On Thu, 27 Sep 2012 12:44:00 -0700, Jim Thompson
wrote:

AC Cap Dropper DC Power Supply

Anyone know of a clever way to regulate other than the typical
brute-force zener clamp?

Not sure exactly what you are looking for, but if you are
using caps to drop voltage I'm guessing this is a "cheap and
cheerful"-type application.

I use a super-simple regulator to drop "dead" 9V batteries
down to 1.5V to run various low-drain devices like clocks
and timers. It's just an NPN (2N3904, etc) with collector
from battery, and emitter driving load. Base "reference" is
a green LED to ground, with a selected resistor from base to
collector. Small enough to wire the whole works onto a 9V
battery clip. Lots of variations: More LEDs for higher
output voltage, Darlingtons for more sensitivity/higher
power, etc.

Forward-biased LEDs have super-sharp knees at low currents,
and the parts bins are full of them.

Best regards,


Bob Masta

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