Need Help creating a timed buzzer (prop bomb)

[ncore]

Hi, I would first like to introduce myself. My name is Nick, I live in PA and my hobby is not in electronics, it is in airsoft. If you don't know what airsoft is, it is a military simulation sport where you carry replica firearms that use batteries, gas, or springs that fire little plastic bbs.

That being said, I am interested in building a prop timed bomb that can be set for x minutes and y seconds and give out a loud (and I mean loud) sound when the timer hits zero.

Obviously you can buy a cheap battery operated kitchen timer at walmart, but the sound of that would not quite be loud enough.

I am not one for electronics (obviously), but I am asking if disconnecting a kitchen timers wiring to it's speaker and instead, hooking it up to a small speaker (from a broken radio or car). Would this work or would there be a problem of not enough voltage going into the larger speaker?

Also, how would I get it to make the sound I want and not an annoying kitchen timer sound?

If anybody has some really good ideas on how to do this effectively without it being too expensive, please help me make this.

Thanks.

 

[KMoffett]

My son played airsoft. Helped him work on a hand grenade. I'm still finding those darn little yellow plastic BBs around the shop...years later. If you're talking an audio boom, that means a big speaker and a big battery. How big a device do you envision?

Ken

 

[ncore]

only about the size of a small briefcase. I would like it to be armed and disarmed, have a visual timer (possible a ticking sound, but unnecessary), and have a very loud noise go off when the timer reaches zero.

The sound that goes off doesn't have to sound like a sonic boom. It has to be loud enough to hear it from far away and quiet enough that your ears don't explode if your standing right next to it.

 

[KMoffett]

A big speaker in a small brief case box would be impossible...but maybe a bunch of small speakers connected in series/parallel could get you enough volume. Direct drive the speaker array from a +12V supply with a MOSFET. The sound could be stored in a PICAXE 08M2 microcontroller and PWM drive the MOSFET.. The controller could be triggered off the kitchen timer, or the whole timer function could be performed in the controller. But, you would need to find someone locally that could do this for you.

Lot of sounds:http://www.shockwave-sound.com/sound-effects/explosion_sounds.html

Ken

 

[ncore]

Thanks, but how would I get a timer to play one specific sound?

The sounds you posted sound cool, but I don't see how I could possible get a kitchen timer of all things to play one.

 

[KMoffett]

The kitchen timer is just the timer portion. You would need a sound recording device like the microcontroller I recommended, or maybe the one out of a greeting card and amplified.

Ken

 

[ncore]

so how would I modify a greeting card to play a sound?

 

[KMoffett]

I'm not sure at this point, but I think it could be done. I would use the microcontroller...because I have them. I may have to play around with the card recorder.

Ken

 

[KMoffett]

I didn't have a greeting card, but I did have a recording picture frame. http://www.radioshack.com/graphics/uc/rsk/Support/ProductManuals/6300977_PM_EN.pdf. The "play" button could be triggered by a transistor that is triggered by the timer's audio output. The "frame's" output could go to an amplifier that would drive the speakers. This would all depend on the particular timer, card, amplifiers and speakers. Too many variables to complete a design here.

Here is a recorder: http://www.radioshack.com/product/index.jsp?productId=2102855
Here is an amplifier. http://www.electronickits.com/kit/complete/ampl/ck706.htm
Speakers out of old desk-top computer external-amp/speakers are compact and put out a lot of volume. http://www.mpja.com/prodinfo.asp?number=14618+SP

Ken