. Older releases are no longer supported.

If it does not do this, you should report a bug a https://github.com/ev3dev/ev3dev/issues. Be sure to read http://www.ev3dev.org/support/#github-issues first.
> 2 votes

---
Tags: ev3dev
---


title: Official LEGO charity programs

text:
# Question
Title: Official LEGO charity programs
Many consumer-oriented corporations have official charity programs where products or money are donated to deserving causes. I was wondering if The LEGO Group has any such programs --- and if so, where can one apply for donations?

For instance, I believe it would bring happiness to hospitalized children to receive a simple Lego set (such as a polybag) to play with.

# Answer
> 7 votes
The first hit on Google for "LEGO charity" is this: http://service.lego.com/en-us/helptopics/lego-company/charity-and-donations. From that page:

> What charitable activities is the LEGO Group involved in?
>
> We take our responsibility for making children's lives better very seriously, so we run a number of charitable programs.
>
> Usually, our local offices use their knowledge of what local children need to partner with initiatives and charities.
>
> On a global level, we help children through the activities of the LEGO Foundation. If you'd like to know more about how we understand our responsibility and what we do, there's lots more information in the About Us section of this website.

Sounds like that should cover your question. Check out the www.legofoundation.com website as well.

---
Tags: lego-group
---


# Question
Title: What brick is this? 1x2 with holes in the short sides
This is my first time doing something like this, so here goes. This is a 1x2 blue brick with holes on each end. Through a hole, you get this view of the center peg and the light coming in through the other hole (pic 3). From the bottom there is the peg, the holes on the sides, and the "Pend" from "Pat Pend" (pic 4). The "Pat" is above, but unable to be seen.

Finally, I have done a lot of research and found a grand total of nothing about it. So, I tried some stuff out and learned that the only thing that fits in the holes are minifigure arms and thus speculated about a 4 arm guy.

Here are my tries at fitting other stuff.

Thanks for looking and sorry for so many pics! -Erich Wacker

# Answer
> 10 votes
This is part 3317.

It's primarily used to hold the bucket on front end loaders. It hasn't been used in a set since the late 90's. Part 3314 is about the only other part that is designed to connect to it that I'm aware of:

Here's an example of this part in use from set 6504:

While I believe that this was the only way to connect to this part used in official sets, I'm sure it may have other uses. It was used to build gas pumps in one set:

---
Tags: part-identification
---


# Question
Title: How many different colours of LEGO bricks are there?
Excluding translucent pieces, how many colours of official LEGO bricks are there?

# Answer
> 28 votes
The official LEGO color chart at Peeron has 111 colors listed. There are 14 listed as "transparent" (or "tr"), so - 97.

The Peeron guide also lists CMYK, RGB, HTML Hex Codes (displayed as the sample), and Pantone numbers for each.

# Answer
> 25 votes
The latest palette officially released by LEGO in 2010 has 51 colors in use, including 33 regular colors, 14 transparent, and 4 "effect" (silver, gold, metallic, phosphorescent).

Of course, as 81bronco points out, there have been a lot more, but these are the one LEGO was effectively using as of January 2010. In the few years before that, LEGO was busy rationalizing its palette of colors to eliminate seldom used colors as much as posible. Considering the downsize to 51, I don't think they've removed any more since.

# Answer
> 22 votes
This Flickr image from Brick Colorstream shows all the known colors of LEGO bricks, charted along a timeline of when they were available. According to that image, there was one new color in 2015, "Conductive Black".

(Click for full size)

# Answer
> 11 votes
According to the LEGO customer service site which allows you to search by color family, there are 9 color families and 23 exact colors:

```
Color Family Exact Color
-------------------------------------------
Black        BLACK
Blue         BRIGHT BLUE
Blue         EARTH BLUE
Blue         MEDIUM BLUE
Blue         TR. BLUE
Blue         TR. LIGHT BLUE
Green        BRIGHT GREEN
Green        BRIGHT YELLOWISH GREEN
Green        DARK GREEN
Green        TR. FLUORE. GREEN
Green        TR. GREEN
Grey         DARK STONE GREY
Grey         MEDIUM STONE GREY
Orange-brown BRIGHT ORANGE
Orange-brown DARK ORANGE
Orange-brown FLAME YELLOWISH ORANGE
Orange-brown REDDISH BROWN
Orange-brown TR. BROWN
Purple       BRIGHT PURPLE
Purple       MEDIUM LILAC
Red          BRIGHT RED
Red          NEW DARK RED
Red          TR. FLUORE.REDD. ORANGE
Red          TR. RED
White        WHITE
Yellow       BRICK YELLOW
Yellow       BRIGHT YELLOW
Yellow       SAND YELLOW
Yellow       TR. YELLOW

```

http://shop.lego.com/en-US/Pick-A-Brick-ByTheme

---
Tags: colour
---


# Question
Title: Where does this green plane fuselage piece come from?
It has the year 2005 on it and the number 22988 I think. Anyone know what it is?

# Answer
> 9 votes
It's the rear end of an aircraft fuselage. It's part number is 54701c02.

It's from one of these two sets:

---
Tags: part-identification, city
---


title: Mindstorms Software Versions

text:
# Question
Title: Mindstorms Software Versions
Here is what I have:

1. Site licences for Mindstorms Software 1.0 (NXT) and EV3.
2. An upgrade to Version 2.0 for the NXT
3. 9 NXT kits
4. 4 EV3 kits
5. 2 Renewable Energy Kits and Temperature sensors

My problem is that on the NXT units, the only version of the software which supports the Renewable energy/temperature sensors is 2.1, which does not appear to be an upgrade to 2.0, but is instead a education site licence version like the ones I have for NXT 1.0 and EV3. Without these I cannot access the blocks to use the Renewable Energy kits and temperature sensors unless I use the EV3 kits.

My questions:

1. Am I right, or is there a way to upgrade 2.0 to 2.1 or 1.0 education to 2.1?
2. is there a way I just haven't been able to figure out to use these sensors with the 2.0 software?
3. Is it worth updating all my existing material for the NXT bricks to program them from the EV3 software as well and dealing with the small issues or not?

I have tried contacting distributors, and looking online has only helped me find the appropriate sensor blocks for the EV3 software.

# Answer
> 4 votes
1. You probably don't need it, but the LEGO Education NXT 2.1 Software is still for sale through LEGO Education (at least in the USA). They do not advertise and upgrade price, but it does not hurt to ask.
2. The Energy Meter blocks are available for download on the LEGO Education website. I went to http://education.lego.com/en-us/downloads and checked the box "Blocks" under "Download Type" and it shows up in the list. It does not say if it is for NXT or EV3 though. Also, I found this for the NXT Temperature sensor.
3. I would not recommend using the EV3 software for programming the NXTs. There are a number of limitations, such as lack of support for 3rd party sensors and lack of support for Bluetooth. Also, I understand the programs take up much more memory this way.

# Answer
> 2 votes
I managed to install my license of Mindstorms Edu NXT v2.0 (Windows 7 x64) and the software has Data Logging and the Temperature Sensor Block.

If you have an upgrade from v1.0 to v2.0 at least the Temperature Sensor Block will be available.

---
Tags: mindstorms, nxt, ev3
---


# Question
Title: How many flexible tracks does it take to make a complete oval?
I have couple of straight tracks, no curved tracks, so the only option now from me is to buy the new 7499 straight + flexible tracks. Therefore:

How many boxes of 7499 tracks do I need to make a complete oval circuit?

There are reviews but none of the is actually mentioning this. No pictures either.

# Answer
Each piece of flex track is equivalent to 1/4 piece of regular track. The standard train curves are 1/16th of a circle and thus an oval shape is not possible, however, with 64 pieces of flex track you could make an oval by squashing the circle a bit. 7499 comes with 16 flexible tracks, so you'll need 4 of them to make a regular train circle.

The flex track can be used to make a smaller circle than the regular track:

but as TheBrickBlogger pointed out, the flex track has performance issues and such a tight circle will be difficult for your trains to navigate. The trains tend to fall off if conditions are not perfect. Over Christmas I built a large layout under my Christmas tree and I had to remove all the flex track in order to prevent derailing. Part of that was due to my train design, part of it was due to the fact that the track was sitting on a mix of carpet and hardwood flooring, but part of it was that the train is very sensitive to bumps in the track and flex track exacerbated those issues. Depending on your engine design you might have more or fewer issues. If you are just pushing the train by hand, it will probably be fine.

Also keep in mind that the standard lego train car with fixed (not swiveling) wheels can only navigate a certain minimum radius. Lego puts the wheels 10 studs apart so that they can just barely make it around the fixed curves. If you build the small flex circle, or squash a 64-flex-track circle into an oval, your tightest curves will for sure be too tight for those cars to navigate.

Normally Lego sells curved track in an expansion kit. It seems that right now (May 2015) the only kit is the 7895 Switching track kit. That kit comes with 4 curved rails and so you'd need to buy 4 of them to make a circle. If that's not your ideal choice of parts, then Bricklink would be best. Or, use this as an excuse to buy a whole train kit, which comes with track, train cars, motors, etc. You can never have too much Lego.
> 9 votes

# Answer
The flexible tracks are not designed to make a full oval, but to add subtle, smaller curves in a train layout, using just a few at a time. If you do use too many flexible tracks next to each other they will slow down your train, they are very noisy, and can even derail the train. Here is an excellent comparison video between the regular curved tracks and the flexible tracks: http://youtu.be/fGcD\_QtOcRQ

If you would like to create a full oval I would suggest that you just get the curved train-tracks on BrickLink as they are currently not available directly from LEGO (except in full train sets). They are about 50 cents each and will be much better for your purpose. You will need 16 of them to make a full circle: http://www.bricklink.com/catalogPG.asp?P=53400&colorID=85
> 7 votes

# Answer
To add to the excellent answers already provided, the cheapest LEGO train set currently available giving you a full oval/circle is 60051 and costs $149.99 in the US Lego store. You might be able to find it slightly cheaper on Amazon.com (currently $127.21 in the US) or ToysRus.com (currently $149.99 so same as LEGO store) sometimes.

The equivalent purchase of 4x 7895 Switching Track is $15.99 in the US Lego Store for each set, so a total of $63.96 for 4.

