How to Build a Simple Robotic Arm From Lego Mindstorms NXT?

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Introduction: How to Build a Simple Robotic Arm From Lego Mindstorms NXT?

Today, I will tell you how I built my robotic arm from Lego Mindstorms NXT.

In fact, I wanted to build a robotic tripod for my camera. I found out, that it's more difficult then it looks. After some experimenting I build this simple robotic arm.

I you want to build it too, you need:
- Lego Mindstorms NXT kit
- a computer
- time...?

There are only two rules you have to follow while building ANY robot:
1. rule: KISS (Keep it simple, stupid!);
2. rule: "The triple-F" rule a.k.a. FFF (Form following function!)

Step 1: Constructing the Base

The base is probably the simplest part of the robot to build. It's just a platform from the robot to stand on. You have to make sure, that it's long and wide enough. The center of gravity must be somewhere on top of the base, if possible, in the middle. Else wise, the robot will fall.

The base (in our case) are just a few beams that support the robot. More advanced robotic arms have motors in the base. These motors than move the arm, without moving themselves. Usually, the base has a motor that rotates the arm, but my arm rotates itself.

You can be much more creative with the construction of the robot then I was.

Step 2: Building the "rotation Module"

This is one of my rare robots that are built from modules. My robotic arm has three modules; one of them is the "rotation module".

It's very simple. It rotates the arm left and right and supports the other two modules. It's based on Matthias Paul Scholz's 90 degree join at:
http://mynxt.matthiaspaulscholz.eu/robots/motor90/index.html

Step 3: Building the "tilt Module"

The second module is the "tilt module". It's placed on the top of the "rotation module". Basically, we have a large gear (which doesn't turn) and a small gear which is driving around the big one. The gear ration is 1:10. That way, the arm can be more precise.

On top of this module there is a small platform, to which the claw is attached, but more about the claw later!

Attaching the two modules together couldn't be simpler. They are held together by a single shaft/axle, around which the "tilt module" spins. The arm can tilt for nearly 90 degrees, that's a lot!

Step 4: The Claw Module

This is the simplest of three modules. All it does is open and close the most basic kind of claws. This module is attached to the platform on the "tilt module".

I'm really sorry, but I'm afraid that I can't tell you much more about it. Pictures tell everything...

Step 5: Attaching the Sensors and Wiring

I used three sensors: light sensor, touch sensor and sound sensor.

The light sensor (Port 3) is located on the claw and lets the robot know, if the ball is there or not (and can recognize the "color" of the ball). The other two sensors are located on the platform of the "tilt module". Touch sensor (Port 1) serves as a sort of a button for me to press while the sound sensor (Port 2) measures the noise level (so I can give the robot commands with a clap for example).

At first, I wanted to include the US sensor as well, but I realized that it's relatively useless. You can still see it on one of the photos, but I removed it afterwards.

Now all that is left to do is the wiring. You must make sure that the wires do not disturb the movement and function in any way. You must also consider wire lengths for each sensor or motor.

Wiring (my robot):
- touch sensor -> Port 1
- sound sensor -> Port 2
- light sensor -> Port 3
- "rotation" motor -> Port A
- "tilt" motor -> Port B
- the claw -> Port C

Step 6: Attaching the NXT Brick

The NXT brick plays the vital role in Mindstorms NXT robotics, so you have to have it somewhere on the robot (or at least somewhere close). In my case only two brick hold together the NXT brick and the robot's base. It's very practical to have it on the base of the robot, 'cuz that makes the robot much more stable.

Step 7: Decoration and Finishing Touches

When you are pleased with how your robot works, you can put some effort into robot's looks. (Just remember the Triple-F rule!) I usually just put some of those odd orange bricks on the robot and that is usually that.
You can be much more creative...

Step 8: Programming

There are 5 programming languages you can use: NXT-G (default language), NXC (not exactly C), Robolab, Robotc, pbLua and NXJ. I used NXT-G (however I a bit tired of NXT-G and that's why I am trying to run away from Mindstorms...).

You are very free with your programming, that's why I won't talk about the programming any more.

Step 9: THE END

So, that's that! Here is a short video!


http://www.youtube.com/watch?v=VrfNUhzBoww
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    179 Comments

    Is there any part you can substitute for the curvy claw grabby things? I dont have any

    Hello, how you all, i am working on a project that is a humanoid robot on lego mind storms nxt 2.0.i am doing coordinate based locomotion . can any body help me in developing the nxt 2.0 software program for the purpose, please.

    That is very cool!!

    I'm so gonna build this! I plan on getting a NXT set in the next few months. So excited!

    Did you use an education set to build this? Because this can't be built with a 2.0 set without a ton of modifications or by trying to use some Technic parts. Also, the link you provided is now invalid, so there is no way to follow those instructions. It would help if you put a disclaimer at the beginning of the instructable to let people know this is old and not complete, and what kind of Mindstorms set is needed (or added-on parts) in order to build it. That way, no one will start building this and then realize they can't complete it (like I just did).

    Did you use an education set to build this? Because this can't be built with a 2.0 set without a ton of modifications or by trying to use some Technic parts. Also, the link you provided is now invalid, so there is no way to follow those instructions. It would help if you put a disclaimer at the beginning of the instructable to let people know this is old and not complete, and what kind of Mindstorms set is needed (or added-on parts) in order to build it. That way, no one will start building this and then realize they can't complete it (like I just did).

    where do you get that little thing that powers it and has the controls on it

    1 reply

    its the mindstorms ntx brick, its the "brain" for the whole robot, it comes with the nxt kit

    I feel like this would probably be more fitting for the NXT Builder's Log, but it is definitely AAAWWWEEESSSOOOMMMEEE!!!

    me 2 :(
    u can still do just change programming

    pretty simple to correct all u have to do is use the weird longshortturnlittlepiecethingymaajigy for claws if u gmd lol u probally wont understand what im sayig. just basically make a few subs for pieces

    no its just that the parts used are different, sound sensor, gears, claws...
    well not claws because we have the angle thing.

    me too *waaaah*