I'll try to answer some of your questions.

1) Some transformers have two primaries. This allows hooking them up in series for 240 volt operation. You must have them wired "in phase" or it will overheat the transformer and damage it. Sometimes there is a color code, sometimes numbers. Sometimes you
can find a datasheet online or from the vendor. You can also test it "trial and error" with a 25 watt light bulb. **Be careful with dangerous voltages*** With an ohmeter, pair off the two primaries. Parallel the inputs and put the bulb in series as if it
were a fuse. If it lights bright, its hooked up wrong. Reverse one set of windings and the light should not light. Check for proper output voltage on the secondary. You now have it wired in phase. Depending on your current demand you may get away with
using just one primary, but the efficiency is somewhat reduced.
There is also the chance that there is only one primary with taps for different mains voltages. i.e. 110, 117, 125. Use the light bulb in series to learn which leads are which.

2) You cannot hook the 16 volt side to a 117 volt source safely. The trasformer will saturate and look like a short. That's what blew the circuit breaker/fuse. For an instant you will get a very high voltage on the 117 volt secondary which may breakdown,
arc and/or catch fire. Don't bother limiting the current. Too dangerous to play with.

3) Ultrasonic. This is possible but you must have a receiving transducer receiver and an ultrasonic source (no problem. just one 555 chip), an audio mixer circuit, and an simple audio preamp/amp and you're set to go.
Rick



Tim Hart wrote:

> HI all...I have a few quick simple questions for the group...
>
> I have a transformer with 4 leads on the AC side and 6 on the output side.  I'm a bit confused...I'm used to 2 on the input side and 3 on the output.  Any idea how to even test the transformer?  I tried measuring the ohms....they are all very close....
>
> Another transformer I have is 110 to 16 volt...I hooked it up backward to see if I could get a few hundred volts AC...nope...it popped my circuit breaker....why did it not act as a step up?  Do I need to limit the current I feed it?
>
> And hearing Ultrasonic.  I want to audibly hear the output of a ultrasonic transmitter....can I build an amp that shifts the frequence down to a level I can hear via a speaker?  Any ideas?
>
> Thanks for hearing me out...I know these are newbie questions....
>
> Thanks,
> Tim
>
> --

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