If you go by absolute price, the 4x7895 is your best option, and you get 8 switches extra, which you could use once you expand your track, or sell back through bricklink or eBay (current US selling price on bricklink is around $3 per switch track) which would reduce the total price by $24, giving you a total price of roughly $40 for the oval.

The 60051 train set does come with batterybox, trainmotor, IR set etc, plus many pieces. The value of that set is probably better than 7895 gives, at a roughly $100 premium over 4x7895 with sellback via Bricklink/eBay etc.

---

Separately, there are 2 more options you can consider:

1. ME Models sells LEGO curve sets with bigger radius than the standard R40 LEGO curves. Their R56 curve pack costs $19 for a half-circle (so $38 for a full circle) plus shipping. They have several other radia as well, but those will cost more. From what I've read the fit with "normal" LEGO is very good and train enthusiasts love these rails.
2. If you don't mind the extra pieces, you can make curves out of straight rails by using this technique (youtube) . The train's movement will be a little jerky but otherwise it works well. You'll just need a lot of space as the radius of such an oval is very large. But most LUGs use this technique in their train layouts, so it is "endorsed by professionals". Basically, you offset the outside joint by half a stud every rail using a 1x3 and a 1x2 jumper. The upside is that you can use this technique to make the outside of the curve 1 plate higher than the inside of the curve to allow your train to "bend" through the curve just like trains in real-life do.
> 3 votes

---
Tags: trains
---


# Question
Title: How to remember initial position of a robot and return to it
I have an EV3 robot with motors, like a car, that can move forward/backward and left/right and have some sensors attached. I want it to remember its initial position by remembering all the movements of motors when robot starts moving, then after some movements, that can be random in time, distance and direction, I want to return it back home.

How can I do this? What is the principle of returning "home" knowing there are no GPS or other helpers?

# Answer
> 4 votes
You have two options.

You can use an accelerometer. Lego sells one that can be found here. There are also aftermarket ones at mindsensors.com. This allows you to independently measure the acceleration of the robot. You have to then integrate this information twice to get positional change. The way to do this is to put it in your control loop and sum up 0.5\*dt\*dt\*a where a is the accelerometer reading (there will be one for each axis of motion) and dt is the time between samples. This nice thing about this is it gives you absolute displacement. That is it accounts for motions that cancel out so you can set a straight line path back.

You can record each displacement into a variable for x and y directions using the servo readings from the motors - remember to reset the encoder value from the servos after each reading. This is harder because you have to account for the geometry of the wheels and keep track of the robot heading - lego also sells a compass sensor if you don't want to deal with finding your heading, but you'll still have to deal with non-spinning turns. It's also prone to accumulation of errors. (the accelerometer is too but not as bad I think.)

Your admonition of 'no other helpers' could be interpreted to mean you don't want the first solution in which case you are left with using the encoders and figuring out the differential motion of your chassis design (which may be non trivial).

# Answer
> 3 votes
## **Get the initial position of an EV3 Motor and return to it.**

**Setup:** I installed Debian Linux on the Mindstorms EV3 brick and I'm using Python 2 to use the ev3.lego package to use the method: `run_position_limited(... , ...)` to spin the motor to a certain angle position.

**Python 2 code**: which gets the initial position of the Motor on program start:

```
from ev3.lego import Motor
c = Motor(port = Motor.PORT.C)

initialMotorLocation= c.read_value("position")
c.run_position_limited(
    position_sp = int(initialMotorLocation) + 150,
    speed_sp = 150)

```

**What it does**

First we import the Motor library from ev3.lego. Then we instantiate a new connection to the Motor on Port C. Then we read the current position of the angle of the motor on start. Store this value permanently so every time we want to move ahead by 150, we add that value to the location it was at start.

**Result:**

If you run this python program many times, the motor will rotate forward by exactly 150 each time, rather than the default behavior: "rotating to exactly position 150", which only holds true until the EV3 brick is rebooted."

**What did we learn:**

We need to learn to read and comprehend the source code ev3.lego documention, Defined here: https://github.com/topikachu/python-ev3

If you scroll down that page you see this command:

```
from ev3.lego import MediumMotor
d = MediumMotor()
d.reset()

```

So the method called `reset` is an additional way to cause the motor to reset it's internal tachometer to 0 at the current location.

**Full Example:**

```
from ev3.lego import Motor
c = Motor(port = Motor.PORT.C)
c.reset()  #Set the internal tachometer back to 0
c.run_position_limited(position_sp = 150, speed_sp = 150)

```

**How to get to these answers on your own:**

You got told that the `reset()` and `read_value` methods will solve your problem. This is not an example of you finding things out for yourself.

Go to the source code: https://github.com/topikachu/python-ev3

Under `python-ev3/ev3/ev3dev.py` you'll see the source code that does the work I've explained above. Notice the properties. You see the integer value called `position` that you were querying above.

Being able to recompile and understand how the library is working from source is the better part of the education the mindstorms EV3 brick aims to teach you. Dig in.

# Answer
> 2 votes
You should look up 'Dead Reckoning'. It is a method where you always know (or guess) your current position by tracking all your previous moves. Knowing your current position, you can then retrace your steps backward or reach any position back calculating a straight line to it (hoping that there's nothing in the way).

Here's the Wikipedia on the subject: Dead reckoning

---
Tags: ev3
---


title: Control two Lego NXTs with an Arduino

text:
# Question
Title: Control two Lego NXTs with an Arduino
I'm new here and also very noob with the Arduino. I have a basic knowledge in Java and some more in C# so code isn't a problem. I can learn it easily.

I have a project assigned. I would like to know if it is there any possibility to control two Lego NXT with an Arduino? I want to give commands/orders via Arduino or at least have communication between both of them.

I have an Arduino Uno and two Lego NXT kits (9797 and 9648).

# Answer
You have a number of options.

* Since you mentioned you know C# the best, have a look at http://monobrick.dk. They have a C# library that lets you remote control the NXT. Then you could use something like http://playground.arduino.cc/Interfacing/Csharp to do the same for the Arduino. UPDATE: MonoBrick project doesn't seem to be around anymore.
* For Java, there is a similar NXT remote control library from http://www.lejos.org/. I imagine you could find something similar for Arduino as well.
* If you want to connect the Arduino directly to the NXT, you can use USB or Bluetooth. Then you can use the information in the NXT Bluetooth Developer Kit (available from http://www.lego.com/en-us/mindstorms/downloads) to develop a program for the Arduino what will be able to communicate with the NXT.
> 3 votes

---
Tags: mindstorms, nxt, electronics, arduino
---


# Question
Title: Where did these small tan bricks come from?
I was going through an old box of LEGO bricks from the 70's and 80's and I found a number of small bricks that appear to be about 2/3 size. They have the LEGO logo, and appear to be the official tan color (05). I can't find a reference anywhere as to their origin.

# Answer
These look like Modulex bricks:

> Modulex was a building system that was designed for adults. It was developed by The LEGO Group at the same time as their Modulex sets were produced from 1963 until 1965, and were exclusively available in parts packs by colour. The LEGO Group made Modulex a separate company in 1965, and the text "LEGO" was removed from the studs and replaced with "M".
>
> Modulex bricks were formed with a cube type 5 to 5 width/length ratio, meaning that, unlike very nearly every product produced by The LEGO Group, they were not compatible with LEGO bricks, which have a 6.5 to 5 width/length ratio. Modulex bricks were available in a wide array of unusual colours, shapes, and sizes.
>
> from Brickipedia
> 7 votes

---
Tags: part-identification, clone-brands
---


# Question
Title: Slow down the mindstorms EV3 motor so target position is not overshot
I have Debian jesse installed on a mindstorms EV3 and I'm using the `ev3.lego` library: https://github.com/topikachu/python-ev3

I want to be able to slow down the motor as it reaches its target destination because if it's going full speed when it gets there, it overshoots its target proportional to how fast it was going.

**Example Python code: When I use this code to spin the motor:**

```
from ev3.lego import Motor
b = Motor(port=Motor.PORT.B)
b.run_position_limited(position_sp = 100, speed_sp = 300)

```

The motor spins to position 100 on the tachometer with speed of 300.

When it gets to its destination, the momentum carries it to position 125 or so. So next time I tell it to go to position 100. It spins up, then overshoots to position 75.

What is the best way to try to minimize this error so I can tell the motor to move to position 100, and it either slows down before it reaches its target, or otherwise freezes the motor when it reaches the destination?

# Answer
> 3 votes
There are two attributes in the python ev3dev Motor class called:

```
ramp_down_sp
ramp_up_sp

```

Link to documentation: http://ddemidov.github.io/ev3dev-lang-python/

**ramp\_down\_sp Ramp Down SP: read/write**

Writing sets the ramp down setpoint. Reading returns the current value. Units are in milliseconds. When set to a value \> 0, the motor will ramp the power sent to the motor from 100% duty cycle down to 0 over the span of this setpoint when stopping the motor. If the starting duty cycle is less than 100%, the ramp time duration will be less than the full span of the setpoint.

**ramp\_up\_sp Ramp Up SP: read/write**

Writing sets the ramp up setpoint. Reading returns the current value. Units are in milliseconds. When set to a value \> 0, the motor will ramp the power sent to the motor from 0 to 100% duty cycle over the span of this setpoint when starting the motor. If the maximum duty cycle is limited by duty\_cycle\_sp or speed regulation, the actual ramp time duration will be less than the setpoint.

Example:

```
from ev3.lego import Motor
b = Motor(port=Motor.PORT.B)
b.ramp_up_sp = 1000
b.ramp_down_sp = 1000
b.run_position_limited(position_sp = 0, speed_sp = 300)

```

What the ramp\_down\_sp does is when the motor is 1000 milliseconds away from its target (doing its own estimations) then ramp down the power from 100% to 0% over exactly 1000 milliseconds.

ramp\_up does a similar thing, except ramps up the power from 0% to 100% over 1000 milliseconds.

This helps avoid unnecessary strain on the motors for applications where building up momentum is important.

