Automatic LED Lamp Diy Circuit with LDR and 555 IC
Assuming that you are already familiar with automatic lights or street lights that will automatically turn on when the sun sets and will turn off automatically when the sun rises.
Those circuits work with a special kind of resistor called LDR(Light dependant resistor)
What is an LDR?
It is a special Resistor, LDR’s resistance will be changed as 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 guy, we can design and build some useful circuits (eg:laser alarm,infrared alarm,morning alarm and many!).
Here is the circuit using IC NE555, the circuit will turn on a pair of white LEDs whenever the darkness falls on the LDR (at night,dark room etc), the R1 is a variable resistor to adjust sensitivity of the circuit.
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)