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Camera Flash Circuit Questions & Comments

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Camera Flash Circuit Questions & Comments

Unread postAuthor: irishguy » Thu Sep 27, 2007 8:33 pm

hi i can seem to get my flash camera to work when the capacitor charges so does the wires now extending from where the bulb was should this happen i cant seem to find the trigger mecanisim that is on most cameras also i was going to make it ultra simple by using a shred of steal wool between the spark gap to get it to work. without the need for a coil oviosly you have to replace the steel wool each time as it gets fryed
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Unread postAuthor: Pete Zaria » Thu Sep 27, 2007 8:40 pm

I'm sorry, I don't understand your question. Would you please try to re-phrase it so that we can understand and help you?

Peace,
Pete Zaria.
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Unread postAuthor: irishguy » Thu Sep 27, 2007 8:42 pm

im probably going to get a coil just have to get up early for a change an find a auto parts store or scrap yard
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Re: flash camra questions and coments

Unread postAuthor: irishguy » Thu Sep 27, 2007 8:44 pm

irishguy wrote:hi i can seem to get my flash camera to work. when the capacitor charges so does the wires now extending from where the bulb. was should this happen? i cant seem to find the trigger mecanisim Where is it. that is on most cameras also i was going to make it ultra simple by using a shred of steal wool between the spark gap to get it to work. without the need for a coil oviosly you have to replace the steel wool each time as it gets fryed
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Unread postAuthor: irishguy » Thu Sep 27, 2007 8:47 pm

someone said there is a place that sell stun guns under a difrent name with the housing removed as there illegal here
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Unread postAuthor: mark.f » Fri Sep 28, 2007 5:20 am

Here's the scoop:

Your camera has three electrodes by the flash bulb. Two are standard positive and negative electrodes that go into either side of the flash bulb. On most cameras, THESE ARE ALWAYS LIVE. As soon as you connect a battery or charge the flash, the voltage from the main capacitor is running across these electrodes.

The third electrode usually takes the form of a metal plate or enclosure around the flash bulb. This plate is connected to a smaller capacitor and a transformer and a switch. When the flash is triggered, it sends a strong pulse of + voltage between the two main electrodes, which ionizes the gas, (or in an ignition's case, air), between them, allowing the current to flow from the capacitor across the gap.

So, for a simple ignition, you would need three electrodes going into your gun. They need to be really close together for this to work in air, as well. Also, the surface area of the third, (triggering), electrode makes a difference as well, but if you've just got three screws meeting a little less than a millimeter apart, it'll work, usually.

If you're considering a cheap and reliable ignition source, you may want to consider what I'm using for ignition once I stop by the Honda place. A small ignition coil is simple to use, and doesn't require much in the way of know-how to operate correctly. Simply:

Obtain coil, plug wire, and a spark plug. These are four one-cylinder applications, in case you haven't figured it out already.

Slice the tip which connects to the plug wire off the spark plug. Drill and tap the flat side to #6-32 threads and thread in a short piece of brass threaded rod. The objective is to have this tip on the outside of your cannon, to hook the plug wire to, and then have the rest of the threaded rod forming the + side of your spark gap on the inside of the cannon.

Obtain an 8 AA battery holder, (Radio Shack). Also, obtain a "normally closed" switch, (meaning operating it opens the circuit). Solder two lengths of wire to the holder's terminals and then crimp on a hoop connector at one end of the positive side, and a Q.D. connector at the negative side, (the Q.D. connectors usually fit over switch terminals quite nicely). The size of the connectors on your ignition coil should be the size of the hoop connectors. Some coils have plug-type connectors which will take some modification to attach to a hoop connector.

Connect the positive end to one end of the ignition coil, (it usually doesn't matter).

Thread in the - side of your spark gap into the chamber. Use a hoop connector, (and washers if the hoop is too big), to connect a wire from the negative end, and run it to the negative side of the coil.

Attach the switch inline with the negative wire of the battery terminal. Connect a wire with a hoop connector and Q.D. connector to the ignition coil.


When all is said and done, with the switch closed, the coil will be "charged" with standard 12v DC through the primary coil. The secondary coil experiences voltage as a function of the rate of change of current in the primary coil. So, when you first hook up the battery, you'll get a spike in the secondary not high enough to spark, but high none the less. Don't touch any of the positive side, (it's plug wire anyway, so it'd be kind of hard, but you never know). It won't kill you, but it will hurt. If you've ever fooled around long enough with mower and ATV ignitions, you know this...
When you operate the switch to open the circuit on the ground side, the electromagnetic field in the primary coil collapses, and the secondary coil experiences a voltage spike as a function of the change in current of the primary coil. This means more current, (meaning another 12v battery with more amperage, like a car battery), equals more spark voltage, but 8 AA's should work great.
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Unread postAuthor: irishguy » Fri Sep 28, 2007 5:46 am

great info thank you.
i got the coil its the single type from a ford clio cost me 30 euros ( ripoff ireland) i can not figure out where the positive and negetive imput well witch is witch any way does it mater
i think the exit positive and negetive is the top and the hoop on the side am i wrong also how big a spark gap can i get away with
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Unread postAuthor: jimmy101 » Fri Sep 28, 2007 10:01 am

Your coil should have three electrical contacts on it. The two small threaded posts with nuts are the coil's + and - inputs. This is where you'll hook up your voltage source. (Frequently these contacts are maarked with "+" and "-" but not always.) The third electrical connection is the the high voltage output of the coil, where the wire to the distributor goes in a car (from the distributor the high voltage is routed to the individual spark plugs).

