ABS Plastic Automatic Emergency Light, for Indoor Outdoor, Industrial, Certification : CE Certified

Listing ID #964139

Automatic Emergency Light is an automatic emergency lamp with day light sensing. This Automatic Emergency Light senses darkness/night and turns ON automatically. Similarly, the Automatic Emergency Light senses day light and turns OFF automatically. Here, lamp is use a batch of light emitting diode (white LED), and its sufficient light for emergency purpose.
About The Circuit :
As shown in the circuit diagram, AC input is given through transformer. The transformer rating depends on the output DC voltage as shown in the table. The AC output voltage obtained from the transformer, is rectified through bridge rectifier designed using four diodes D1 to D4. Capacitors C1 is used to filter the AC signal. The rectified filtered output is given to diode D6& D7 for reverse current protection. When the light level is low the resistance of the LDR is high. This prevents current from flowing to the base of the transistors. Consequently the LED does not light. LDRs or Light Dependent Resistors are very useful especially in light/dark sensor circuits. Normally the resistance of an LDR is very high, sometimes as high as 1000 000 ohms, but when they are illuminated with light resistance drops dramatically.VR1 is used for sensitivity of LDR adjustment.VR2 can control the reference voltage adjustment. The 5mm LDR is just mounted on top of the emergency light. LDR is used to avoid it lighting up during day time or when the room lights are ON. However, when light shines onto the LDR its resistance falls and current flows into the base of the first transistor and then the second transistor. The LED D5 is indicates DC power ON from mains. The DC power to charge the 9V battery through D6 & D7. When mains supply is off, the current flows the circuit through 9V battery and lights illuminated. 2 LEDs are used in series; the dropping resistance (R9, 10, 11) and 2 LEDs light up with small current that is required for a single LED, by which energy is saved to a great extent.