SMC03A analogue voltage interface with PWM signal


I am currently using an SMC03A to control a 12V linear actuator with potentiometer feedback as an engine throttle control.

Until recently I have been using an RC signal to control the SMC03A, but have encountered noise issues from our electric motors/drives that can corrupt the RC signal.

Having failed to isolate the noise issue, today I’ve tried to use the analogue voltage interface, with a PWM signal from our microcontroller.

The SMC03A works fine when a 10K potentiometer is used as the input, but the PWM signal (for test purposes set at 50% 5V to approximate 2.5V) causes the actuator to constantly cycle between it’s extreme positions.

I thought this might be a sampling issue on the SMC03A, so have tried different clock frequencies for the PWM signal. I’ve gone as far as 8MHz (max clock) on the microcontroller, with a 256 step PWM, so approximately 30KHz. Changing the frequency doesn’t make much difference to the cycling of the actuator position.

Unfortunately, serial communications isn’t an easy option with our current hardware, so I need to persevere with the analogue interface option.

Is it possible to make the SMC03A accept a PWM signal as an analogue voltage?




What are you doing to filter the PWM output from your microcontroller?

- Jan

Hi Jan

No filtering - I think that’s the problem.

I’ve successfully used PWM signals in place of analogue voltages on other drives we are using, so I think they must have some filtering on-board.

I’m going to try a resistor-capacitor low-pass filter today. I’ll admit that analogue electronics is a bit of a black art to me, so any suggestions will be appreciated.

If that doesn’t work, I’ve got a DAC chip to try later. I’ll post my results here in case they are useful to anyone else.




A simple low-pass filter (1K resistor in series with the signal, 10uF capacitor from the signal connection to ground) has sorted my problem. The Pololu is no seeing a steady analogue voltage, instead of my PWM signal.

Hope this is of help to others.