adjustable 1.5A power supply transformer

JoeMorris · Joined: Apr 26, 2009 Posts: 161 Location: Brighton

Hi, I have a few of these power supply boards. They specify a centre tapped transformer, but would they work using dual 15v secondary windings with both neutral wires together as the centre tap?
(this transformer
http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=UK&WT.z_homepage_link=hp_go_button&KeyWords=TE62063-ND&x=0&y=0)
Thanks

Joe

Uncle Krunkus · Posted: Wed Dec 09, 2009 2:24 pm Post subject:

Yeah, that's fine Joe.
Just make sure you wire the outputs in phase.
For example,
There'll be 4 output wires, and the side of the transformer will show them as White/Orange/Yellow/Blue - 15-0-15-0
In this case you need to use the Orange/Yellow together as the centre tap. (or the White/Blue) but not the Orange/Blue. Does that make sense?
Get it checked by an electrician if you have any doubts at all.
Also keep in mind that that particular transformer won't deliver 1Amp per rail. It's rated at about 800mA in series, so I wouldn't push it past 500mA (per rail)

Skrog Productions · Posted: Mon Dec 28, 2009 5:03 am Post subject:

Hi Joe & Andy ,
I'm interested in what problems would ouccur if the secondarys were wired out of phase, has anyone wired a toroidal like that and found exessive hum or very hot regulators or even a potential voltage difference to mains earth from the center tap ????.

Dave (Trying to expand my knowledge of synth power supplys )

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Uncle Krunkus · Posted: Mon Dec 28, 2009 1:42 pm Post subject:

It may have no effect.
But it's not the kinda thing I'd like to try. Laughing

Skrog Productions · Posted: Sat Jan 02, 2010 3:56 am Post subject:

hey Andy, happy new year.

I'll get back to you on this one, i think i may have inadvertently tried this on the asm supply Embarassed

, the synth works great but my 15V regs could cook a lovely sunday roast Shocked

, i really will have to pay attention more in future Smile

Dave.

delayed · Joined: Jun 24, 2008 Posts: 130 Location: TN

Kinda off topic here, but can you take a 15v ac wall wart and make a Y power cable (female to male + male) and be okay? Is there any issues with this?

Basically having two outputs on one wall wart but by making the cable I will not have to cut up the wall wart's cable.

I want to do this for two of Ray's older 1A power boards. I have the +-12VDC power boards running on two different wall warts right now, and would like to only carry around one.

benuron · Joined: Nov 22, 2009 Posts: 11 Location: Portugal

This is a good site about transformers
http://sound.westhost.com/xfmr2.htm#8.series-parallel

To connect the output transformer you should connect one start winding of one rail to the end winding of the other.

JoeMorris
The wires you have to connect are the green with the blue or the red with the brown.
See the pdf

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

Joe, The model 62063 that you have chosen is 2X15V, but it should give 2X18 in order to supply if needed +/-15V.
LM317 data says 3V ≤ (VIN − VOUT) ≤ 40V.
So it should be better the model 62064.

Uncle, I think that the secondary should be configured OUT of phase. http://en.wikipedia.org/wiki/Centre_tap

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

benuron, when I posted I didnt see your post.

Good link.

Uncle Krunkus · Posted: Mon Jan 04, 2010 3:10 am Post subject:

Yeah, Sound, schematically that's what I meant. I just thought that would be called in phase. Most transformers have a pic on the side which says something like "15-0/15-0". So for a positive excursion on the primary, the second "0" is -15 with respect to the second 15, so by connecting the middle "0-15" together, you create a +15,0,-15 arrangement. (or something like that)
Anyone with more experience in PSUs is welcome to jump in and "set the record straight" Very Happy

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

Aha, I think that the key is in the link of Benuron, where is explained that is possible connect two secondary in parallel or series and in phase or out of phase. So as I understood the correct name for the configuration needed in bipolar or split supplies is in series and out of phase.

Out of phase assure that the positive and negative rails always receive current, now by one secondary, after by the other depending on the phase.

benuron · Joined: Nov 22, 2009 Posts: 11 Location: Portugal

I'm still learning about transformers and psu but this is what I've discovered so far.

When you buy a transformer the manufacturer tell's in a datasheet or in the box of the product where the windings start. This is normaly marked with a point or asterisk. When you know that information it's easy...the start of one winding rail goes to the end of the other winding rail.

I think they must be out of phase to cancel each one and give the 0 volts.

sorry the english Wink

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

benuron · Joined: Nov 22, 2009 Posts: 11 Location: Portugal

JoeMorris · Joined: Apr 26, 2009 Posts: 161 Location: Brighton

Thanks for your help people. I built two of these and they work very well.
Joe