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disposable camera transformer

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lynx

Member
Hello!
this place is really great! i'm glad i found it... :)

i got a transformer from a broken camera which i want to use to step up
the voltage from 3V source. I need to know if it is suitable for voltages up to 600V and also i want to figure out if the transformer works fine. One side has 2 pins and from the other side 3 pins, how am i suppose to measure it with my multimeter so i can figure out if it's fine? what readings i should see?
 

lynx

Member
one side with the 2 pins i believe it's the input.. the step up transformers i think they are backwards so the input is the secondary and at the other side where the three pins are must be the output (primary) with the middle pin to be center tapped.

but got confused while i'm checking it with a multimeter because the input has very low resistance and on the output only two pins give a reading on my DMM.

any help guys?
 

lynx

Member
yes i know! :)
i only want to make sure the transformer is fine because when i probe the
output pins one of them behaves NC while it shouldn't... so i need to know how to check the transformer before i start to build any circuits.

about the voltage are you sure it can go only up to 300V? i don't care about the current i only need few mA!!!
 

colin55

Well-Known Member
The two pins that detect zero ohms are actually the primary and will measure less than 1 ohm.

You need to know the circuit as the transformer may be in a blocking oscillator mode and may have a feedback winding.
By connecting it to 3v, the AC output will be over 600v. They produce over 300v on a 1.5v cell. But you must know the circuit.
 

Hero999

Banned
You should get more than 600V from 3VAC, I make it nearer 850V.

If the transformer increase a 1.5V square wave to 300V, that's a turns ratio of 200, 3V has a peak voltage of 4.24V, multiplied by 200 and rectified into a capacitor this gives 848V.

Of course it's probably operated in flyback mode so you'll probably get much less than 848V, if connected to a sine wave, it'll probably be nearer 85V.

Of course you probably meant 3VDC.

I don't know whether the transformer can take 600V on it's secondary, it probably can but you'll need to double the driver frequency to prevent saturation.

I wouldn't push it much beyond 600V because the insulation probably won't stand it.
 

lynx

Member
could you or someone else give me more details?

for example you said

The two pins that detect zero ohms are actually the primary and will measure less than 1 ohm..
this is the input which is the secondary as the transformer is backwards connected when you step up the voltage.


and second thing you said

You need to know the circuit as the transformer may be in a blocking oscillator mode and may have a feedback winding.
how can i figure out that? i only know that the one side of the transformer has 2 pins (less than 1 ohm) and on the other side has 3 pins which the 2 of them conduct (less than 1 ohm) and the other looks like it doesn't conduct with the others so it behaves like NC while i think it shouldn't.
 

lynx

Member
hi! you really mean 85V or is it typo?
can you also answer the rest of my questions?


Of course it's probably operated in flyback mode so you'll probably get much less than 848V, if connected to a sine wave, it'll probably be nearer 85V.
 

colin55

Well-Known Member
This is the type of circuit you will need. The feedback winding is part of the secondary winding. The frequency of operation is determined by the inductance of the transformer.

 
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lynx

Member
colin55 still i haven't figured out if the transformer is fine! :) it could be burned.. how should i check it with my DMM and what should i expect?
 

colin55

Well-Known Member
The secondary could be as high as 300 to 500 ohms and it is very unlikely that it is burnt out.

Digital cameras are free from any photo shop. I got 40 of them for $1.50 each for a project.
 
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lynx

Member
The secondary could be as high as 300 to 500 ohms and it is very unlikely that it is burnt out.

Digital cameras are free from any photo shop. I got 40 of them for $1.50 each for a project.
ok...

the side with the 2 pins i get less than 1 ohm and the side with the 3 pins one of them doesn't conduct with the other two.

so what's the case?
 

colin55

Well-Known Member
Does the case have a solderable pin and does it look like one of the wires from the transformer is conencted to the case?
 

Hero999

Banned
hi! you really mean 85V or is it typo?
can you also answer the rest of my questions?
No it wasn't a typo, the transformer won't give such a high output voltage when driven with a pure sine wave. The transformer is probably used in flyback mode so the secondary voltage is over ten times the turns ratio.
 

lynx

Member
Does the case have a solderable pin and does it look like one of the wires from the transformer is conencted to the case?
the pin that doesn't seem to conduct with the other 2 on the same side has a wire on it comming out from the transformer.
 

Sceadwian

Banned
Probably internally shorted. If a transformer is gradually overloaded to failure it would make sense that it's one of the winding in the middle of the transformer where the heat is most intense.
 
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