Instructables

Make a cheap electronic detonator!

You can use this to detonate a sonic grenade, firework, lights, anything! Super cheap and reliable, $5 project.
 
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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: http://unitednuclear.com/wire.htm
Aron3132 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!
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.
bighead54542 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?
weezee023 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.
gedion40005 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)  gedion40005 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 matt5 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)  gedion40005 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 matt3 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 matt5 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)  gedion40005 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 matt5 years ago
thanks, ill let you know how it goes.
tdwp11224 years ago
I don't know jack about relays-where did you get it and what type is it?
google it
nturner4 years ago
 how do you wire the relay? and can you use the same concept on a two way radio speaker for a detonator? 
akinich4 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
akinich
Minifig6664 years ago
 Leave this thing by the side of the road and the bomb squad will be all over it in second.
dodo1014 years ago
check my kitchen timer video:

http://www.youtube.com/watch?v=gpegSBDOts0
tcm844 years ago
Wow! That purple touch sensitive explosive glued to the speaker is really great idea!
jsaul24 years ago
Hello-
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?
russiankid4 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.4 years ago
Hehehehe, although its not the most original i always had some fun with it when i was younger
Draco69735 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-vad5 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-vad5 years ago
(removed by author or community request)
Take the battery out?
(removed by author or community request)
A Safety Switch; It's easy to build a switch which MUST be held at angle or it won't fire. Most modern heaters have this mechanism in them, you could steal one from Mom's bathroom portable heater lol, just don't be shocked when it then falls over and burns the house down... It's probably easier to build a contact which to cut the power to the main timer / detonator if the unit falls over. Alternatively, and very VERY cheap, would be to take a reed switch, ( you can make from a tin can ) with springs to keep the switch closed. Then take a plastic "shim" or "connection barrier" and slide it between the reed switch contacts... attach a length of fishing line or twine and the thing can't go off until you pull the plastic "safety" off and activate the circuitry. This allows you to GET AWAY FROM THE DEVICE.
(removed by author or community request)
Frogie, You are Right. SAFETY is paramount. This is only a 2nd backup safety switch... the real important switch would be an "Attitude Switch" to stop the timer if the "project" fell over or otherwise got out of true 90 degrees. I just made one out of an "Airborne" bottle... and a lead ball 1/2" and two wires, some electrical tape. It triggers at 50 degrees tip. This makes it possible to have a non vertical launch without mods... but it triggers well dead on at 50 degrees. I'll try to post an instructable but the bloody Airborne bottles have changed... now they have a snap on cap! :—(
(removed by author or community request)
You need to check out the Australian Bottle Rocket gang...

http://home.people.net.au/~aircommand/index.htm

These folks have spent a lot of time making Rockets work.
Or that...
I'd say running away would do pretty well heh.
You could add a switch to the circuit and just turn it off. (I think...)
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.

http://www.radioshack.com/product/index.jsp?productId=2062479

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
icemanx235 years ago
I'm from iraq and i would like to ask "can i use this to detonate explosive?' Just kidding.
Armaggedon5 years ago
does it work?
jpgg925 years ago
how would i rig this up to shut something off ?
matt (author)  jpgg925 years ago
use a not-gate (inverter)
can u post a schematic?
spinach_dip8 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 abend5 years ago
dude i got a 12v relay from radioshack yesterday for like $6
matt (author)  abend8 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.
SANY0236.JPG
Thanks! Now all I've got to do is find a screwdriver...
Screwdriver so you can reach the Dip?
OMG YOU ARE FUNNY!!!! LOL
huh? sarcasm?
Can I have some dip?
NO. oops i mean yes
so ur the new spinach dip?
LOL ROFLCOPTER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Who needs a relay? What's wrong with a transistor?
cpf klee27x7 years ago
I dont think transistors would work either (see post below).
yes, a relay would word.
cpf spinach_dip7 years ago
Problem- With relays and a piezoelectric beeper this wouldn't work. The way the IC in the clock makes the piezo beeper beep is to send it effectively AC, and as you probably know, relays don't like AC.
Ian01 cpf7 years ago
Couldn't you use an AC relay?
no such thing. however, you could build a bridge rectifier, hook it up with a capacitor, and you'd be set.
actually that would be a pulsed DC, a little different from AC. all you need is a capacitor to smooth the signal out. in the event that is actually IS AC, the hook up a full-wave bridge rectifier (that has a name that makes it overrated) before the capacitor.
they have tons of cheap relays at
http://www.allelectronics.com/cgi-bin/category/500/Relays.html

