Voltage regulator with alternate voltage source...
wdonzelli at gmail.com
Fri Apr 8 13:42:44 CDT 2016
> 1) The 7805 is actually a Motorola MC7805CP, date
> code 7308 with gold leads. Very hard to exactly
Is that the big flat plastic package with the wide flat leads? I might
have a few of those around, but I agree, not an easy variant to find.
> 1) I have a 12 volt DC supply. 12 volts seems to be
> within the VIN range for the 7805s whose data
> sheets I've now read. Can I simply apply 12 volts?
Yes, but that regulator might get mighty hot! I would not do this for
fear of cooking the poor thing.
> 2) Could I place a resistor in series between the 12V
> supply and the 7805 to drop the voltage at the 7805
> to somewhere around 8?
Yes, you could do this. Pick an appropriate power resistor, or use a
big wirewound rheostat.
> 3) If I was to "tack on" a jumper between VIN and VOUT,
> would that protect the 7805 and allow me to power the
> circuit with 5 volts?
I would not do this at all.
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