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Ultimatespudgun.com ignitor question

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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Ultimatespudgun.com ignitor question

Unread postAuthor: supercannons » Mon Sep 27, 2010 2:59 am

referring to this ignition:
http://ultimatespudgun.com/30kv-igniter-p-219.html

I was just wondering how the coil could generate enough of a spark from the 9volt battery, does it act like a capacitor that stores energy?

It would be greatly appreciated if someone could tell me how it works cause i was going to build one for my self (cause im stingey and i didnt want to buy the one on the website =P)

thanks guys
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Unread postAuthor: Technician1002 » Mon Sep 27, 2010 4:23 am

It has much more than just a coil. I don't think you will be successful building one and saving money. This igniter has several components. The small yellow transformer is part of an inverter to charge a capacitor to several hundred volts. The second part is a Capacitive Discharge Ignition. (CDI) That uses the second coil on the left to change about a 300 volt pulse into the 30KV ignition output.

Are you ready to engineer one of these from scratch?
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Re: Ultimatespudgun.com ignitor question

Unread postAuthor: jackssmirkingrevenge » Mon Sep 27, 2010 4:52 am

supercannons wrote:(cause im stingey and i didnt want to buy the one on the website =P)


If it was needlessly overpriced I would understand, but for less than $25, you really are stingy :D can you find a stungun for cheaper?
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Unread postAuthor: Gaderelguitarist » Mon Sep 27, 2010 9:42 am

I actually bought this system and have come to the conclusion that it will out-live any spudgun that I build. So really, you're buying an ignition circuit that you'll be able to reuse and reuse again for better, more advanced future builds.
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Unread postAuthor: jimmy101 » Mon Sep 27, 2010 1:19 pm

If you are good at collecting junk parts, and if size and appearance aren't important, you can probably build an ignition system for a couple bucks. Scrounge up an old automotive ignition coil from a junkyard, and an automotive relay (from the same car), and a 12V battery that can supply serious current (as in at least a few tens of amps, typical car batteries will source a couple hundred amps).

Wire the relay up as a "buzz coil" (Google for it) and pulse the 12V into the automotive coil's primary. That's basically how car ignition circuits used to work. (The distributer rotor carries out the function of the buzz coil).

It'll make nice sparks but it'll be big and cumbersome. A $15 stun gun is a better choice, though cheapo stun guns aren't all that robust.

Tech's description of how the circuits work is correct. The circuit isn't all that complex but in practice it is a PITA to make. High voltage coils aren't all that common. Keeping the HV from arcing where you don't want an arc is a challenge. Basically a low voltage DC source (like a single 1.5V battery) is pulsed into a 1:200 turns ratio transformer. The output of the transformer is rectified with a single diode and used to charge up a photo cap (typically a couple MFD rated at 300V or so). The 300V stored in the cap is then dumped through another high turns transformer (1:10 or 1:100) to step the pulse from 300V to a couple KV to a few tens of KV.
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Unread postAuthor: supercannons » Mon Sep 27, 2010 8:46 pm

Technician1002 wrote:Are you ready to engineer one of these from scratch?


yeh no worries, im studying mechanical engineering at uni so i think i should be alright with all the circuits and systems its just the components i need


thanks everyone for their reply's greatly appreciated :D
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Unread postAuthor: Technician1002 » Mon Sep 27, 2010 9:27 pm

Mechanical engineering does not teach electronics basics. Would you be able to choose a proper high voltage switch to pulse the ~300 volts DC into the high voltage transformer and prevent it from getting fried?

I'm ISCET certified, so I am worried.
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Unread postAuthor: supercannons » Tue Sep 28, 2010 5:05 am

i studied systems for 2years in years 11 and 12 in high school which taught me the basics for electronics but maybe i should stick with a pizzo now that i think about it
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Unread postAuthor: bighead33 » Tue Sep 28, 2010 6:19 pm

i think you guys are just over exaggerating, from my opinion it wouldn't be that hard to build one all you have to do is take a 9v battery amp it up to a bout 300-400v (using a transformer) store it in a high voltage capacitor then use a SPDT coil relay as a throw switch and a rectifier to prevent a capacitor discharge back into the circuit simple :roll: :wink: .
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Last edited by bighead33 on Tue Sep 28, 2010 9:11 pm, edited 1 time in total.
some day spudfiles is going to take over the world.
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Unread postAuthor: whoa044 » Tue Sep 28, 2010 7:22 pm

Spark plugs take large voltages to make the gap, and the gap is only 0.02 inches. Now imagine stun guns, the gap is huge, once again, even higher voltages.

I once used a 250,000v stun gun, and had a gap of a little less than an inch. It worked great. Buy a cheap one off of ebay, or a defence website, that has a voltage between 200 and 500kv.

You can find some very cheap stun guns, and take them apart. All you need to do then is wire it to two electrodes in the combustion chamber.
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Unread postAuthor: Technician1002 » Tue Sep 28, 2010 7:22 pm

bighead33 wrote:i think you guys are gust over exasperating, from my opinion it wouldn't that hard to build all you have to do is take a 9v battery amp it up to a bout 300-400v (using a transformer) store it in a high voltage capacitor then use a SPDT coil relay as a throw switch and a rectifier to prevent a capacitor discharge back into the circuit simple :roll: :wink: .


Absolutely true. This is often done. Look for all the ignition systems using a disposable camera flash and an ignition coil. To get the ~250 volts, the camera flash is used to generate the voltage used to discharge into the ignition coil. They don't cycle at 10 sparks per second though and are quite a bit bigger.

Very few people build their own camera flash inverters as it is much cheaper to take one from a disposable camera for free.

For a faster cycle time, the flash capacitor can be replaced with a much smaller one more suitable for the ignition coil instead of the flashtube. Replacing the ~50uF cap with a ~0.3uF mylar cap works well.

Note the original ignition is using one of those caps. It is the reddish brown object along the side. I'm guessing it is in the value range of 0.22uF at about 250 - 350 volts.

Does anyone with a Spudtech ignition wish to confirm the value marked on the reddish brown capacitor?
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