Automatic LED lamp
I assume that you are already familiar with automatic emergency lights or street lights that will automatically turn on when the sun sets and will turn off automatically when the sun rises,those circuits all work with a special kind of resistor called LDR(Light dependant resistor)
the LDR’s resistance will be changed according to the amount of light falls on it, for example: its resistance is high around 1M (1 mega ohm=1000K) in darkness and about 5K in daylight! So using this tiny ‘thing’ we can design and build a plenty of useful circuits (eg:laser alarm,infrared alarm,morning alarm and many!).
here is a simple circuit using IC NE555, the circuit will turn on a pair of white LEDs whenever the darkness falls on the atmosphere, the R1 is a variable resistor to adjust sensitivity of the circuit. For the ease of use this circuit can be operated using four 1.5V batteries = 6V so it will become a portable emergency light!
Components you need
R1 – 100K variable resistor
R2 – 100E
LED – White LEDs(maximum 7)
IC1 – NE555
LD1 – Common LDR
Note: a 10V/100uf capacitor with correct polarity may be added between ‘+’ and ‘-‘ to reduce ripple and a 100n(104) capacitor on the pin5 Of 555 for a stable operation(only if needed),
Designed and tested by: Loneziddik
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