My favorite electronics site
nivaneus6 years ago
So the way this would make something explode is through the alarm system? Would the alarm generate enough energy to set off a fuse?
if you want to set off a fuse, use the process using nichrome wire in the last step. in this case, you would take out the alarm and replace it with the nichrome wire unit.
Alright thanks.
how would i wire to something like this but without a fuse
I want to run into a mall with that piece hanging out of my backpack screaming "allah akbar!!" haha. I would never do that though. just thought it was a funny thought so i wanted to share it. De ja vu. wow. amen.
hahahaha so true. You WILL get shot if you do that. it would be funny if you actually rigged up a small charge, like a little firecracker, and let it out. would scare the crap out of people who saw the timer and saw you run down a hall or behind a corner, and then the timer went off denotating the little cracker. they would take a dump in their pants! and then homeland security would make sure that you "disappeared" without a trace. or maybe they would knock on your door and confiscate, your... egg timer, hahahahaha
yeah,where!?
Demented7 years ago
What am I supposed to detonate actually? And where do I hook up the wires of the explosive?
nkk07 Demented6 years ago
its not HOW TO MAKE A BOMB instructable work it out for yourself
isnowhere8 years ago
its a couple of steps better than the knife or distillary... surely its aims are to find IPs of people who want things to go akaboom like all those previously blacklisted litrature items, by idealistic argentinians
wats "akaboom" LOL!!!
matt (author)  isnowhere8 years ago
Is it just me, or does this comment not make sense at all?
vrogy matt8 years ago
Where is akaboom anyways?
splat vrogy8 years ago
I think he ment kaboom
Rasmus01036 years ago
I can think of a problem that can ruin it. Most timers beep when a button is pressed of when its less then 10 sec left and if you connect it to fireworks it will detonate in your hands. Is there a electronic part that stops a current until you send another current in it and then sends it on?
Bubomb8 years ago
Its impossible to tell tone of voice when you read a post like this on the internet, so I just wanted to say this ahead of time. This isn’t an angry rant. it’s a disappointed one… I think its sad how much we have forgotten about our own rights over the past few years. Every one is going so over the top with this terrorist stuff that we’re afraid to take a piss any more. We forget we have the right to say or write about whatever we want. Its Pop-culture that looks down on words like “electronic detonator” you wont get arrested for mentioning it. Theoretically I could post a How To on making a doomsday device that targets politicians and presidents and be in no trouble at all until I actually made or threatened to use one. As for this timer, this is nothing. I am a member of the Western Pyrotechnics Association and can tell you from first hand experience that devices like this are used during the most patriotic holiday of all; the 4th of July. The person who posted this project puts himself in no danger. Especially when you consider the fact that there are places on the internet that tell you how to make the explosives that would actually do any damage and even those cant be taken down until they meet incredibly specific criteria or your lawyer sucks. ;p
agreed. in fact it actually kinda scares me that this all is common knowledge.
Actually, what scares me is that it ISN'T common knowledge... how hard is it to wire a timer to a relay to trigger something else? and yet, if you ask someone on the street, they would be dumb-founded... But I won't get into a rant about the US education system... this isn't the place.
I meant it is common knowledge among hobbyists. I agree that more people should know how to work with electricity, but less should know how to make explosives out of household items.
Kaiven Bubomb6 years ago
since you're a member of the Western Pyrotechnics Association, i was wondering if you can help me with my detonatar, which has a timer, awesome for large mortar fireworks.