---
Tags: ev3, motor, ev3dev
---


# Question
Title: Using the NBR 1036 Barometer with the EV3
I just purchased the HiTechnic Barometer from LEGO, thinking the Block was available for the EV3. Theory says that I can use NXT Block in the EV3. Can anyone point me in the right direction?

# Answer
> 1 votes
I'm not sure where you got your theory, but no NXT blocks will not work in EV3 software.

You may be able to use this with the LEGO EV3 software using the generic I2C block developed by Dexter Industries.

Otherwise, you should look into using a 3rd party programming environment/OS for the EV3 (EV3Basic, ev3dev, leJOS, MonoBrick, etc.)

---
Tags: mindstorms, ev3
---


# Question
Title: How did the LEGO 7862 Remote Controlled Decoupling and Signal work?
I've never seen this set in person, although it appears occasionally in 12V Lego train system images. I've never seen it used, or described.

How did the *LEGO 7862 Remote Controlled Decoupling and Signal 12V* work? What is the 'Signal' component of the decoupler?

# Answer
> 6 votes
It basically forces the coupling magnets to separate via the pins pointing downwards from the magnet holders:

Here's a demo.

---
Tags: trains, remote-control, 12v
---


title: Inverting motor's rotation

text:
# Question
Title: Inverting motor's rotation
I've designed a robot with two motors. It works as follows:

The first motor is attached to the the person's arm, the second motor receives the calculated movement and moves accordingly.

When the person moves his hand (open/close) the other robot moves the the opposite direction; upon opening it closes and vise-versa.

I've tried to invert the movement by multiplying by -1 but the second motor keeps moving on his own. I've tried multiplying the results of both motors, before subtracting, with no success.

The 'code' does the following:

1. I take the movements of motors A and B
2. Subtract value of motor A from motor B's
3. Save the result to a variable-'moveDist'
4. Take the absolute value after subtraction for comparison
5. If greater than 6, pass 'moveDist' value to the second motor.

# Answer
> 0 votes
I found a solution: I multiplied the master motor's value by -1. So, the calculation was: (a-b) it changed to : (-a-b). The result was passed to the slave motor and it did the job.

# Answer
> 0 votes
I think the main problem is, that you use the "Motor on for # degrees". The program will wait until this command is executed (i.e. the required turn is made), and this can take quite long. The next measurement of the angle difference is taken after that. Having a high start deviation and/or fast turning rates of your reference motor, you will not get a stable result. Instead I propose to use the angle difference for the "Power" input of the "Motor on" command. In that scenario the angle difference is measured very often, and the "slave" motor is following your "master" motor very pecisely.

---
Tags: ev3, motor
---


# Question
Title: Are 10682 "Creative Suitcase" and 10695 "Creative Building Box" compatible?
I just wanted to be sure if these two sets 10682 and 10695 are compatible.

# Answer
Yes. These two sets, and basically every other LEGO set that has been produced, are compatible with one another. The major exception to this rule is DUPLO, which is twice the size of regular LEGO system bricks. However, even DUPLO is compatible in some ways.

These two sets are both essentially just boxes with lots of bricks in them. They may include some instructions and ideas, but they are designed to allow children to build creatively. Combining pieces from both of these sets will only add to fun!
> 4 votes

---
Tags: sets, compatibility
---


# Question
Title: Is there a site where I can put in a set of individual lego bricks (by part ID) and get an optimized list of stores to buy (to minimize shipping)
I'm new to this site, so please forgive me if this is a duplicate.

**Background story** I got my 6 years old the Lego City Arctic largest set, and then realized he had previously had 2 other arctic sets, that sadly, he lost some parts for...

I have sorted through all of his legos (yes, I do have a life, but this was rewarding on unbelievable and weird levels) and checked marked all the pieces he had. I narrowed it down to the few that he was missing and got their ID number.

I Googled my way into http://www.wallofbricks.com/ and was able to find stores that sell all those pieces!

**Problem**

The big problem as you might have guess is that it would cost more than re-buying that set again. The difference is not the individual piece cost of course, but the shipping.

The issue stems from the obvious reason that not all stores have all pieces, so you just pay a lot in shipping...

Now, I'm sure that if I cross reference the online stores that sell all the parts, I'll be able to find some, that might not have the cheapest price, but have more than one piece in stock.

**Question** This is a very interesting optimization problem to solve, and I was wondering if there is any website that lets you answer the give question:

Given a list of missing pieces and quantities, and the original set cost - finds either the combination of stores such that the piece costs + the shipping is less than the original set, or suggest that buying the original set will be cheaper.

# Answer
> 5 votes
There are two pieces of software that lets you do this for Bricklink: Brickficiency and Brick Wizard. The latter seems updated more often, but I don't know if they produce different results.

---
Tags: shopping
---


# Question
Title: Can anyone help id this partial build/set?
I found this partial set bagged at Savers, looked interesting. But searching thru peeron, I cannot figure out what set this might belong to. Is anybody familiar with what set this might be associated with ? Back and front designations are really just arbitrary, as I don't exactly know what I have here. The black bricks hanging out on the top of the "back" side view are technic bricks 1x16 with holes. The sides of the base, if you will, are composed of 6 technic bricks 1x14 with holes, 3 on each side.

# Answer
This is from the Clone Turbo Tank.
> 6 votes

---
Tags: star-wars, set-identification
---


# Question
Title: How can I transmit horizontal torque to vertical?
I have a setup where I have a step motor which I am attaching a gear onto. The motor will make the gear stand horizontal in a small vehicle. Is there any good gear combinations of LEGO gears that can transform the horizontal torque of the gear into vertical torque that drives the wheels of the small car I am building?

Are there multiple combinations of LEGO gears that can provide this kind of torque transmission?

# Answer
> 11 votes
There are a number of ways to do this. Here is one of the easiest and earliest methods:

For that design, you'll need this part (3650):

And one of the 8-tooth gear variants:

You'll also need suitable Technic axles, Technic bricks (3700 is used above), and Technic plates (32001 in the example) to match your overall design needs.

You can also do something similar using a combination of bevel gears or double bevel gears:

# Answer
> 10 votes
I'd like to cover two other techniques that work well, they both transmit horizontal torque to vertical but in slightly different ways that I believe may be useful for different situations.

---

## Worm Gears

Worm gears are fairly small (less than two studs long). Worm gears are designed to be operated in one direction and can only be driven by the axle with the worm gear. You can get some very high gear ratios when combining a worm gear with another gear.

## Knob Wheel

Knob wheels are only compatible with other knob wheels, they cannot be used with gears. They can be used parallel (like standard gears) and at 90 degree angles (like crown/bevel gears).

I find knob gears are easier and more comfortable to turn by hand and they appear to be more commonly included with recent Technic sets.

---
Tags: motor, gears
---


# Question
Title: usage of ev3 ultrasonic sensor in lejos behavior based programming
I'm using ev3 ultrasonic sensor. And I'm writing a behavior based lejos code. I want to do some tasks when the ultrasonic sensor detects an object which is not further than 30 cm's. And this is my code:

```
public UltrasonicSensor(Port port)
    {
        sonar = new EV3UltrasonicSensor(port);
        sonar.getDistanceMode().fetchSample(value, 0);
    }

    @Override
    public boolean takeControl() {
        // TODO Auto-generated method stub
        return value[0] < 0.3;

    public void action() {
        ....
    }

    @Override
    public void suppress() {
        // TODO Auto-generated method stub
        suppressed = true;
    }

```

But I think it is not the right way. How can I implement it in the right way?

Thanks for help,

# Answer
You can use the `lejos.ev3.robotics.RangeFinder` abstraction class:

```
EV3UltrasonicSensor sensorUS;
RangeFinder sonar;

public UltrasonicSensor(Port port) {
    sensorUS = new EV3UltrasonicSensor(port);
    sonar = new RangeFinder(sensorUS);
}

@Override
public boolean takeControl() {
    return sonar.getRange() < 0.3;
}

```

Use the `float getRange()` method to retrieve the distance to the nearest object.
> 1 votes

---
Tags: ev3, sensor-ultrasonic, lejos
---


# Question
Title: How to run two LEGO electric trains at the same time?
I have a LEGO city built with a train encircling it. The track is the classic style with metal railings running through it. I have a switch track as well that is connected to an NXT robot to switch the track each time a train comes by.

The problem is, there are areas where the trains run into each other because there isn't enough power running through certain areas of the track or too much power. I have 2 of those power consoles connected to the tracks.

Does anyone know how I can have these two running at the same speed without slowing down and crashing into each other?

# Answer
This probably isn't going to be solved without either changing to remote controlled PF trains or creating a complex control system.

Even if you were able to supply the exact same constant voltage to both trains, they'd both need to have precisely the same motor characteristics, weight, and aerodynamic properties. That's going to be difficult.

One way to address this is to create track blocks that are electrically isolated and can be controlled independently. You can isolate the track sections using tape at the joints, or you can physically cut the metal rails. You could then connect these blocks up to your NXT and build some sensors to determine what speed the trains need to run in these sections in order to not hit each other.
> 6 votes

# Answer
I know that Lego Trains expert Michael Gale (not sure if he has an account here on StackExchange) is working on a DCC module for Lego 9V trains. He has details and pictures up on his Flickr Feed. This would allow you to control multiple trains on the same 9V track, without needing to do electrical isolation. You would still need to build some sort of sensing (either accellerometer or IR distance sensor or something like that) to make the speed of the trains the same to compensate for motor and wheel characteristics. And you would need to invest in a DCC controller trafo.
> 3 votes

---
Tags: trains
---


# Question
Title: Is there a modern equivalent for windscreen piece 6152?
For a creation I'm building, I am using a white windscreen piece (part ID 6152).

Looks like this piece was last produced in the late 1990's. Is there a modern equivalent that preserves this general shape?

