Light-controlled LED lighting

This is an LED lighting lamp with light control function . It does not work during the day and automatically lights up at night. The lamp uses 42 high-brightness white light-emitting diodes, 3 of which are connected in series, and then connected in parallel to the power supply . It is suitable for lighting stairs, corridors, etc.

Circuit working principle

The circuit is shown in the figure. The 220V AC is limited by capacitors, bridge rectifiers, filters, and voltage regulators to obtain a stable 12V DC at both ends A and B. During the day, the photoresistor RG is exposed to natural light and presents a low resistance. The base potential of the transistor VT is low and is reverse biased. Therefore, VT is cut off, the gate of the unidirectional thyristor VS is turned off at a low level, and the LED does not light up. After dark, the photoresistor RG presents a high resistance due to the lack of light, VT is turned on, and the gate of VS is turned on by a forward trigger voltage, and the LED is powered on and emits light. Switch K is a manual control switch. As long as K is closed, the LED can emit light regardless of day or night.

Component selection and production debugging

C1 uses a polyester capacitor with a withstand voltage of more than 400V, which can be replaced by an electric fan capacitor. R1~R4 use 1/2W metal film resistors, and RP uses a small variable resistor. Rectifier diodes D1~D4 use 1N4007, and electrolytic capacitor C2 uses a 25V withstand voltage aluminum electrolytic capacitor. RG uses an MC45 photoresistor (bright resistance is not more than 5kΩ, dark resistance is not less than 1MΩ). DW uses a 1W/12V voltage regulator diode, and VS uses a 1A unidirectional thyristor. The model is optional. Since the human eye will be dazzled by the light-emitting diode, the LED light source should be modified to make its light diffusely reflected. The assembled LED lamp is installed in the abandoned round ceiling lamp cover, and RG is placed in a place where natural light is exposed and where moonlight cannot shine. Connect 220V AC power and slowly adjust RP so that the LED is not bright during the day and bright at night.

Editor's Note

In the future, this year's "Development and Innovation" edition will serve product development, technological innovation, patent application, etc. for product developers of small and medium-sized enterprises and amateur inventors; provide technical support for the entire process including product project establishment, software and hardware design, key component selection, assembly and debugging, and market launch; at the same time, this edition will strengthen the interaction between readers, editors and authors, exchange experiences, and work together to overcome technical difficulties; we sincerely hope that readers and authors of this edition will provide this edition with "blood" and "flesh" manuscripts.