Smart Waste Management System Using Arduino Nano, Ultrasonic Sensor & GSM Module

Project Overview

This IoT project transforms an ordinary dustbin into a smart bin that monitors its fill level autonomously. An HC-SR04 ultrasonic sensor measures the distance from the lid to the garbage surface. The Arduino Nano converts this into a fill percentage and triggers LED indicators, a buzzer, and a GSM SMS alert as thresholds are crossed.

📡

Ultrasonic Sensing

HC-SR04 measures garbage distance every 60 seconds. Formula: Distance = (Duration × 0.034) / 2

📱

GSM SMS Alert

SIM800/SIM900 sends an SMS to the waste authority when fill level ≥ 80%.

☀️

Solar Powered

Solar panel + Li-ion battery + buck converter for 24/7 autonomous, off-grid operation.

💡

LED Indicators

Green / Yellow / Red LEDs give instant visual feedback on bin fill status at a glance.

Components List

🔷

Arduino Nano

ATmega328P, 5V

×1

🔊

HC-SR04

Ultrasonic sensor

×1

📡

SIM800 / SIM900

GSM module + SIM

×1

☀️

Solar Panel

5V–6V, 1W–3W

×1

🔋

Li-ion Battery

3.7V / 18650

×1

⚡

Buck Converter

MP1584 / LM2596

×1

🔔

Buzzer

5V active buzzer

×1

🔴

LEDs (R/Y/G)

+ 220Ω resistors

×3

🔌

Jumper Wires

M-to-F assorted

×12+

📦

Only SoftwareSerial (built-in) is required. No additional libraries needed. GSM uses AT commands over serial.

Wiring Diagram

Pin Reference Table

Module	Module Pin	Arduino Nano Pin	Notes
HC-SR04	VCC	5V
HC-SR04	GND	GND
HC-SR04	TRIG	D2	Output from Arduino
HC-SR04	ECHO	D3	Input to Arduino
GSM (SIM800/900)	TX	D4 (SoftSerial RX)	GSM TX → Nano D4
GSM (SIM800/900)	RX	D5 (SoftSerial TX)	Use voltage divider for 3.3V GSM
GSM (SIM800/900)	VCC	4V (external)	SIM800 needs 3.7–4.2V, 2A — use separate regulator
Buzzer	+	D6	Active buzzer
Green LED + 220Ω	Anode	D7	Cathode → GND
Yellow LED + 220Ω	Anode	D8	Cathode → GND
Red LED + 220Ω	Anode	D9	Cathode → GND
Buck Converter Out	5V OUT	VIN	Powers entire system

⚠️

GSM Power: SIM800/SIM900 draws up to 2A peak during transmission. Never power it from the Arduino's 5V pin — use a dedicated 3.7V–4.2V supply or buck converter output directly. Brownouts will cause resets.

Working Logic

The system uses two core calculations. First, distance is measured by timing the echo pulse. Second, distance is inverted into a fill percentage using Arduino's map() function.

// 1. Distance measurement

duration = pulseIn(ECHO_PIN, HIGH);

distance = duration × 0.034 / 2; // cm

// 2. Fill % (0cm = full, binHeight = empty)

fillLevel = map(distance, 0, binHeight, 100, 0);

// binHeight = 30 cm (adjust for your actual bin)

Decision Flow

Condition	Green LED	Yellow LED	Red LED	Buzzer	SMS
`fillLevel ≤ 50`	✅ ON	❌ OFF	❌ OFF	❌ OFF	❌ No
`fillLevel 51–79`	❌ OFF	✅ ON	❌ OFF	❌ OFF	❌ No
`fillLevel ≥ 80`	❌ OFF	❌ OFF	✅ ON	✅ ON	✅ Sent!

⏱️

The loop runs a 60-second delay between readings to save power and prevent SMS flooding. For testing, reduce to delay(5000) temporarily.

Interactive Bin Simulator

🗑️ Drag the slider to simulate fill level

🔊

HC-SR04

30%

Fill Level30%

Distance (cm)21 cm

LED Status Green ON

BuzzerOFF

SMS AlertNo

Garbage fill level: 30%

📱 SMS Sent: "Bin is 80% full. Please empty." → +91xxxxxxxxxx

GSM SMS Alert Setup

The system sends SMS via AT commands over SoftwareSerial. Three commands are chained together:

AT+CMGF=1

Set SMS text mode (instead of PDU). Must be sent before every message session.

AT+CMGS="…"

Set the destination phone number. Replace +91xxxxxxxxxx with your real number in E.164 format.

gsm.write(26)

ASCII code 26 = Ctrl+Z — signals end of SMS body and triggers the send.

Step-by-Step: Configuring the GSM Module

#	Action
1	Insert an active SIM card (voice + data plan, SMS enabled) into the SIM800/SIM900 slot.
2	Power GSM from a dedicated 4V / 2A supply — NOT from Arduino's 5V pin.
3	Check for a steady 1-second blink on the module's NET LED — this confirms network registration.
4	Replace `+91xxxxxxxxxx` in the code with your authority's phone number.
5	Upload code and open Serial Monitor at 9600 baud — on startup you should see "Smart Waste Management System Initialized" and an SMS sent.
6	Cover the HC-SR04 with your hand to simulate a full bin. When distance < 6 cm (80% of 30 cm bin), the red LED, buzzer and SMS will trigger.

⚠️

The sendSMS() function is called inside the ≥80% condition with a 60-second delay. In production, add a sent flag (bool smsSent = false;) to prevent repeated SMS every minute when the bin stays full.

Solar Power System

The system runs 24/7 without mains power using a solar-charged lithium battery with a buck converter for stable 5V output.

