Motors example problems


#1

My BrickPi is an advanced one. And I have the same trouble: the motor is not moving. The sensor inputs do work, the encoder is also working when moving the motor manually. Measuring the black and white line while running the motor test in python shows a changing voltage. Its the same with battery and 9v power supply.

Does anybody have a hint what is wrong or what I can do to get the motor running?


#2

Hey Pingineer, I moved this to a new topic as that one is getting confusing.

Ok, so it sounds like you might have a bum motor chip. It’s unlikely that both motor chips are bad though. Can I ask a few quick questions:

  • Can you describe what you’re doing with the “black and white line”? What voltage are you measuring?
  • What happens when you run one of our motor test examples? I assume in python?
  • Just to confirm: your other sensors (like a touch sensor or something) are returning correct values? It sounds like you’ve run a few example programs and the motors are the only thing giving you trouble?

#3

Hey Pingineer, I moved this to a new topic as that one is getting confusing.

Ok, thank you.

Ok, so it sounds like you might have a bum motor chip. It’s unlikely that both motor chips are bad though. Can I ask a few quick questions:

Sure.

  • Can you describe what you’re doing with the “black and white line”? What voltage are you measuring?

I attached a voltmeter instead of the motor to that both lines. Then I started the python example “LEGO-Motor_Test.py” for the motor. I can measure a voltage depending on the motor speed (changed in the python code). Up to 8.6 volt at a speed of 255. The example changes the direction of the motor and by that the voltage is changing from plus to minus and back.

  • What happens when you run one of our motor test examples? I assume in python?

See also above. The motor is not working on any port - I changed the code to program each port. I found out that the voltage is breaking down to 0 volt when the motor is attached.

  • Just to confirm: your other sensors (like a touch sensor or something) are returning correct values?

Yes. The touch sensors are working fine. As well the encoders of the motors. I can see the value of the encoder variable counting when I turn the motor manually. That ensures me that the BrickPi is working. The other sensors I have to check but I think it will not give additional information on my motor problem.

  • It sounds like you’ve run a few example programs and the motors are the only thing giving you trouble?

Right. But only the power output for the motors (see above). I tested that with three different LEGO motors and checked the motors with the mindstorms. The motors are ok but all of them do not work with the BrickPi. I used different power supplies (Battery and stabilized power source).


#4

So, could you have a bum motor? Is there a way you could try a second motor, not the one you’re using?

I can’t think of why this would happen otherwise. It sounds like everything else on the BrickPi is working properly. The chip could be fried though, if you can try it with one other motor and just see if that’s the issue, we could probably call it fried and try to setup an exchange.


#5

Ok. I did the following now: I connected the motor with two test cables directly to the pins 3 and 6 of the SN75441 which are the outputs MAO0 and MAO1 for motor A. Then the motor is working when the example code is running. Afterwards I double checked by connecting the motor with the NXT cable. The motor is again not working, but encoder is counting when turning it manually. Testing other NXT motors showed the same results.

I think by that it is clear that my BrickPi has a defect.

I already got a mail from John to start an exchange. Thank you very much for your support.


#6

Pingineer, it sounds like either the SN chip is busted or not properly soldered. Since you’re seeing a voltage, I’m betting it’s a problem with the SN chip.

I’m glad you contacted us to get it replaced; please let us know how the replacement works out! thanks for your patience in troubleshooting this issue.