[sdiy] wall wart confusion

[Aleks Clark]

yea, just use an 18v wall wart. what would have been 0 would be -9, and what
would have been +18 would be 9. Like Laurie said, it's a matter of relative
potential.

On 2/27/06, amokan <amokan at gmail.com> wrote:
>
> So, are there wallwarts that will do +/- ? Am I better off using an AC
> wallwart and then building one of the many power supply circuits available
> online?
>
> I really just want something cheap and that only involves 1 plug. I also
> want to avoid anything much more than a regulator in my circuit to keep it
> small.
>
> I've never really put much thought into this until now. All of my circuits
> are done on a breadboard with a bench supply and by the time I get them in a
> frac, they just plug into my main supply that "magically" works :)
>
> Thanks again everyone. Sorry to drag this thread on.
>
>
>
> On 2/27/06, Laurie Biddulph <elby_designs at ozemail.com.au > wrote:
> >
> > If the outputs are truly isolated from the mains power (specifically
> > that is not connected to the Earth pin - which they should be) then you can
> > connect the positive of one wallwart to the 0V of the other. This (double)
> > 0V connection is connected to the 0V connection of your module and you then
> > have +ve (from the free positive lead) and -V (from the free 0V lead).
> >
> > What you won't get is tracking between the outputs so one might go up
> > while the other droops etc. If you are using these to power regulators in
> > your circuit then this will be less of a concern. You will also need to
> > power outlets and if your wallwarts are large then it may not be possible to
> > get 2 on to them (double) outlet.
> >
> > The size of a wallwart is a possible indication of wether it is a
> > transformer or switching design but not always.  A low power transformer
> > unit will be quite small. Usually there is next to no weight in the
> > switching designs. Above should hol true for these as well as the outputs
> > should be totally floating.
> >
> > Best Regards
> >
> > (Mr) Laurie Biddulph
> > Mobile: 0404 846 943
> >
> > Elby Designs
> > ABN: 70 022 727 605
> > http://www.elby-designs.com
> >
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> > ----- Original Message -----
> >  *From:* amokan <amokan at gmail.com>
> > *To:* synth-diy <synth-diy at dropmix.xs4all.nl>
> > *Sent:* Monday, February 27, 2006 5:20 PM
> > *Subject:* [sdiy] wall wart confusion
> >
> > I didn't pay attention back in high school electronics when it came to
> > power supplies so please forgive me if this is a newbie question...
> >
> > I've built bipolar supply kits for modular use but never really
> > understood _how_ they work. Negative supplies are a mystery to me. I know
> > there is a difference between ground and the negative rail, but I don't know
> > what the difference is. A 9v battery is in-fact bipolar, yes?
> >
> > Long story short, I'm working on modules that will run in a stomp box
> > format and I'm trying to figure out the cheapest & easiest way to power
> > them. I know I could use the dual 9v battery solution to power them
> > (assuming the circuits could run at 9v) but I'd really like to just use a
> > standard 9v or 12v dc wallwart that I have laying around the house. How do I
> > get a negative voltage off of a standard 12v wall wart? Is it already there
> > normally, or just a positive and a ground?
> >
> > Sorry for rambling. If there is a web resource explaining this, please
> > let me know.
> >
> > Thanks!
> >
> >
>


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