Does this two circuit have the same output? - Page 2 - diyAudio
 Does this two circuit have the same output?
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 31st May 2010, 08:29 PM #11 diyAudio Member     Join Date: Sep 2002 Location: Lakewood, Ohio It took me awhile to figure out that in the second drawing the bridge to circuit "A" is not a bridge, it's just two diodes. __________________ Kevin
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Join Date: Jan 2010
Quote:
 Originally Posted by Speedskater It took me awhile to figure out that in the second drawing the bridge to circuit "A" is not a bridge, it's just two diodes.
yea. actually i should avoid the two diodes.

thanks.

 5th June 2010, 02:55 PM #13 diyAudio Member   Join Date: Jun 2008 Hi Motbuddy, I'm trying to build the exact same circuit as yours. I want to have 3 voltages: +5V, +12V and -12V. I'm doing the first design like yours. I want to use 2 transformers as I can use a lower voltage one for the +5V supply so that I don't have to dissipate so much heat with the regulator on this rail. I need 2.6A on the +5V rail. What I concerned is the ground. There are two separate grounds on the two circuits, one using the center tap from the +/-12V circuit, the other one is not using center tap as ground. Would the two circuits work together by connecting the two different grounds together?
 5th June 2010, 03:36 PM #14 diyAudio Member   Join Date: Jul 2004 Location: Scottish Borders Hi, you use the word circuits. A circuit is a circular type loop. What goes out in the flow must come back in the return. If it can't it's not a circuit. Can the two circuits operate correctly if they are completely independent. Or asked another way, do the circuits need to be connected together for the two circuits to operate? __________________ regards Andrew T. Sent from my desktop computer using a keyboard
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Join Date: Jun 2008
Quote:
 Originally Posted by AndrewT Hi, you use the word circuits. A circuit is a circular type loop. What goes out in the flow must come back in the return. If it can't it's not a circuit. Can the two circuits operate correctly if they are completely independent. Or asked another way, do the circuits need to be connected together for the two circuits to operate?
Of course I know the 2 circuits will work independently.

I mean I want to use both circuits if (ground) connected together. The device I'm powering requires all 3 voltages (+5, +12, -12) simultaneously.

If not, can I use a center tapped transformer in the top circuit, and use a dual half wave rectification (2 diodes), so both circuit grounds are connected to the CT in each separate transformer?

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Join Date: Jul 2004
Location: Scottish Borders
Quote:
 Originally Posted by Kuro I want to use 2 transformers ................. Would the two circuits work together by connecting the two different grounds together?
will the two circuits work independently?
Quote:
 I know the 2 circuits will work independently.
then why do you need to connect them together?

The two transformers will create two isolated supplies that can power two isolated circuits. They don't need to be connected together.
__________________
regards Andrew T.
Sent from my desktop computer using a keyboard

 6th June 2010, 02:12 AM #17 diyAudio Member   Join Date: Jun 2008 I guess I've not been too clear. The word "circuit" refer to the two rectifying circuits in this topic. The device I'm powering is actually just one physical circuit, which requires +5, +12 and -12V. My device was powered by a SMPS and I want to change it to Linear PS. But I want to minimize power dissipation on the 5V rail so I use a transformer with 7VAC secondary. Now I've two linear power supplies, one providing 5V and the other providing +/-12V DC. Can I physically connect both supplies to my device as I noticed that the +/-12V one has ground in the CT of the transformer, but the +5V one has ground on one end of the transformer's secondary. The two "grounds" are not in phase during an AC cycle. What I worry is that these two grounds may have different potential... BTW, I have the parts, but the supplies have not been built yet.
 6th June 2010, 09:33 AM #18 diyAudio Member   Join Date: Jul 2004 Location: Scottish Borders the two transformers and their PSU each give an isolated output flow and return. The 12V version could be 0,12,24Vdc or 0,-12,-24Vdc or 12,0,-12Vdc or any other combination that covers a range of 24V,i.e. 100,112,124Vdc. The 5V version could be 0,5Vdc, or 0,-5Vdc, or 12,17Vdc, etc If you link any ONE output from the 12 to any ONE output from the 5 then you will have one common voltage and the three other voltages. I cannot tell you if the 4 power input terminals are designed to work well together with a common 0Vdc. __________________ regards Andrew T. Sent from my desktop computer using a keyboard
diyAudio Member

Join Date: Jun 2008
Quote:
 Originally Posted by AndrewT the two transformers and their PSU each give an isolated output flow and return. The 12V version could be 0,12,24Vdc or 0,-12,-24Vdc or 12,0,-12Vdc or any other combination that covers a range of 24V,i.e. 100,112,124Vdc. The 5V version could be 0,5Vdc, or 0,-5Vdc, or 12,17Vdc, etc If you link any ONE output from the 12 to any ONE output from the 5 then you will have one common voltage and the three other voltages. I cannot tell you if the 4 power input terminals are designed to work well together with a common 0Vdc.
That essentially was my question. So I guess no real answer...

 7th June 2010, 01:40 AM #20 diyAudio Member   Join Date: Jan 2010 hi kuro, if u are asking about the first circuit that i built which is using two transformers. yes,it works.i connect both circuits' GND together.if u dont connect the GND together it wont work and it will work just like two independent circuit. Hope this will help.

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