Recycle wood to make electronic scale | Details

After clean my house, I had some pine pallets left and tried to think for recycle them.

Here is a electronic diagram that I follow from: https://circuitjournal.com/50kg-load-cells-with-HX711

But I used Wemos D1 Mini and Oled 1306 instead Arduino Uno:

Also changed sketch for this boards. Here is wiring diagram:

OLED->WEMOS D1 MINI: VCC:3V3; GND:G; SCL:D1; SDA:D2
HX711->WEMOS D1 MINI: VCC:5V; GND:G; DT: D4; SCK:D3

Here is quick prototype:

Ugly huh ?

There are some 3d printer components here:

-50kg Loadcell Bracket versionF (https://www.thingiverse.com/thing:2624188)
-Case (https://www.thingiverse.com/thing:6090225)

Before upload final sketch, check I2C adress with this code:

/* 
* i2c_port_address_scanner
* Scans ports D0 to D7 on an ESP8266 and searches for I2C device. based on the original code
* available on Arduino.cc and later improved by user Krodal and Nick Gammon (www.gammon.com.au/forum/?id=10896)
* D8 throws exceptions thus it has been left out
*
*/

#include <Wire.h>

void setup() {
  Serial.begin(115200);
  while (!Serial);             // Leonardo: wait for serial monitor
  Serial.println("\n\nI2C Scanner to scan for devices on each port pair D0 to D7");
  scanPorts();
}

uint8_t portArray[] = {16, 5, 4, 0, 2, 14, 12, 13};
//String portMap[] = {"D0", "D1", "D2", "D3", "D4", "D5", "D6", "D7"}; //for Wemos
String portMap[] = {"GPIO16", "GPIO5", "GPIO4", "GPIO0", "GPIO2", "GPIO14", "GPIO12", "GPIO13"};

void scanPorts() { 
  for (uint8_t i = 0; i < sizeof(portArray); i++) {
    for (uint8_t j = 0; j < sizeof(portArray); j++) {
      if (i != j){
        Serial.print("Scanning (SDA : SCL) - " + portMap[i] + " : " + portMap[j] + " - ");
        Wire.begin(portArray[i], portArray[j]);
        check_if_exist_I2C();
      }
    }
  }
}

void check_if_exist_I2C() {
  byte error, address;
  int nDevices;
  nDevices = 0;
  for (address = 1; address < 127; address++ )  {
    // The i2c_scanner uses the return value of
    // the Write.endTransmisstion to see if
    // a device did acknowledge to the address.
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0){
      Serial.print("I2C device found at address 0x");
      if (address < 16)
        Serial.print("0");
      Serial.print(address, HEX);
      Serial.println("  !");

      nDevices++;
    } else if (error == 4) {
      Serial.print("Unknow error at address 0x");
      if (address < 16)
        Serial.print("0");
      Serial.println(address, HEX);
    }
  } //for loop
  if (nDevices == 0)
    Serial.println("No I2C devices found");
  else
    Serial.println("**********************************\n");
  //delay(1000);           // wait 1 seconds for next scan, did not find it necessary
}

void loop() {
}

I modified sketch for my new wiring diagram:

/**
 * Complete project details at https://RandomNerdTutorials.com/esp8266-load-cell-hx711/
 * 
 * HX711 library for Arduino - example file
 * https://github.com/bogde/HX711
 *
 * MIT License
 * (c) 2018 Bogdan Necula
 *
**/

#include <Arduino.h>
#include "HX711.h"

#include <Wire.h>               // Only needed for Arduino 1.6.5 and earlier
#include "SSD1306Wire.h"        // legacy: #include "SSD1306.h"

// Initialize the OLED display using Arduino Wire:
SSD1306Wire display(0x3C, SDA, SCL);   // ADDRESS, SDA, SCL  -  SDA and SCL usually populate automatically based on your board's pins_arduino.h e.g. https://github.com/esp8266/Arduino/blob/master/variants/nodemcu/pins_arduino.h

// HX711 circuit wiring
const int LOADCELL_DOUT_PIN = 2;//D4
const int LOADCELL_SCK_PIN = 0;//D3

HX711 scale;
int reading;
int lastReading;

void setup() {
  Serial.begin(115200);
  
  // Initialising the UI will init the display too.
  display.init();
  display.flipScreenVertically();
  display.setFont(ArialMT_Plain_10);

  drawProgressBarDemo();

  scale.begin(LOADCELL_DOUT_PIN, LOADCELL_SCK_PIN);
        
  scale.set_scale(24.91974);
  //scale.set_scale(-471.497);                      // this value is obtained by calibrating the scale with known weights; see the README for details
  scale.tare();               // reset the scale to 0

}


void drawProgressBarDemo() {
  
  for (int counter=0; counter<500; counter++)
  {
    int progress = (counter / 5) % 100;
    // clear the display
    display.clear();
    // draw the progress bar
    display.drawProgressBar(0, 32, 120, 10, progress);
  
    // draw the percentage as String
    display.setTextAlignment(TEXT_ALIGN_CENTER);
    display.drawString(64, 15, String(progress) + "%");
  
    // write the buffer to the display
    display.display();
  }
}
void loop() {
  // clear the display
  display.clear();
  
  display.setTextAlignment(TEXT_ALIGN_LEFT);
  display.setFont(ArialMT_Plain_10);
  display.drawString(0, 10, "CAN NANG:");
  
  display.setFont(ArialMT_Plain_24);  

    reading = round(scale.get_units(10));
   
    if(reading <= 50){
      reading = 0;
    }
    if(reading - lastReading >= 50){
      display.drawString(0,26,String(reading)+" g");
    } 
    else {
      display.drawString(0,26,String(lastReading)+" g");
    }
   
    lastReading = reading;
 
  
  // write the buffer to the display
  display.display();

  scale.power_down();             // put the ADC in sleep mode
  
  delay(100);
  scale.power_up();
  
}

And it worked:

Project Details