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Disposable camera transformer

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flannelhead

Mon Aug 13 2007, 11:17AM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

Hi there!
I've got a question about a disposable camera transformer. My transformer goes into a circuit like this, except it has got a 2SD2504 instead of 2SD965. So, what I want to do, is to rebuild the inverter part and use it with 10 volts instead of the typical 1.5 volts for higher output voltages. I've tried this, but there was some arc-over and then the transistor died. So, should I replace the transistor with some other transistor (2n3055)? And if so, what should I modify in the circuit?

Sulaiman

Mon Aug 13 2007, 11:48AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I think that those little transformers are already near their limits with 1.5 V input
in terms of voltage insulation, power throughput and primary current.
The circuit is AFAIK a blocking-oscillator operating as a forward-converter
so Output Voltage is proportional to Input voltage (once the capacitor is charged)
I don't think that more can be had from this circuit by changing the transistor.

Just take one and slowly increase the input voltage until it starts to fail, then reduce the voltage a little.

For much higher voltage and/or current you will need a different transformer and circuit.
Monitor flybacks are good, so are TV flybacks and ignition coils.

flannelhead

Mon Aug 13 2007, 11:55AM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

Ok.
Is the single transistor flyback driver safe to build and use for an almost complete beginner? And would a 8x1.2v nimh battery pack be enough for powering the driver?

Sulaiman

Mon Aug 13 2007, 12:10PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I HATE that 'single transistor flyback driver' - even though it works.
(it works by saturating the core every cycle, wasting lots of power)

I use a 555 driving a MOSFET or IGBT, look around, I'm sure you'll find a circuit diagram.

Look in our HvWiki first !

flannelhead

Tue Aug 14 2007, 05:00PM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

What do you think about this:
TLC555 and BD243C driving the disposable camera transformer. I've found a circuit for that(it's actually a flyback driver). I would replace the resistor with trimpots. That thing would be powered with 3 volts or some.

Sulaiman

Tue Aug 14 2007, 05:52PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

That circuit should work as published but
- I doubt it's worth it for a disposable camera transformer
- it's not very good as the transistor voltage rating is too low for good results with a normal flyback transformer
- I prefer to use mosfet or igbt transistors rather than bipolar transistors when driven directly by a 555
- that circuit will probably slowly destroy the transistor as there is no snubber or clamp for the flyback voltage

Look for a transistor that is designed for the job, e.g. IRGS14C40L

ShawnLG

Tue Aug 14 2007, 06:46PM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

You would need to use a TV flyback or some other higher voltage transformer to get higher voltage. You always could put a CW multiplyer on the output.

sparky

Tue Aug 14 2007, 10:20PM

Registered Member #530 Joined: Sat Feb 17 2007, 07:56AM
Location: Victoria BC, Canada
Posts: 178

OR... run the flash output into an induction coil. I used an industrial flash outputs raw into a car ignition coil... talk about sparks! Gotta be 75 kV at least!!

teravolt

Thu Aug 16 2007, 03:41AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

maximuim voltage is probibly 1500v peak out. ignition coil is good but also you could make a dublier using 1n4007 and ceramic disk caps

CT2

Sat Aug 18 2007, 04:36PM

Registered Member #180 Joined: Thu Feb 16 2006, 02:12AM
Location: Ontario, Canada
Posts: 187

If you want some big sparks from disposable cameras then you can do what I did. Go to a camera/film developing store, ask for all the used disposables and you'll likely get a big box. Start by taking them all apart, and then you'll have a bunch of flash circuit boards infront of you. Take out the circuit for the transformer, it's a transistor and resistor. Then take all the rectifying diodes and trigger capacitors off all of the circuit boards. Now you have all the parts you need, arrange the diodes and caps to form a multiplier and stick it on the end of the transformer. Then if you want you can use your new little power supply to charge a capacitor and dump that into a flyback/iggy to make even longer sparks. It's free and fun I guess, I have like 100 disposables in my basement right now

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