The automatic light circuit describe here is a simple 220V automatic circuit which is very easy to construct and very few components are used which are supper cheap. The main component of this circuit is the versatile 555 timer IC which is used in most electronics projects for timer control function.
This circuit works on the day light or the sun light first ray. It will wake you up when first ray of sun light falls on the sensor of the circuit. The circuit can control any light of your choice like simple and old incandescent light, cfl, florescent, mercury light or led ligh which is under 5A and 220V rating. The relay used in this circuit if of 5A rating. You can use heavy contacts relay also for driving more loads and heavy ampere usage.
The circuit construction is easy enough. This circuit can be constructed both on pref board or on specially made PCB. The PCB pattern and components layout will be given latter on this page. The circuit comprise of IC 555 timer, one bridge rectifier, a zener diode of value 12V 400mw, PC817A Optoisolator, a flywheeling diode, an LDR as light sensor and a few small resistors and capacitors. A relay is used as output load driver. The relay is a single pole and single through type. Anyhow you can use any type of relay according to your requirements. The circuit has a wide voltage range. The power supply depends upon the relay voltage and other components values. 12V power feed could ideal for this circuit as 12v DC relays are very commonly available and they are cheap as they are frequent used in most customer electronics.
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| 555 IC timer based automatic lighting circuit |
The circuit schematic above shows that the day and night sensor here is one LDR from LG company which is GL5528. LDR is the light dependent resistor. You can use any other equivalent LDR too if the same number is not available easily to you. The LDR here makes a potential devider circuit with combination to R2 resistor which is 100K. Through R3 resistor the variable voltage from the junction of this voltage devider is fed to the junction of of pins 2 and 6 of the timer IC 555. Timer IC 555 is controlling the relay PL1.
The circuit function in the way that when the input to the IC exceeds 8.1V then the output pin of the IC number 3 becomes low and current flows through the relay. And when the input to the IC from the voltage devider circuit is below 4.1V the IC output pin 3 becomes high and there is no current flow through relay. Hence relay becomes off.
Light bulb is connected to the relay in the way that the relay contacts are coming in series to one wire of the light bulb. So when the contacts closes, the light glow and when the contracts opens, the light bulb become dark. There in no other connection of the light bulb to any other part of the circuit. The light bulb is a 220V ac mains device and such voltage are not fed inside the circuit.
For powering up the circuit capacitor type doping power supply is used. This arrangement is especially made to make it supper cheap and to conserve the space on the circuit board. As the intention is to fix this circuit in light bulb holder. You can use any transformer type or switch mode type power supply of your choice. As these capacitor dropping type power supplies are simple but they are not such promising.
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