loading
Combine a mint tin, piezo siren and some basic components into a personal alarm that's both functional and visually pleasing. This design involves connecting a 12 volt A23 battery to a piezo siren through a toggle switch and a tact switch. The toggle switch is used to arm the device (preventing accidental activation) and the tact switch activates it. I've created a video that covers the basic steps of building the alarm. Grab a cold one and take a couple of minutes to view and enjoy. If you liked the video, please consider subscribing to my youtube channel as this helps towards producing more videos and projects.

Step 1: Materials

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 ).
* Resistor value calculated for a 2v 20ma LED

Affiliate links provided for appropriate products on Amazon.com and DealExtreme.com

Tools:
  • Soldering equipment
  • Small pliers and other basic hardware
  • Drill
  • Hot glue gun

Step 2: Prepare Components

So you can measure your components and determine their placement within the tin, they need to be prepared for installation. This involves disassembling your piezo alarm and adding the resistor to your LED.

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

We need holes for both switches, the LED and the speaker. It may be a tight squeeze fitting all your components into the tin so be sure to measure them and calculate where they can be located without obstructing one another. The placement shown in the image worked for the components I used. The bulkier toggle switch is located at the base of the tin and the smaller tact switch closest to the lid, allowing the battery to fit into the top portion of the tin so you can replace it down the track.

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

Connect up all the components as per the wiring diagram provided. I used 10cm lengths of hookup wire which allows some wire to play with when installing everything into the tin but not so much that you will have difficulty stuffing it all in there.

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

This part will take some patience but given time, a steady hand and a cold drink you'll have it installed. Your mileage may vary depending on the parts used and their size but this worked for me.

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.
I want to buy one if possible <br>Also how long can you set the alarm for can it last a whole night?
Just make a split in the wires with two copper pieces, then put a plastic pin or something that wont conduct electricity. So you turn it on. the pin gets pulled the copper comes together and the alarm is activated.
hey,could we use the buzzer which is used as a cycle horn. <br> <br> <br> <br> <br> <br>
can you use a 9v battery instead of a 12v?
Sure could, however you will need to confirm your piezo siren can accept 9v and ensure the 9v battery will fit in your tin with the rest of the components.You could then use a resistor of 390 ohm or higher due to the lower source voltage.
Easy and so interesting but sir i use any speaker without kit?
Its Easy Enough hahah !<br>
Cool!<br>
I really like this. <br>My only comment is i would worry about the toggle switch getting switched or broken when carried in a purse or pocket. maybe a slide switch instead of the toggle? <br>I bought a small alarm for my wife when she was taking some night class's. what i liked about it was that it had a strap connected to a pull pin. She would carry it in an outside pocket of her purse with the pull strap hanging out. when you pulled the pin that alarm would go off and couldn't be shut off without reinserting the pin in case her purse got snatched (it also had a switch that would activate it before the pin would work). it was much biggeer than this....about the size of a cell phone so i really like yours. I wonder if something like that would work with yours? the idea is that in the event of an emergency you could pull the pin and drop the alarm. ideally the bad guy would go after the alarm to try to deactivate it buying you time to escape. <br>you can also rig the trigger strap to connect to a door knob so that if an intruder opened the door it would trigger the alarm. <br>you may also want to make it a little harder to change the battery so that an attacker couldn't simply pull the battery. maybe simply reverse the battery holder so that the battery faces the inside of the tin? <br>just some thoughts. <br>these aren't criticisms. I really like the project. these are just my thoughts for refinement. <br>nice job.
Excellent suggestions, all feedback's welcome.<br><br>A slide switch would be an appropriate alternative to the toggle and less likely to get caught on the assorted jungle of objects in my girlfriends bag :P<br><br>Really love that pull pin idea, allowing quick activation of the alarm. Not too sure of any off the shelf parts that could achieve it but it's an interesting feature to explore for a version 2.0.
If you add a latching relay (or a relay wired up to latch on) then you won't need to hold onto the tactile (momentary switch) - matter of fact I made something similar, but I was using it more like a sonic grenade... matter of fact that's the same piezo siren! (Though I probably paid more than you ,buying it from Radioshack &gt;&lt; )
Great suggestion, might have to build the siren circuitry incorporating some of these new ideas for a version 2.0 and just use a simple piezo buzzer. Sonic grenade is an awesome use of the siren, could get some good scares out of it I'd say.
can you make and sell these by any chance?
If there's enough interest in the project I would definitely look into it. Not sure how much more work I'll have with my current job which would free up some time. If this becomes a possibility I'll send you a PM.
A nice little first project, but it seems kinda pointless.
How loud is it?
Good question, the sirens rated at 100db. Measured it with the iphone app 'Decibel' and it reaches 100db. Not sure how accurate that is but it's pretty loud.
Dowload Audacity and use that to measure the decibels. <br><br>Nice project.
Very cool!

About This Instructable

15,808views

177favorites

License:

Bio: A tech and gadget enthusiast who enjoys building and creating DIY projects. Check out my projects and tutorials on Instructables and x2Jiggy.com!
More by x2Jiggy:Compact Fluorescent Grow Light Atari Combo Controller Portable Phone Speaker (LM380) 
Add instructable to: