Timer (thing)

This writeup will describe how to make a timer to set off a Pyrotechnics device.

How timers can be useful

In general, using timers when working with pyrotechnics is not a very good idea - the timing of performances is rarely accurate, and if a performance is aborted, the prop is still active. Also, if an actor is too close to the prop, you can't stop the prop from igniting. bad idea. Using radio or remote controlled detonators makes a lot more sense.

How to make a timer

The easiest (and cheapest) way to make a timer is to get one of those cute little digital kitchen timer clocks - the kind where you punch in a number of minutes and press start, and it starts beeping after X minutes.

What you do, is that you pick the clock apart, and remove the (usually a piezo-ish) speaker that makes the sound. You now want to get the cables that went to the speaker-thingie (if there are none, solder on some - this might be a little tricky, depending on the timer) Then, hook it up as follows:

              ------------
             | +--------+ |
             | |        | | 
             | +--------+ |
             |            | 
             |KITCHEN TIME|
             +---+--------+ 
                 |
                 |
                 |
  --------       |               
   9V     |------T--------------+   
 Battery |                      +--+------------ 
          |------------------------+Electronic fuse
  --------                         +-----------

Usually, your kitchen timer alone will not deliver enough power to set off the fuse by itself, but this can be resolved by using a simple transistor

That was it, really! No ticking clocks, no big bars of dynamite.. With some practice, you can fit this whole mecanism (and a load of actual explosive material) in a box the size of a regular coke can.

A word of advice

This, like the Motion Detonator is a self contained system. That means that if you decide not to use the prop, you are in trouble - if there is less than a minute left untill the timer goes off, it is a bad idea to go close to the prop. At the same time, some timers have the bad habit of going "beep" when you start the timer. Usually (i.e when you use the timer for what it's intended) this is annoying. If the "beep" sets off an explosion between your hands, it's more than just annoying. Make sure that your timer doesn't go "beep" when you press start.

Usually when I make these kinds of props, I include a safety loop. In other words, add a switch and a LED. The LED is coupled straight to the battery, and lights up when the switch is on. This way, you can easily determine if the prop is "armed" or not. This also allows you to use timers that say "beep" - you just start the timer, and then flick the switch.

In any case, as mentioned, timers are a bad idea.