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Flyback help

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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Flyback help

Unread postAuthor: enigmacipher » Thu Aug 21, 2008 4:54 pm

Alright... I am entirely new to spudfiles, (this is my first post)
and to building combustions.

I want to start a spray & pray cannon, but I refuse to use a piezo or a stungun, because piezos suck and I am not aloud to order stunguns online.

Anyways, some time ago I bought a 1980s "portable" 12v CRT television. Like all CRTs, it contains a flyback transformer which looks just like most flybacks, but alot smaller. its only a couple inches tall and ~1in diameter, and I did not want to remove it from the TV's PCB yet. I have tested the output and it seems to be only enough for a 3-5 mm spark, but still decent.

Unfortunately, documentation on flybacks is few and far between, so I dont have any idea how to use the ten+ leads on the flyback.

Could anybody shed some light on how to use flybacks? or at least point me in the right direction?
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Unread postAuthor: SEAKING9006 » Thu Aug 21, 2008 5:03 pm

Try looking here.
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Re: Flyback help

Unread postAuthor: starman » Thu Aug 21, 2008 5:07 pm

enigmacipher wrote:Alright... I am entirely new to spudfiles, (this is my first post)
and to building combustions.

I want to start a spray & pray cannon, but I refuse to use a piezo or a stungun, because piezos suck and I am not aloud to order stunguns online.



Are you in a state or country where stunguns are illegal? Making a flyback work is possible but will be big effort in itself. BCarms will sell you a stungun that has been "legalized" by pulling the guts out of the handle making it a simple "high voltage circuit".

Also, if you mount the piezo properly it can be very effective as well.
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Unread postAuthor: enigmacipher » Thu Aug 21, 2008 5:15 pm

I actually havent checked local laws about stunguns, but If you happen to know, I live in wisconsin, USA.

My issue is not laws, however, it is my parents. I have no credit card, or paypal or any means of ordering online, and I can't convince my parents to buy something that says "high voltage" on it.

edit: I have checked the spudfiles wiki, (which is pretty small btw) and found almost no specific documentation on flybacks.

Thanks for the help.
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Unread postAuthor: potatoflinger » Thu Aug 21, 2008 5:32 pm

Have a look at this It has a diagram that should help you quite a bit.
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Unread postAuthor: starman » Thu Aug 21, 2008 6:00 pm

enigmacipher wrote:My issue is not laws, however, it is my parents. I have no credit card, or paypal or any means of ordering online, and I can't convince my parents to buy something that says "high voltage" on it.

edit: I have checked the spudfiles wiki, (which is pretty small btw) and found almost no specific documentation on flybacks.

Thanks for the help.


That's because there's no need to work with flybacks...only a few have.

Just buy a prepay debit card...a lot of guys around here do that. Also a flyback is just as HV as a stun gun and probably not as safe overall to work with since you will be directly building support circuits to drive the flyback.
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Last edited by starman on Thu Aug 21, 2008 6:48 pm, edited 1 time in total.
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Unread postAuthor: Fnord » Thu Aug 21, 2008 6:39 pm

That's because there's no need to work with flybacks...only a few have.


I got one working, for a while at least. I recommend you do try it at some point just for the sake of gaining knowledge. It can be very frustrating, but if you have patients and know all your components are good then it isn't really hard.

Also, mine fried itself when I tried running 12vts through it (Just a warning).
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Unread postAuthor: rp181 » Thu Aug 21, 2008 7:58 pm

can you post a pic? theres new modern types with cylnider secondary, with the ferrite close to the body, or far a way. If there is room, then wind some coils around the exposed ferrite, and use the schematic posted. Hold the HV wire ( one coming from the top) and change it between the pins (you can do this before removing it from the board) and see which gives the longest arc, use this as the other electrode.

These flybacks are low power, the transistor in the schematic should work fine.
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Unread postAuthor: enigmacipher » Thu Aug 21, 2008 8:26 pm

Hmm.. the flyback is extremely small. its about 3/4 in dia and 1.5 in tall. Its entirely encased in plastic and has a high voltage anode at the top and several unknown electrodes at the bottom.

I have not dissembled it or even removed it from the PCB. The anode produces a 3 mm constant, hot purple spark when held near the ground from an AC wall outlet.

It is currently jury-rigged to work while still in the PCB to produce voltage. it produces a painful but harmless spark when a a few tens of milliamps 12v DC is applied to the batter terminals.

It is undocumented and I dont want to dissemble it, and since it was only a buck, I think i'll just stick to a disposable camera.

HOWEVER. I want to know how possible it is to use that prepaid debit card. I am a minor, and I wanted to know if it is possible to buy one if I am underage... (USA) Otherwise does anybody know a way to mail cash to someplace and get money in a paypal? I have plenty of cash. lol.
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Unread postAuthor: SEAKING9006 » Thu Aug 21, 2008 8:36 pm

Prepaid credit/debit cards are available at places like Walgreens and CVS. They're just like gift cards or game time cards, and you can recharge them with cash. Instead of mailing cash to paypal, I would recommend going through a Prepaid card.
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Unread postAuthor: TurboSuper » Thu Aug 21, 2008 9:56 pm

...
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Last edited by TurboSuper on Thu Aug 21, 2008 9:57 pm, edited 1 time in total.
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Unread postAuthor: rp181 » Thu Aug 21, 2008 9:57 pm

if you have a camera flash, unsolder the xenon tube, and coonect the two two the flyback (batt terms), with a switch.
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Unread postAuthor: enigmacipher » Thu Aug 21, 2008 10:02 pm

and that will produce what voltage? 250 kv? I only need like 10.
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Unread postAuthor: rp181 » Thu Aug 21, 2008 10:48 pm

voltage doesnt matter, as long as its enough to arc. Its current that gets a brighter spark. Capacitors supply lots of current in a short pulse, which is perfect.

You said 3mm spark, thats about 3.5Kv with 12v in.

Assuming a capacitor value of 200v, that gets you ~50KV, with a hotter spark then with a constant driver.
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Unread postAuthor: psycix » Fri Aug 22, 2008 8:25 am

My issue is not laws, however, it is my parents. I have no credit card, or paypal or any means of ordering online, and I can't convince my parents to buy something that says "high voltage" on it.

So you may not buy an high voltage circuit, but you can get a flyback?!
Flybacks ARE high-voltage circuits.
And for a spark, you will need high voltage (or else you got to glow up a wire)
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