Hello everyone,
I tried searching for older posts, but could not find anything related.
I want to control a 3 phase industrial electric motor.
Basic options: start, stop, change speed.
I have a frequency inverter.
The analog controls diagram is in the attached file.
I wonder if I could control the inverter with arduino through simple NPN transistors using PWM? Inverter works on 24V, and current is mere 20mA. so to start and stop the inverter should not be a problem, with some 30V NPN transistor.
I am more worried about the potentiometer function. Can I use npn transistor and PWM for frequency manipulation(motor speed)? Or should I use something more sophisticated, like digital potentiometer?
Also, are there any precautions as various pull-up/down resistors, diodes, for circuit protection? I will use a 1k resistor between transistors base and arduino.
Any thoughts and ideas are welcome 
Thanx
P.S. modified the diagram a bit, for clearance
