Ignition system help!

[Spudgun on Crack]

Is it possible to use a flyback transformer and a camera circuit to make a spark.

I read the wiki on the ignition coil and the camera circuit and how you can discharge it into a coil to produce a spark.

I would hook a camera flash circuit up to a coil on the flyback and then discharge it, but would this produce a large arc?

I am not concerned as to if it harms the flyback (I have a bunch) but I need to make an ignition system out of parts that i already have.

[SpudFarm]

use just the coil and the camera

[Spudgun on Crack]

What do you mean just the coil and the camera?

Do you mean hook up the camera without a capacitor to the coil?

I thought about that but I don't know if it works or not.

[psycix]

Use it with the following things:
Flyback circuit
Capacitor
Coil

Use the flyback to charge the cap, and then dump the cap trough the coil.
A high voltage spark will be generated.

[Spudgun on Crack]

I got the flyback to make a spark, it was not very big (1in or less)

that was with 3 capacitors in series for a total of about 1000v and then i discharger it through the coil but it is not that big.

Any ideas why? I mean 12v can make a huge arc so why can't 1000v make a huge arc for a second?

[TurboSuper]

You connect the capacitor of the camera flash to the coil through a switch of some kind. That way, it discharges a 200V-300V pulse with a healthy amount of current through a step-up so you get a nice arc.

Anything more than that is just overkill, really.

[DYI]

You won't get a spark much longer than 1.25" from a standard ignition coil, as it'll start arcing through the internal insulation of the coil. If you need impressively high voltages, you'll either need to make your own step up coil with better insulation, or make a Marx generator, either of which would only be moderately difficult.

[JDP12]

look on the wiki they have an article about it I believe

[jimmy101]

I got the flyback to make a spark, it was not very big (1in or less)

that was with 3 capacitors in series for a total of about 1000v and then i discharger it through the coil but it is not that big.

Any ideas why? I mean 12v can make a huge arc so why can't 1000v make a huge arc for a second?

The power into the coil controls the power out of the coil. Power is not just a function of the input voltage. It is the input voltage times the input current. A 12V car type battery can supply ~300 amps (or more) at 12V. That's 3.6KW. A 120VAC wall outlet is usually limited to 15 Amps, so it can only supply about 1.8KW. The car battery, even though it is lower voltage, supplies twice as much power as the wall outlet.

Coils, transfomers and the like are even more complex than the simple power equation suggests. The rate of current rise and fall controls the output voltage. Furthermore, transformers are generally designed for a particular current rise/fall rate. Get to far away from the desinged rate and the transformers efficience drops way off. Flybacks are generally designed to be operated at either 25KHz or 50 KHz (IIRC). Get too far away from that and the don't work nearly as well.


More importantly than all the stuff above, why would you want a bigger and/or more powerful spark? You don't need it. A combustion spudgun needs less than a millijoule to ignite. If you can see the spark (no matter how small the gap) it is sufficient to ignite a 1x mixture.

A 120 MFD phtocap charged to 300V contains ~5.4 joules. That's roughly 10,000 times more energy than is needed to ignite the fuel.

An average sized spud gun will launch a 100g spud with about 500 J of kinetic energy. So, the extra 5J from a high powered spark source has no affect on the performance of the gun.

If your setup will consitently spark across a 1/8" gap it'll ignite a 1x gun.

[Spudgun on Crack]

I got it to work ok so now I am going to put the unit (Modded camera circuit, switches and battery) In a project box and then have the flyback mounted in a box say directly under the gun because its just to bulky to but in one big box.

If you don't know what camera mod I am using its on youtube.com



I made the video so please leave comments!!!!!!!

As soon as I finish it (1 to 3 hours) I will post a few pictures.

[TurboSuper]

Cool video! Just one question: You say it charges very quickly...is this because it can handle more input voltage when it's isolated? How much did you use?

[jimmy101]

Spudgun on Crack: Nice job on the video. Never thought about hacking out just the high voltage oscillator from the photoflash board, that's an excellent idea.

Is it possible to omit the diode from your setup and use the one on the flash board or is the one on the board in an inconvenient place?

BTW, there is a small low ESR cap and another transformer on the board. You might be able to slice out that part of the board and use it as a wimpy spark source. Basically, the small cap does what the photocap does and the other transofmer does what a car ingition transformer or a flyback transformer does. You should be abe to get 5~10KV from the second transfomer, though at pretty low power levels (even for a HV spark).

TurboSuper: I wouldn't expect it to charge much quicker after this mod compared with the original board. If you put a volt meter across the cap a one or two second charge won't get the cap's voltage anywhere near the 300~330V that it'll get to after several seconds of charging. If SPOC had fully charged the cap the spark he got when he shorted the cap with the screwdriver would have been a fair bit bigger and louder.