110VDC isolated p'supply

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Robert Davies 20 years ago

Can anyone please tell me if this is good practice for building a

110VDC split rail power supply?

I intend to use 2 x 12VAC (unearthed) wall socket adaptors. Each output is connected to the 12V side of 110V-12V transformer. The 110V sides are connected in series, with the common becoming virtual earth. One set of the usual rectifier and caps are then wired across this and to each lead respectively to create the + and - rails.

I understand the back-to-back transformers provide isolation or safety by limiting the current. However, I am unsure to what degree or if the current ratings of the components are relevant as limiting factors.

Thank you for any advice.

Robert Davies

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Fred Bloggs 20 years ago

The "wall socket" adapters would have to be anti-phase for this to produce anything, and then you would have 24VAC across the 110-12 transformer 12VAC coil which will cause it to saturate. Why don't you use a single 115:230 CT transformer at the appropriate VA rating?

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Phil Allison 20 years ago

"Robert Davies"

** Yes - it is *not* good practice.

** First error - better use just one.

Wire the two 12 volt AC load windings in parallel.

This way the DC rails will remain balanced at all times.

** Second error - better use a 9 volt AC adaptor.

** 110 volts AC translates into 150 volts DC when rectified and filtered.

The use of a 9 volt AC adaptor will bring the DC voltage closer to your need.

** The scheme is good only for low load currents - 30 to 40 mA @ 200 volts.

There are complicating issues with transformer magnetising current being in the wrong winding AND the rms value of the pulse like current delivery in such DC supplies.

Lotsa luck.

...... Phil

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Phil Allison 20 years ago

** Nonsense.

** There are *TWO* 110 - 12 volt transformers in the scheme.

" The 110V sides are connected in series, .... ".

Try learning to read sometime - d*****ad !!!

** Cos he has lots of 110 - 12 volt adaptors handy ?

....... Phil

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Fred Bloggs 20 years ago

Why didn't the moron say 2x 110-12 transformers as with the "adaptors?" It is quite possible he was talking about an international use transformer with 2x 115 primaries, idiot. The voltage regulation will stink worse than your fetid corpse.

Who can read moron-ese better than you. He will still have to pay attention to phase on the 115V coils, idiot.

Are they all of the same type and rating, idiot? Looks like you haven't gotten to square two on this, overlooking numerous critical safety, fire, and personal injury hazards as described in your precious AS/NZS

3000; you did get to square one, that is to say, you communicate perfectly with fellow moron rig-it-up types....

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Fred Bloggs 20 years ago

I see now the OP is Australian- the most ignorant crap queries come from that hell-hole cesspool. No wonder you so readily understood the gist of his babble- being a fellow turd and all that you are...

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Phil Allison 20 years ago

"Fred Bloggs" = anonymous cunt

** Leard to read simple English - d*****ad .

Shame you have no chance of learning to think.

You evil, criminal POS !!!

....... Phil

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Phil Allison 20 years ago

"Fred Bloggs" = anonymous Yank cunt

** Learn to read simple English - d*****ad .

Shame you have no chance of learning to think.

You criminal POS !!!

....... Phil

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Fred Bloggs 20 years ago

Reading entails slightly more than sounding out the words for aural processing as you do. The description was ambiguous and incomplete and therefore indecipherable at the level of understanding necessary for a reasonable response. Only an idiot such as yourself would think otherwise.

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Fred Bloggs 20 years ago

Reading entails slightly more than sounding out the words for aural processing as you do. The description was ambiguous and incomplete and therefore indecipherable at the level of understanding necessary for a reasonable response. Only an idiot such as yourself would think otherwise.

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Phil Allison 20 years ago

"Fred Bloggs" = anonymous Yank cunt

** Learn to read simple English - d*****ad .

Shame you have NO chance of learning how to think.

You are a criminal POS !!!

....... Phil

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Phil Allison 20 years ago

"Fred Bloggs" = anonymous Yank cunt

** Learn to read simple English - d*****ad .

Shame you have no chance of ever learning to think.

You ARE a criminal POS !!!

....... Phil

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Rich Grise 20 years ago

Yes, you can do this, and the limiting factors are isolation, which a wall wart should have at least a couple hundred volts isolation, and the power capability.

Add up the volt-amps of your outputs, and add, say, 20% to 50%; then that should be the total volt-amps of the two wall-warts.

In other words, if you have a 12V, 1A wall wart, then you could get

120 (I'm using 120 because it's a more common way of referring to line voltage, and it's _s00000_ much easier to do the arithmetic) V at somewhat less than .1A - power out equals power in minus losses.

And, of course, you know that a rectifier/filter on a 110V secondary will produce ~154V no-load, right? :-)

Good Luck! Rich

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110VDC isolated p'supply

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