# Answer
> 10 votes
The windscreen you mentioned has been retired, however you can still get it on BrickLink. It is available inexpensively in several colors: http://www.bricklink.com/catalogItem.asp?P=6152

If you want to use a modern version, this wedge is pretty close in shape and is available in current sets: http://www.bricklink.com/catalogItem.asp?P=6153b

As a reference, here are all the LEGO windscreens LEGO ever made. You can browse them by year released and sets they appear in: http://www.bricklink.com/catalogList.asp?catType=P&catString=115

And here are all the wedge elements LEGO ever made. They tend to use these more often these days, most likely because of the stronger/thicker walls: http://www.bricklink.com/catalogList.asp?catType=P&catString=42

---
Tags: piece-information
---


title: How can I build a Lego rubik's cube?

text:
# Question
Title: How can I build a Lego rubik's cube?
How can I build a LEGO Rubik's cube, I have 2 of them, and I've built them several times, but how can I build a LEGO Rubik's cube.

# Answer
There seems to be basically two choices. You can either build a larger version than the traditional cube, or you can build something that doesn't stay together very well.

There's a nice example of a small cube on Sebastians Sand's Brickshelf:

While this looks like it would work, I can't imagine that it holds together through many rotations.

If you are willing to build something a bit larger, there are some good examples available, but it looks like it gets fairly complicated.
> 15 votes

# Answer
Here is a video on how to stick LEGO bricks on to a Rubik's cube.

https://www.youtube.com/watch?v=FrbBZ4EytHs

You're welcome.
> -2 votes

---
Tags: building
---


# Question
Title: How can I remove fast glue (Cyanoacrylate) from LEGO bricks?
I recently bought some second-hand LEGO bricks. Some of these bricks have quick glue on them.

How can I get rid of the glue?

# Answer
According to Wikipedia acetone can help soften cyanoacrylate, but it also dissolves ABS, so you might want to avoid that.

Another website advises for using soap and water, although it seems dubious to me whether it would make any difference, this method certainly won't damage your parts (unless they are electronic or have stickers), so you might as well give it a try.

Heating the CA can also soften it to ease removal, but beware that ABS is also susceptible to melting.

There are also commercial products designed to soften and remove CA glue from various surfaces, but you should always check whether they play nicely with the ABS or would they also soften your bricks.

As a last resort, however time consuming it might be, shaving the glue off using precision blades is a surefire way if you can work with such precision and have the required time. Using sandpaper and polishing after the process can save a bit of time though.
> 2 votes

---
Tags: glue
---


title: Basic bricks in Ninjago Spinners sets

text:
# Question
Title: Basic bricks in Ninjago Spinners sets
Every Ninjago spinner set contains basic bricks of the same color: two 1X2 bricks and a 2x2 flat.

See: http://brickset.com/sets?query=spinners

What is the purpose for these bricks?

# Answer
These parts are used to hold the cards upright as shown in the instructions:
> 4 votes

---
Tags: ninjago
---


# Question
Title: LEGO Mindstorms NXT - NXC compiler for OS X
I need an IDE for LEGO Mindstorms on my Mac, but I only found a few for Linux and Windows but not for Mac. I found NeXT Tools, but the newest version isn't compatible with Yosemite. If I execute it, it will throw an error, so I need some compiler for Yosemite.

Thanks

# Answer
It is possible to use XCode. You need to download the NXC compiler (the linked page says NBC, but it included NXC as well). Then, write a Makefile that calls the NXC compiler.

If the compiler does not work on Yosemite, the source code is available from that link as well.

A detailed tutorial on using XCode with NXC can be found here.
> 1 votes

---
Tags: mindstorms
---


# Question
Title: Large trap door - alternative to door with frame 4595708
I need to build a large trap door, the trap door 4x5 with frame 6x8 is too small for my model. Other doors/hinges seem to have too much resistance and the door doesn't fall by itself, it must be rotated. Do you have any ideas as to which parts I could use? I thought I could use 3 of these doors together, the problem is finding the right counterpart.

# Answer
This hinge combined with a technic pin lets you easily make large trap doors. You can see a train-track-sized trap door in this model using two of these parts. In this model the trap door falls down when you retract an axle that normally holds it up. Other arrangements are possible.

The beauty of this particular hinge is that it is symmetrical, so there aren't two different halves to keep track of, and you can use any kind of technic pin you want. The relatively long plate on it makes it sturdier than some of the older variants like this one.
> 4 votes

# Answer
You can build your own trap door from System and Technic pieces. Use plates for the surface and frame (maybre reinforced by bricks if necessary), and attach one or more (depending on the weight and size) Technic joints underneath. I have no pieces with me at the moment, so I can't show you, but if you need clarifications, I'll look up images of the pieces I'd use.
> 2 votes

---
Tags: building, technic
---


title: How to read the EV3 display

text:
# Question
Title: How to read the EV3 display
Is there a users guide or something similar that describes in detail all the images that one sees on the display? There seems to be a lot of stuff there, but no explanation.

# Answer
For most of the screens, you can find detailed descriptions in the Users Guide found on LEGO MINDSTORMS download page. Additionally, there is some information in the help file of the EV3 programming software.

The best resource I have come across that shows "everything", though, is the *Apps \> General Information: Userinterface* section of the documentation from the lms2012 source code. The source code is officially available from the "Advanced..." section of the LEGO MINDSTORMS download page.

You can also find the compiled documentation hosted at http://ev3.fantastic.computer/doxygen/uiapp.html.

I've included the relevant images below as well in case links break.

Although this shows "everything" it does no have much in the way of detailed descriptions. On the other hand, it does provide some hints to some obscure things that are not documented anywhere else.
> 4 votes

---
Tags: ev3
---


# Question
Title: Where can I learn how to program an NXT using C#?
I've been toying around with my NXT 2.0 set for a few years now and I would like to learn how to program it using C# language. I have no experience in coding and I am definitely not a computer geek. Are there any tutorials that can give me a headstart in this thing?

# Answer
You could start here for example: LEGO MINDSTORMS NXT Tutorials Overview

For a generic C# introduction see here: C# Tutorials or The complete C# Tutorial or C# Tutorial or just do a Google search for "C# tutorial".
> 2 votes

---
Tags: programming
---


title: Would LEGO use recycled plastic?

text:
# Question
Title: Would LEGO use recycled plastic?
I have been studying the application of new recycling technologies because I am concerned with plastic pollution. I have thought of a way to apply new technology differently but the missing piece of the picture was how to find a company that would be willing to work with our city to apply this technology.

With 9% percent or less of plastics being recycled in America because of sourcing and down-cycle challenges, LEGO is positioned to positively transform the way plastics are used and galvanize support for their brand. It would really just take a single industrial leader, operating at scale to make it happen. Others would follow.

If LEGO could transform the way that plastics were produced, and create living wage jobs, would they?

In other words, do they have any motivation to use recycled plastics, or hire American workers, and if so, what motivations?

# Answer
> 4 votes
The LEGO Group has already created clear sustainability goals.

TLG is currently investing money to try to find sustainable and non-petroleum based ways to design LEGO bricks. Here's some info about the new Sustainable Materials Center that TLG is working on:

http://www.lego.com/en-us/aboutus/news-room/2015/june/sustainable-materials-centre

It sounds like they are investing significant money (1 billion DKK, ~150 million USD) and manpower (100 new employees) into solving this problem. They have also made it clear that they want to keep their focus on product quality while exploring sustainable technologies, so it sounds like whatever new plastics they develop will need to be at least as high quality as ABS.

If you are interested in collaborating with them on this, you'll need to get in touch with TLG directly. This is a fan-moderated FAQ site, so you are unlikely to get a response from a LEGO employee. I'd recommend using the "Contact Us" page on LEGO.com.

# Answer
> 0 votes
Unlikely, since TLG prides themselves on high quality, which somewhat contradicts the notion of reused materials. But there are more practical concerns too:

I'm far from an expert in plastic manufacturing, but I guess it wouldn't be trivial to gather the trash, clean it from any foreign materials, sort by color, remelt and recast into bricks.

Also, recycling would be much better suited to high volume items, like packaging materials, where allowed tolerances are an order of magnitude larger.

LEGO bricks have a very high life expectancy, apart from breaking due to excessive forces or discoloration caused by chemical reactions (which in itself makes recycling quite complicated - who would like their "new" white bricks already yellowed?), there aren't any ways that would transform usable bricks into recyclable trash, so even if implemented, the scale and therefore the environmental impact of this operation would surely be negligible compared to plastic bottle caps for example.

---
Tags: plastics
---


# Question
Title: Connecting to NXT Brick via Processing over Bluetooth
I am attempting to control my NXT model via the Processing programming language rather than the provided language based on LabView. When I can establish a connection over Bluetooth, this works rather well, but establishing the connection itself is problematic. It appears to work only every dozen tries or so.

My question is, what are some good troubleshooting steps for this type of activity? I can see the NXT brick in my list of Bluetooth devices on my laptop (Win7 64-bit), and I can even see it in the list of devices when I run a test script in Processing. My laptop appears on the list of devices on my NXT brick, but the connection icon at the top of the NXT window only shows "\<" rather than "\<\>".

I believe I am using the latest firmware version (1.31). The other settings listed are:

AVR & BC4 - 1.01

What else can I attempt to try? I am attempting to connect to other Bluetooth devices (iPhone, Wiimote) but have not found the necessary libraries to allow those connections yet.

# Answer
> 2 votes
You can use any programming language you like to remotely control the NXT provided that it can access a serial port of your computer. The Bluetooth connection on the NXT provides a virtual serial port. You can see this by opening "Devices and Printers" and double-clicking on the NXT (provided that you have already paired it). Then have a look at the "Services" tab in the window that opens.

In the screenshot above, my NXT provides a serial port on COM4. Yours may be a different number.

So you need to do two things:

1. Figure out how to open a COM port on Windows using the Processing programming language.
2. Use the information in the NXT Bluetooth Developer Kit (available from the LEGO MINDSTORMS download page) to send commands to your NXT.

To use other Bluetooth devices with your NXT, you will need to relay the information though a computer to translate it into the commands from the NXT Bluetooth Developer Kit. In the case of the iPhone, you could write a custom program just as you would for a regular computer.

---
Tags: nxt, bluetooth
---


title: Programming NXT color sensor with NXC?

text:
# Question
Title: Programming NXT color sensor with NXC?
Currently I am working Lego robot that solves 2x2x2 Rubik's cube. I am programming Lego Mindstorms NXT 2.0 color sensor in BricxCC.

