0.0047 uF @400 V*
|| |
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|| | | |
| | 1.5V
120 VAC --- --- to clock
^ _
| |
10K | |
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can trickle-charge a Seth Thomas quartz clock with hands and a AA battery
("Replace every 12 months or in case of suddenly inaccurate timekeeping.")
The trickle-charged battery might last 10 years.

The battery current jumps when the second hand ticks, but a 1K resistor
and a 10K microfarad smoothing capacitor reveal an average 95 microamps
= 60Hzx2xsqrt(2)x120VxC, which makes C = 0.0047 uF, one of the 150 caps
in Digikey's $29.95 M400-KIT-ND. Their P10KBACT-ND 10K resistors cost
$15.86/1000... 1N5231BD1CTND 5.1V zener diodes cost $13.65/100. Their
number is 1-800-344-4539. Most orders are shipped in 12-14 minutes.

This circuit uses about 1.5Vx95uA = 142 microwatts, ie 1.2 Wh/year worth
$0.000125 at 10 cents/kWh. It's probably illegal. Don't try this at home.

Nick