Arduino Mega and 2x Dual MC33926 Motor Driver Carries

I’ve got a robot with two MC33926 Dual Motor Driver Carriers that drive two 25D Pololu motors. When I get everything wired together, One Carrier drives the first two motors just fine, but the third motor is at only a partial speed, and the fourth one doesn’t even turn. Mixing and passing the wires around gets the same result. Checked the battery connections, I’m reading 12V from my battery, 5V out from my regulator. I’m using the 12 V into the Arduino Mega Vin and 12 V into both the MC33926’s. Checked the status pins, they pull weak high, so no error detected. The motors were under zero load. Pinout was changed about a million times to try and figure out if it was an arduino pin problem, but nothing helped.

Are these carriers just not compatible with the mega? Can I only run one instead of two?


What are you using as a 12v supply? Can you post pictures here that show all of your connections including any soldered connections you might have made? How are you controlling the pins? Those carrier boards should work with an Arduino Mega and, if you have the right I/O pins available, it should be possible to run more than one board on a single microcontroller.


12V LiPo, run through a switch, switch connections are spade connectors that we made sure were very tight fits. From there, we’ve got 12V running into the Vin Header on the arduino mega (Jumper), the Vin pins of the MC33926 (Screw Terminals), and a 5V Regulator (Screw Terminal). One Ground Bar for everything (Screw Terminals). 5V Regulator powers the MC33926 on the Vin pin of the logic portion of the chip. GPIOs from the Mega to the Control Pins and the PWM pins on the MC33926 with jumpers.

Code used analog write for PWM and Digital Write for control pins.

Unfortunately don’t have ability to take pictures, Robot is traveling back from competition, and the Mega was our backup plan that didn’t work…

That sounds like a pretty complicated setup for troubleshooting. You might try to simplify your setup to test the different components individually to be sure all of the hardware is working.

When you say " 5V Regulator powers the MC33926 on the Vin pin of the logic portion of the chip.", do you mean you are powering the VDD pin on the MC33926 with a 5V regulator? The VIN pin on the logic side of the board is directly connected to the VIN screw terminal, which it sounds like is connected to your 12V LiPo battery.

Did you try to swap the driver boards to see if the problems stayed with motor driver board or the specific pins on the microcontroller?