Arduino project · Fire, gas and safety · Easy
RFID Unknown Tag Alarm
A buzzer and a red LED warn when an unknown tag is shown.
What you will learn
- How to find unknown cards
- How a list of known cards works
- How alarms react to bad input
How it works
Card number 3 means "not in the list". Then the buzzer and the red LED are switched on.
Try this next
- Count the wrong tags and lock after 3.
- Send an SMS on a wrong tag.
- Add a camera trigger.
The simulator program and explanation on this page are original. The idea follows a classic Arduino project that students have built for years.
Parts: sensors and actuators (tap to show or hide)
Try the inputs (virtual sensors)
Pins (you can change them)
| Part | Arduino pin (change it here) | How to wire it |
|---|
Every wire, one by one
Red rail = 5 V from the Arduino 5V pin. Black rail = GND. The coloured wires carry signals. Match the wire colours on the drawing to this list.
| # | Colour | From (part and leg) | To |
|---|
Steps run from top to bottom, then start again. While the simulation runs, the active step is highlighted in green.
Quantities come from the parts you added. The store links open a search for that item on Robu.in, Amazon.in and ThinkRobotics, so you always see what is in stock today. Check the model, voltage and price before you order.
| # | Item | Qty | Search term | Buy / compare |
|---|
The PDF has the circuit sketch, pin table, every wire, sequence, full code, the parts list with store links, do’s and don’ts for each part, and the safety notes. The project file lets you come back and keep editing.
In the real world
A locked door with an alarm
Show an unknown card in the simulator. The door stays shut, the red lamp lights and the buzzer sounds.
Tip: use the gold tab at the bottom of the circuit drawing to pull the real-world view up over the Arduino board. Your parts stay visible above it, so you can press a button and watch the real scene react.
- RFID card = a card shown to the reader
- Buzzer = the alarm beep
- Red LED = access denied