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Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
I recently made a spud gun and i was looking for a simple, yet effective, ignition system. I hatched the idea of winding A new primary on an old magneto and discharge a capacitor through it. That would send high voltage through a spark plug that would ignite the gases. It worked quite well. I used 5 turns off to the side of the coil, since i could not wind it where the coil was cause there was no room on the core. I discharged a 600uf capacitor charged to 50 volts through the primary. Unfortunately, after about 10-20 shots, it arced internally. I got a BBQ igniter later for the gun. It works just like a flyback with a diac to discharge capacitors through its primary. You could use a diac or thyristor(scr) to discharge it. It would have to be a diac triggering an scr i guess since it is high current. Or you could just connect an scr to a switch to discharge it whenever you want. Just thought i would throw that out there.
Registered Member #477
Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546
If you're mainly after a spud gun application, what about just taking the little piezo igniter out of a piezo-based barbecue lighter? Unless the propellant requires a flame (or something flame-like such as an arc), it seems like that would be the absolute simplest possible thing. Heck, you could probably even reuse the trigger I've never heard of a flyback-like or coil-based barbecue lighter
Registered Member #952
Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388
I've learned from my experience that these piezo igniters don't work reliably enough for that kind of an application. The spark is absolutely too weak. I've myself been working on a modded camera flash circuit. I've done like this: I removed the flash tube and attached long wires to the capacitor. I also soldered one wire on the trigger transformer output. Then I put the ends of the wires so that the capacitor wires had the trigger transformer wire between each other with a small gap. Now what happens? When you push the trigger switch on the flash board, a small spark comes from the trigger wire. Now the air is ionized, so the energy stored in the capacitor has a free way to go. That results to a quite nice BANG, which surely ignites the propellant better than a piezo ignitor.
But anyway, if you don't mind a bit of effort, gut a laser printer. They generally have this ever so cuuute little flyback transformers, which when combined with the usual 1 transistor flyback driver or a 555 driver, generate an excellent continuous spark.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
The purpose of this thread was to give some ideas about high voltage generators. My head is not right today so i didn't really think it through when i made this thread. I am currently using a piezo igniter and it works great. I was just talking about my high voltage generator because when i was younger i always wanted to make high voltage with easy to get stuff. I posted to help those like me, not to get help with my spud gun.
Registered Member #477
Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546
Kind of depends on the relative importance of the means and the ends then, doesn't it? HV for HV's sake can be gotten by buying a NST from somebody on eBay, and that probably wins the simplicity award any day (unless you count shuffling your feet on carpet or vigorously petting your cat). If the means matter more, then maybe you buy the cat on eBay
I expect most people who build flyback drivers or murder disposable cameras can think of easier ways of getting HV, but didn't pursue them because they seemed boring.
Are you really just looking for people's favorite "beginner's HV"-type projects?
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
J. Aaron Holmes wrote ...
Kind of depends on the relative importance of the means and the ends then, doesn't it? HV for HV's sake can be gotten by buying a NST from somebody on eBay, and that probably wins the simplicity award any day (unless you count shuffling your feet on carpet or vigorously petting your cat). If the means matter more, then maybe you buy the cat on eBay
I expect most people who build flyback drivers or murder disposable cameras can think of easier ways of getting HV, but didn't pursue them because they seemed boring.
Are you really just looking for people's favorite "beginner's HV"-type projects?
Cheers, Aaron, N7OE
Well i have 2 nst's. 720 watt and 180 watt. I just wanted something that was portable. I am not looking for simple hv sources, i am just telling people about mine. Unfortunately, only the pro's are looking at my thread, and this is for beginners that don't have any stuff for other circuits.
Registered Member #1316
Joined: Thu Feb 14 2008, 03:35AM
Location: Cambridge, MA
Posts: 365
How about a flash camera charing a cap to be discharged through two reverse parallel flash camera trigger coils? All you need is a sidac for triggering or a diac plus SCR. try 3 or 4 flash caps in series to reduce total uf therefor peak power.
Registered Member #1408
Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
If you live in the USA there is a wonderful source of a "micro NST". The outdoor bug killers that use a UV tube and have a dual mesh screen (and hang like a lantern) have a wonderful little dual coil "E" transformer in them. It puts out perhaps 3kv AC and is easy to use for small applications. Even a new one would only cost $29. Arc is about a bit over a centimeter and pretty strong for the size of the little fellow. Working off the mains it also has a ballast but that may be for the lamp; as it doesn't get warm even after a lengthy use.
The quality varies. There are Chinese poorly made ones out now but if you can find a older one, the "micro NST" is made much better. It's all copper wiring and the coils are very easy to rewind if you want. I found one and simply wanted to see how it put out it's arc and was wonderfully surprised with a fairly well made (potted) little mains fed transformer.
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Simple high voltage generator.
I've never heard of a flyback-like or coil-based barbecue lighter 
