Fareed Mohmed← All projects

Arduino project · Fire, gas and safety · Easy

Knock and Vibration Alarm

Any shake or knock sets off a buzzer and a red LED.

What you will learn

  • How a vibration switch works
  • How to use a digital input
  • Where knock alarms are used

How it works

When the SW-420 sees a shake, its output goes HIGH, and the program turns on the buzzer and LED.

Try this next

  • Count knocks with a variable.
  • Use it on a cupboard or locker.
  • Add a latch so the alarm stays on.

The simulator program and explanation on this page are original. The idea follows a classic Arduino project that students have built for years.

1Choose your Arduino board
2Build the circuit
Parts: sensors and actuators (tap to show or hide)

Try the inputs (virtual sensors)

Pins (you can change them)

PartArduino 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.

#ColourFrom (part and leg)To
3Define the sequence

Steps run from top to bottom, then start again. While the simulation runs, the active step is highlighted in green.

4Arduino code





5Parts list and where to buy


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.


#ItemQtySearch termBuy / compare



6Export








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.



7Learn: do’s, don’ts, cautions and tips





In the real world
An alarm box that notices movement
Tilt, knock or touch in the simulator. The buzzer rings and the red beacon flashes in the real room.
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.