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Where can I get this transformer?

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In the project https://www.electro-tech-online.com/threads/simple-lie-detector.40/ I wanted to know where I might find the transformer? I have all the other parts put together and just need the transformer. I dont know a lot about transformers and did not know what that 200K to 1K was? I asked a guy at radioshack and I think he did not know what I was talking about. He said they have transformers but I did not what to get. If you know of a electronic device that has this transformer in it please tell me I might have it and can take it apart.


Thanks,
Kyle
 
what you need is called a mini-audio transformer. It comes in a package no bigger than .5"x.5"x.5" and has 4 leads coming out.

i can't remember where i got mine, however i remember it was rather hard to find.

But yea, ask for a mini-audio and they should start knowing what you are talking about more.

good luck
david
 
The transformer described is a 1,000 ohm center tapped - using one half or 500 ohms. The other side is 200,000 ohms so the ratio is 1 to 400.

From what I know of transformers the turns ratio is what really matters however the impedance also matters in some situations. I don't know if this is one of those situations. Now for the confusing part - I don't think the 1k side actually measures 1k and the 200k side 200k but there are some rules of thumb on what the actual impedance should be. I recall something like 4x the actual impedance but someone else will have to confirm that. It's the turns ratio that will match a 1k circuit to a 200k circuit.

While I do believe that the circuit works I'd have trouble expecting an audio transformer to have a construction that would tolerate high voltages for any amount of time.

So in your search, look for small audio transformers with a ratio of 1 to 400 or 400 to 1 and you might get closer to what you need. Newark Electronics, MCM and others like Jameco might have them. I actually have one very similar - 600 ohms on one side and very high on the other side - made for some kind of telephone or transmittter interface.

Hope this helps.
 
After searching I found this transformer and wanted to know if this would work? Sense I dont really understand transformers yet.

http://www.jameco.com/cgi-bin/ncomm...br=355000&cgrfnbr=501&ctgys= Thanks, Kyle
 
stevez said:
The transformer described is a 1,000 ohm center tapped - using one half or 500 ohms. The other side is 200,000 ohms so the ratio is 1 to 400.

From what I know of transformers the turns ratio is what really matters however the impedance also matters in some situations. I don't know if this is one of those situations. Now for the confusing part - I don't think the 1k side actually measures 1k and the 200k side 200k but there are some rules of thumb on what the actual impedance should be. I recall something like 4x the actual impedance but someone else will have to confirm that. It's the turns ratio that will match a 1k circuit to a 200k circuit.

While I do believe that the circuit works I'd have trouble expecting an audio transformer to have a construction that would tolerate high voltages for any amount of time.

So in your search, look for small audio transformers with a ratio of 1 to 400 or 400 to 1 and you might get closer to what you need. Newark Electronics, MCM and others like Jameco might have them. I actually have one very similar - 600 ohms on one side and very high on the other side - made for some kind of telephone or transmittter interface.

Hope this helps.

The impedance ratio is the square of the turns ratio, so a 1:200 impedance ratio is only a 1:14 turns ratio. Using half the primary winding, the turns ratio will be 1:28. I don't think this is a direct indication of the output voltage, because the current is interrupted, which makes it a flyback pulse generator, and the voltage becomes a function of stray capacitance, load resistance (the victim's skin), etc.
 
Be careful you don't blow 20 bucks. This part ain't the one you're looking for. The one you want is 1K:200k. This part is 1k:20k.
Digikey has a Mil spec part for $21 that meets your requirements. The Digikey p/n is 237-1137-ND.
I think I would shop some more.
 
Woops. Miscounted the zeros. Anyway, $20 is wat too much for these things. I would expect to find one (actually, in my junk box) at a parts store (certainly not Radio Shack) for $3 - $5 - tops.
 
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