Make a Cheap Electronic Detonator!





Introduction: Make a Cheap Electronic Detonator!

About: I liked designing and building things long before I became an engineer, now I get paid to do it!

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

Step 1: 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!

Step 2: What to Detonate?

I picked up a 90dB window alarm, and was going to use that for a sonic grenade, then I found a 105dB personal alarm, and decided it would be better!

Step 3: Building.

-This is where the fun starts, smash open the clock and the and locate the wires running to the tiny alarm speaker.
-This will be a low voltage out put so you will have to connect those wires through a relay to allow a higher voltage (usually 4.5V) to be sent to the personal alarm. otherwise it will not be loud enough.
-Carefully smash open the alarm (you will need to preserve part of the case, because the speaker needs to vibrate in it to amplify the noise)
connect the wires to the alarm speaker to the relay (note the correct polarity)

This is pretty much it, set the alarm clock to go off at a certain time, and its output will be sent to the relay, which will set off the alarm!!! This makes a great alarm clock for someone that doesnt like to wake up!!!

Step 4: Optional

Of course you could have used the timer if you wanted to make a count-down detonater... and instead of an alarm at the end of the relay, how bout an explosive?

Get some nichrome wire, and thread it through a safety fuse, and connect the wire to the relay, for a more detailed how-to on electrical igniters visit UN:



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    Thats cool! I used a cell phone to detonate mine. I made it so that when you call it sets off the firework!

    1 reply

    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.

    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?

    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.

    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?

    7 replies

    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?

    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.


    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.

    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.

    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


    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.

    thanks, ill let you know how it goes.

    I don't know jack about relays-where did you get it and what type is it?

    1 reply

     how do you wire the relay? and can you use the same concept on a two way radio speaker for a detonator? 

    dude i have the same alarm clock
    i opened it up and the wire came of from the solder joint
    i need ur help

     Leave this thing by the side of the road and the bomb squad will be all over it in second.

    check my kitchen timer video:

    Wow! That purple touch sensitive explosive glued to the speaker is really great idea!