A crappy sensor night light S-3547 (SP-291SE)
(Reverse Engineered Schematics)
A schematic of a cheap sensor night light from a supermarket, type S-3547, model SP-291SE. It uses dropping resistors to power 8 cool white LEDs, in which 90% of the input power is wasted as heat. The cover is quite poorly translucent, which also does not add to the efficiency. At night, it consumes 0.83W. During the day, when turned off, 0.91W - more than when it is lit at night! The circuit with a phototransistor and a transistor turns off the LEDs by shorting them. The distance between the paths on the PCB is quite small for the mains voltage.
S-3547 sensor night light from above
S-3547 sensor night light from below
S-3547 sensor night light - label
S-3547 sensor night light - open
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