Continuous Servo Control PCB
An ENPH 259 follow-on: close a motor control loop without a microcontroller in the middle. The board measures shaft motion digitally, converts the count back into a voltage, and closes the loop with an analog PI controller and a MOSFET H-bridge driver.
The sensor is a slotted disk on the shaft. Pulses feed a counter that's latched right before a periodic reset, giving a sampled measure of rotational speed. An R-2R ladder converts the latched binary value to a voltage; that voltage is compared to a reference, and the error goes through the PI stage before driving the motor. Digital counting, analog control, one board. The system needs external +5 V, ground, -5 V, and a 5 Hz clock, since the clock sets the counting window.
I built and powered up the board, but I didn't save a step response or any other closed-loop measurement, so I can't put a real accuracy number on it. What I have is a board whose stages all produce the expected signals on the bench.
Board render:
Schematic (page 1):
PCB front (page 1):
