TReX Jr. attached to Arduino Duemi Problem

Hey, as a quick preface I am completely new to robotics and have learned everything I know from the user guides and this forum.

However, there is one thing that I haven’t seen mentioned and I can’t figure out.

I’m trying to just simply drive a motor from motor channel one. Everything looks fine when I upload my Arduino program, except BOTH the red and green LED lights by M1 are lit up (from what I read, indicating that motor is trying to move both forwards and backwards at the same time).

There are delays in my code, and I’m sure I’m only trying to get it to move forward, but the result is that the motor simply makes a high-pitch noise with no rotation. Additionally, I’m powering everything with 5V, which I realize is the minimum for the motor driver. Additionally, the motor is rated for 24V, but from what I understand it should still at least rotate, just not at maximum power.

Any help would be greatly appreciated.


Seeing both motor indicator LEDs on isn’t necessarily indicative of a problem. When using speeds under 100%, one LED will be on during the active/driving portion of the duty cycle and the other LED will be on during the low portion of the duty cycle. I think this is what you’re seeing, but there are a few ways to test this:

  1. If you disconnect the motor, you should only see the motor LED on (the one that corresponds with the direction you are trying to drive the motor).

  2. If you sent the motor speed to 100%, you should only see one motor LED on.

I suspect power problems are responsible for your lack of motor movement. How are you powering everything in your system? What speed are you trying to drive the motor at? Can you post your code (please simplify it to the shortest program that should work but doesn’t)?

- Ben

Thanks, those tips should really help.

I actually have the code on a different computer, so I don’t have access right now. I’m powering it with a USB to the Arduino though (so I’m guessing this is the main problem, not providing the full 5V). I’m going to try a better power source tomorrow and if I still have problems (which I’m sure I will eventually at least), I’ll be sure to give more info.

Thanks again.

You definitely should not be trying to power a 24V motor off of USB. USB should not be used for applications that draw more than a few hundred milliamps. The sound you heard was current going through the motor at the PWM frequency, but there was not enough power to make the motor start turning. You need to use an appropriate power supply, such as a a battery pack connected directly to the TReX Jr’s inputs.

Do you know the stall current of your motor?

- Ben