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Hooking up Transformer

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mondo8205

New Member
I purchased a 42TM013-RC transfomer from Mouser. I want to have 12Vac on the primary side and around 1000Vac on the secondary side. There are 3 pins on the primary and 3 pins on the secondary side. So if I have 2 wires on the primary and 2 wires coming off the secondary side, how would I wiring this up????

Attached is the datasheet for the transformer
 

throbscottle

Well-Known Member
But this is an audio transformer - it's designed to connect an audio output stage to some kind of speaker. The turns ratio is 11.486 to 1, so with the transformer connected in reverse, which I presume you intend to do, you will only get about 138 volts out of the other side - oh, actually by using half your "primary" you could get double that. Still nowhere close to the 1000 volts you are after though. And just because the insulation will stand 2100vdc for 1 minute doesn't make this a suitable device to run with 1000 volts on one side!

If you really want to use this, there are plenty of schematics for boost circuits around on the net.
 

throbscottle

Well-Known Member
I see what you mean - that does look like impedances ratio on the circuit. Not being familiar with 555 timer circuits myself, but I guess there is some pretty hard switching occurring across the transformer's primary, which will produce the high voltages due to back emf (same principle as car ignition coil).

Connect the 8 ohm side of the transformer to the transistor and the 1k side to the voltage multiplier and you should be good.
 

mondo8205

New Member
So I do not use any of the center taps. ?
Primary Side hit the 2 outside pins with the signal?
Secondary side hit the 2 outside pins for the rest of the circuit?

Yea the 555 should be switching at 2kHz
 

throbscottle

Well-Known Member
No centre taps are shown in the schematic, so don't connect them, unless you are experimenting, but where producing 1000's of volts is concerned be very careful...!
 

MikeMl

Well-Known Member
Most Helpful Member
The bulk of the voltage multiplication in this circuit comes from the diode/capacitor ladder circuit; not the transformer.

If a transformer winding is rated for voltage use (as in a power transformer), then a center tap is used when needing to drive a primary with half the voltage. e.g. a power transformer can have a rating like 120V/240V, meaning that if you want to drive it with 120V, you would connect power to 1-2 with 3 floating. If you want to drive it with 240V, you would connect power to 1-3 with 2 floating.

If a transformer is rated for impedance (as in an audio transformer), then the impedance goes as the square of the turns ratio, so if 2 is a "center-tap", and 1-3 is rated 16 Ohms, then 1-2 or 2-3 would be 4 Ohms. Sometimes on audio transformers, the tap is not centered, in which case you might find something like 1-2 is 3.2 Ohms, 2-3 is ~8 Ohms and 1-3 is ~16 Ohms...

btw-A 'stun-gun' is a very dangerous implement, especially to you. If you threatened me with your homebrew "stun-gun", I would take it away from you, and then proceed to beat the crap out of you...;)
 
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mondo8205

New Member
OK one last question what are the black dots on the datasheet? The dots are on winding drawings on the top right.
 

MikeMl

Well-Known Member
Most Helpful Member
Those are the winding polarity dots. Current in to a dotted terminal on the primary winding causes current to flow in to the dotted terminal on the secondary.
 
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