Step 1: Materials
- Mint Tin. The dimensions of my tin are 40mm x 77mm x 22mm.
- Mini piezo siren capable of being run by a 12v power source. ( Amazon )
- A23 12v battery ( Amazon / DealExtreme ) and holder
- Toggle switch ( Amazon )
- Tact switch or other momentary on switch ( Amazon )
- Red 5mm LED ( Amazon / DealExtreme ) and a resistor exceeding 500ohms*. I used a 620 ohm resistor ( Amazon ).
Affiliate links provided for appropriate products on Amazon.com and DealExtreme.com
- Soldering equipment
- Small pliers and other basic hardware
- Hot glue gun
Step 2: Prepare Components
My piezo alarm required removing two screws located on the back. The speaker could then be pried free with a flat head screwdriver and the circuit board removed with a pair of pliers. I also extended the speakers wiring to make it easier to work with when installing into the tin later on.
The LEDs legs were bent flat against the base and the resistor added to the positive leg. It doesn't matter which side you add the resistor to as long as you note which leg is the positive and negative.
Step 3: Mark and Drill
Apply masking tape to the tin to easily mark the holes with a pencil. I also placed the tin on paper towel while drilling to prevent scratching.
Step 4: Wire It Up
Once you've got it all together, test your setup by installing the A23 battery into it's holder. The LED should light up once the toggle switch is activated and only allow the alarm to sound when the device is armed. Now you've confirmed it's working, you can move on to assembling the alarm.
Step 5: Stuff It All in the Tin
The circuitry for the piezo alarm was hot glued into the base of the tin. The toggle switch was then installed using pliers, followed by the LED and the tact switch. Be generous with the hot glue to ensure everything stays put. The speaker is then pushed into place, don't be concerned if it doesn't line up perfectly with the holes drilled. The battery and holder is then installed in the top of the tin facing upward to allow the user to replace the battery if need be.
The lid on my tin wouldn't close properly and required I give one side a trim with a dremel. That's it! You should now have a functioning personal alarm. Test that it works correctly and roam the streets with the knowledge you can make a lot of noise should someone cause you trouble.
More projects and videos at x2Jiggy.com. You can also follow my twitter feed @x2Jiggy.