adjustable shielded coil pins?

[tylerz]

Hi I have searched the net everywhere for this basic question, but nothing
turned up. I have some adjustable shielded coils (the little square packages
with the bobbin inside), which have 5 pins coming out of the bobbin and 2
pins due to the shield. Pulling it apart it has wires coming from the coils
to all the pins. This made me believe that it was a transformer of some
kind, which is what I want. So, I intended to test this to see if I could
induce a votage from one set of pins to the other by hooking a digital
voltmeter to one set of pins and switching power on and off to the other set
of pins. I tried a 1V to a 9V and never see any induced voltage.

So my questions are:

What is the standard pin layout of these types of inductors/transformers?
Are they meant to induce voltage from one coil to the other when all 5 pins
are connected to the coils?
Is my testing appropriate and if not what is the simplest way of testing
this?

Thanks for any assistance offered,

Tyler

 

[Joe McElvenney]

Hi,

What is the standard pin layout of these types of inductors/transformers?

There isn't one really, just dozens of variations on a theme. Assuming that
the item you have is an RF transformer, try a search for TOKO inductors (a
very common make) and see if any of the basing diagrams fit your transformer.

With five wires it is probable that there are two windings with one of them
being tapped. You can find plenty of these on old transistor radios in the
form of IF transformers tuned to either 10.7MHz or 455kHz depending on whether
the set is for FM or AM.

Are they meant to induce voltage from one coil to the other when all 5 pins
are connected to the coils?

If it indeed has two windings, then you would have to connect your voltage
across one winding and detect the induced voltage across the other - that is,
a minimum of four wires. If it were a tapped winding however, then one wire
would be common to both and only three are needed.

Is my testing appropriate and if not what is the simplest way of testing
this?

Your problem would be the response time of the DVM. The most that you are
likely to see is a slight twitching of the digits. To do this properly you
really need an analogue meter or an oscilloscope with a reasonably fast
timebase but a slow speed screen such as in a storage scope.

Try finding a mains or an audio transformer, since these have a much
greater mutual inductance, and borrow an analogue meter from somewhere (they
are much better for some things) and try again to rediscover Faraday's laws
that way.


All the best - Joe