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Registered Member #1107
Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792
i am going to attempt to make a 555 powered driver for a camera flash inverter transformer and i was wondering if anyone knows or has tested the approximate frequency that is it operating at.
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
To clarify, my measured 1.4kHz was with no load, so should be the same freq as a fully charged capacitor. Based on the tone, the frequency is obviously increasing as the capacitor charges (as load impedance goes up).
Plus, it was not a sine or square wave, it was a sort of half sine wave from low to high, then a very fast transition back to low. I'd show a scope shot, but don't feel like setting it up right now. Oh and I took my measurement before the rectifying diode, so I was seeing the full AC cycle.
Those chargers are based on a voltage feedback system, so don't expect the turn ratios to work out the way you'd think. I'm sure you've noticed that output voltage is the same whether you feed it 1.5V or 3V.
The good thing is, that ferrite core can probably go much higher than 1.4kHz, so you may be able to get significantly more volts/turn with a 555 driver (say 20kHz or so?)
EDIT: Camera was a cheap Fujifilm something-or-other. Single-transistor based.
Registered Member #1103
Joined: Mon Nov 05 2007, 06:02PM
Location: Houston
Posts: 80
wrote ... Those chargers are based on a voltage feedback system, so don't expect the turn ratios to work out the way you'd think. I'm sure you've noticed that output voltage is the same whether you feed it 1.5V or 3V.
Not always true! I have a few camera boards that allows up to 5v input and gives around 700v output. With only 1.5v they give around 250 volts output.
I used these:
I was able to run a small voltage multiplier from one of these with 5v input.
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
Wow, thats pretty cool, Logan. I may order a few of those as spares in case my boost converter craps out on me. The only ones I have ever experimented with are Fujifilm and Kodak; perhaps the boards you linked are from cheaper cameras.
For us its cool of course, but in terms of real-world practicality it can't be good. Charge voltage drops linearly with battery voltage, plus if you get an alkaline battery with higher than normal voltage it would overcharge the capacitor.
Oh and if I were you teslacoolguy, I would use a multiturn trimmer pot for frequency adjustment, but leaving 1.4kHz at the low end of that range, say 1kHz to 15kHz. Don't know haw many volts the insulation can take, but you could certainly afford to find the limit since they are so plentiful!
Registered Member #1103
Joined: Mon Nov 05 2007, 06:02PM
Location: Houston
Posts: 80
I've never tried putting any in series, but I suppose you could put one or two in series. Heck, they're super cheap. Buy 5 bucks worth and start experimenting.
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Disposible camera inverter question
