A closed-loop controller that keeps a motor or small engine running at a constant speed (RPM) despite load changes. A speed sensor (Hall/optical) measures RPM; a microcontroller compares it with the setpoint and adjusts the actuator using PWM (for DC/BLDC motors) or a servo/stepper (for throttle on small engines). Built-in PID control, soft start, and safety cut-offs prevent overspeed and stalling. Ideal for conveyors, pumps, fans, lab rigs, and portable gensets.

Parts Used:

1. Microcontroller (Arduino/ESP32/STM32): Reads RPM, runs PID, outputs control
2. Speed Sensor: Hall effect sensor + magnet, optical encoder, or tachogenerator (ADC)
3. Actuator / Power Stage:
4. DC/BLDC motors: H-bridge/MOSFET driver (L298N, BTS7960) or ESC (for BLDC)
5. Engine throttle: Servo/stepper to move throttle valve/linkage
6. Setpoint Input: Potentiometer/rotary encoder or keypad buttons
7. Display (Optional): OLED/LCD for set RPM, actual RPM, PID status
8. Current Sensor (Optional): ACS712/shunt for overcurrent protection
9. Power Supplies: 5 V/3.3 V for logic; separate supply for motor/servo
10. Safety & Protection: Fuse, E-stop, TVS diode, reverse-polarity protection, watchdog
11. Connectivity (Optional): ESP32 Wi-Fi/MQTT/Blynk for logs, tuning, alerts
12. Enclosure & Wiring: Terminal blocks, shielded cables, mounting hardware