You can here, please, because i would love your help ;)
question: how would you defuse this? like if you hooked it up and then had second thoughts?
Cut the blue wire.
Oh, okay. Is that supplying the power or what exactly does the blue wire do? Just wondering. : )
Step 3: the output to the piezo (blue) is used as the trigger in this device.
Interesting... Is that the same principle you would use to de-fuse a bomb? Disconnect the trigger (I'm feeling slightly James Bondish today!) ? :)
movie-bombs are stupid. the hero always has to decide which wire to cut. its VERY VERY VERY simple. cut the wire going from the detonation device to the actual igniter. (I.E. nichrome wire, blasting cap, you name it.) or you could just pull the igniter out of the explosives themselves.
True... but if I were building one that I knew was going to be found, I would make put fail-safes against that... -have the timer turn OFF the normally closed relay... anyone cutting the wire would make it explode -install a secondary igniter that will detonate when someone touches the first one (ie pulling the igniter out) but, thats' IF I were building one...
Kaiven jongscx6 years ago
lol IF i were building one, i MIGHT use this idea.
Oh. I think I understand now. Thanks!
hey can a wireless dorbell work to set off a fuse???? thanks
yes. quite possible. but you'd either have to have some with some expertise in electronics do it, or show them an exact diagram of the doorbell circuit and have them tell you what to do.
uzerzero6 years ago
Could you break open a lightbulb and pull the filament out and use that as an ignition wire, as a substitute for Nichrome wire? They both will heat up when a current is passed through them, although I don't know if the tungsten filament is hot enough to actually light something on fire. Just curious before I crack open a bunch of lightbulbs in pursuit of this theory.
seems possible. however, you can get nichrome wire out of any appliance with a heating element....curling iron, hair dryer, toaster, you name it. you want the wire that turns red when the appliance is on.
how to detonate?
roachmatt7 years ago
Would the wires from the alarm clock have enuf powere to detonate an explosive? Maybe if it was atached to the devices you place in the model rocket engines that detonate it?
Honestly did you read it??? You conect it to a low volage/low current relay. Then use the other wires of the relay to switch a higher voltage(4.5v) _
HOMEPIE647 years ago
this would be awesome to hook up to fire works on 4th of July
zecandyman7 years ago
i love the way he says "carefully smash open"
j.w_lewis7 years ago
haha im gonna put one in my class at school
rudybaylor8 years ago
I tried to do this earlier this summer before viewing this page... to no avail. The problem is that you cant just buy any timer. You must have gotten lucky with your timer, because the cheap 5$ timer I bought didn't put out enough current to do diddly squat with. Get this: it put out such a low current that adding any sort of connection (wire, relay, or transistor) between the leads of the buzzer would actually turn the timer off. It would reach zero, and turn off. Very frustrating. This is a simple idea, but not very reliable. I'm building a timer using a 555 timer circuit which is MUCH more reliable. Maybe I'll post when I'm done.
ll.138 years ago
yo people take a chill pill it is not worth getting worked up about
trekinhipe8 years ago
I agree completely with the 'pro info' posters, in factI have used similar detonators in one of my ex-hobbies...High powered rocketry as second stage ignitors and recovery 'chute ignitors, as well as the sonic alarm as a recovery device for finding my rockets in trees and large fields. One of the reasons it's an ex-hobby is that BATF is now requiring explosives use permits and fingerprinting in order to buy some of the larger motors and chemicals needed to 'roll your own'. It used to be a hobby, and now it's gotten to be a BIG hassel and no fun anymore. But, that being said, you can find all kinds of information on any one of a million rocketry sites on related subjects. If you think the 'terrorists' don't already know all this, then you're living in a dream world.
bildnething8 years ago
just to let you know..incase you didnt catch this...your essentially taking apart and alarm clock to make another alarm clock...lol...i like the bomb ignition better...spend your time writing bout that then i'll come back
But it's a louder alarm clock :) . . .
saites20018 years ago
Is it really such a good idea to post bomb instructions (step 4)? Interesting article, though.
Would this project be any different if he was hooking up a relay & toaster to the clock? Not at all. Science really isn't about what it is, but what you make of it! If your stupid enough to make a bomb, then I hope you blow yourself up trying. There has been instructables about phone bugs and other potentially malicious stuff. They do all share one thing in common, they were posted for the sake of discovering how stuff works. This project is not different, imho.
godsdog xsmurf8 years ago
Agreed...Technically, this is no different than posting instructions on how to sharpen a knife, or how to make your own micro-distillery (anyone...nudge, nudge...) It is what you make of it.
jcrae godsdog8 years ago
www.homedistiller.org (the Bible of hobby distilling)
Point taken.
stourleyk8 years ago
"Is it just me, or does this comment not make sense at all?" -It's just you. See comment below. "Where is akaboom anyways?" -Playing stupid doesn't make your point of view accurate. "this doesn't carry the current needed to fire off an Estes rocket, much less what you are freaking about." -Just plain wrong. "if you want to go muckin' around with fertilizer and sulpher it's your own silly fault" -And the fault of those who aided and abetted you. "Get real, this is such a non-issue. This project is so obvious anyone who couldn't figure it out couldn't make an explosive device to hook it to anyway." -If it's not an issue you wouldn't have posted. And if the project were so obvious it wouldn't have been posted, either.
jridley8 years ago
Get real, this is such a non-issue. This project is so obvious anyone who couldn't figure it out couldn't make an explosive device to hook it to anyway. Hell, I built a more complex remote detonator than this for a prank at my high school graduation, and it only took about 10 minutes.
jridley jridley8 years ago
BTW I wasn't ragging on the project, it's cool. I was talking about the people who somehow think this is going to enable terrorism. Yeah, because everyone knows that terrorists are too dumb to attach a low voltage relay to a clock without instructions.
Elcubanito8 years ago
Someones going to get a Anal Exam from the FBI!
The polite way to say this would be "Full cavity search"!
davidh8 years ago
What next - mix your own explosives? Ever seen what a home made bomb can do to a subway train ?
jtobako davidh8 years ago
explosives are easy, detinaters are difficult-and this doesn't carry the current needed to fire off an Estes rocket, much less what you are freaking about.
ll.13 jtobako8 years ago
jtobako absoloutly old boy and anyway if you want to go muckin' around with fertilizer and sulpher it's your own silly fault.(there are a lot of decent pyrotechnic websites around (but it's up to you to find them) ) This guy was only stating what the detonater MAY be able to do (he only posted it for the public interest (weel i think so but i may wrong))