Pinout

HX711 load-cell amplifier pinout

Pins

MCU side: VCC (2.7–5V), DT/DOUT (data), SCK (clock — NOT I2C, a custom 2-wire protocol), GND
Load-cell side: E+ / E− (excitation), A+ / A− (channel A signal)
B+ / B− — second input channel (fixed gain 32)
Red = E+, black = E−, white = A−, green = A+ on most 4-wire cells

Supply voltage	2.6–5.5 V
ADC resolution	24 bit
Channel A gain	128 or 64 (±20 mV / ±40 mV full scale at 5 V)
Channel B gain	32 (±80 mV full scale at 5 V)
Output data rate	10 or 80 samples/s (RATE pin; most modules 10)
Interface	2-wire serial (DOUT + PD_SCK), not I2C
Supply current	< 1.5 mA normal, < 1 µA power-down
Power-down	PD_SCK held HIGH > 60 µs
Load cell	4-wire full Wheatstone bridge

HC-SR04 ultrasonic distance sensor (4-pin)Supply voltage: 5 V DC; Working current: 15 mA; Logic level: 5 V (TRIG and ECHO)
DHT11 / DHT22 temperature & humidity sensor (4-pin)Supply voltage: DHT11: 3–5.5 V; DHT22: 3.3–6 V; Interface: Single-wire digital (proprietary, not 1-Wire); Pull-up on DATA: 4.7–10 kΩ to VCC
PIR motion sensor (HC-SR501, 3-pin)Supply voltage: 4.5–20 V DC (5 V typical, onboard 3.3 V regulator); Quiescent current: < 50 µA; Output level: 3.3 V HIGH / 0 V LOW
Hall effect sensor module (KY-003, A3144, 3-pin)Sensor IC: A3144 unipolar Hall-effect switch; Supply voltage: 4.5–24 V (A3144 rating; 5 V typical); Supply current: ≈4.4 mA typical (chip)
DS18B20 temperature sensor (1-Wire, TO-92)Supply voltage: 3.0–5.5 V (or parasite power from DQ); Interface: 1-Wire, unique 64-bit ROM code per sensor; Pull-up on DQ: 4.7 kΩ to VDD
MPU6050 accelerometer/gyro module (GY-521, I2C)Board supply: 3.3–5 V (onboard 3.3 V regulator); Chip supply: 2.375–3.46 V; Interface: I2C, up to 400 kHz
Rotary encoder module (KY-040, 5-pin)Supply voltage: 3.3–5 V; Output: 2-channel quadrature (CLK, DT); Pull-ups: 10 kΩ on CLK and DT; none on SW
BMP280 / BME280 barometric module (GY-BMP280, I2C/SPI)Board supply: GY-BMP280-3.3: 3.3 V only; boards with LDO: 3.3–5 V; Chip supply: 1.71–3.6 V; Interface: I2C (up to 3.4 MHz) or SPI (up to 10 MHz)