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HX711 3‑Channel 24‑Bit PGA

3 channel 24-bit programmable gain amplifier for pressure, load cell via I2C

Board Topside

Overview

The HX711 3‑Channel PGA is a compact, high‑precision amplifier and 24‑bit ADC module for bridge‑type sensors (load cells, pressure transducers, strain gauges, etc.). Based on the Avia HX711, this board provides three independent channels of selectable gain (32, 64, 128) and dual‑rate output (10 SPS, 80 SPS). All three channels are accessible via a standard single‑row 0.1" connector for effortless integration with any microcontroller.

Board Layout PDF

  • Dimensions: 33 mm × 51 mm
  • Supply Voltage: 2.7 – 5.5 V
  • Operating Temp: −40 °C – +85 °C

Key Features

  • 3 channels of 24‑bit ADC (HX711)
  • 🔧 Programmable gain: 32, 64, 128 via RATE pin
  • ⚙️ Dual sample rate: 10 SPS or 80 SPS
  • 📶 On‑chip analog regulator (no external regulator needed)
  • On‑chip oscillator (no crystal required)
  • 🔗 Simple two‑wire (DOUT/PD_SCK) interface per channel
  • 🔌 Single 10‑pin header (power + three DOUT/SCK pairs)

Pinout (J1)

Pin Name Description
1 VSUP Analog power input (2.7–5.5 V)
2 BASE On‑chip regulator control output
3 AVDD Analog VDD (regulated)
4 VFB Regulator control input
5 AGND Analog ground
6 VBG Bandgap reference bypass
7 INNA Ch. A negative input (sensor bridge −)
8 INPA Ch. A positive input (sensor bridge +)
9 INNB Ch. B negative input
10 INPB Ch. B positive input
11 PD_SCK (SCK1) Channel 1 clock
12 DOUT (SDA1) Channel 1 data out
13 PD_SCK2 (SCK2) Channel 2 clock
14 DOUT2 (SDA2) Channel 2 data out
15 PD_SCK3 (SCK3) Channel 3 clock
16 DOUT3 (SDA3) Channel 3 data out

NOTE: Although labelled as SDA/SCK, the HX711 uses a proprietary 2‑wire protocol: DOUT (data) and PD_SCK (clock).

Getting Started

  1. Power: Connect VSUP (pin 1) to 3.3 V or 5 V.
  2. Logic Level: Tie AVDD/VDD to the same supply or to your MCU logic level (2.7–5.5 V).
  3. Ground: Connect AGND to system ground.
  4. Data: For each channel, connect DOUTx to your MCU data‑in pin and PD_SCKx to your clock‑out pin.

Example (Arduino)

#include <HX711.h>

HX711 scale1;  // channel 1
HX711 scale2;  // channel 2
HX711 scale3;  // channel 3

void setup() {
  Serial.begin(9600);
  scale1.begin(/* dout=*/ A1, /* pd_sck=*/ A0);
  scale2.begin(/* dout=*/ A3, /* pd_sck=*/ A2);
  scale3.begin(/* dout=*/ A5, /* pd_sck=*/ A4);

  scale1.set_gain(128);
  scale2.set_gain(128);
  scale3.set_gain(128);
}

void loop() {
  Serial.print("Ch1: "); Serial.println(scale1.read());
  Serial.print("Ch2: "); Serial.println(scale2.read());
  Serial.print("Ch3: "); Serial.println(scale3.read());
  delay(500);
}

(Adjust pins and gain/rate as needed.)

Schematics & Layout

Bill of Materials

Qty Part Value/Type
11 C1–C5, C10, C12 0.1 µF, 0603
4 C6, C7, C9, C16 10 µF, 1210
3 L1–L3 3.3 µH, 0805
3 Q1–Q3 MMBT4403 (SOT‑23)
3 R1, R9, R14 20 kΩ, 0603
3 R2, R8, R13 8.2 kΩ, 0603
6 R3, R4, R6, R7, R11, R12 100 Ω, 0603
3 R5, R10, R15 10 kΩ, 0603
1 J1 1 × 9 P header, 2.54 mm
3 JP2‑1, JP2‑2, JP2‑3 1 × 4 P header, 2.54 mm
3 U1–U3 HX711 (SO‑16)

For the complete BOM spreadsheet, see HX711_mux_BOM.xlsx.

Gerber & Manufacturing

Resources & Datasheets

License

Distributed under the MIT License. See LICENSE for details.


Designed & maintained by Adit Mehta
GitHub: @aditmehta0

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3 channel 24-bit programmable gain amplifier for pressure, load cell via I2C

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