Modified LED Nite Lite

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Modified LED Night Light David A. Johnson, P.E.
Night Light Front	Night Light Side	Night Light Back

Night Light Inside with 3 LEDs	Night light Inside with 10 Surface Mount LEDs	Old light on left, modified light on right

The circuit uses the classic series capacitor method to produce a current limiting LED driver, powered from the AC line. The series capacitor forms a constant current source and will route the same amount of current through the parts, even if 3 or 30 LEDs were used in series. This type of circuit made it much easier to insert 10 series wired LEDs instead of the three original devices. I also switched from a NPN darlington driver circuit to a single n-channel FET. This made it easier to select the right resistor value to turn off the light in the day. I set the required CdS cell resistance at about 100K, so anything less than that in resistance should keep the LEDs turned off. I did have to change the resistor R2 to a 39v zener diode do limit the peak voltage across the filter capacitor C1, when the LEDs are turned off during daylight.

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