The two things I wanted it to do are
1-Have a pull switch, like a grenade would
2-Provide a small delay between the pulling of the pin and the first noises it made
This is my first instructable, so I welcome any feedback you may have.
Step 1: Get Some Parts Together
You also need a container to put it in, bits of wire, bits of metal, solder, soldering iron, a spring, a tiny push button switch (mine came from a VCR) and other misc garbage type trash.
Step 2: Do Up the Lid
Out of your misc trash, find something non-conducting and round to use as the pull-pin. (I used a chunk of plastic from the broke VCR, it tapers out a bit making it perfect, won't fall through the hole). Drill an appropriately sized hole in the centre of the lid for it.
On the underside, on either side of the hole, attach pieces of scrap metal. I had originally tried gluing them down, but it didn't work so well, so I drilled holes and used tiny nuts and bolts that I had also scavenged.
Also, I drilled holes for the small reset button, and an optional LED indicator light that tells you when the pin is pulled and the thing is working.
To do the actual pin switch part of the lid will take some trial and error. I used a spring that had a low stiffness and attached it between the metal parts so that it reached across them when the pin was out, and was pressed away when the pin was in.
At this point I soldered wires to all of the things that I had attached to the lid. Be sure to choose an appropriate length of wire.
Step 3: Doing the Delay Circuit Bit
If you have a bread board, I recommend doing up the circuit on that first to test out the length of the delay, and how the alarm sounds when it turns on. The values you end up using for the components will most likely vary depending on what kind of transistors and alarm and all of that you use.
A couple of notes about this circuit -
-Because of the components I had, it isn't very grenade like in the fact that it there is no sound from the buzzer for a few seconds, and then it slowy turns on
-The reset button is there because after pulling the pin the first time and having the buzzer sound, the capacitor needs to be discharged to have the delay the second time. On its own, this takes forever.
-I used regular AA batteries, the alarm came withs its own button cells, totaling to more than 3 volts, but I took them out to use in something else. Do what you please here (as with the whole thing).
-My components are mounted on a piece of a soda pop box, again due to the fact that I didn't want to order any of that circuit board stuff and I didn't have any on hand. The components are attached using the wire wrap techniques with a little bit of soldering at the connections to make sure things didn't shake loose.
Step 4: Attach the Batteries, Alarm, LED, and Switches to the Board.
For the alarm, I just left it all in the case and put the alarm out to where the batteries used to be in the alarm. At this point, I took some things out of the alarm that it wasn't going to need to be used for this for use in something else (switches).
Make sure the positive and negatives are going to the right places. This shouldn't be hard to figure out.
Step 5: Finish Up
You can also cut out parts of the container to allow the sound out of it better, or attach the pieces a bit better inside so it can be thrown or suchlike. I wasn't to worried about this part as I have been mainly using it to go off when doors are opened.
Kinda of a trivial toy when finished, but I find it entertaining.