Where to find step-up transformer?

[koljo45]

Last few days I have been trying to power up a 400V capacitor with no luck. I need to make a circuit similar to a flash circuit from a disposable camera. I tried with few different transformers from old pc power supplies, but with no luck. I understand how transformers work. You need AC or pulses of DC trough the smaller coil to induce bigger voltage on the bigger coil. http://www.repairfaq.org/sam/strbfaq.htm I found circuit design here, it's under "Super Simple Inverter". My real problem is finding a transformer that will suit my needs. I would also like to know if its possible to just use a step-down transformer with its pins other way round? I get the idea of center tapping in transformers, but what is the main difference between center tapped and non center tapped? I noticed in the schematic that always one of the center tapped coils is charged, so does this mean that center tapped transformers are more efficient? I use 5V 450mA power adapter, and arduino to make pulsating dc current. I studied lot of camera flash circuits, but I still don't get some of the more in depth thing about transformers. Till now I only managed to measure AC voltage of few mV on the secondary coil, it makes a LED turn off and on. I know the noob  force is strong within me . I would appreciate any help.

[tiltit]

Hi,
You could build a simple boost converter with a Mosfet a diode and a inductor and drive it with pwm. There are also schematics online meant to drive nixie tubes like this one http://www.aplomb.nl/TechStuff/Switcher/Switcher.html.

Edit: This link is better. http://threeneurons.wordpress.com/nixie-power-supply/hv-supply-kit/

[Zero999]

My advice is to just build the super simple inverter schematic. You just need a centre tapped mains transformer.
http://www.repairfaq.org/sam/strbfaq.htm#strbssi

[Richard Crowley]

Strobe lights typically use special transformers with a very high turns ratio. To take a low battery voltage up to 100s of volts to charge up the capacitor.  For example...

Tiny Inverter Transformer - Designed for tiny strobe lights this small inverter transformer converts 3VDC into 200VAC when used with a simple 2 transistor circuit. Size only .4" square x .35" H. Has 4 pins. Complete with schematic of a simple strobe using this transformer.
G13599
http://www.goldmine-elec-products.com/prodinfo.asp?number=G13599

[koljo45]

Tnx for the response. I'm reading trough tiltit's link. Hope it helps.

[SL4P]

@mirsaeed -
TWO SINS...

• cross-posting and
• hijacking someone else's thread

GO AWAY.

[CatalinaWOW]

Many times you can just reverse a step down transformer, but you need to watch the voltage capability of the (original) primary.  It may or may not be able to take the voltage you are now forcing it to operate at.  Be aware that success once, or for a few minutes does not assure that the transformer is safe to operate long term in this mode.

[Audioguru]

If you use a 120VAC to 12VAC transformer backwards and feed it a 12Vp-p squarewave then its output will be less than 120VAC because it is actually a 120VAC to 14VAC transformer that has a 2V loss when loaded. The if you feed it 12V p-p to the "12V" winding the output will be (12V/14Vx 120V=) 102.9V without a load and less when loaded.