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Toroidal transformer, where is the GND?
Toroidal transformer, where is the GND?
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Old 7th July 2019, 09:01 PM   #1
MilanAudio is offline MilanAudio  Czech Republic
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Question Toroidal transformer, where is the GND?

Hello guys,

I do soldering for years and I'm still missing some basics. GND is part of it.

I have few strong toroidal transformers, but non has V-GND-V. I have two wires AC primary and two wires AC secondary. How I can make missing ground?

I know that some custom made toroidal has leaded wire from the middle of secondary wiring, I suppose it should be the ground...

Well I would like to make some GND on toroidal transformers, because I will need V+ GND V- for my amps. Any idea?

Thanks for help!

Milan
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Old 7th July 2019, 09:08 PM   #2
oiphy is offline oiphy  Norway
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Toroidal transformer, where is the GND?
use ground from wall socket direct to chassis.
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Old 7th July 2019, 09:13 PM   #3
rayma is online now rayma  United States
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Quote:
Originally Posted by MilanAudio View Post
I would like to make some GND on toroidal transformers, because
I will need V+ GND V- for my amps.
Most toroids now have two secondaries, instead of one center-tapped secondary.
To get a center tap, just connect the two secondaries in series, with the correct
relative polarities. Each secondary should be rated for the proper voltage needed.

Last edited by rayma; 7th July 2019 at 09:22 PM.
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Old 7th July 2019, 09:14 PM   #4
MilanAudio is offline MilanAudio  Czech Republic
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Quote:
Originally Posted by oiphy View Post
use ground from wall socket direct to chassis.
It is really that simple? I thought it will be more sophisticated when audio amp will be powered. And GND with speakers will be shared. Is that OK? I guess to avoid noise I should use some coils...

Also in emi/rfi filters are Neutral and Live shorted to GND over caps.
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Old 7th July 2019, 09:18 PM   #5
rayma is online now rayma  United States
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Quote:
Originally Posted by MilanAudio View Post
It is really that simple?
No, there is a misunderstanding. This has nothing to do with the utility safety ground.

The center tap of the series secondaries is the power supply common (0V),
which may or may not be connected to the utility safety ground.
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File Type: pdf diode-full-wave-bridge-rectifier-dual-supply.pdf (14.5 KB, 53 views)

Last edited by rayma; 7th July 2019 at 09:26 PM.
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Old 7th July 2019, 09:21 PM   #6
scottjoplin is offline scottjoplin  Wales
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MilanAudio, what you are calling GND is really 0V.
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Old 7th July 2019, 09:26 PM   #7
MilanAudio is offline MilanAudio  Czech Republic
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Quote:
Originally Posted by rayma View Post
Most toroids now have two secondaries, instead of one center-tapped secondary.
To get a center tap, just connect the two secondaries in series, with the correct
relative polarities. Each secondary should be rated for the proper FWCT voltage needed.
Center Tapped Full Wave Rectifier - File Exchange - MATLAB Central
I was thinking about connecting two secondary wirings! But I was not so sure... It's better to ask somebody who's really experienced. Thank you!

And what I should do with two transformers which has only one secondary wiring? I was reading that secondary wiring is below primary wiring, so I guess I won't be able to do modification.

Last edited by MilanAudio; 7th July 2019 at 09:43 PM.
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Old 7th July 2019, 09:30 PM   #8
rayma is online now rayma  United States
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Quote:
Originally Posted by MilanAudio View Post
what I should do with two transformers which has only one secondary wiring?
I was reading that secondary wiring is below primary wiring, so I guess I won't
be able to do modification.
Please do not attempt to modify the transformers, this is dangerous.
If each transformer has the correct secondary voltage, you could
make a single DC supply with each, and then connect the two DC
outputs in series, with the connection point serving as the common (0V).
This is not ideal compared to a single transformer, but it would work.
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Old 7th July 2019, 09:35 PM   #9
MarcelvdG is offline MarcelvdG  Netherlands
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Take two of those transformers, connect the primaries in parallel and the secondaries in series maybe (or actually you should first give each transformer its own fuse before connecting the mains sides in parallel).
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Old 7th July 2019, 09:36 PM   #10
MilanAudio is offline MilanAudio  Czech Republic
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Quote:
Originally Posted by scottjoplin View Post
MilanAudio, what you are calling GND is really 0V.
Yes, perhaps. On the scheme is written 35+ GND 35- and the GND is shared with one speaker wire, amps are two mono blocks.

Well, if it would be up to me I would just connect dc and forgot about the ground but it would not be 100% OK.
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