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42TM018 Pinout and grounding

Started by zpyder, October 05, 2006, 06:01:22 PM

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zpyder

October 05, 2006, 06:01:22 PM
Hi there

Just got some 42TM018's in from Mouser... I've never worked with these, or any other transformer before, so of course I'm excited.

I have a couple questions about using these though.  Firstly, since this is a 1:1 Xfrmer, can I assume that either side could be the primary OR the secondary, and that this component is "non-polarized" in that it doesn't matter which way I plug it in?

And also, refering to this schematic: http://www.geofex.com/FX_images/splitter.gif, I see that both sides of the transformer are shown with two leads each, yet my 42TM018's have 3 leads on each side -- what gives??

thanks,
zpyder
www.mattrabe.com/ultraterrestrial Ultraterrestrial - Just doing our little part to make new rock go where it should have gone in the late-90's, instead of the bullshit you hear on the radio today.

Gilles C

#2
October 06, 2006, 12:10:07 AM Last Edit: October 06, 2006, 12:13:13 AM by Gilles C
It does not matter how you connect them in, but depending on how you connect the secondary (output), the signal will be IN PHASE or OUT OF PHASE with the input signal.

Because of that, we could say they are polarised. Normally, there are dots to indicate which wires to use to keep the signal in phase.

Ok, I found the 42TM018 specs to show the dots I was talking about.

http://www.mouser.com/catalog/specsheets/164267.pdf

Gilles

zpyder

#3
October 06, 2006, 03:07:49 PM
Alright sweet...

So pins 1 & 6 are the dotted ones, which indicate that they are connected to the BEGINNING (right?? I think so) of the windings, and pins 3 & 4 are going to be my grounds... pins 2 & 5 are center tap and in this case have no application, so I'll just leave em hanging or cut them off...

cheers,
zpyder
www.mattrabe.com/ultraterrestrial Ultraterrestrial - Just doing our little part to make new rock go where it should have gone in the late-90's, instead of the bullshit you hear on the radio today.

Gilles C

#4
October 06, 2006, 07:34:04 PM
In the specsheet from Mouser, the dots are on pins 1 & 4, and then the ground sides would be 3 & 6

Gilles

Gilles C

#5
October 07, 2006, 12:36:22 AM
This evening, I re-checked the last circuit I tested with a 42TM018 and realised that I wired the secondary (output) upside down. I also noticed that detail in a layout in the Layout Gallery.

So I took a signal generator and an oscillocope and tested the pin-out of the transformer, just for fun. I also made a little drawing to make it easier to remember how to connect it correctly.

I did not include the resistor and the cap to make it simple. It was just to be used as a reminder. And it's always easier to remember or to understand with a drawing.

So here it is, in case it can help.



Gilles

zpyder

#6
October 09, 2006, 12:44:30 PM
Oh man, I wish I'd read this over the weekend.  I isolated a splitter circuit that I have on a protoboard with two 42TM018's - but I did it backwards.

Oddly enough... it worked.  Hmmm.... Considering it's an AC signal going through there, I would guess my signal just got flipped (180 degrees out of phase)...

interesting

cheers,
zpyder
www.mattrabe.com/ultraterrestrial Ultraterrestrial - Just doing our little part to make new rock go where it should have gone in the late-90's, instead of the bullshit you hear on the radio today.

Gilles C

#7
October 09, 2006, 02:22:58 PM
Exact.

It's not worst than using a transistor design that have the same result sometimes, depending on the number of transistors used etc... And the same thing happens with opamps.

The important things were that you understood how a transformer works, and why the dots are there in a schematic.

The only other detail about this phase thing is when you mix 2 signals from 2 effects. If one of them is out of phase with the other one, they may cancel (only a bit or a lot) each other depending on how similar they are.

Btw, if you were to use the correct phase (dot side) for one transformer in the splitter, and reverse it for the other output, you could have some cancellation in the sound you would hear when using 2 amplifiers at the same time. But if you use the same connection for both transformers, it's ok.

Gilles

zpyder

#8
October 09, 2006, 03:39:52 PM
Coooooooool... I love it when I figure stuff out...

So I'd bet I could design a tremelo-type effect using one 42TM018 transformer out-of phase, a 555, and a cmos switch like the 4053... hmmm... i wonder if the 555 outputs a voltage or a pulse or what...

thanks for the input gilles!!  That is quite a handy diagram you drew up...

There's one thing I still don't know about transformers though, and that is what would I see if I plugged an oscope onto the center tap (pin 5)?  Flat-line?

cheers
zpyder
www.mattrabe.com/ultraterrestrial Ultraterrestrial - Just doing our little part to make new rock go where it should have gone in the late-90's, instead of the bullshit you hear on the radio today.

Gilles C

#9
October 09, 2006, 07:14:40 PM Last Edit: October 09, 2006, 07:18:37 PM by Gilles C
You would see half the signal you have at the full winding. (Having the ground side of the probe at pin 6, and measuring at pin 5 (ct) with the probe).

It's exactly like a power transformer with a center-tap. If you have a 24VAC transformer with a center tap, you would have 12VAC at the center-tap.

Gilles
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