Building a simple alarm that alerts you when someone opens your door can be a straightforward DIY electronics project using just a few common components. With some basic electronic skills and the right parts, you can create your own compact and customizable security device to notify you of any unwanted visitors. Follow these steps to learn how to make your own door opening alarm at home.

What You Will Need

To build a basic DIY door alarm, you will need:

Additionally, you may want header pins, resistors, capacitors, and a power switch. Having a soldering iron, wire cutters, and basic hand tools will also help.

Circuit Design

The alarm uses a simple circuit consisting of just a few parts wired together:

Here is a circuit diagram showing how to wire up the components:

How to Build a Simple DIY Electronic Alarm That Alerts You When Someone Opens Your Door

Simple door alarm circuit diagram (Image credit: AllAboutCircuits)

For detailed schematics of complete DIY door alarms, refer to these example projects:


Follow these steps to build your door opening alarm:

1. Prepare the enclosure

Select a plastic enclosure box just large enough to fit your circuit board and battery comfortably inside. Mark and drill holes for the buzzer, micro-USB port, power switch, and any status LEDs.

2. Add components to the circuit board

If using a solderable breadboard or perfboard, insert and solder header pins. Then add the microcontroller, buzzer, reed switch terminals, power switch, status LEDs, resistors, and capacitors as per your circuit schematic.

For a non-solder breadboard, simply insert jumper wires and press components into place.

3. Upload alarm code

Using the Arduino IDE or other firmware programming tool, upload your programmed alarm code onto the microcontroller. This code activates the buzzer when the reed switch opens.

4. Connect reed switch and mount magnet

Connect two wires from the reed switch pins on the circuit board to your door frame and door edge. Mount the magnet on the door to align with the reed switch when closed.

5. Power and test

Supply power from the 9V battery and turn on the alarm. Check that the buzzer sounds when you open the door. Troubleshoot any issues with your wiring or code.

6. Enclose the circuit

Once working, mount the circuit board with standoffs inside the enclosure. Connect the 9V battery clip and screw on the back cover. Your DIY Arduino door alarm is now ready for installation!

Installing and Using Your Alarm

To install and operate your DIY door alarm:

With a basic understanding of electronics and some DIY skills, building your own Arduino door alarm is both fun and practical. Customize it to suit your needs for the ultimate smart home security on a budget.