Help! Modifications on 3pi robot

Hello I have modified the 3pi robot changing the 30:1 motors to 10:1 motors in order to run more and the robot doesnt work proparly. Im using the demo programs and i dont know why with this changes of the motors the 3pi doesnt work proparly. What changes do i have to made to the demo programs in order to work with 10:1 motors os 5:1 motors? Thanks.

Can you describe what the problem is? I don’t know exactly what you mean by “doesn’t work properly”. Could it be that one or both motors are in backwards? In general, the 3pi could go a lot faster with those motors, so you might need to turn down the speed settings in any program that you try using.

Thanks for replying paul. The proble is that it makes circles when i turn it on and doesnt follow any time the line with the demos program (pid and not pid). I also have modified the speed down in order not to go very fast but it also doesnt work :(. Do you know if i have to modified any part of the code? Thanks


I don’t expect the 3pi to work with the 10:1 motors; if it does, it will be much more difficult to control since acceleration will be a lot lower (imagine just having fifth gear in your car). If you pick it up and can command the motors to turn in the correct directions, the 3pi is working, in which case it will be up to you to make the software handle the lower acceleration. Just lowering the speed setting might not cut it since you would be left too little power to even start moving.

- Jan

oh i see… :frowning: and it can be made anything more in chasis or hardware to improve the speed? The competitions i see reach the 1.6 m/s and pololu is only 1/2 with the 30:1 reduction…Do you know any other plataforms like pololu in which i can reach that speed or more? Thanks.

You should be able to get to about 1 m/s with the stock 3pi, so if you’re only seeing half of that, you’re already getting limited by your software, so you might work on that more before changing your hardware. I do not know of faster complete robot kits, but you could make something faster using the parts we have available. For instance, you could use the 30:1 or 50:1 HP motors with bigger wheels. Getting the sensors farther from the wheels will also make the control easier.

- Jan

I agree that it’s going to be hard to make the 10:1’s work with the 3pi, if it’s even possible. A good place to start would be to write a program to gradually increase the motor speed, displaying it on the screen, and pay attention to when the 3pi starts to drive. With the 30:1 motors, my 3pi does not move at all below a speed setting of about 20; with the 10:1 motors, this starting point might be much higher.

If you do this, could you tell us when they start moving and what happens at a speed slightly above the minimum speed? It’s possible that your 3pi will always be either stuck or going uncontrollably fast.


Hi paul, thanks another time. Be sure i would inform all you about the new tests with the motors. Thanks for all your help.