On 2010-11-25 13:24, David Duffy (AVD) wrote:

Now, this isn't directly related to the actual problem,
but who knows...

> As for power, there's not much to the circuit. A 12V battery
> via a 1N4007, into a 78L05 with a 100uF on the input.

The smoothing cap on the *input* side of a 78(L)05 is usualy
there to "smooth" the supply from the power source. Now, a
*battery* will probably not need to be smoothed at all.

I would use smaller caps, whatever is recomended ny the 78L05
datashett for stabilizing.

I checked one from National, and it specifies 0.33 uF
at the input and 0.01 uF at the output. I think the *output*
cap is the one that is realy important here (to supress
self-oscillation), the input cap is only needed if the
input power source isn't smooth enough already (a battery
probaly is).

What is the reason for the 100 uF cap between the battery
and the 78L05 ? Intermittent larger current drains ?

Jan-Erik.


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