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101 Ways (Not Really) To Use a Camera Flash...

A place to ask general spud cannon related questions.
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Unread postAuthor: mark.f » Tue Jan 08, 2008 9:19 pm

Well, I've accomplished the first and most simple setup. This is the tube switched ignition coil. Basically, all I just did was wire the primary of the ignition coil in series with the lead coming off the "ground" end of the flash tube. I left the ionization plate intact and taped behind the flash tube to maintain function, so all you have to do is trigger the flash and the current will flow through the tube and then through the coil. The only modifications to the photoflash circuit were the coil wired in series coming off the flashtube, and a toggle switch wired in place of the shutter switch, (two thin leads of metal that touch together when shutter is triggered).

The setup and a picture of a spark that came off the coil are below. My estimate is a 3/2 centimeters spark gap, which would ballpark the voltage around 30 kV, from what I've read. Moreover, this would allow a 3/8" spark gap in a hybrid with a 4:1 compression mixture.... The picture's a little grainy, because I took it from a video, of which my camera does not take very high quality.

Next I'll be moving on to the charging circuit. I have to get some more photoflash circuits, though. Luckily, I found thislink on AllElectronics.
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spark.jpg
Again, my guesstimate was 3/2 centimeters.
spark.jpg (20.47 KiB) Viewed 498 times
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Unread postAuthor: Novacastrian » Tue Jan 08, 2008 9:25 pm

God i wish i was good at electronics, im alright at basic stuff but bring the words flashtube, diode etc into the equation and im screwed! :lol:

Looks good for what it's worth from me!
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Unread postAuthor: brogdenlaxmiddie » Tue Jan 08, 2008 9:35 pm

dont forget to orrectly house the unit in a protective container :D
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Unread postAuthor: GalFisk » Wed Jan 09, 2008 2:14 am

The output frequency of the inverter is in the >10 kHz range (it's the frequency of the whine you hear when the circuit is charging, and it's higher the less load you put on the circuit).
The trigger cap is a normal type of small high voltage cap, possibly with polyester or polypropylene dielectric. A disc cap with the same capacity and voltage rating would be too large. The properties of this little cap are not critical, I've used all sorts.
Edit: Oops, posted before reading the entire thread.
Nice to see the tube switched design working, I like it the most because it doesn't put any extra strain on the camera flash circuit, and it's also very simple to construct.
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Unread postAuthor: jimmy101 » Thu Jan 10, 2008 1:10 pm

Nice job Mark, it looks good. (The Wiki page on ignition systems sure could use a couple pictures, hint hint).

Going back to some of the earlier posts I think I know where I was looking at things differently than Hotwired.

These disposable flash boards can be divided into two basic circuit types. It appears that the one Hotwired is fiddling with uses a flyback transformer (three coils) as the main (300v) transfomer. The board I've fiddle with the most uses a seperate oscilator (resistor, cap and transistor) and a standard two coil transfomer.

I've fiddle with a spice model of the flyback circuit and it looks to me like the flyback is putting out ~300V pulses, in an approximate sine wave and there is no voltage doubler. Any SPICE simulation of a transformer is pretty tricky since you never know what the actual inductance of the transfomer are, you have to guess at a lot of component values.

If anybody is interested I'll post the SPICE model results.
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Unread postAuthor: jimmy101 » Thu Jan 10, 2008 1:43 pm

GalFisk wrote:The output frequency of the inverter is in the >10 kHz range (it's the frequency of the whine you hear when the circuit is charging, and it's higher the less load you put on the circuit).
The trigger cap is a normal type of small high voltage cap, possibly with polyester or polypropylene dielectric. A disc cap with the same capacity and voltage rating would be too large. The properties of this little cap are not critical, I've used all sorts.
Edit: Oops, posted before reading the entire thread.
Nice to see the tube switched design working, I like it the most because it doesn't put any extra strain on the camera flash circuit, and it's also very simple to construct.

Depending on the details of the circuit the trigger cap is rated at 50V to 300V, actual values are usually about 100V. At 0.022uF they are pretty small caps. Any old cap will work but to get the best performance you need a low ESR cap. If any old cap worked reasonably well then the board manufacturers would not be using such an expensive cap. An 0.022uF, 100V ceramic disk cap costs less than a penny in bulk. The low ESR caps are more expensive. This looks like the cap most of my photoboards use.

I wonder if you could replace the 0.022uF cap with say a 0.22uF cap and boost the trigger voltage and current enough to get it to be useable as an ignition system?

I suppose if you dumped the 120uF/300V photocap through the trigger transformer you would fry the tansformer. Sounds like a fun experiment. :D

I wonder if the circuit below would work to (1) boost the power of the trigger voltage (but not the voltage) and (2) make the trigger fire repetively instead of just once.
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Attachments
cyclic_trigger.gif
From the left side of the schematic;
1. 300V poser source, diode and photocap allready on the photoflash board.
2. Add a push button switch, 100K resistor and boost the capacitance of the trigger cap.
3. Use a neon bulb as the trigger.
4. Use the trigger coil fromthe photoflash board.
cyclic_trigger.gif (10.92 KiB) Viewed 443 times
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Unread postAuthor: nz_cannons » Thu Jan 10, 2008 6:58 pm

I did some playing round with these circuits a while back, I wrote a wee how-to on using one to make a spark, it's floating around in the how-to section somewhere.

Just done with an SCR. Simple, safe, reliable.

50mm sparks from one cap.
90mm sparks from same cap with two coils.
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Attachments
new spark1.jpg
Motorcycle coil.
spark 95mm2.jpeg
Two car coils.

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