I already have RGB data with the command `ReadSensorColorRaw`. I heard that it is easier to get the colour from HSL format. I've tried a lot of algorithms, but none succeeded. How I can fix it to work?'

Also I heard that I need to calibrate white balance. How can I do this??

# Answer
> 1 votes
Since you are trying to solve a Rubik's cube, check out the source code for the MindCuber. The solution there is that the values are not actually converted into colors. Rather the raw values are converted to HSV and then sorted by hue. The actual value does not matter, just how close it is to the other values.

The Mindcuber also has a white calibration. This is used to identify the white values and removed them from the list before sorting which is useful since white doesn't have a meaningful hue value.

# Answer
> 0 votes
I'm not entirely sure if you need the raw data, but if you're just looking to read the different colour values, there is a much easier way.

To turn on and set up the sensor, use `SetSensorColorFull(S3);`. Then to retrieve the value just use `Sensor(S3)`. The value returned will be an integer from 1 to 6, corresponding to the following colour values:

```
1 = black
2 = blue
3 = green
4 = yellow
5 = red
6 = white

```

Here is a sample program that will read the current value from the colour sensor and print the colour name on the NXT screen:

```
task main() {
    string sColor;
    int nColor;

    // Turn on the sensor
    SetSensorColorFull(S3);

    while (1) {

        // Read the numerical color value from the sensor
        nColor = Sensor(S3);

        // Determine the color name from its number
        switch(nColor) {
            case 1: sColor = "Black";
            case 2: sColor = "Blue";
            case 3: sColor = "Green";
            case 4: sColor = "Yellow";
            case 5: sColor = "Red";
            case 6: sColor = "White";
            default: sColor = "???";
        }

        // Print the color name to the LCD screen
        ClearScreen();
        TextOut(0, 56, NumToStr(nColor) + ". " + sColor);

        // Wait until the color changes
        while( Sensor(S3) == nColor );
    }
}

```

# Answer
> 0 votes
The following works if you just want the builtin six/seven colors, without any calibration.

```
task main() {
  SetColorSensorFull(S3);
  while(true){
    int value=Sensor(S3);
    // value now contains 1 for black, 2 for blue, 3 for green, 4 for yello, 5 for red, 6 for white, and something else for an unknown color.
  }

```

However, if you want to do proportional control, want more colors, or aren't satisfied with the builtin thresholds, you'll need to use the RGB or HSL values. Here's RGB (Threshold is of course, my own defined struct and my solution to this problem):

```
struct Threshold{
  int minR, minG, minB;
  unsigned int maxR, maxG, maxB;
};

bool InRange(ColorSensorReadType &csr, Threshold &thresh){
  bool in=true;
  in&=csr.NormalizedArray[0]<=thresh.maxR;
  in&=csr.NormalizedArray[1]<=thresh.maxG;
  in&=csr.NormalizedArray[2]<=thresh.maxB;
  in&=csr.NormalizedArray[0]>=thresh.minR;
  in&=csr.NormalizedArray[1]>=thresh.minG;
  in&=csr.NormalizedArray[2]>=thresh.minB;
  return in;
}

Threshold Red={180,20,20,250,130,130},
Green={90,160,90,160,255,160},
Blue={40,100,160,80,150,200},
White={210,210,210,300,300,300},
GroundBlack={0,0,0,150,150,150},
GroundGreen={120,180,120,170,220,160};

task main(){
  SetSensorColorFull(S2);
  ColorSensorReadType csr;
  csr.Port=S2;

  while(true){
    SysColorSensorRead(csr);
    ClearScreen();
    NumOut(0,LCD_LINE1,csr.NormalizedArray[0]);
    NumOut(0,LCD_LINE2,csr.NormalizedArray[1]);
    NumOut(0,LCD_LINE3,csr.NormalizedArray[2]);

    if(InRange(csr,Blue)){
      TextOut(0,LCD_LINE5,"BLUE!");
    }else if(InRange(csr,Green)){
      TextOut(0,LCD_LINE5,"GREEN!");
    }else if(InRange(csr,White)){
      TextOut(0,LCD_LINE5,"WHITE!");
    }

    Wait(10);
  }
}

```

If you want to transform into HSV values, try this:

```
struct Threshold{
  int minR, minG, minB;
  unsigned int maxR, maxG, maxB;
};

struct HSVThreshold{
  int minH, minS, minV;
  unsigned int maxH, maxS, maxV;
};

struct HSVColor{
  int hue, sat, val;
}
void RGBToHSV(ColorSensorReadType &csr, HSVColor &color){
  int maxColor=csr.NormalizedArray[0], minColor=csr.NormalizedArray[0];
  for (int i=1;i<3;i++) {
    if (maxColor<csr.NormalizedArray[i]) maxColor = csr.NormalizedArray[i];
    if (minColor>csr.NormalizedArray[i]) minColor = csr.NormalizedArray[i];
  }
  if (minColor==maxColor) {
    color.val=minColor;
    color.sat=0;
    color.hue=0;
  } else {
    int d = (r==minColor) ? g-b : ((b==minColor) ? r-g : b-r);
    int h = (r==minColor) ? 3 : ((b==minColor) ? 1 : 5);
    color.hue=60*(h-d/(maxColor-minColor));
    color.sat=(maxColor-minColor)/maxColor;
    color.val=maxColor;
  }
}

bool InRange(ColorSensorReadType &csr, Threshold &thresh){
  bool in=true;
  in&=csr.NormalizedArray[0]<=thresh.maxR;
  in&=csr.NormalizedArray[1]<=thresh.maxG;
  in&=csr.NormalizedArray[2]<=thresh.maxB;
  in&=csr.NormalizedArray[0]>=thresh.minR;
  in&=csr.NormalizedArray[1]>=thresh.minG;
  in&=csr.NormalizedArray[2]>=thresh.minB;
  return in;
}
bool InRange(HSVColor color, HSVThreshold &thresh){
  bool in=true;
  in&=color.hue<=thresh.maxH;
  in&=color.sat<=thresh.maxS;
  in&=color.val<=thresh.maxV;
  in&=color.hue>=thresh.minH;
  in&=color.sat>=thresh.minS;
  in&=color.val>=thresh.minV;
  return in;
}

Threshold Red={180,20,20,250,130,130},
Green={90,160,90,160,255,160},
Blue={40,100,160,80,150,200},
White={210,210,210,300,300,300},
GroundBlack={0,0,0,150,150,150},
GroundGreen={120,180,120,170,220,160};

// Define your own HSVThresholds here

task main(){
  SetSensorColorFull(S2);
  ColorSensorReadType csr;
  csr.Port=S2;

  while(true){
    SysColorSensorRead(csr);
    HSVColor color;
    RGBToHSV(csr,color);

    ClearScreen();
    NumOut(0,LCD_LINE1,color.hue);
    NumOut(0,LCD_LINE2,color.sat);
    NumOut(0,LCD_LINE3,color.val);

    Wait(10);
  }
}

```

---
Tags: mindstorms, nxt, programming, nxc, sensor-colour
---


title: EV3 turning in circles

text:
# Question
Title: EV3 turning in circles
New programmer feeling my way around. I set the most simple "steering block" to 25, the power to 50, and the number of motor rotations to 40 or 50.

Then I let it run expecting the bot to go in a circle. Instead it circled around somewhat erratically with roughly the right radius, but without coming anywhere close to following the same track.

Hard to tell exactly what it was doing but maybe the outside wheel on the turn was moving steadily forward and the inside wheel (the slower one) was progressing unevenly.

What do I need to do to get nice clean circles?

# Answer
> 2 votes
It is quite common for the tires to slip and cause this type of behavior. For example, here is a similar question. The answer here is the same.

* Make sure your center of gravity puts most of the weight of your bot on the drive wheels.
* Make sure the tires and the surface your are driving on are free of dirt/dust.
* Use sensors to help compensate for any slippage of the wheels.

If you only want your robot to go in a perfect circle and nothing else, you could fix a beam to the floor on one end an your robot on the other so that it cannot deviate from the circle.

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Tags: mindstorms, ev3, programming
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# Question
Title: Is there a standard distribution of minifigs when you purchase an entire case?
The last couple of times I purchased a case of collectable minifigures, each one had three complete sets (16 x 3), plus an extra 12 remainder of random minifigs. My last case I ordered only had two complete sets, and the remainder of minifigs had a much wider variance (five of one minifig, none extra of others).

Should each case contain three sets, or is it truly random?

# Answer
Every box contains the same distribtion of minifigs. For example see this review on www.eurobricks.com of series 13 has the same distribution as my box. (links to his other CMF reviews are on the bottom of the first post)

For most series boxes contains 3 full sets and 12 remaining ones.

Series 9, 10 & 11 contain only 2 complete sets, with 2, 4 or 6 bags of the same minifigs. These boxes where also available as 'half' with only 30 bags. This way these boxes contains 1 complete serie.
> 2 votes

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Tags: collectable-minifigures
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# Question
Title: Is there a standard scale for building "minifig scale" creations?
I've seen many impressive models built to "minifig scale" (e.g. the enormous **USS Harry S. Truman** aircraft carrier), but is there a standard (or at least widely adopted) scale e.g. 1:60 that these models obey?

It seems any scale based on the height of a minifig won't work due to the fact the minifigs are not well proportioned for people. For example, I stand taller than my car (as do most people) yet trying to build a LEGO car that is less than four bricks high would be extremely difficult and result in an unusual looking model.

Are there any tips on choosing a scale that allows well proportioned looking models, that doesn't dwarf the LEGO minifigures that ride in/on them? Is "minifig scale" dependent on the type of model (vehicle/castle) or generally deemed to be whatever looks about right?

# Answer
It's usually 1:40, based on the minifig size.

However, keep in mind that a minifig doesn't have the same proportions as a full-size human being, so scaling from real-world to minifig-world is not an exact science. Just have a look at LEGO cars, you'll see that they don't really match real cars.
> 6 votes

# Answer
I think what is interesting is that buildings are usually scaled to things other than minifigures.

For instance, a aircraft carrier would be built to airplane's scale, not the actual minifigures.

