Voltage regulator with alternate voltage source...
wh.sudbrink at verizon.net
Fri Apr 8 13:18:14 CDT 2016
First, a few quick "whys":
1) The 7805 is actually a Motorola MC7805CP, date
code 7308 with gold leads. Very hard to exactly
2) As per the design of the unit, the 7805 is soldered
to the foil side of a single sided, copper clad
circuit board with no through hole plating. Lifting
the traces seems like a significant possibility that
I don't want to risk.
3) I'm still waiting for the components to build the
8 volt power supply. Hopefully they will arrive
4) No, one thing missing from my bench, that I've
never really needed up to now, is a good adjustable
DC supply. My have to ask for one for Christmas.
Three thoughts have come to me since my original post.
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?
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?
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?
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