Ignition coil for flashtubes as HV transformer?I want to make a few hundred volts at very low current, a few uA.These trigger tubes for flash tubes seem to do 200V in 4000V out,by discharging a cap in the primary. They are dirt cheap here.So the transformer ratio is 1 : 20.I am thinking about PWMing one to make 500 V peak from 5 V DC.As I do not have one yet, does anybody know the inductance of these things?I used one a hundred years ago in a flash tube trigger circuit...Should have measured it..

An easy source of trigger transformers is disposable cameras - but the transformer is tiny.Photography shops return the disposable cameras to the factory for recycling and in the UK they get around £50 for a sack full.Some shops will let you scrounge a few cameras to experiment with, others charge between £0.50p & £1 per camera.

Ignition coil for flashtubes as HV transformer?

Aug 29, 2011 23 Replies

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Ian Field 14 years ago

I already pointed that out a few days ago.

Its worth getting as many as possible to pick a few inverter transformers apart to study the windings.

Most put the secondary & rectifier in series with the base winding (that's why the HT is usually negative) when the capacitor is discharged, the secondary charging current pulses are added to the base winding to increase the pulsed collector current, as the capacitor reaches full charge the current pulses due to the secondary diminish, leaving only the base bias resistor to sustain oscillation.

That produces rapid recharge after a flash but economises battery drain while the flash is at the ready for the next picture.

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Baron 14 years ago

Hi Ian, Ian Field Inscribed thus:

Sorry ! Only got back from 6 weeks abroad Saturday. I've got Knode set to collect only the newest 100 posts.

Interesting ! I've not played around too much with them.

I've half a dozen Kodak ones to pull apart when I get the time. ;-)

Best Regards: Baron.

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Ian Field 14 years ago

A very small number of types rely entirely on the secondary current pulses for feedback - I've tried to replicate this with random ferrite cored transformers salvaged from scrap TVs/monitors etc, but only with limited success.

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Jan Panteltje 14 years ago

On a sunny day (Sat, 03 Sep 2011 09:34:14 -0700) it happened Robert Baer wrote in :

I did not want to order just one to test, so I wound one with 16.5 primary and 500 secundary, without iron core. Not very usable .....

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