On some coils one of the two input connections is missing and the entire metal case of the coil is one of the electrical contacts. Usually, this type of coil will have a metal bracket welded to it and the bracket will have a hole. On a car, the bracket gets bolted to the metal frame and acts as one of the electrical connections.

You might take at look at this spudwiki: http://www.spudfiles.com/spud_wiki/inde ... /Spark_Gap (and the pages that link to it)
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Unread postAuthor: shiftyguy » Fri Sep 28, 2007 11:14 am

The camera runs on 1.5 volt does anyone think that there would be a problem if I used the 12v from the coil to run the camera as well? Or will i burn it out? What if i added 3-4 more condencers would it work then?
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Unread postAuthor: jimmy101 » Fri Sep 28, 2007 12:10 pm

shiftyguy wrote:The camera runs on 1.5 volt does anyone think that there would be a problem if I used the 12v from the coil to run the camera as well? Or will i burn it out? What if i added 3-4 more condencers would it work then?

I'm confused, why do you have 12V for the coil but 1.5 volt for the camera flash?

If you use a camera flash board, supplied by a 1.5V battery, then the output from the flash board is the ~300V from the big-ass storage cap. That 300V is what is fed into igntion coil. No need for a 12V power supply.

Is the 12V supply to run a relay?

As to using a 12V power supply to run the flash board... probably won't work. I've tried using a 9V battery instead of the 1.5V battery and you get arcing on the board and various components get hot. You might be able to put say a 1K resistor in series between the 12V supply and the flash board but you still might fry somehting on the board. Worth a try if you have a couple of the boards and you got them for free.

You could use a voltage divider to get 1.5V from the 12V power supply (a trasnformer won't work) but it is pretty inefficient. If the 12V supply is a "wall wart" then efficeince is probably not a big conern.
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Unread postAuthor: mark.f » Fri Sep 28, 2007 4:39 pm

There is no way a USED ignition coil should have cost you 30 euros, (about 40 bucks over here). I can go grab a coil from AutoZone for 15 bucks here in the U.S., and that's for a car. I'm fixing to go buy a Fourtrax Rancher coil from the Honda place, and it'll cost me less that that. I even bought a new coil-pack for my truck, (two small coils going to four ports), a while ago that cost me only 35 bucks, (about 25 euros).

The coils I've seen, it didn't really matter where the + or - side went to, but a newer one may be different. Both terminals were connected to the primary "coil" in the ignition coil, (although I'm under the influence that an ignition coil is an autotransformer, which doesn't really have separate primary and secondary coils). I guess it may matter for some, but the one I've tinkered with didn't matter. Newer cars are starting not to have single coils so much as they have coil packs or coil-on-plug ignition. Every truck I've looked at so far uses coil packs. Most small cars I've looked at all the way up to 2000 use single coils, though. What year car is your coil off of? If it's pretty old, you probably don't have to worry about which side is positive or negative.

Let us know how it turns out for you. If you're looking for a switch to use, my friend's cannon uses a mini-switch pushbutton type that's normally open. You just press it closed, and then let up off it to fire. This is a source of many jokes between us about what would happen if you pressed the button and then had to cancel firing. You'd have to hold down the button to keep it from shooting. Kind of like an old playstation, when you'd use to threaten your brother with turning it off. :P
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Unread postAuthor: CpTn_lAw » Fri Sep 28, 2007 4:49 pm

flash camera make huge badass sparks...very bright and very small bu intense and hot.
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Unread postAuthor: mark.f » Fri Sep 28, 2007 7:37 pm

Alright, ya'll are lucky I was bored...

I built a small flash camera ignition device just to show you a little what it should look like. The only picture of a spark I was able to get it sort of trippy, though. The camera didn't quite catch the spark, but you can see an "ember" trailing away from the device.

BTW, this was the first camera I had that I actually had to wind the shutter mechanism to get the trigger to work. Might be something to consider.
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Not a very good shot of the spark, but you can see the aftermath.
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Unread postAuthor: Pete Zaria » Fri Sep 28, 2007 7:41 pm

Very cool setup.
I experimented with a 3-point-gap system in an older launcher. I cut a very short (1/2" long) section of 1" PVC, with 3 screws in it like you've done, and glued that to the inside of the chamber. It worked OK, but the electrodes required a lot of adjusting, and there was obvious corrosion from the repeated high-current arcs.

PS - Edited name of topic, because "flash camra questins and coments" didn't look very good on the Recent Topics list.
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Unread postAuthor: CpTn_lAw » Sat Sep 29, 2007 5:14 am

Ok, now i'd like to clear a point. My ignition setup has just been finished, and i did some adjustments. My capacitor is 330V 120µF , and my spark gap is working even if the electrodes are 4mm far from each others. At this poit, is does a very (very...) loud crack and extremely bright (blinding) arc. I'l post a video on youtube later today. i found that the commonly used center-placed ionisator wire is not good. It must be placed beneath the two electrodes coming from both positive and negative leads. it is right that if the HV wire is in the middle of the two electrodes, the arc is working only if it is 1mm .
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