ZMPT101B AC voltage sensor module with ESP32

Supply 3.3-5 V Bus ANALOG Measures voltage

Pins and ESP32 wiring

Pin	Role	ESP32 pin	Notes
VCC	Power	3V3	Use 3V3 so OUT stays under 3.3 V. Some boards have a second GND pin
OUT	Analog output	D34	AC wave centred on VCC/2; set the amplitude with the trimmer. To an ADC pin (prefer ADC1: GPIO 32 to 39)
GND	Ground	GND
L	Not wired to the ESP32	—	MAINS input! Only a qualified person connects this. Never to the ESP32
N	Not wired to the ESP32	—	MAINS input! Only a qualified person connects this. Never to the ESP32

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

ZMPT101B voltage transformer datasheet, 2 mA:2 mA current transformer for voltage sensing
Espressif ESP32 Technical Reference Manual, ADC: input range and attenuation

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