Arduino to control existing PWM board?

Projects General Guidance
1

Essentially I have a fully working project which has a typical PSU to PWM to (very large) Motor.

All that I need to control here is the speed of the motor and the on off switch. Currently this is being done by turning a pot (10k) on the PWM and using a rocker switch (tada!)

I now want to adapt this so that the speed can be automated via the Arduino. My initial though was to replace the pot on the PWM with a digital pot controlled by the Arduino.

Am I on the right track here or is there a better way to achieve this? Will this work at all?

This is my first project with smaller electronics. I usually build larger (dare I say clumsier) contraptions where you dont need to think about...debouncing!? As such I may have left out some crucial details, please let me know and thanks in advance for any advice.

Krish

2

widget:
the speed can be automated via the Arduino.

What does this mean? Are you intending to have the Arduino detect the speed and adjust the power to move the speed towards some target? How would the target be defined/displayed? How much of the existing PWM driver would you use?

3

Sorry, a bit more clarity.

The current setup has a 90v 15:1 motor being controlled by a quantum electronics board. This board is handling the power supply (240v ->90v @ 3a) This board also is handling the PWM controlling the speed. The speed is determined from a 10k Pot (multimeter reads 3v across it)

All I want to replace ideally is the 10k pot which controls the speed of the motor.

I want to replace this pot completely so that rather than having a knob with which to adjust speed, I can write a program to change speed over time or according to other conditions.

I hope thats a bit clearer.

4

Yes, a 10K digital pot should be able to replace the manual pot. That would be the easiest solution.

A relay can replace the on-off switch, but I would keep an emergency override switch in case the Arduino starts doing something you didn't intend. Always have a kill switch in automated equipment.

5

Thanks,

Is it ok that either side of the digital pot ie the Arduino and the pwm are on separate circuits?

6

The ground of the motor controller and the ground of the Arduino should be connected together.

7

Great thanks.

And finally, this is going to sound like a very noob question but I dont want to get this one wrong.

My multimeter reads +3v one way across the pot and -3v the other way. As such can I assume the pin touched by the black wire was the ground in the positive reading and red in the negative reading?

8

Yes, that is correct. There are cases where it might not be true, but that is very rare.

And please ask noob questions here before blowing anything up :slight_smile: trust me on that!

9

Hehe, indeed.

Thanks for your help, i'll let you know how I get one.