Most buildings are scaled to the size of the LEGO doors & windows.
> 5 votes

# Answer
Minifigs don't have the same proportions as average humans. They are comparable to a 600 pound male. Based on minifig height, the scale is about 1:45. Based on minifig width, the scale is about 1:32. If you're making a building, you probably want to follow a 1:45 scale. If you're making a vehicle, you probably want to go with a 1:32 scale. One rule of thumb I read is that each pip equals about 1 foot.
> 5 votes

# Answer
Minifigures are not to scale. Lego has a greater emphasis on play then realism, so every thing is scaled to suit the minifigures.
> 3 votes

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Tags: minifigures, scale, moc
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# Question
Title: What is the difference between these two Technic half bushings?
While randomly browsing some LEGO sites, I came across a weird (to me anyway) looking bushing. Its part 4265c. Below is one of the images describing it and the left one I recognize, but the right one I have never seen. It looks like there is some built-in play to the axis.

So my questions:

1. Are the two bushings on the image interchangeable?
2. Are they both really referred to by the same id (4265c)?
3. Is there any practical difference between the two?
4. Are there any specific use cases where the second would be preferred over the first one?

# Answer
They both appear to have the same part ID despite being quite different.

Sariel answers most of your questions in *The Unofficial LEGO Technic Builder's Guide*.

> **toothed half bush with a cutout**
>
> The second variant, the toothed half bush with a cutout, is exactly what its name implies: a copy of the previous version with part of the axle hole cut out, which makes the axle hole large (see Figure 4-13).
>
> This modification was introduced to make it easier for children to take half bushes on and off the axles, and that's exactly what makes it much less popular with builders: These bushes are more likely to shift when stressed than the first variant.
>
> Other than that, it has every quality of the original toothed half bush except that, having been introduced a few years later, it's newer and thus made of strong material.
>
> (Chapter 4. Page 36.)

Pawel "Sariel" Kmiec, 2012. *The Unofficial LEGO Technic Builder's Guide*. 1 Edition. No Starch Press.
> 6 votes

# Answer
Interesting... brickowl lists the right picture for 4265c while peeron lists the left picture.

This leads me to think that both are interchangeable and that the one in the right picture is a more cost-efficient version of 4265c (using slightly less ABS). Lego Pick-a-Brick also shows the version in the picture on the right.
> 0 votes

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Tags: piece-information, technic
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title: LEGO Set 10188 Help on Step 160

text:
# Question
Title: LEGO Set 10188 Help on Step 160
I have the LEGO Star Wars Death Star set 10188. I am stuck on step 160 because when I try to clip the parts into a circle, parts snap off and I can't seem to bend it down. Thank You.

# Answer
> 3 votes
I'd double check that you've got all 16 links in the chain - if you're trying to squeeze it into a circle with less than that it won't fit. Also double check the placement of the pieces from sub-steps 7 and 8.

Finally, when forming the circle, try carefully working your way around from one end, moving completing each bracket before moving on to the next - possible starting with just one click each, and then going back and adding another as needed.

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Tags: instructions
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title: A custom LEGO velociraptor

text:
# Question
Title: A custom LEGO velociraptor
I would like to make a custom paint job on a LEGO velociraptor (to look more like the one in the LEGO Jurassic World game), but I don't want to paint it myself because I can't paint for the life of me so it would look bad and it probably wouldn't move. So I looked for a website to see if I could have one printed but I can't seem to find anything. Could someone help?

# Answer
> 5 votes
In my understanding of the question, you want to take an existing LEGO velociraptor and repaint it, but you are afraid that doing a custom paint job will rub off quickly.

There is no easy solution for this, but here are a few tips:

1. You could send an email to the guys at minifigs.me and see if they would be willing to help you with this, either as a one-off job (but it will cost you) or as an offering they wish to add to their collection. Their contact form is \[here\].(http://minifigs.me/make-me-a-minifig/contact/)
2. You could try and do this yourself. Removing the existing print from a raptor fig should be relatively easy (this article at Eurobricks recommends Brasso and a paper towel/rag/cotton ball) even though that is very mildly abrasive and hence might leave some minor scratches. Brickjournal ran a series of articles back in 2008 about minifig customization - I found this online copy that explains how to give LEGO pieces a new paint color - they recommend acrylic paint. I also found this link describing how to prime & paint LEGO minifigures. They recommend priming and sealing on top of an acrylic paint job.
3. To get the finer details, consider using a Sharpie pen.

Net - Customizing your velociraptor is definitely possible, but there is no "ready-to-go" customization service for this yet. Doing it yourself can be done, but it is not easy nor quick to do this, especially not if you're doing it the first time. Definitely not a job for kids.

# Answer
> 2 votes
If I understood your question correctly, you wish to build a velociraptor yourself, from basic bricks (as opposed to the single functional unit that LEGO introduced as part of the Jurassic World line). In this case I have no idea what search did you do, but just doing a Google search for "lego velociraptor" results in several models of varying proportions and looks:

As for the painting and printing, could you please clarify your question? Why do you wish to paint or print and exactly what?

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Tags: lego-group, customization
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title: Groove dimension of 4216 or 88393?

text:
# Question
Title: Groove dimension of 4216 or 88393?
What is the dimension of the groove of LEGO part #4216 or #88393?

# Answer
> 4 votes
According to LDraw, the slot is 8 LDU wide (1 plate, 3.2mm) and 5 LDU deep (quarter module or stud, 2.0mm). Here's the relevant quads from the LDraw file for reference:

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Tags: piece-information, size
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title: EV3 IR, ultrasonic senosor datasheets

text:
# Question
Title: EV3 IR, ultrasonic senosor datasheets
I want to connect EV3 IR and ultrasonic sensors to my Arduino. Unfortunately could not find any good documents describing how to use/control them.

Could you please help?

Thank you very much.

# Answer
LEGO has released the source code for the EV3, so you can see how it works. Look for the "EV3 Firmware Source Code" at http://www.lego.com/en-gb/mindstorms/downloads.

You can also find the documentation generated from this source code at http://ev3.fantastic.computer/doxygen/index.html. In particular, these sensors are documented at http://ev3.fantastic.computer/doxygen/UartProtocol.html. But beware! The documentation on the UART sensors is not 100% correct. When in doubt, trust the actual code and not the comments.

And finally, don't forget to search for existing Arduino libraries for these sensors. Unless you want to implement your own library just for the sake of doing it yourself, you can save yourself some work. For example, you can find a library at https://github.com/lawrie/EV3\_Dexter\_Industries\_Sensors/tree/master/EV3\_arduino from one of the leJOS core contributors.
> 3 votes

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Tags: ev3, electronics
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# Question
Title: Is it possible to change the language in the EV3 Education software?
I have only 1 language in menu "Edit - Change language":

Is it possible to add another language packs to EV3?

# Answer
I see that you have the Education version of the EV3 software. I would suggest checking with the LEGO Education support. It may be different from the retail version in this regard.

For the retail version:

From the MINDSTORMS Support page:

> 3.3 What languages are the LEGO® MINDSTORMS® EV3 Home Edition Software available in?
>
> You can download the EV3 Software for free from LEGO.com/mindstorms in the following languages:
>
> ```
> Chinese (Simplified)
> Danish
> Dutch
> US English
> French
> German
> Japanese
> Korean
> Russian
> Spanish (ESSA)
>
> ```

These are available via the respective download pages. For example, the US English version is downloaded at http://www.lego.com/en-us/mindstorms/downloads/download-software. However, the installer is for the whole program. There are not "language packs" that contain just the languages.

To test, I installed the German version in addition to the English version and now I have two languages available on the Edit menu.
> 2 votes

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Tags: ev3, education
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# Question
Title: I need a block that can combine a movement program with NXTbee radio
I am a student. I am working on a science project using LEGO Mindstorms robots enhanced with NXTbees creating a mesh network.

My engineering mentor has me using LabVIEW. I am trying to find a block that can combine a movement program (senses a block in the robot path, stops, then change direction) with NXTbee radio.

I want the NXTbee to override the Bluetooth in the LEGO Mindstorms program. I have tried a number of avenues seeking help, but they haven't worked out. Can anyone help?

# Answer
> 1 votes
There is a LabVIEW block for the NXTBee. For example, here is a tutorial from the manufacturer.

# Answer
> 0 votes
For mesh you will need the series 2 XBee's I think. It is doable by putting the series 1 to broadcast mode, but series 2 can do real mesh.

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Tags: nxt, programming, bluetooth, labview
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# Question
Title: How can the new LEGO pneumatics be used for trains?
LEGO came out with new pneumatics. Since I'm a train guy (my wife is more into technic and already saving money for the Mercedes ;)) I was wondering, how could we apply the new things for Trains?!

# Answer
> 2 votes
The "obvious" way would be using pneumatic cylinders in steam engines, but they would be probably way too large and out of colour. The air supply would also not be trivial, hoses would look and work awfully, and integrated compressors would take up a lot of space in addition to the usually installed electrical components. This could be eased by building a separate wagon (or more) for them and routing the electrical current and air hoses between the wagons and the engine.

For some examples watch these two videos.

Another way would be building tipper wagons that use pneumatics, then you'd probably have less color clash, the same with using pneumatics to open and close the doors on passenger carriages (maybe linking more doors to a single cylinder).

A pneumatically powered rail crane would also look and work great, provided that you can fit all the control valves into the structure.

For stationary applications track switches are mentioned in the other answer, but you can also power boom gates at level crossings and cranes at cargo terminals. In these cases you would have a much easier time fitting all the components, but the hoses could become way too long.

# Answer
> 4 votes
The first thing that came up in my mind when reading your question is: operate switches on your track using pneumatics. You'll require a lot of hose, and would need to experiment a bit with how long the tubes can be without losing too much pressure, but the actuators could operate the switch handles easily, and you can route the hoses under buildings or even under your train table.

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Tags: trains
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# Question
Title: What can I use to glue LEGO bricks to Metal?
So I have no roof lining in my car and instead of replacing it with another carpet I thought covering it in Lego would look pretty cool

What would be the best way to glue the LEGO to the metal of my roof?

I've got a hot glue gun but not to sure it'll work.

