I have developed a soft-starter for a project of mine. I am using an Arduino Uno to generate PWM to an OAC-5 relay that turns on and off the voltage across my bridge rectifier.
Here is a simple block diagram:
Everything is working fine, it blocks the in-rush current as its supposed to, however I can't generate a clean response:
Without my soft starter the motors in-rush current reached 8 A. So from this we could see that the application is working, however I'm not liking that noise.
I know its from the PWM, as you could see the faster it speeds up the faster the load reaches it's maximum voltage.
Any thoughts on this? Is the relay switching too fast? or is my Arduino frequency too fast for the relay & motor?
*Note: A typical desired step response for a soft-starter is shown here:
Also, my method of current measurement was putting a 10ohm resistor in series with the motor, and measuring the voltage across it to calculate current.