[sdiy] wall wart confusion

[amokan]

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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