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Meta Title: How to Build a Smart LPG Auto-Reorder System Using ESP32 and IoT
Meta Description: Learn how to build a Smart LPG Auto-Reorder System using ESP32, load cells, GSM, and IoT technology. Includes wiring diagrams, bill of materials, circuit diagrams, flowcharts, troubleshooting tips, and real-world
Running out of cooking gas unexpectedly is a common problem in many households and restaurants. A Smart LPG Auto-Reorder System continuously monitors the remaining gas in a cylinder and automatically sends alerts or books a refill when gas levels become critically low.
This project combines ESP32, load cell sensors, GSM communication, cloud dashboards, and IoT technologies, making it an excellent project for Engineering, ICT, Computer Science, Physics, and Applied Technology categories.
Quick Answer: Smart LPG Auto-Reorder Wiring Diagram
If you want to build the project immediately, use the following wiring configuration.
| Component | Pin | ESP32 Pin |
|---|---|---|
| HX711 DT | DT | GPIO19 |
| HX711 SCK | SCK | GPIO18 |
| GSM Module SIM800L TX | TX | GPIO16 |
| GSM Module SIM800L RX | RX | GPIO17 |
| OLED Display SDA | SDA | GPIO21 |
| OLED Display SCL | SCL | GPIO22 |
| Buzzer | Positive | GPIO23 |
| RGB LED | Signal | GPIO25 |
| Wi-Fi | Built into ESP32 | — |
Important: SIM800L modules require a stable external 4V power supply due to high current requirements.
System Workflow
Gas Cylinder → Load Cell → HX711 Amplifier → ESP32 → SMS Notification → Automatic Reorder
5
Why Build a Smart LPG Auto-Reorder System?
Many homes discover their LPG cylinder is empty only when cooking.
A smart monitoring system helps:
Benefits
- Prevents unexpected gas shortages
- Provides refill reminders
- Automatically books gas refills
- Reduces inconvenience
- Improves household planning
- Supports smart home automation
How Does the Smart LPG Auto-Reorder System Work?
The system consists of four major sections.
1. Weight Measurement
A load cell continuously measures the weight of the LPG cylinder.
2. Signal Processing
The HX711 converts tiny load cell signals into digital values.
3. ESP32 Analysis
The ESP32 calculates remaining gas percentage and predicts usage.
4. Notification System
If gas levels fall below a threshold:
- SMS alerts are sent.
- Mobile notifications are generated.
- Automatic reorder requests can be triggered.
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Bill of Materials (BOM)
| Component | Quantity | Purpose |
|---|---|---|
| ESP32 Development Board | 1 | Main controller |
| Load Cell (20–50 kg) | 1 | Measures cylinder weight |
| HX711 Amplifier Module | 1 | Amplifies load cell signals |
| SIM800L GSM Module | 1 | SMS notifications |
| OLED Display | 1 | Displays gas level |
| RGB LED | 1 | Status indicator |
| Piezo Buzzer | 1 | Audible alerts |
| Breadboard | 1 | Circuit assembly |
| Jumper Wires | Several | Connections |
| Power Supply | 1 | System power |
Estimated Project Cost
| Item | Approximate Cost |
|---|---|
| ESP32 | $8 |
| Load Cell | $8 |
| HX711 | $3 |
| SIM800L | $8 |
| OLED Display | $5 |
| Miscellaneous | $10 |
Estimated Total Cost: $40–50
Components Overview
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Key Features
✅ Real-time gas monitoring
✅ Automatic refill notifications
✅ SMS alerts
✅ Cloud dashboard
✅ Consumption prediction
✅ Low gas warning system
✅ Smart home integration
Block Diagram
LPG Cylinder
↓
Load Cell
↓
HX711 Module
↓
ESP32 Controller
↓
OLED + GSM + Cloud Dashboard
↓
User Notification
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Circuit Connections Explained
HX711 Module
- DT → GPIO19
- SCK → GPIO18
- VCC → 5V
- GND → GND
OLED Display
- SDA → GPIO21
- SCL → GPIO22
GSM Module
- TX → GPIO16
- RX → GPIO17
Indicators
RGB LED → GPIO25
Buzzer → GPIO23
Step-by-Step Guide: How to Build a Smart LPG Auto-Reorder System
Step 1: Install the Load Cell
Mount the load cell beneath the LPG cylinder platform.
Ensure stable and accurate weight measurement.
Step 2: Connect Electronics
Wire the HX711, ESP32, GSM module, OLED, and indicators according to the connection table.
Step 3: Upload the ESP32 Program
The ESP32 program should:
- Continuously read cylinder weight.
- Calculate remaining LPG percentage.
- Predict refill dates.
- Send notifications.
Example logic:
IF LPG Level < 20%
Display Warning
Send SMS Alert
Initiate Auto-Reorder
ELSE
Display Remaining GasStep 4: Configure Notifications
Set:
- User phone number
- LPG supplier contact
- Cloud dashboard settings
Step 5: Test the System
Simulate decreasing cylinder weight and verify:
- OLED updates
- SMS notifications
- Alarm activation
- Cloud synchronization
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ESP32 Program Logic
The ESP32 continuously repeats the following process:
- Read load cell values.
- Calculate remaining gas percentage.
- Estimate remaining usage days.
- Display status.
- Send notifications if necessary.
- Upload data to cloud dashboards.
Mathematical Calculation
LPG Percentage Formula
Remaining Gas (%) =
(Current Weight - Empty Cylinder Weight)
----------------------------------------- ×100
(Full Cylinder Weight - Empty Weight)Applications
This system can be used in:
- Homes
- Hotels
- Restaurants
- Schools
- Hospitals
- Commercial kitchens
- Industrial gas monitoring
Advantages and Limitations
Advantages
- Prevents unexpected gas shortages
- Easy to build
- Real-time monitoring
- Expandable to smart homes
- Supports predictive analytics
Limitations
- Requires load cell calibration
- GSM modules require stable power
- Cylinder movement may affect readings
Future Improvements
You can improve this project by adding:
AI Prediction
Predict refill dates based on usage patterns.
Mobile Application
Track gas consumption remotely.
Voice Assistant Integration
Check gas levels using voice commands.
QR-Based Automatic Booking
Automatically order gas through supplier APIs.
Solar Power
Create a fully self-powered system.
How to Fix Common ESP32 Upload Errors
Error: Failed Connecting to ESP32
Solutions
- Hold BOOT button during upload.
- Check USB drivers.
- Replace USB cable.
Error: Load Cell Gives Incorrect Readings
Solutions
- Recalibrate HX711.
- Verify load cell mounting.
- Remove vibrations.
Error: GSM Module Cannot Send SMS
Solutions
- Use external 4V power supply.
- Verify SIM card activation.
- Check network signal strength.
Error: OLED Does Not Display
Solutions
- Verify SDA/SCL wiring.
- Check I2C address.
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Final Thoughts
Learning how to build a Smart LPG Auto-Reorder System is one of the most practical IoT projects for modern homes.
By combining ESP32, load cells, GSM communication, and cloud analytics, you can create a system that prevents unexpected gas shortages and automates refill management.
