A wall-wart alternative

nicksanspam · 2006-01-05T05:41:36+00:00

I finally got tired of replacing the 2 C-cells in a clock with a movingpendulum, so I measured the current (3 volts at 340 microamps) and builta charge pump like this, viewed in a fixed font: 0.047 uF @400 V || |-----------||--------------------->|------------> || | | | | | 3V120 VAC --- --- to clock ^ _ 0.047 uF @400 V | | || | |-----------||-----------------------------------> ||I used two caps in case one shorts and for some ground isolation. The diodesare 5.1 V zeners ($1.29 for 2 at Radio Shack) to limit the clock voltage ifsomeone unplugs the batteries. This circuit supplies 390 microamps. I hopeto avoid replacing the batteries until their shelf life runs out in 2012 :-)This could be useful for lots of low-power stuff, eg smoke detectors.Nick

Jan 05, 2006 60 Replies

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George Ghio 20 years ago

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A wall-wart alternative

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