This project describes how to build a simple, safe, and reliable electronic detonator. All the parts should total under 25$, and all but one of the parts can be bought at radio shack. This detonator includes numerous safety features such as a detachable power supply, an ARM switch, and an indicator light.
Step 1: Parts List
What I like about this project, is that all the parts can be bought in one place, and the one part that couldnt be bought at Radio Shack had to be mail ordered anyway, so I wound up only making one trip. I include the model #'s when I could find them.
1. Project box (As close to 3x2x1.5 as you can get, remember you need enough room to hold the components but you want a good fit for your hand)
2. A momentary push switch (Model: 275-609)
3. Toggle Switch with On/Off Label Plate (Model:275-602)
4. 5mm Green LED (Model: 276-022)
5. 1/8" Mono Panel-Mount Audio Jack (Model: 274-251) its a 3 pack see but you only need 1.
6. 1/4" mono Panel-Mount Audio Jack (Catalog #: 274-252)
7. 1/8 Mono Phone Plug (Model: 274-286)
8. 2-Conductor Standard Phone Plug (Model: 274-1544) I think thats the one I got, Its got the picture on the website that most looks like mine, however, I'm sure any 1/4" mono (even stereo but then you'd have to pay closer attention to your wiring) plug would work.
9. Soldering Iron and solder
10. 2-Conductor Intercom Wire (Model: 278-857) Im pretty sure thats the wire I bought.
11. Heavy-Duty 9V Snap Connectors (Model: 270-324) Like the other packages it has more then you need
12. 8 AA Battery Holder (Model: 270-407)
13. 8-Pack AA Enercell® Alkaline Batteries (Model: 23-874)
14. Slim Line 2" Alligator Clips (Model: 270-346)
15. Drill with assorted bits
16. Spare hookup wire (You can cut off some of the intercom wire if you need to)
17. Nichrome wire (Can either be bought on e-bay or Unitednuclear.com) make sure you don't get the wire too thick I use unitednuclear.com, but I don't know what gauge it is.
18. I'm assuming you have tools like screwdrivers and wire cutters.
Step 2: Create the Power Supply
Because this is one of the simplest steps I put it first.
1. Cut 2.5 feet off the end of the intercom wire.
2. Strip 1" off each end of each of the 2 wires.
3. Connect one of the stripped off ends of the wire to the 9v battery clip. You can connect the wires like I demonstrate in the crummily drawn diagram.
4. Snap the 9v battery clip onto the 8 AA holder.
5. Unscrew the 1/8" mono plug, slide the black plastic piece onto the other side of the 3ft section of intercom wire, connect the 2 stripped wire ends to the mono plug (make sure they dont touch each other, you can separate them with a piece of electrical tape), slide the black plastic piece over the connection you just made and screw it back onto the plug.
6. Put the batteries in their holder.
When you are done you should have something that looks like the 3rd picture below.
Step 3: Building the Detonator
This is the most complex step. It requires drilling into the plastic casing, screwing in all the pieces, and then wiring them. If you do not have scrap connection wire you can cut off another foot of the intercom wire and use that. For the wiring you can just wrap the wire around each connection, however if the wire wont stay or its too tight of a space to wrap it, you can use the soldering iron and a bit of solder to ensure a good connection.
Use the picture for the best description of where everything should be placed on the box. And the "wiring diagram" for how to connect the wires, because its hard to tell where the wires should connect from the photos.
I am going to refer to the 3 different faces (the ones we use) of the box as top, front, and bottom. In the photo the top is the one with the red push button, and the 1/4" socket. Before you start drilling open the case and take out anything inside (circuit boards, screws, ets).
1. Find a drill bit that matches up with the size of the 1/4" socket. (Remember that all the parts (button, switch, sockets) can be unscrewed. This is so you can push it in from one side, and then screw the other piece on the other side to tighten it to the case. When you choose a drill bit size for each different part, make sure you go by the size of the smallest part of the component that will be pushed through. It may sound confusing, but it should make more sense if you have the components in your hands)
2. Drill that size hole on the bottom of the case.
3. Repeat those steps for the rest of the components, with the switch and LED on the front side, and the push button and 1/4" jack on the top. Note: If you are right handed put the button on the top right side, left handed - top left side. This is so when you are holding it in your hand your thumb will be over the button
4. Now screw all the components in their places (if the LED dosent stay in the hole you can use a bit of glue, on the bottom side, to keep it there.
5. Wire it according to the diagram. Note: The push button is on the top left side in the diagram because the point of view is from the underside of the box.
6. The diagram is pretty self-exclamatory, the blue lines are the wire (duh), the blue blobs are where the wire joins with 2 other wires, and just one big NOTE: wire the LED LAST, before you wire it plug in the power and flip the switch to on, hold the wires to the led one way and then another, see the LED (should) only light up one way, and that is the way you should wire it. (This is because LED's are polarized meaning they will only work when they have current flow through them in 1 specific direction)
When you are done, close the case, and go to the next step.
Step 4: Making the Hookup Wire
This step is very simple and only takes a couple of minutes. Before you begin, decide how you want to store the wire, if you want to keep it wrapped around the spool or if you will just wrap it around the detonator. I just wrap it around the detonator, but it seems more authentic if you leave it on the spool.
1. If you are wrapping it around the detonator, just unravel all of the wire off the spool, strip an inch from both wires on each end, connect the 1/4" mono plug the same way as the other plug, and connect the alligator clips to the other end.
2. If you are keeping the wire on the spool, unravel all of it, strip an inch from both wires on each end, feed about a foot of the wire through the hole on the spool (As shown in the diagram) and out the hole in the top. Then wrap the long part of the wire around the spool and attatch the plug and the alligator clips (The plug goes on the foot long piece comming out of the top of the spool and the alligator clips go on the end of the wire wrapped around the spool)
Now you are ready to set everything up.
Step 5: Setting Up the Detonator
Warning: Make sure the battery pack isnt plugged into the detonator until the end of the setup.
Take an inch long piece of nichrome wire and tape it to whatever needs to be ignited. Connecting it to something to be ignited is a lot easier with a piece of my fuse, which can be made here https://www.instructables.com/id/E9ZBOE35P9EPA8KZXX/. If you use the fuse all you need to do is split a short section of the end of it and put the nichrome between the split strings, and tape it on, making sure that there is enough nichrome left to put the alligator clips on. If you do not use the fuse you need to make sure that the nichrome is touching what needs to be ignited.
Unravel the wire until you feel you are a safe distance from what your igniting, plug the 1/4" plug in, make sure its unarmed (Toggle set to off), plug in the battery, arm it, countdown and push the red button.
It should work, if not make sure all your connections are ok, clean the alligator clips and try again. If it still dosent work make sure you have a high enough gague of nichrome wire.
It works because the detonator is basically an elaborate on/off switch keeping the 12v from the batteries from going over the nichrome until the right moment. Nichrome is a special type of wire that increases its resistance when electricity is passed through it, and because of this it is used mostly as a heating element in hairdryers and toasters. However, the heat it produces can also be used to ignite fireworks and other things as demonstrated in this project.