There are a few things you could do.  If you experiment with any regularity,
a lab supply purchase isn't something you'd regret.  You can get one without
breaking the bank if you shop around a bit.

Something you might want to consider is a current limiting supply for
experimentation purposes.  Its really easy to cook something with a moment
of carelessness and a 7 amp psu.  A supply that scrambles when a current
level is crossed can save your experiment from that wonderful epoxy smell.

http://www.elexp.com/tst_1802.htm

is an example of a fairly cheap lab supply.  I haven't personally used this
but it looks OK for the price.  Shop around first if you decide to purchase
one a supply.

You might think about building a lab supply as an educational experience.
I've built a few in EE school and they were pretty fun projects.  I still
actually use one of them fairly regularly, even with the "store bought" ones
I have access to now.  There are lots of schematics out on the web
describing this --some even with a lm317 and outboard transistors.

http://myweb.cableone.net/wheedal/pcbconstruct/psu_cv.jpg
is a picture of a supply I did when in school.  Enclosed in a discarded UPS
box.  LCD driven with 16f84/external adc.

Switchers generate noise, so they might not be the first choice for a lab
supply if you are doing small signal analog/12bit adc stuff as well.

Just my $.02 and worth about as much.

-----Original Message-----
On Behalf Of Michael Olson


I've been using a Radio Shack 13.8VDC/3A supply feeding a
LM317 w/ Heat Sink for my breadboarding setup so far. But

I don't think my current configuration is going to be good
for a steady 4.4W even if I improve the heatsink. I'm debating
between the quick fixes and something I don't see outgrowing
any time soon.

Options I'm considering now are

1 - Moving over to a 5V switching setup, perhaps the PT5101A.
    (http://focus.ti.com/docs/prod/folders/print/pt5101.html)

2 - Find a 5V switching wall wart, or a 7V unregulated to feed
    a 7805.

3 - Raiding e-Bay for a new bench power supply.
    (Any shopping tips?)

4 - The Fun solution:
    Converting an Antec QuietPower. It seems to me that by
    just installing the power supply into a project box and
    hooking up via an ATX 20 pin connector that you could
    preserve the warrenty and certifications. I was thinking
    it might be a fun project to put a front panel Voltage
    and Current meter for each output and perhaps a setable
    emergency shutoff based on the current being drawn. Any
    reason I couldn't use a PICs A/D inputs referencing a
    precision voltage reference hooked up across the output
    for the voltage and across a very low value resistor for
    the current? While this has a great deal of appeal it's a
    bit more of a down the road solution as I need a better
    power supply now.

Are there better options I'm missing or anything wrong with
the ideas I have so far?

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