Product Running out Detector

/*

Product Running Out Detector for Intro to Physical Computing Project 2

This project uses a load cell to measure the weight of a product

such as a bottle of conditioner to detect when it’s running low.

The LED strip shows the current fill level by color, starting as

light purple before setup and gradually shifting from green

when full to red when almost empty. A button is used to set the

full reference weight.

This code was entirely written by ChatGPT. I did do revisions, so this is just a summary of the prompts put together.

Prompt: I want you to write me a complete Arduino sketch for a project

that uses a load cell and a Pololu LED strip to detect how much of something

is left, like a bottle of conditioner. When it first turns on, the LEDs

should be light purple until I press a button on pin 7, which sets whatever

Weight is on the scale as the full amount. After that, the LEDs should turn

green when the product is full, red when it is empty, and blink red when it

is almost empty. The serial monitor should show the live readings, including

the current weight, the full weight, and the percentage level. The goal is to

make a simple and clear product running out detector.

Pin Mapping:

Arduino pin | Role   | Description

------------------------------------------------------------

4            | Input  | HX711 DOUT 

5            | Input  | HX711 SCK 

7            | Input  | Button 

12           | Output | LED strip DIN

Code released to the public domain by the author, 11/12/2025

Danely Rodriguez, danelyr@andrew.cmu.edu

*/

#include <HX711_ADC.h>

#include <PololuLedStrip.h>

// ---- Pins ----

const uint8_t HX711_DOUT = 4;

const uint8_t HX711_SCK  = 5;

const uint8_t BUTTON_PIN = 7;   // button to GND

PololuLedStrip<12> ledStrip;    // DIN on pin 12

// ---- LED strip ----

#define LED_COUNT 10

rgb_color colors[LED_COUNT];

// ---- Scale ----

HX711_ADC LoadCell(HX711_DOUT, HX711_SCK);

float calibrationValue = 696.0f; // your calibration value

// ---- State ----

float FULL_GRAMS = 0.0f;

bool  fullSet    = false;

// ---- Button debounce ----

bool lastBtn = HIGH;

unsigned long lastChange = 0;

const unsigned long DEBOUNCE_MS = 40;

// ---- Blink state ----

bool blinkState = false;

unsigned long lastBlink = 0;

const unsigned long BLINK_INTERVAL = 500; // 0.5s

// ---- Helpers ----

void showSolid(uint8_t r, uint8_t g, uint8_t b) {

 for (int i = 0; i < LED_COUNT; i++) colors[i] = rgb_color(r, g, b);

 ledStrip.write(colors, LED_COUNT);

}

void showLevelBar(float frac) {

 if (frac < 0) frac = 0;

 if (frac > 1) frac = 1;

 int greens = (int)floor(frac * LED_COUNT + 1e-6f);

 for (int i = 0; i < LED_COUNT; i++)

   colors[i] = (i < greens) ? rgb_color(0, 180, 0) : rgb_color(180, 0, 0);

 ledStrip.write(colors, LED_COUNT);

}

// ---- Setup ----

void setup() {

 Serial.begin(57600);

 pinMode(BUTTON_PIN, INPUT_PULLUP);

 // Quick LED test

 showSolid(0, 180, 0); delay(300);

 showSolid(180, 0, 0); delay(300);

 showSolid(0, 0, 0);

 // Load cell setup

 LoadCell.begin();

 LoadCell.setReverseOutput();

 LoadCell.start(2000, true);

 if (LoadCell.getTareTimeoutFlag()) {

   Serial.println("HX711 timeout. Check wiring.");

   showSolid(180, 0, 0);

   while (1) {}

 }

 LoadCell.setCalFactor(calibrationValue);

 Serial.println("Press button (D7→GND) to set current weight as FULL.");

 // Standby: solid light purple until FULL is set

 showSolid(120, 0, 120);

}

// ---- Loop ----

void loop() {

 static bool newDataReady = false;

 if (LoadCell.update()) newDataReady = true;

 // ----- BUTTON -----

 bool nowBtn = digitalRead(BUTTON_PIN);

 unsigned long now = millis();

 if (nowBtn != lastBtn && (now - lastChange) > DEBOUNCE_MS) {

   lastChange = now;

   if (nowBtn == LOW && lastBtn == HIGH) {

     float grams = LoadCell.getData();

     Serial.print("Button press. Current weight = ");

     Serial.print(grams, 1); Serial.println(" g");

     if (isfinite(grams) && grams > 20.0f) {

       FULL_GRAMS = grams;

       fullSet = true;

       Serial.print("FULL set to "); Serial.print(FULL_GRAMS, 1); Serial.println(" g");

       // confirm with a quick blue blink

       showSolid(0, 0, 180); delay(200);

     } else {

       Serial.println("Not setting FULL (weight too small).");

     }

   }

   lastBtn = nowBtn;

 }

 // ---- Standby purple until FULL is set ----

 if (!fullSet) {

   showSolid(120, 0, 120);   // solid light purple idle

   return;                   // skip rest until FULL is captured

 }

 // ----- LED BAR -----

 if (newDataReady) {

   float grams = LoadCell.getData();

   if (!isfinite(grams) || grams < 0) grams = 0;

   float frac = 0.0f;

   if (FULL_GRAMS > 0.0f) {

     frac = grams / FULL_GRAMS;

     if (frac < 0) frac = 0;

     if (frac > 1) frac = 1;

   }

   // Blink if empty (<= 5%)

   if (frac <= 0.05) {

     if (now - lastBlink > BLINK_INTERVAL) {

       lastBlink = now;

       blinkState = !blinkState;

       showSolid(blinkState ? 180 : 0, 0, 0); // red on/off

     }

   } else {

     showLevelBar(frac);

   }

   // Debug print to Serial

   static unsigned long lastPrint = 0;

   if (now - lastPrint > 400) {

     Serial.print("Weight: "); Serial.print(grams, 1); Serial.print(" g | ");

     Serial.print("Full: ");   Serial.print(FULL_GRAMS, 1); Serial.print(" g | ");

     Serial.print("Level: ");  Serial.print(frac * 100.0f, 1); Serial.println("%");

     lastPrint = now;

   }

   newDataReady = false;

 }

}