Voltage sensor module (0-25 V divider) with ESP32

Supply 3.3-5 V Bus ANALOG Measures voltage

Pins and ESP32 wiring

Pin	Role	ESP32 pin	Notes
S	Analog output	D34	Input voltage divided by 5. Keep the measured voltage under about 16 V so S stays below 3.3 V
+	Not wired to the ESP32	—	Not connected inside the module
-	Ground	GND
VCC_IN	Not wired to the ESP32	—	Screw terminal: voltage to measure
GND_IN	Not wired to the ESP32	—	Screw terminal: ground of the measured circuit

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);  // S on GPIO 34
  Serial.println(mv);
  delay(200);
}

Generic 0-25 V voltage sensor module, 30 kΩ / 7.5 kΩ resistor divider (ratio 1:5)

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