RFID NFC Reader/Writer Module V3 PN532

Features:

• Complete kit including weight module, HX711 chip, and load cell amplifier
• High-precision electronic scale applications
• Environmentally friendly materials used in load cell
• 5kg load capacity
• Two selectable differential input channels
• Internal 24-bit ADC amplifier
• On-chip active low-noise PGA with selectable gain of 32, 64, and 128
• On-chip power supply regulator for load cell and ADC analog supply
• Output sensing range depends on input voltage
• Easy DIY and portable

Specifications:

• Operating Voltage: 2.6 - 5.5V
• Operating Current: < 1.5mA
• Standby Current: < 1µA
• Load Cell Size: 80 x 12.7 x 12.7 mm
• Module Size: 24 x 16 mm

Applications:

• Kitchen and food scales
• Postal scales for envelopes and packages
• Industrial weighing of small objects or parts
• Medical and health scales requiring high accuracy

Pin Connections:

Sample Project:

Circuit:

The HX711 amplifier communicates via a two-wire interface connected to any digital pins of your Arduino board. In this example, the data pin (DT) connects to Pin 2 and the clock pin (CLK) to Pin 3.

Library:

Add the HX711 Library to your Arduino IDE.

Code - Calibration:

#include "HX711.h"

// HX711 circuit wiring
const int LOADCELL_DOUT_PIN = 2;
const int LOADCELL_SCK_PIN = 3;

HX711 scale;

void setup() {
  Serial.begin(57600);
  scale.begin(LOADCELL_DOUT_PIN, LOADCELL_SCK_PIN);
}

void loop() {
  if (scale.is_ready()) {
    scale.set_scale();
    Serial.println("Tare... remove any weights from the scale.");
    delay(5000);
    scale.tare();
    Serial.println("Tare done...");
    Serial.print("Place a known weight on the scale...");
    delay(5000);
    long reading = scale.get_units(10);
    Serial.print("Result: ");
    Serial.println(reading);
  } else {
    Serial.println("HX711 not found.");
  }
  delay(1000);
}
// Calibration factor = (reading) / (known weight)

Upload the code, open the Serial Monitor at 57600 baud, press reset, and follow the prompts to remove weights, place a known weight, and calculate your calibration factor.

Code - Weighing Objects:

#include "HX711.h"

// HX711 circuit wiring
const int LOADCELL_DOUT_PIN = 2;
const int LOADCELL_SCK_PIN = 3;

HX711 scale;

void setup() {
  Serial.begin(57600);
  Serial.println("HX711 Demo");
  Serial.println("Initializing the scale");
  scale.begin(LOADCELL_DOUT_PIN, LOADCELL_SCK_PIN);
  scale.set_scale(-459.542); // Use your calibration factor here
  scale.tare();
  Serial.println("Scale ready");
}

void loop() {
  Serial.print("Reading: ");
  Serial.println(scale.get_units(10), 1);
  delay(5000);
}

References:

• HX711 Load Cell Tutorial Video
• Complete Project Details