☀️

Solar Panel

5V–6V · 1–3W

→

🔋

Li-ion Battery

3.7V · 18650

→

⚡

Buck Converter

Out: 5V · 2A

→

🔷

Arduino Nano

VIN · 5V rail

📡

GSM (4V tap)

Separate reg

💡

Add a TP4056 solar charging module between the solar panel and Li-ion battery for safe overcharge protection. This makes the system truly field-deployable.

Full Arduino Code

Update binHeight to your actual dustbin depth in centimetres, and replace the phone number with your authority's number before uploading.

Arduino / C++

#include <SoftwareSerial.h>

#define TRIG_PIN    2   // Ultrasonic Trigger
#define ECHO_PIN    3   // Ultrasonic Echo
#define GSM_TX      4   // SoftSerial RX ← GSM TX
#define GSM_RX      5   // SoftSerial TX → GSM RX
#define BUZZER_PIN  6   // Buzzer
#define GREEN_LED   7   // Green LED  (0–50%)
#define YELLOW_LED  8   // Yellow LED (50–80%)
#define RED_LED     9   // Red LED    (80%+)

SoftwareSerial gsm(GSM_RX, GSM_TX); // RX=D5, TX=D4

const int binHeight = 30;  // ← Set your bin depth in cm
long duration;
int  distance, fillLevel;
bool smsSent = false;       // prevents repeated SMS while full

void setup() {
  pinMode(TRIG_PIN,   OUTPUT);
  pinMode(ECHO_PIN,   INPUT);
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(GREEN_LED,  OUTPUT);
  pinMode(YELLOW_LED, OUTPUT);
  pinMode(RED_LED,    OUTPUT);

  Serial.begin(9600);
  gsm.begin(9600);

  // Startup confirmation SMS
  sendSMS("Smart Waste Management System Initialized");
  delay(2000);
}

void loop() {
  // ── Measure distance ──
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  duration  = pulseIn(ECHO_PIN, HIGH);
  distance  = duration * 0.034 / 2;          // cm
  fillLevel = map(distance, 0, binHeight, 100, 0); // %
  fillLevel = constrain(fillLevel, 0, 100);   // clamp

  Serial.print("Distance: "); Serial.print(distance);
  Serial.print(" cm | Fill: "); Serial.print(fillLevel); Serial.println("%");

  // ── Update LEDs and alerts ──
  if (fillLevel <= 50) {
    digitalWrite(GREEN_LED,  HIGH);
    digitalWrite(YELLOW_LED, LOW);
    digitalWrite(RED_LED,    LOW);
    digitalWrite(BUZZER_PIN, LOW);
    smsSent = false;   // reset flag when bin is emptied
    Serial.println("Status: OK — Under 50%");

  } else if (fillLevel > 50 && fillLevel < 80) {
    digitalWrite(GREEN_LED,  LOW);
    digitalWrite(YELLOW_LED, HIGH);
    digitalWrite(RED_LED,    LOW);
    digitalWrite(BUZZER_PIN, LOW);
    smsSent = false;
    Serial.println("Status: Warning — 50–80%");

  } else if (fillLevel >= 80) {
    digitalWrite(GREEN_LED,  LOW);
    digitalWrite(YELLOW_LED, LOW);
    digitalWrite(RED_LED,    HIGH);
    digitalWrite(BUZZER_PIN, HIGH);
    Serial.println("Status: FULL — Alert!");
    if (!smsSent) {              // send only once per fill event
      sendSMS("Bin is 80% full. Please empty.");
      smsSent = true;
    }
  }

  delay(60000);  // read every 60 seconds (change to 5000 for testing)
}

// ── GSM SMS function ──
void sendSMS(String message) {
  gsm.print("AT+CMGF=1\r");                   // Text mode
  delay(100);
  gsm.print("AT+CMGS=\"+91xxxxxxxxxx\"\r");     // ← Your number
  delay(100);
  gsm.print(message);
  delay(100);
  gsm.write(26);   // Ctrl+Z = send
  delay(1000);
}

✅

The code above adds constrain() and a smsSent flag improvement over the original — prevents SMS spam if the bin stays full across multiple readings.

Online Simulation

▶ Try it in Wokwi or CirkitDesigner

Simulate the full circuit online — control the HC-SR04 distance value and watch LEDs and buzzer respond. GSM behaviour can be verified via Serial Monitor.

Open Wokwi Open CirkitDesigner

Simulation Steps

#	Step
1	Go to Wokwi, start a new Arduino Nano project.
2	Paste the `diagram.json` above to auto-add HC-SR04, 3 LEDs with resistors, and buzzer.
3	Paste the code into `sketch.ino`. Change `delay(60000)` to `delay(2000)` for faster simulation.
4	Click ▶ Start Simulation. Open Serial Monitor to see fill percentages.
5	Click the HC-SR04 in the simulator and drag the distance slider. Set to 5 cm → bin reports ~83% full → Red LED + buzzer activate.
6	Set distance to 20 cm → ~33% full → Green LED on. Set to 12 cm → ~60% → Yellow LED on.
7	For CirkitDesigner: add SIM800 component for full GSM SMS simulation of the alert message.

Applications & Upgrades

🏙️Smart City bins

🏗️Construction sites

🏥Hospital waste

🚉Railway stations

🏠Apartments

🏫Smart campus

🏭Industrial bins

🎓Diploma projects

Possible Upgrades

☁️

IoT Cloud Dashboard

Swap GSM for ESP8266 — push fill data to ThingSpeak or Blynk for a live web dashboard.

🗺️

GPS Location

Add a GPS module to report the exact bin location in the SMS for smart route planning.

🔥

Odour / Gas Sensor

Add MQ-135 to detect methane from decomposing waste and trigger early alerts.

📱

Mobile App

Build a Flutter/React Native app that receives push notifications from multiple smart bins on a map.

ROBOTICS

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