No motor LED activity on Pololu Trex

Hi there :slight_smile:
I bought a Pololu TReX to control DC motors. Have plugged in a 7.5V battery pack and connected it to Arduino Uno via serial interface. When I send in a simple code to control motor 1, there is no motor LED activity from the lower board at all.

The blue power LED, red status LED & green blinking status LED works, but the motor LEDs do not light up and neither do motors turn

I’ve checked the motors by connecting them directly to the battery and they work. Also checked the serial connection by asking the Trex for status using serial commands and these have worked too. This is a new Trex just unwrapped from the box, so I’ve not made any changes to the serial configurations too.

Here’s a picture of my setup:

Is there anything that I might have missed?

Any help is greatly appreciated!


(do apologise if this has been covered somewhere else, but have been searching over last 2 days and could not find anything similar)

PS: The arduino sketch I used:

Sketch.txt (980 Bytes)

Hi, managed to get it to work after throwing another 3V battery in!


I am glad you were able to get your TReX working. The TReX should have been able to operate fine at 7.5V. It sounds like there might have been some kind of power issue like the batteries not being fully charged. Did you connect the 3V battery in series with the 7.5V pack? Have you checked to make sure our 7.5V pack is not dead?