Trex Jr and Dagu Rover 5

Hi, I purchased the Rover 5 w/encoders and the Trex Jr to work on a robot project but I’m having a few issues.

  1. When I send a command to the Trex Jr (from my Arduino) I get a weird high pitch sound coming from the motors.
  2. When I send a command to move both motors, one moves and the other doesn’t do anything - the high pitch sound in still present.
  3. When the motor does move, it’s not constant - it accelerates a little then decelerates but never stays constant.

I’ve got the Trex and RX/TX lines connect to SO/SI per the instruction manual. currently I’ve got the Rover on a stand so the motors don’t have to deal with any friction for the moment. Power is coming from my power supply 15V/3A max.

Here’s a code snippet:

char command = 0x80;
char byte1 = command | M1 | direct;

M1 is a define I use in the code and is set to 0xC0.

Any ideas what I’m doing wrong?



Even though you have the chassis up in the air, the tracks are still likely causing a serious load on the motors. I suspect that high-pitched sound is the PWM whine. It looks like you are setting the duty cycle to 32/127, which might be too low for the motors to spin. I recommend trying half-speed forward on each motor individually, and, if that works, try them both at the same time. Please note that 15V is almost double the rated voltage for the motors in that chassis, and 3A may be insufficient, since the stall current of one of the motors is 2.4A at 7.2V. Using the provided 6-AA battery holder as your supply would help avoid these various power-supply-related issues.

- Ryan

Hi Ryan,

Thanks for the suggestions. I’ll try them out and report back.