Picture of Make a cheap electronic detonator!
You can use this to detonate a sonic grenade, firework, lights, anything! Super cheap and reliable, $5 project.

Step 1: Get your materials

Picture of Get your materials
-Depending on what you want to do, I suggest you pickup an alarm clock (with sound) or kitchen timer. Both were $1 at Dollarama!
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Aron3133 years ago
Thats cool! I used a cell phone to detonate mine. I made it so that when you call it sets off the firework!
Aron313, Im trying to detonate it with a cell phone also, can you tell me how you did it for yourself?
Should I just buy any type of alarm clock, what gauge nichrome wire would be perfect, do I need a specific kind of relay or is there a basic relay that would would work on any design. By the way I want to use fireworks instead of a personal alarm.
bighead54543 years ago
Would it be possible to change what is played when the alarm goes off? Such as changing it to sound an explosion for a prop?
weezee024 years ago
can i connect the alarm clock to a voice recorder so that whenever i set an alarm, it will playback my voice? thanks in advance, it is for our thesis.
gedion40006 years ago
I have a timer much like this one but when the alarm goes off it beeps, its not a continuous sound, will the current from the short beeps be enough to activate the relay? or does it need to be constant. i want a count down timer to power a relay to fire off a confetti cannon. i was hoping to use an electromechanical relay for its looks, but is there another one that might work better?
matt (author)  gedion40006 years ago
If your sound input is not continuous use a latching relay. This is essentially a flip-flop and a relay combination. Did you already buy relays?
gedion4000 matt6 years ago
no i haven't gotten relays yet. i had actually looked at the latching relay option late last night. from what i can tell you need the charges to be reversed in order to turn it off again, any suggestions on that aspect? i was also not sure of how much input they typically need to switch. the alarm i currently have sweeps from .45 volts to .27 volts. about every second or so, but it beeps really fast so i think my meeter is a little to slow to get a super accurate reading.
matt (author)  gedion40006 years ago
There are many relays available. If you cant find one that has a very low turn on voltage, then buy a transistor with a low threshold voltage, or a low voltage relay. And have it connect a source that has voltage high enough to trigger your latching relay. Then your circuit will look like this: Timer signal--> transistor --> latching relay Yes reverse voltage is needed to switch the latching relay. But for your application, a one time firing confetti gun, nothing matters after its been fired. Just disconnect the power to the circuit and then use it again.
jpoopdog matt4 years ago
heres a better idea, use a signal relay, with the source current (the sound output), passing through a low current high voltage (e.g A23, 12v) battery. signal relays can turn on high voltages with extremely low currents, such as mine which can turn on up to 15V 5A, using a current at least 5V 5ua (thats the next lowest form of miliamps), which is 0.005 or so miliamps. i have tested this instructable with my signal relays and they work fine, i also discoverd, with my cheap digital alarm clock, that on the microprocesor, or whatever the long black thing with all the pins has (i forgto the name), i remember if i shorted the first and second pins on one side while the alarm went off, or begun it with shorted, the alarm beep would be contant, and oddly become increasingly loud also, but only for 20seconds before it stoped.
gedion4000 matt6 years ago
thanks Matt, i didn't think about using a transistor to fire the relay, ill have to work something out like that if i cant find the right latch. i will also have to figure out some kind of switch to reverse the voltage, the cannon needs to be reset within a few minuets to be used over and over again
matt (author)  gedion40006 years ago
Heres an idea for the reset switch: From your battery source run a line, that goes through a push button, and a diode to your relay (make sure its reverse polarity). Then the button will be used to reset it. Also put a diode on the output from the transistor. The diodes will prevent the reverse voltage from going into and damaging your transistor and your power source. Good luck, let me know how you make out.
gedion4000 matt6 years ago
thanks, ill let you know how it goes.
tdwp11225 years ago
I don't know jack about relays-where did you get it and what type is it?
google it
nturner5 years ago
 how do you wire the relay? and can you use the same concept on a two way radio speaker for a detonator? 
akinich5 years ago
dude i have the same alarm clock
i opened it up and the wire came of from the solder joint
i need ur help
Minifig6665 years ago
 Leave this thing by the side of the road and the bomb squad will be all over it in second.
dodo1015 years ago
check my kitchen timer video:

tcm845 years ago
Wow! That purple touch sensitive explosive glued to the speaker is really great idea!
jsaul25 years ago
Cool idea--- I'd like to use the guts of a digital, or even analog alarm clock to rig an old portable record player to work as a bedside alarm clock. This would have a record play as a wake-up in the morning... I think it may be a bit more complicated to rig the alarm circuit for this, as the device should still have an on/off switch for normal operation, plus an alarm activated "on." Not sure how to go about any of it- this would be my first such project. Any advice or ideas?
russiankid6 years ago
well in the picture u dont have a seprate battery for the higher voltage of the personal alarm and that that doesnt look like relay can u help out
Lance Mt.6 years ago
Hehehehe, although its not the most original i always had some fun with it when i was younger
Draco69736 years ago
In this photo you can clearly see a resistor- the dark, cylinder at the top/left -and a small transistor- a smaller dark shape- just below and right of the resistor. It is helpful for you to know the function of these components and how to connect them to accomplish the desired outcome of this Instructable. Don't give up! It can be done!
e-vad6 years ago
ok.. i am kinda new to this stuff. and i have worked with some basic wiring but when it comes to a relay i have no clue, so could some one maybe make an instructable or just tell me where to hook the wires up and where they are coming from.
matt (author)  e-vad6 years ago
i'd like the alarm to throw a 24 volt sprinkler valve. anyone know how?
Hi... You need a relay to fire the 24 v. circuit which can be triggered by the small voltage coming out of the speaker terminals. You would hook the Relay between 3- 9v. batteries connected in parallel and then to your sprinkler valve, using the timer / relay to fire the valve.


This relay from Radio Shack should do nicely.
The batteries, while DC, work fine with the AC Sprinkler valves, Just don't hold the button down too long or it could burn out the wiring in the Valve.
thanks a million!
Sure... I tried to send a diagram but something about formatting stopped it. Good luck and BE SAFE! Mark
icemanx236 years ago
I'm from iraq and i would like to ask "can i use this to detonate explosive?' Just kidding.
Armaggedon6 years ago
does it work?
jpgg926 years ago
how would i rig this up to shut something off ?
matt (author)  jpgg926 years ago
use a not-gate (inverter)
can u post a schematic?
spinach_dip9 years ago
I'm looking to cannibalize the mess of broken electronics in my attic, and need a suitable relay. Any idea where I might be able to pry such a model out?
There is a low voltage relay in a lot of phones and modems. It is usually near the connectors for the phone line, and usually about an inch long. Other than that, it's a bit hard to describe, since it varies from phone to phone.
CameronC abend7 years ago
dude i got a 12v relay from radioshack yesterday for like $6
matt (author)  abend9 years ago
I pulled a relay off an old fax modem, but you can just buy one from an electronics shop....... you can also use a transistor depending on what you want to accomplish.
Thanks! Now all I've got to do is find a screwdriver...
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