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AC/DC clock circuit

2017-01-08 22:28  
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AC/DC clock circuit
When AC municipal electric power is cut off, MCD2 photoelectric isolator perceives the voltage drop, made Schmitt trigger fliped, so the stobe input terminal of clock chip is grouding, the dispaly is not show again. Then the 9V reserve cell is charge to circuit automatically, but the display is no power consumption, so the total current of circuit consumption is not the 200mA AC power, but is 12mA. 1000mA*h battery can keep the clock work for a few days, 2 LEDs add colon betwwen hours, points and seconds, they are drived by gate line. so when the display don't show time, this two colons are still lightening , but only consume 1mA current.