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Battery-powered Night Lamp 1

2016-05-09 19:38  
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Battery-powered Night Lamp 1
Parts:R1,R2 1M 1/4W ResistorsR3 47K 1/4W Resistor (optional: see Notes)R4 Photo resistor (any type, optional: see Notes)C1 100nF 63V Polyester CapacitorC2 220µF 25V Electrolytic CapacitorD1 LED Red 10mm. Ultra-bright (see Notes)D2 1N5819 40V 1A Schottky-barrier Diode (see Notes)IC1 7555 or TS555CN CMos Timer ICB1 1.5V Battery (AA or AAA cell etc.) Device purpose:This circuit is usable as a Night Lamp when a wall mains socket is not available to plug-in an ever running small neon lamp device. In order to ensure minimum battery consumption, one 1.5V cell is used, and a simple voltage doubler drives a pulsating ultra-bright LED: current drawing is less than 500µA.An optional Photo resistor switches-off the circuit in daylight or when room lamps illuminate, allowing further current economy.This device will run for about 3 months continuously on an ordinary AA sized cell or for around 6 months on an alkaline type cell but, adding the Photo resistor circuitry, running time will be doubled or, very likely, triplicated. Circuit operation:IC1 generates a square wave at about 4Hz frequency. C2 & D2 form a voltage doubler, necessary to raise the battery voltage to a peak value able to drive the LED. Notes:IC1 must be a CMos type: only these devices can safely operate at 1.5V supply or less.If you are not needing Photo resistor operation, omit R3 & R4 and connect pin 4 of IC1 to positive supply.Ordinary LEDs can be used, but light intensity will be poor.An ordinary 1N4148 type diode can be used instead of the 1N5819 Schottky-barrier type diode, but LED intensity will be reduced due to the higher voltage drop.Any Schottky-barrier type diode can be used in place of the 1N5819.