22-03-2015, 02:18 AM
i want the circuit diagram and module as well as information about the module of 8051 microcontroller based security light at midnight. please use at89c51 ..and also show the source code for it...
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microcontroller based security light at midnight
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i want the circuit diagram and module as well as information about the module of 8051 microcontroller based security light at midnight. please use at89c51 ..and also show the source code for it...
17-03-2017, 02:30 PM
Most robberies occur after midnight when people enter the second phase of sleep called "paradoxical" sleep. Here is an energy-saving circuit that causes thieves to abort the burglary attempt by turning on potential intrusion sites (such as the kitchen or backyard) around 1:00 am. It restarts automatically in the morning.
The circuit is fully automatic and uses a CMOS IC 4060 CD to obtain the desired time delay. The light dependent resistor LDR1 controls the reset pin 12 of IC1 for its automatic action.
During the day, the low resistance of LDR1 makes the pin 12 of IC1 'high', so it does not oscillate. After sunset, the high resistance of LDR1 causes pin 12 of IC1 to 'low' and begin to oscillate, which is indicated by the blinking of LED2 connected to pin 7 of IC1. The values of the oscillator components (resistors R1 and R2 and capacitor C4) are chosen such that the output pin 3 of IC1 goes 'high' after seven hours, ie about 1 am. This high output activates triac 1 (BT136) via LED1 and R3.
The bulb L1 connected between the phase line and the terminal M2 of the triac 1 is illuminated when the triac door 1 obtains the activation voltage of the pin 3 of IC1. It stays on until the pin 12 of IC1 is raised again in the morning.
The capacitors C1 and C3 act as reserves of energy, so IC1 keeps oscillating even if there is power interruption for a few seconds. Capacitor C2 maintains trigger IC1 during daytime, so slight changes in light intensity do not affect the circuit. Using the VR1 preset you can adjust the sensitivity of LDR1.
The circuit power supply is derived from a transformer X1 (primary 230V AC at 0-9V, 300mA secondary), rectified by a full-wave rectifier comprising diodes D1 to D4 and filtered by capacitor C1.
Mount the circuit in a general purpose PCB with adequate spacing between the components. Cover exposed components wires. Using the S1 switch, you can manually turn on the lamp. Place the unit in a plastic box and mount in a place that allows adequate daylight.
Caution. Since the circuit uses 230V AC, many of its points are at mains voltage. It could give you lethal shock if you're not careful. So if you do not know much about working with line voltages, do not try to build this circuit. EFY shall not be liable for any resulting loss or damage.
![[Image: 4A8_feb_efy.png]](http://electronicsforu.com/wp-contents/uploads/2016/05/4A8_feb_efy.png)
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