Posts Tagged ‘CdS photocell’:

2022-04-07 Audible Light Meter

This circuit could be used for blind to sense light. It’s a similar circuit to the police siren. The two transistors have a current gain of 200 X 200 or 40,000 so even a very tiny Q1 base current – microamps – causes a very large Q2 collector current. So a very small amount of

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2011-12-02 Watson’s Blue Blinky Joule Thief Flasher

I built this Blue Blinky and installed the partly used AA cell on Dec 1, 2007.  For most of the next 21 months, on or about the first of the month I published a short blog on how it was doing.  As the cell ran down it got dimmer and dimmer, but continued to flash,

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