WS55-220 BLDC Controller adapt to 0-5v control

[landomartti]

@bjorntocreate

You created a post, which is now locked, mentioning something about the WS55-220 BLDC controller and bypassing the input control limitation of 0-10v signal or potentiometer.

“The unit is marked 10V on the case, but the board is marked 5V, which got me thinking, so I traced pin 6 the speed pin, met a diode then a resistor and then a GPIO of the STM32... so I bypassed the diode and resistor and plonked a 3v3 PWM signal directly on it, low and behold I could take it to 100% DC and spin my motor to 3000RPM, I then decided to mock up a quick push button affair and I was able to fully control the motor, from a PWM signal generated from the MCU.”

I have this same controller and am trying to control using 0-5v or 0-5v PWM from a GRBL CNC control board made by sainsmart for the 3018 PROVER.

Can you explain more how you accomplished this and if I could do a similar thing so that the controller will accept 0-5v instead of 0-10v?

[landomartti]

I figured it out. There is a 20k ohm resistor between the SV input (PIN number 6) and the STM32F. This is part of a voltage divider circuit to step the 10v max input down to a 3.3v max input at the STM32F.

I removed the 20k ohm resistor as outlined in this image.

And then replaced it with a 4k ohm resistor, soldered on the back of the board, through the hole next to the 20k ohm resistor to the SV pin solder trace.

I had to play around with the resistor size until I landed on 3.3v (with 5v DC into SV and ground) between the trace where the blue arrow is and ground.