This is a light control function with LED lights, it does not work during the day, lights automatically at night. The sharing of 42 bright white light emitting diodes, each of three series, in parallel with each other and then connected to the power of two Swiss, for staircases, such as aisle lighting.
Circuit principle circuit as shown.

220V AC current limit by the capacitor, bridge rectifier, filter, regulator, in the A, B at both ends to obtain a stable 12V DC. Photoresistor RG in the day by the natural light exposure showed low resistance, the base potential of transistor VT is low, and is anti-bias, VT As a result, very low one-way door VS SCR is turned off, LED does not light. To the RG after dark because no light sensitive resistor showing high resistance, VT conduction, VS has a positive gate trigger voltage that turns on, LED power light. K switch to manual control switch, as long as K is closed, regardless of day and night, LED can emit light.
Component selection and production debugging
C1 selection pressure of more than 400V polyester capacitor, fan capacitor can be used instead. R1 ~ R4 selected 1/2W metal film resistors, RP use small variable resistor. Rectifier diode D1 ~ D4 use 1N4007, 25V electrolytic capacitor aluminum electrolytic capacitor C2 voltage selection. RG selected MC45 photosensitive resistor (light resistance is not greater than 5kΩ, dark resistance of not less than lMΩ). Zener diode used 1W/12V DW, VS using one-way SCR 1A, model optional. Since the human eye to be light-emitting diodes produce light glare, so to be transformed on the LED light source, to produce diffuse light, LED lights will soon assembled round ceiling mount hood abandoned, RG placed in a natural light to the place, is also a place where you can not moonlight. Connected to the 220V alternating current, and slowly adjust the RP, so in the daytime LED does not light, LED night light can be.