Hi Ioannis,

Thanks for your input, much appreciated.
As previously stated, this is the first stage of a much larger project - to re-power my lathe with a 180Vdc 2HP treadmill motor. Knowing that the final design will involve isolation between control and motor drive stages, I decided to replace my transistor gate drive circuit with an opto-isolated MOSFET driver (FOD3180). Also, I was experiencing lots of noise on my breadboard layout so keeping powr supplies isolated in my prototype development PCB can only be a benefit.

Attached is a copy of my new circuit diagram:

incPID_16F684_V4.pdf

JP1 & JP2 allow me to select one of two feedback sources; the analog output from the LM2907 (0-5V) or a pulse train from the shaft encoder (0-5.5kHz 50% duty cycle). My preference will be to use the pulse train and merely count pulses in my program to determine rotation speed but it was easy enough to fit both into my PCB design.

I have used multi-turn pots (VR2-VR6) to adjust the gain for the five different PID terms so, theoretically, I should be able to tune the system "on the fly". I will be able to display variables on the 4x20 LCD which will help me "see" what is happening.

The PCB (165mm x 115mm) has been exposed and etched and is ready for drilling and populating - hopefullt this will be completed tonight. I will keep you updated with more news soon.

Cheers
Barry