PID CNC Spindle control using heater and thermistor feedback

[CNCModeller]

Hi All,
I've been thinking about how to do closed loop control of a cnc spindle.

My idea is to use heater pwm and temp feedback inputs.

My thoughts are that a thermistor must be part of a voltage divider and as such I could replace that voltage divider with a digital potentiometer. I guess I'd need to find the other side of the reference resistor and solder a connection to the board at that location. I'd probably need to remove that resistor too.

I could then write some simple code in an Arduino to take encoder signals from the spindle and send them to the digital potentiometer as speed feedback.

Once feedback is in place I could drive the spindle from the heater pwm and close the loop with heater temperature signal and heater pid.

Am I smoking something, or is the a potential solution?

Any constructive thoughts would be great.

All the best
Barry M

[o_lampe]

@cncmodeller You are basically looking for a frequency2voltage converter or DA converter.
How many pulses do you get at full speed?