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calibrate/calibrate.ino

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+/*
+ Example using the SparkFun HX711 breakout board with a scale
+ By: Nathan Seidle
+ SparkFun Electronics
+ Date: November 19th, 2014
+ License: This code is public domain but you buy me a beer if you use this and we meet someday (Beerware license).
+
+ This is the calibration sketch. Use it to determine the calibration_factor that the main example uses. It also
+ outputs the zero_factor useful for projects that have a permanent mass on the scale in between power cycles.
+
+ Setup your scale and start the sketch WITHOUT a weight on the scale
+ Once readings are displayed place the weight on the scale
+ Press +/- or a/z to adjust the calibration_factor until the output readings match the known weight
+ Use this calibration_factor on the example sketch
+
+ This example assumes pounds (lbs). If you prefer kilograms, change the Serial.print(" lbs"); line to kg. The
+ calibration factor will be significantly different but it will be linearly related to lbs (1 lbs = 0.453592 kg).
+
+ Your calibration factor may be very positive or very negative. It all depends on the setup of your scale system
+ and the direction the sensors deflect from zero state
+ This example code uses bogde's excellent library: https://github.com/bogde/HX711
+ bogde's library is released under a GNU GENERAL PUBLIC LICENSE
+ Arduino pin 2 -> HX711 CLK
+ 3 -> DOUT
+ 5V -> VCC
+ GND -> GND
+
+ Most any pin on the Arduino Uno will be compatible with DOUT/CLK.
+
+ The HX711 board can be powered from 2.7V to 5V so the Arduino 5V power should be fine.
+
+*/
+
+#include "HX711.h"
+
+#define DOUT  30
+#define CLK  27
+
+HX711 scale;
+
+float calibration_factor = -7050; //-7050 worked for my 440lb max scale setup
+
+void setup() {
+  Serial.begin(115200);
+  Serial.println("HX711 calibration sketch");
+  Serial.println("Remove all weight from scale");
+  Serial.println("After readings begin, place known weight on scale");
+  Serial.println("Press + or a to increase calibration factor");
+  Serial.println("Press - or z to decrease calibration factor");
+
+  scale.begin(DOUT, CLK);
+  digitalWrite(CLK, LOW); // hangs without this
+  scale.set_scale();
+  scale.tare(); //Reset the scale to 0
+
+  long zero_factor = scale.read_average(); //Get a baseline reading
+  Serial.print("Zero factor: "); //This can be used to remove the need to tare the scale. Useful in permanent scale projects.
+  Serial.println(zero_factor);
+}
+
+void loop() {
+
+  scale.set_scale(calibration_factor); //Adjust to this calibration factor
+
+  Serial.print("Reading: ");
+  Serial.print(scale.get_units(), 1);
+  Serial.print(" lbs"); //Change this to kg and re-adjust the calibration factor if you follow SI units like a sane person
+  Serial.print(" calibration_factor: ");
+  Serial.print(calibration_factor);
+  Serial.println();
+
+  if(Serial.available())
+  {
+    char temp = Serial.read();
+    if(temp == '+' || temp == 'a')
+      calibration_factor += 10;
+    else if(temp == '-' || temp == 'z')
+      calibration_factor -= 10;
+  }
+}