# Answer
> 2 votes
This sounds like a job for "Amazing Goop." It's available at Home Depot and other big stores, at least in the US. There are a few varieties, including one for automotive use. It pretty much sticks anything to anything, and once cured, it's on for good. I've used it for gluing LEGO pieces onto a curved metal surface, and was very happy with the results. It's a little tricky to work with because it's such sticky stuff, but once you get the hang of it, it's not too bad. What's great about it is you have a fairly long working time to get the glue on your pieces and get them into place before it dries out. Also it is very strong, and stays flexible, which will be essential to hold up to the vibrations of a car. One trick will be holding things in place while the glue cures. Maybe try doing small sections at a time, and using tape to hold the pieces in place. Also consider gluing pieces onto baseplates, and then gluing the baseplates to your car roof. It has a strong odor, not terribly unpleasant, but you might not want to drive your car for a few days after gluing. Good luck!

# Answer
> 0 votes
Try using double sided tape. But I recommend using the soft stuff so if you hit your head it's not as bad.

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Tags: glue
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# Question
Title: Do you use the plastic buckets for purposes other than organizing your bricks?
We have several bucket sets like #5560.

Now that our collection is growing, it's becoming harder to find what we need in the buckets even though we have them sorted by color. Plus they are in a rather tall, wobbly stack in a corner and they keep getting knocked over.

So I'm thinking of organizing the bricks into small drawers and getting rid of the buckets entirely. But that leaves me with a million ugly pink and blue buckets that have no purpose.

I'm big on repurposing items rather than throwing them away. So tell me: what can I use these buckets for rather than storing LEGO bricks?

# Answer
> 1 votes
Well the buckets themselves have value. If you can't use them you could sell them to people who want them.

Your example set #5560 has an original box only listing on BrickLink, as do many other of the brick boxes, run a search for "brick box" you'll find lots.

The prices vary from a few dollars, to ~$20 for you example. They don't seem to be big sellers, but there are some sales.

If you have a lot of them and/or you want them gone quicker set up an eBay listing for all of them.

# Answer
> 1 votes
If you can't sell them making sand castles with them is an option I suppose. I would stick them in the loft for the future though if it were me. Simply because if you ever sell your LEGO boxed sets are always better and command a higher price.

# Answer
> 1 votes
I don't find them very useful for storing bricks, but have used them as interim storage during a massive sorting project. Also used 2 to grow tomatoes last year, but they tipped over frequently. Best use I've found is as a small wastepaper basket. (I recycle most paper, but I don't know what else to call a small trash receptacle.)

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Tags: piece-information, storage
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# Question
Title: How do you construct odd-angles on buildings
I was thinking of building a model of the famous Castillo de San Marco located in Saint Augustine, Florida. A small bit of research shows that Legoland has a replica (flickr link) and that there are other castle MOCs with similar odd (non-90\*) angles.

I saw one person build them with hinge-pieces (like this MOC of Fort George) but that doesn't feel authentic.

My question: how did they build those non-90-degree angled walls and retain the points?

# Answer
Scale is the obvious answer. The Legoland model is huge, which means you're not seeing the brick-level quantisation as easily (quantisation is most obviously seen in mosaics but that works in 3D too).

Getting the same effect at smaller scales usually means a lot of SNOT and using sloped bricks. These days there is a huge range of slopes available, from 4 high, 1 deep to 1 high, 6 or 8 wide. If you flip those on their side (SNOT) that gives you a wide range of angles. But of course this can be very expensive as you end up using a lot of rare sloped parts. For micromodels this can be the only workable approach, and a carefully selected stack of cheese wedges can look great.

A simpler SNOT approach is to use tiles with hinges to minimise the discontinuities at the corners. Instead of a brick width (5mm) you have 1/3 of a brick height (8/3 mm = ~2.6mm), and it's often possible to move things so that there's no obvious discontinuity, just the tile end that's at 90° rather than the actual angle. If you're building a brick or stonework wall using a lot of 1x2 tiles with 1x1 tiles as the endworks can be very effective, especially if you mix the various shades of grey. Like this: http://www.flickr.com/photos/legoarts/5548508462/ Modifying that technique to have a backing plate, hinges, and extending the plates 1 stud past the edge of the plate to reduce the "height" offset works well.

Another approach is to give up on studs altogether and use Technic beams. That gives you rounded corners instead, but can be effective with larger models (but the colour palette is limited and it can be expensive). This allows you to easily build round structures and varying curves.

For smaller curves it's possible to bend Lego walls. If you search for lego circular walls there are a lot of images. The basic technique is to mix in more round elements as the curve gets sharper. I've also seen a Lego wave built this way out of transparent 1x2 plates.
> 12 votes

# Answer
Yeah you pretty much have the two choices you outlined... hinges or make it so big that the squareness of the bricks melts into nothingness at that resolution.

OR... build your structure over tiles and use single studs, like at the ends of the ends of the hypotenuse of a 3-4-5 triangle... but that will be seriously flimsy the higher you build the walls, unless you use hinges.
> 1 votes

# Answer
A straight forward wall of Lego bricks will have some pliability that can be used to a Master Builder's advantage. I did manage to find a YouTube video that sums it up nicely. https://www.youtube.com/watch?v=9U-n1NZYNpI
> 1 votes

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Tags: building, moc, castle, angles
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# Question
Title: Can I safely dissassemble a 74569 motor (the old, fast 9v one)
I have an ancient 74569 motor:

Unfortunately, it's broken: The shaft spins freely by hand, but when I connect power to it, it doesn't spin at all.

I would like to see if I can just open it and place a new DC motor inside, but without breaking it if possible – has anyone opened one of these before or posted instructions as to how?

I was thinking something like this motor:

would fit inside it, but of course I would check the dimensions first and make sure it's not a bad solder joint or something else.

I see Philo has disassembled its replacement here, but I don't see anything similar for the 74569.

# Answer
> 12 votes
Well, I opened it up without much success, and took some pictures of the process:

At first I tried pushing/prying the light grey tabs away from the dark gray "bottom", but those weren't budging

So plan B: wedge it apart:

It was opening, but I was also distorting the plastic in the process - perhaps if I had a hot air station or something, I could have of softened it, but eventually it gave way:

I didn't open it just yet, but rather went to work on the other side - I made my way around from the front/back, as it seemed easier than going at it directly from the side. Anyways, it was much easier than the first side, and I got it open:

Nothing fell out, and I didn't rip any wires out by opening it, so I proceeded to take out the motor:

This is where something finally fell out - there was a little "spacer" disk (visible in the top-left) that was between the end of the axle and the back side of the plastic housing.

After that, the electrical connection assembly slid off easily - not sure what the component is or how to test if it's good, but it seems like it was made such that it's replaceable - no solder was used, just metal "crimps"

This is where I found out that the motor itself is good if I just connect a battery to it directly, so I think I may end up drilling some holes and have a DIY wire coming out the back - all the contacts on the inside seemed good and clean, but unfortunately the bottom seems to be rusted to the point of not making contact anymore.

I think it will snap back together just fine, but it will have scars from the surgery.

For anyone curious, the motor itself is a mabuchi 70586, but any FC-280 motor should fit.

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Tags: motor, customization, repair, disassembly, discontinued
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# Question
Title: Which program do I use to program my rcx 1.0 or 1.5
I am getting an RCX and I know it is ether a 1.0 or a 1.5. Which program do I use to program my RCX?

# Answer
> 1 votes
You really have two major choices:

1. Try to acquire, install, and run the official Lego software for the RCX.
2. Use some third-party tool to develop programs that can be uploaded and run on the brick.

(1) is getting harder and harder to do on modern computers. Personally, I would not bother trying.

(2) means choosing some third-party tooling. The other answer that refers to BricxCC falls into this category. (You should check out the "RCX" section at that link for more information.) Many of the third-party tools for the RCX brick are pretty much no longer under active development.

But this does not mean that they don't work, or aren't useful.

Some decisions you need to make are: do you need an IDE? Are you comfortable at the command line? What platform will you be hosting the development tools on? Do you want to use the default firmware, or use a third-party that replaces the default firmware?

For example, there is a tool called NQC which is a C-like language and brick API with a facility for uploading compiled brick programs and firmwares to all RCX bricks. It can also set the clock, launch specific programs stored on the brick, and even use the brick as a datalogger. It requires an RCX 1.0, 1.5 or 2.x compatible firmware.

LeJOS is a tiny Java compiler and runtime that needs its own firmware which it loads onto the brick. I think people have figured out how to use Eclipse as an IDE for LeJOS.

Full disclosure: I maintain my own fork for NQC on GitHub, and I'm pretty sure it is the only fork under semi-active development. If you need official firmwares for the RCX brick, I've included them in this project as a convenience. Remember that you can use *any* compatible firmware on a 1.0 or 1.5 brick. That is, if you want a 2.x brick, just install the 2.x firmware.

# Answer
> 0 votes
I like http://bricxcc.sourceforge.net the best for the RCX! Keep in min that the RCX will loose it's firmware if your batteries are empty or - when powered via 9V - it loses it's power.

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Tags: mindstorms, programming, rcx
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# Question
Title: How to design ackermann steering with lego wheel bearing front?
I wanted to use a steering system based on the 11949 part:

But I am not sure how to use it in an ackermann system \- I would like to be able to have drive and suspension on the wheel, and this piece seems like the only "reasonable" solution for combining the two into something that is relatively compact + sturdy, so is there any possible way using this piece?

# Answer
> 3 votes
Here is a possible implementation using this exact part: Video .

There are also several other solutions with different pieces if you need more inspiration or explanation: Animated GIF, 4 wheel steering, Top-down view.

# Answer
> 1 votes
In the Ackermann system the lines through the rotating point of the wheel hub and the trackrod joint intersect on the rear axle. This works when the trackrod lenght is shorter than the hub turning point distance.

For this part to work, you need to have a fixed ratio between axle track and wheelbase. So a long narrow car won't work and a short, wide car won't either. Find the ratio by extending the line with a thead or string.

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Tags: building, technic, steering, mechanical
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# Question
Title: Can the rcx work without the infrared tower
I'm getting a rcx 1.0 or 1.5 and it's not coming with the tower. Can I still program it, using some sort of cable?

