LM393 slotted optical speed sensor (FC-03) with ESP32

Supply 3.3-5 V Bus GPIO Measures rotation, speed

Pins and ESP32 wiring

Pin	Role	ESP32 pin	Notes
VCC	Power	3V3	Use 3V3 so DO stays at 3.3 V
GND	Ground	GND
DO	Output (the part drives it)	D25	Pulse each time the slot is blocked. Count with an interrupt
AO	Analog output	D34	Raw light level. Optional. To an ADC pin (prefer ADC1: GPIO 32 to 39)

Suggested wiring for the 30-pin ESP32 DevKit, avoiding flash, input-only and strapping pins. BoardPilot checks it for you as you wire.

void setup() { Serial.begin(115200); }

void loop() {
  int mv = analogReadMilliVolts(34);  // AO on GPIO 34
  Serial.println(mv);
  delay(200);
}

Texas Instruments LM393 datasheet, Comparator output (open collector with pull-up on the module)

Part data: CC BY 4.0, free to reuse with credit to BoardPilot.