Duress Code Alert System Kit with Arduino Uno + Relay
Build a Silent Duress Alarm with Arduino Uno – Sends Hidden SMS When You Need Help
Every part needed, pre-tested for compatibility, with an AI build companion trained on this exact project. Shipped from Bengaluru in 3-5 days.
You’ll craft a working access control system that hides a life-saving secret. Enter one PIN on the keypad and the relay unlocks normally. Enter a second, pre-programmed duress PIN and the system unlocks identically on the outside — but behind the scenes it dispatches a silent SMS to a trusted contact. Perfect for hostel corridors, lab doors, or personal safety scenarios, this project puts advanced embedded security concepts in your hands.
What You'll Build
By the end of this build, you’ll hold a compact, battery-ready (through the buck converter) device that reads keypad entries, drives a 0.96” OLED display, toggles a relay, and uses a SIM800L GSM module for discreet alerts. You’ll have a fully functional prototype you can mount in an enclosure and present as a final-year engineering project or a Smart India Hackathon security solution.
What You'll Learn
- Interface a 4x4 matrix keypad with Arduino Uno using the Keypad library and implement debouncing.
- Send and receive SMS via AT commands on the SIM800L module, including network registration and message formatting.
- Code a two-tier PIN logic that seamlessly triggers a silent alert without displaying any difference on the OLED or relay behaviour.
- Solder the entire circuit on prototype boards, manage power with an LM2596 buck converter, and place decoupling capacitors to stabilise GSM transmission spikes.
Kit Contents
| Component | Quantity |
|---|---|
| Arduino Uno R3 | 1 |
| 4x4 Keypad | 1 |
| SIM800L GSM | 1 |
| 5V Relay Module | 1 |
| LM2596 Buck Converter | 1 |
| 0.96in OLED | 1 |
| 1000µF 25V Capacitors | 2 |
| 10kΩ Resistors | 5 |
| 100nF Capacitors | 5 |
| PCB Prototype Board | 2 |
| Soldering Iron | 1 |
| Solder Wire | 1 |
Why Buy This Kit Instead of Sourcing Parts Separately
| Factor | Sourcing Separately | Compoden Kit |
|---|---|---|
| Compatibility checks | You verify every part | Pre-tested as a system |
| Build support | Forums and scattered tutorials | AI companion trained on this exact project |
| Time to first working build | Days of debugging | Hours, with step-by-step guidance |
| Shipping coordination | Multiple sellers, multiple delays | One shipment from Bengaluru in 3-5 days |
Who This Kit Is For
This is for the advanced student who already knows Arduino basics and is comfortable soldering. If you’re a B.Tech (ECE/EEE) student building a final‑year security project, a Smart India Hackathon team prototyping a discreet alert system, or a hostel resident looking to add a hidden safety net to your door, this kit gives you the exact hardware and learning pathway. CBSE Class 12 and ATL Tinkering Lab mentors will find it a rigorous step up from entry‑level kits.
Built and Backed by Compoden
Every Compoden kit ships with an AI build companion trained on this exact project — accessible via a QR code on the box, with WhatsApp and email backup. We've spent 10 years building projects for makers, schools, and institutions across India. If a part fails because of a manufacturing defect, replace it free within 7 days.
What if I get stuck during the build?
The AI companion walks you through each wiring step and code upload. If you need a human touch, WhatsApp our support team with your order ID — we’ll help you debug in real time.
How does the duress PIN work without arousing suspicion?
The Arduino checks the entered PIN against two stored values. Both trigger the relay and show the same “Access Granted” on the OLED, but the duress version also executes a hidden function that sends an SMS. The relay click and display timing are identical, so an observer sees only a normal unlock.
Do I need a separate SIM card for the GSM module?
Yes, insert any 2G‑capable SIM (Airtel, Vodafone Idea, or BSNL) with SMS balance into the SIM800L holder. The module requires a 2G network; if your area has only 4G/5G, use a SIM that falls back to 2G for SMS.
Can I modify the SMS message and recipient number?
Absolutely. The AI companion and supplied circuit diagram guide you through editing the Arduino sketch. You can change the alert text, add multiple recipients, or even trigger a call instead of an SMS — all with simple AT command modifications.
Two PINs on keypad — real PIN unlocks, duress PIN sends silent SMS alarm while appearing to unlock.
What's in this kit
- Arduino Uno R3
- 4x4 Keypad
- SIM800L GSM
- 5V Relay Module
- LM2596 Buck Converter
- 0.96in OLED
- 1000µF 25V Caps x2
- 10kΩ Resistors x5
- 100nF Caps x5
- PCB Prototype Board x2
- Soldering Iron
- Solder Wire
Choose your assembly option:
- Soldering Kit — 25W soldering iron, 60/40 solder wire, flux, and small perfboard for permanent assembly.
- Breadboard Combo — 800-point full-size breadboard with 65-piece jumper wire pack for solderless prototyping.
Shipping Information
- Prepaid Orders: ₹75 for orders up to ₹999, FREE shipping above ₹999
- COD Orders: ₹125 shipping + ₹50 COD fee = ₹175 total
- Delivery Timeline: Dispatch in 1-2 days, delivery in 2-7 days depending on location
Returns & Warranty
- 7-Day Return: Manufacturing defects only (approval required)
- Warranty: 7 days from delivery
- Non-Returnable: Batteries, consumables, cut wires, clearance items