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'simple 7805 breadboard power supplies'
2003\05\10@175750 by Tony Harris

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You really don't need a cap on the middle pin - the middle pin is tied to
ground (for ground reference for the chip), and if you put a cap to it, what
would you put it between, connecting to positive supply is the same as input
pin to ground, and regulated is the same as output to ground...

The places you need caps are on the input, and on the output. Take a look at
this datasheet...

http://www.national.com/ds/LM/LM340.pdf

It has a typical config for a fixed output regulator.

Personally, I like a decent sized cap on the input to limit input
fluctuations, and a not as big one on the output of the regulator.  I'd say
your first cap (100uF) on input, second (10uF) on output, and save the 100nF
for use as a decoupling cap somewhere in what uses the power supply :)  I
would also consider a diode for a discharge path (see later in the data
sheet)


-Tony

{Original Message removed}

2003\05\10@180624 by Marc Nicholas

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Tony...

That was just the sort of constructive feedback I was looking for! :-)

Thx,

-marc

On 10/5/03 18:04, "Tony Harris" <spam_OUTtonyTakeThisOuTspamELROYNET.COM> wrote:

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> {Original Message removed}

2003\05\10@192521 by Dave VanHorn

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> > I would also consider a diode for a discharge path (see later in the
> data sheet)

Absolutely.
Diodes are very cheap, compared to time lost in a failed supply.
It doesn't take much output C to kill the reg if there's ever a short on
the input side.

I'd do input and output LEDs, same reason.

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2003\05\10@194008 by Marc Nicholas

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Would a 1N4001 be adequate?


-marc

On 10/5/03 19:23, "Dave VanHorn" <dvanhornspamKILLspamCEDAR.NET> wrote:

{Quote hidden}

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Marc Nicholas Geekythings Inc. C/416.543.4896
UNIX, Database, Security and Networking Consulting

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