Summary of Arduino Load Cell / Scale
This project creates a programmable Arduino-based weighing scale using a postal scale load cell, an INA125P amplifier, and Arduino code for calibration and reading load values. The load cell's four wires are connected to the amplifier, which boosts the signal for Arduino's analog input. Calibration involves taking readings with two known weights to enable linear interpolation for accurate measurements. An update suggests using the HX711 24-bit ADC amplifier module for better performance.
Parts used in the Arduino Load Cell / Scale Project:
- Load Cell (from Accuteck W-8260-86W Postal Scale)
- Arduino Board
- INA125P Amplifier
- 10 ohm Resistor
- Optional: HX711 24-bit ADC Amplifier Module (improved version)
From the minds at http://arduinotronics.blogspot.com/
Important Update!
Since so many people were having problems with the INA125P, we now have a new and improved version that uses the Hx711 24bit ADC amplifier module. http://arduinotronics.blogspot.com/2015/06/arduino-hx711-digital-scale.html My goal was to create a programmable scale for weighing objects, parts counting, even directing product flow on a conveyor system.
I needed a load cell, a Arduino, and an amplifier.
Step 1: The Load Cell
On this load cell (from a Accuteck W-8260-86W Postal Scale) the 4 wires coming from the load cell are:
Red: Excitation +
White: Signal +
Green: Signal –
Black: Excitation –
This matches the GSE / NCI / Sensotec wiring scheme.
http://www.controlweigh.com/loadcell_colors.htm
I disconnected the 4 wires from the control board in the scale, so they would be available for the next step.
Step 2: The Amplifier
To increase the output of the load cell so that the Arduino can read it on an analog input, we will need a INA125P amplifier and a 10 ohm resistor. Connect to the Arduino as indicated on the attached schematic.
Data Sheet: http://www.ti.com/lit/ds/symlink/ina125.pdf
Step 3: The Code
// Arduino as load cell amplifier
// by Christian Liljedahl
// christian.liljedahl.dk
// Load cells are linear. So once you have established two data pairs, you can interpolate the rest.
// Step 1: Upload this sketch to your Arduino board
// You need two loads of well know weight. In this example A = 10 kg. B = 30 kg
// Put on load A
// read the analog value showing (this is analogvalA)
// put on load B
// read the analog value B
// Enter you own analog values here
float loadA = 10; // kg
int analogvalA = 200; // analog reading taken with load A on the load cell
float loadB = 30; // kg
int analogvalB = 600; // analog reading taken with load B on the load cell
// Upload the sketch again, and confirm, that the kilo-reading from the serial output now is correct, using your known loads
float analogValueAverage = 0;
// How often do we do readings?
long time = 0; //
int timeBetweenReadings = 200; // We want a reading every 200 ms;
void setup() {
Serial.begin(9600);
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