Homemade ignition help

[souljahz_unite]

Hey there,

Im currently working on a different ignition than the usual bbq ignitor and things like that. Ive taken apart a disposable camera and plan to use the circuit inside to create my spark. I wanted to make it a remote detonator kidn of feel so Ive enclosed the project into a project box to hold everything. From the project box, two wires will run and attach to the cannon's screws which is my spark-gap in the cannon.

Here's the question however, ive got everything wired up so taht when you push teh push button, the capacitor begins to charge up. The led i have will light up (its just replacing the ooriginal led on teh circuit board from the camera) but next is where i get stuck. Everything is charged and ready to fire, however i'd like ot use my on/off toggle switch so that it fires (discharges the capacitor).

How would i wire the on/off toggle switch into the circuitry so taht when the switch is flipped from off to on, the capacitor will discharge sending the voltage through the wires and into my cannon?

Theres a picture attached so that you see what the setup looks like. Hopefully itll help explain my idea.

[Fnord]

Err.. this isn't a difficult problem. Think about how you "discharge" a battery. You can identify the capacitor on the board, right?


The detonator in the picture looks very well-made. Surely if you can build that, you can figure this out?

[souljahz_unite]

Ive tried but the only solution i have come up with is that i wire in the toggle switch so that it comes in the way of the positive lead from the capacitor.

The negative lead will go straight to the connector out of teh box, while the positive lead from the capacitor will go to the toggle, and the other side of the toggle goes to the positive? Will this work?

Ive thourally thought about this but im so confused at how teh capacitor works with it charging and discharging. The only discharge ive done is shorting the capacitor to get rid of any built up charge so its safe to handle.

[jrrdw]

Here is a how to if you haven't seen it. click me

[SpudFarm]

those flash circuits (?) are acctualy pretty hard to mount in something like that iv`e tryed it but the charging button thing was hard to connect to a switch (thats my model of the circuit) but i am going to give it one more try and get it up and running (if i can)

yes i know i am a noob in electric stuff

[TurboSuper]

Okay:

A capacitor is kind of like a battery; if you connect it to a power source, it will charge up to match the battery voltage. Then, you can disconnect it from the power source and use it just like it were a battery, although it will discharge much more rapidly.

Therefore, your flash circuit is pushing ~200V into the capacitor. To discharge it, you need to connect a resistive load in parallel with it, much like with a battery. This is your short (which is effectively 0 ohms, so you get a huge current spike and thus a spark), but it can also be your ignition coil or whatever.

Hope that clears it up some.

[ralphd]

There should of been 2 trip wires from the shutter or a single that gets grounded. If you can wait, I'll pick one up this weekend and check it out. I will be building another launcher sometime soon and I want a better ignition system. What make is it? I see flashes all the time when I go to the thrift stores but never concidered them for my launcher.

[TwitchTheAussie]

Im still confused about triggering them too. The wiki doesnt help me much.

[BigGrib]

I would use a two circuit on-off-on spring loaded switch one side to charge the capacitor and the other side to discharge it. if that makes any sense to anyone

[souljahz_unite]

Makes sense to me BigCrib, i jsut like the feel about having that push button and the l.e.d lighting.

I did some researching and saw some pictures of some people wiring capacitors to discharge and came up with this. It is quite simple and doesnt need the complicated work as in the wiki.

All you do is have one lead from the capacitor ( possibly from one end of the flash tube ) and connect it to one of the connectors you'd plug wires into. Then, the other end of the tube has a wire running to one end of the switch. The other connector of the switch is then wired to the second connector u'd plug wires into. Anyone know if i was fed bs? Or will it work?[/img]

[BigGrib]

you know i built an ignition system for something i cannot discuss, but it could also be used for a model rocket ignition system but i used an generic ignition key switch that i got from napa and i wired it in so that i flip the key to the on position and covered toggle switches for 4 different circuits and then use the start position on the key switch for ignition of those selected circuits. also have lights indicating which circuits are hot for ignition. it's a pretty cool setup all in all. i also used quick connectors for each circuit for easy assembly and disassembly, it merely plugs into my cigarette lighter in my truck and i can run things up to 500 feet away.

[TurboSuper]

Makes sense to me BigCrib, i jsut like the feel about having that push button and the l.e.d lighting.

I did some researching and saw some pictures of some people wiring capacitors to discharge and came up with this. It is quite simple and doesnt need the complicated work as in the wiki.

All you do is have one lead from the capacitor ( possibly from one end of the flash tube ) and connect it to one of the connectors you'd plug wires into. Then, the other end of the tube has a wire running to one end of the switch. The other connector of the switch is then wired to the second connector u'd plug wires into. Anyone know if i was fed bs? Or will it work?[/img]

Yup, that sounds like it should work. The only danger is the current spike welding the switch closed, which is why the wiki reccomends using a more complicated setup involving an automotive relay.

Personally, I've dumped a cap through a small push-button switch and it was fine.

[souljahz_unite]

TurboSuper wrote:

Yup, that sounds like it should work. The only danger is the current spike welding the switch closed, which is why the wiki reccomends using a more complicated setup involving an automotive relay.

Personally, I've dumped a cap through a small push-button switch and it was fine.

Yeah i read about that too but i think the capacitor is small enoigh so that nothign too big liek that can happen. Hopefully not otherwise ill have to invest in doing the relau option and buying a new switch. I beleive the capacitor puts out 330V so in omparison to some bigger caps im hoping it doesnt do anythign of the sort.

[mark.f]

Here's the problem though. A capacitor doesn't have enough voltage to produce the spark required for easy, reliable ignition of a combustible mixture. Most designs step up the voltage from the capacitor dump to working levels, or they lower the resistance of the air by ionizing it between the two electrodes, (think three spark method).

The simplest way I have seen a flash-ignition done is what killjoy used on FEAR. You would simply wire that toggle switch in place of the switch on the circuit board which triggers the flash, (the one that powers the small HV transformer which ionizes the gas in the flashbulb), and then wire an ignition coil in series between the flash-bulb and the return to the capacitor. The locale on the circuit board of all of this is really dependent of the brand of camera, but a little time and you'll find it. All you're basically doing here is using the flash bulb as a switch to control the capacitor dump through the ignition coil, which will create a high enough DI/Dt through the primary to create significant voltages across the secondary.

Good luck with the build. What kind of camera are you using, and have you already taken out the flash and whatnot?

[souljahz_unite]

Yea, I bought a Kodak camera and already have the circuit board out. The charger for the capacitor was hard to wire because it was three connections that had to go to one wire, and then a middle connecter (the push button wires like that). Im wiring in the toggle today or tomorrow probably with the method i mentioned above cuz im not much of a electronic know-how person. If it doesn't work i might try the other methods or just ditch the project i was hoping it owuldnt become too complicated although probably for those with some electronic knowhow it wont be too bad?