# Answer
No you can't. But IR towers are pretty cheap, especially the older serial ones (you have to add an USB to serial converter to use the latter version on modern computers)
> 2 votes

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Tags: mindstorms, rcx
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# Question
Title: Is LEGO Junior compatible with regular LEGO?
Does LEGO Junior fit with regular LEGO? Say for 8-12 year olds? I want to make sure it is not obsolete and can be used as the child grows alongside the LEGO collection.

# Answer
Yes. These sets are fully compatible with other LEGO sets.

LEGO Junior is simply a theme within the LEGO System (just like City or Star Wars). It uses exactly the same bricks as regular LEGO. The models in Juniors sets tend to be simpler and use more basic bricks, but the bricks are all compatible.

The main "incompatibility" within the LEGO System is from DUPLO to regular LEGO, but there is even quite a lot of interoperability between these as shown here:

Are DUPLO blocks compatible with LEGO blocks in any way?
> 5 votes

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Tags: compatibility, juniors
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# Question
Title: Is it possible to use DUPLO bricks in LDD?
Is there a way to import DUPLO bricks to Lego Digital Designer? Or is there another way to make DUPLO build instructions?

# Answer
LDD is a closed world where people can't add its own parts. If you want to create Duplo building instructions you should use LDraw that has many Duplo parts in its library, and allows you to create the missing ones if needed.
> 6 votes

# Answer
Short answer is no. Maybe they will add it in the future, though.
> 1 votes

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Tags: duplo, ldd
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# Question
Title: What is wrong with a Lego pneumatics system that won't go?
I own a LEGO Technic Unimog U-400 (part number 8110) and have been very pleased so far with the performance of its pneumatic system. However, after storing for just a month or two (after a good 5+ months of hard use), the pneumatic actuators in the crane did not work, even with brand new batteries. I disconnected all of the hoses and felt that the actuators had more friction than they had previously had when the model was working well, which led me to oil them with vegetable oil, along with the pneumatic piston pump.

When I reconnected all of the hoses, switches, connections and tried it out, the second actuator (the one controlled by the middle switch) and the third actuator (the one that powers the claw) still didn't work, while the first actuator (the one controlled by the first switch from the left) worked as good as new. I have checked and double checked the connections. What is the problem here and how can I fix it? Apologies for bad grammar and/or bad formatting.

EDIT: I tested several times and the first cylinder actually isn't working well either. So really none of the three is working now.

# Answer
I was going to recommend lubricating the pistons, but seeing you already did exactly that, I can only say you should try to isolate the source(s) of the problem.

Since you have at least one working cylinder, the compressor and the feed tubes should be all right. This leaves the following possible points of failure: switches, subsystem hoses, working cylinders. Try disconnecting the hoses from the switches to see if the valves work well, and try connecting the compressor directly to the hoses the valves control to check the individual pneumatic circuits.

If a hose has developed a leak, you can also find it using a long hose (to protect the electronics) that is known to be leakproof and a bowl of water.

If the pistons are proven to be stuck, you can try the steps outlined in this answer.
> 2 votes

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Tags: technic, pneumatic
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# Question
Title: Could I do datalogging in Mindstorms EV3 Home edition?
Apparently datalogging is an integrated part of the educational EV3 software. But I got the Home edition. Is there some module or thing I can use to get datalogging functionality in my Home edition?

Or do I need to build it myself?

# Answer
Data logging is one of the things you are paying extra for when you purchase the Education software. Data logging is turned off in the Home version frimware and there is no means to configure data logging using the Home version software.

The firmware is open source, so technically, you could download it, figure out how to build it and turn on the data logging in the firmware, but then you would still need to reverse engineer a way to configure it.

If you don't need a very high sample rate (10-15 samples per second or less, probably), you could come up with something using an existing remote control library to log the data via USB or Bluetooth. For example, LeJOS and MonoBrick both have remote control libraries that would make it easy to write your own data logging program.

For a higher sample rate, you could write a program that runs on the brick using a 3rd party firmware/SD card image.
> 3 votes

# Answer
Actually yes, you can do data logging on your home edition. The firmware is capable to run programs that have been created on the education edition and contain the block "Data logging". In this block you define which sensor is logged etc. When the program runs it creates a log file on the brick. This file contains the logged data. The file contains some binary data for each log value, you have to figure out the format of it to change it to readable data.

Once you open a program containing the "Data logging" block on your home edition, you will be able to copy and change this block in any way.

Here is a Project containing the "Data logging" block: http://1drv.ms/1EcmjGD
> 2 votes

# Answer
Yes you could. If you can get your hands on the education software, you can upload the EV3 education firmware onto the home edition brick. Here are the steps:

* Shut off brick
* Hold down right and middle buttons
* When it says updating..
* Then plug into computer with the educational version of software
* Open up Tools
* Firmware update
* Click on firmware update….choose recent version
* Click download

Tried it on my home EV3 and converted it to education.. Now data logging is present and works.
> 1 votes

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Tags: mindstorms, ev3
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title: What is this cylinder like part?

text:
# Question
Title: What is this cylinder like part?
I found a pair of these among some parts I bought. It looks like some sort of cylinder, which could hold an axle for a piston.

Is that correct, and how would I use it then?

# Answer
> 5 votes
This is one half of a "hydraulic" cylinder used like in the bucket of 7685-1: Dozer.

This element is Fric. Element, Cylinder and used often used in combination with Stick 6M W/Flange

# Answer
> 1 votes
This, at least as far as my experience goes, is used simply to create extra friction in joints; to make something poseable yet stiff and able to hold its position. Sorry no pic, but a good example is the 8996 Scorpio XV1, a walking machine that uses these to keep the legs stationary unless you actually want to move them.

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Tags: piece-information, part-identification, pneumatic
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# Question
Title: How important is a center differential on a 4WD model?
I am looking to make a 4WD, single-engine powered vehicle, and I have seen others such as this which use three differentials to distribute the power to all 4 wheels:

http://www.eurobricks.com/forum/index.php?showtopic=79535&st=0

I am not quite understanding the need for the center differential - what would happen if you simply had one gear drive two followers, i.e. one for the front and one for the back? traditionally a differential is used when one side would spin more/faster than the other, such as when a vehicle is turning, but I am not imagining a situation where the front end will travel more than the back end, so why was it designed like this?

P.S. - yes, there is all sorts of discussion in that thread already about the center differential, and the tldr version is that it's dead-simple to replace if you want to, and many people have their own opinions, but not so much "why" or where the forces go/what it would look like if you do remove it

# Answer
> 3 votes
There are all kinds of situations where the front and rear axle may not rotate at the same speed. Imagine for example a bicycle taking a turn while remaining vertical. When viewed from the top (using a planar projection), the bicycle rotates around a point that's at the intersection between lines perpendicular to each wheel. Here's an ASCII-art illustration of the situation:

```
   / front wheel
  /.
 /    .
         .
  |         .
  | - - - - -  x rotation axis
  | rear wheel

```

The front wheel is further from the rotation axis than the rear wheel, thus it moves faster relative to the ground. This is the same with a four-wheeled vehicle : the speed of the center of both axles relative to the ground is not the same when turning, hence the center differential. The smaller the turn radius, the more difference there will be between axle speeds.

# Answer
> 3 votes
Well, the center diff allows the front and rear axles to turn at different speeds, which is useful to put less stress on drivetrain parts that are constantly moving around. However, for a Lego model it is probably not required, since it most likely would not move at speeds required to necessitate one. Building one in would add realism, but you would need to keep in mind that with a center diff, the torque all tends to go to the axle with the least traction.

EDIT: Why the front and rear axles sometimes move different speeds, why it matters

Imagine a four-wheel-drive vehicle, with a center diff, moving at a decent speed. It encounters a bump in the shape of a half-sphere, approximately 2 inches across, on the right side. The right front wheel will encounter the bump first. As the vehicle drives two inches over the bump, the rear wheels both travel two inches. However, the right front wheel, following the shape of the bump, travels pi x 1 (the radius of the bump) inches, or approximately 3.1 in. Since the right front wheel covered a farther distance than the rear wheels during the same period of time, it went faster than they did. This translates to a slight difference in speed between the front driveshaft and the rear one, which is easily handled by the center diff. However, the same scenario applied to a vehicle with no center diff could bend or break the driveshaft, as the rear section and front section try to go at different speeds. At LEGO scale, however, this difference could probably be absorbed by the flexibility of LEGO parts without incurring any damage.

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Tags: building, technic, design, gears
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# Question
Title: Linear Actuator of the boom of 42006 jams
I just built a 42006 excavator, and the Linear Actuator jams such that it can't be rotated. I think that the overly sharp angle of the u-joint at the top of the boom is the reason.

Is there a workaround?

# Answer
> 2 votes
First off, you should check the instructions to see if you made a mistake before going into some long repair method. Even if you find no mistake, what I would do is disassemble the entire crane assembly and then reassemble it; this would fix problems you may not have noticed. Another thing you could do is remove the actuator and fully extend and retract it a couple of times. If you feel any extra friction while doing this, than the actuator might need lubrication.

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Tags: technic
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# Question
Title: Where can I get a large number of LEGO bricks cheap?
Yes, I see other people's amazing MOC's all the time, and think, "man, I could totally do that if I had enough bricks." The problem is, I don't really know where to look for a whole bunch of LEGO bricks that aren't in set form. I would really like the pile to include normal and Technic bricks, as well as some specialized parts such as gears, transmission pieces, wheels and tank tracks, but don't need any minifigure parts.

# Answer
MOC-ers use BrickLink.com, the Unofficial Online LEGO Marketplace. It is similar to eBay in the sense that buyers and sellers are from all over the world, but BrickLink is only for LEGO. All elements are neatly organized into categories, and every LEGO element ever made is catalogued. Link to BrickLink Catalog Page: http://www.bricklink.com/catalogTree.asp?itemType=P

You can build up your Wanted List, then purchase the pieces you need from various sellers. (By building a Wanted List you can find sellers who have most of the items you need, thus reducing shipping fees.) Most BrickLink sellers have very reasonable prices and excellent service - they are LEGO fans themselves. Just make sure you check their feedback and terms before purchasing.

BrickLink is a MOC-er's heaven. :)
> 2 votes

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Tags: shopping
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