I needed to make a cheap, nice and reliable detonator for explosives, rockets, fireworks and anything else that needs to be ignited from a safe distance. This is the result. Igniting explosives using a detonator is much more safer than just using a lighter. And it's also way cooler.
WARNING: ALWAYS HANDLE EXPLOSIVES WITH EXTREME CARE. IGNITING ELECTRONICALLY IS MUCH SAFER BUT STILL, YOU SHOULD BE VERY CAREFUL. ALWAYS LOOK UP THE MINIMUM SAFE DISTANCE OF THE EXPLOSIVE AND PREPARE THE FIRING GROUND ACCORDING TO THAT.
Step 1: Parts
Step 2: Drill Hole
The first thing you need to do is to drill a 23mm (0.9") hole in center of the top cover of the project box for the push button. It's a pretty big hole, so I recommend using a drill press. When you have the hole, then you can secure the push button onto the top cover of the project box.
Step 3: Circuit
It's time for some soldering! Just connect all of the components according to the included circuit diagram. Because the fire button is NoC (normally closed) I needed to somehow invert the signal from the button. I tried using a NOT logic gate, but that didn't work so I ended up with SPDT relay.
The circuit works this way: If there is voltage at the relay coil, the electric match is disconnected from the battery. But if you press the fire button, the relay switches to normally closed gate and the match will catch fire. Also there is a safety switch to make sure that the match doesn't catch fire accidentally. The power switch is there because the relay coil is drawing some current and that could discharge the battery after some time.
Step 4: Putting Everything Together
If your circuit works fine, you can secure everything into the project box. I recommend using hot glue gun. You also need to make holes in the rubber grommets for both of the switches and for the cable. Also, I put a screw terminal on outside of the box, so I don't have to carry the long cable everywhere.
Step 5: Using the Device
You're done! If you did everything correctly, you have a cheap and compact explosives detonator. If you use it with cable shorter than 30 meters then you need just 9V battery to run the circuit. But if your cable is longer than 30 meters the power losses are getting high so you should have more 9V batteries connected in series. Remember to use this device very carefuly and finally, have some fun! There is even a video demonstration. BTW, sorry for the video quality.
Note: ALWAYS FLICK THE POWER SWITCH ONLY WHEN THE SAFETY SWITCH IS TURNED OFF otherwise you risk the explosives firing too early.