BH1750 with Arduino Nano

Wiring for the GY-302 BH1750 light sensor on the Arduino Nano (ATmega328P, 5 V logic), chosen with the same pin rules BoardPilot uses: default buses first, and no pins that are used for flash, USB, the debugger or booting.

Wiring

BH1750 pin	Role	Arduino Nano pin	Notes
VCC	Power	5V
GND	Ground	GND
SCL	I2C clock (SCL)	A5 (PC5)
SDA	I2C data (SDA)	A4 (PC4)
ADDR	Not wired to the board	not connected	Address select: LOW or open = 0x23, HIGH = 0x5C

Check before you power it on

Supply: 5 V from the 5V pin.
I2C uses the board’s default pins A4 (SDA) and A5 (SCL). Most modules include pull-up resistors; if the part is not found, check them and swap-test SDA/SCL.

Test code (Arduino)

#include <Wire.h>

void setup() {
  Serial.begin(115200);
  Wire.begin();  // SDA = A4, SCL = A5 (the board's default I2C pins)
  Wire.beginTransmission(0x23);
  bool found = Wire.endTransmission() == 0;
  Serial.println(found ? "GY-302 BH1750 light sensor found at 0x23" : "Not found: check power, GND and SDA/SCL");
}

void loop() {}

Arduino board: arduino:avr:nano. Clones with the old bootloader upload at 57600 baud: choose “ATmega328P (Old Bootloader)” if uploads fail.

Questions

Which Arduino Nano pins do I use for the BH1750?

VCC → 5V, GND → GND, SCL → A5 (PC5), SDA → A4 (PC4).

Does the BH1750 work with the Arduino Nano at 5 V?

Yes: the BH1750 runs at 3.3-5 V and the Arduino Nano uses 5 V signals, so no level shifting is needed.

What is the I2C address of the BH1750?

0x23 or 0x5C. An I2C scan (BoardPilot does it for you) shows which one your module uses.

BoardPilot checks this wiring in 3D as you build it, and finds crossed or missing wires on the real board.

Download BoardPilot

Full Arduino Nano pinout · GY-302 BH1750 light sensor: all pins and data

The BH1750 on other boards

ESP32 DevKit Arduino Mega 2560 R3 Arduino Uno R3 WeAct Black Pill STM32F411CE ESP32-C3-DevKitM-1 ESP32-S3-DevKitC-1 Nordic nRF52840 DK NUCLEO-F401RE Raspberry Pi Pico 2 Raspberry Pi Pico W Raspberry Pi Pico Teensy 4.1

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