PWM controlar to work with reverse polarity relay

Thread Starter


Joined Mar 25, 2021
Following my other thread in the building a motorised camera slider

I plan on having a motor controlled by a PWM to reduce the speed of the motor for time-laps photography

and adding a reverse polarity relay so I can add end limiter switches at both ends of the slider, this is the reverse polarity relay I bought

How this should be wired up

Both work 100% as planned when wired on their own, but once I wire then to work together is when there is an issue, this is how I have wired them up for now

The issue I have is if the PWM is set bellow 35% - 50% duty, the reverse polarity relay won’t trigger the polarity

As both PWM controller and the reverse polarity relay are not polarity changeable, I was thinking something wired like this might work, keeping both right polarity and full volts

The issue I have is I don’t know what relay and the wiring to the (yellow) relay is for this to work, and help is much appreciated


Joined Oct 7, 2019
The motor runs off the power from the PWM.
The relay and switches run from the battery. (They do not care what the PWM duty cycle is)