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Security system with anti-theft alarm

2016-02-19 15:17  
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This alarm circuit is suitable to drive an intruder or a thief. As the main component is a sensor which is a component of LDR (Different Light Resistance) is placed on the hidden but open lighting available. In principle, this circuit will sound an alarm when there is light shining through the LDR / was inhibited by a person or a movement by the sensor. The following is a schematic drawing:

Security system with anti theft alarm1 Security system with anti theft alarm

In the picture above the transistor works for emitter current through the terminal with negative polarity, the collector terminal a few volts more positive than the other emitter terminal and base terminal is more positive than 0.7 V the other emitter terminals. SCR function is similar to the transistor emitter current through the terminal with negative polarity, the collector terminal a few volts more positive than the other emitter terminal and base terminal is more positive than 0.7 V the other emitter terminals. LDR (Light Dependent Resistor) which consists of a semiconductor plate with two electrodes on the surface. Under the bright lights, lots of electrons out of atoms so that the semiconductor material a low electrical resistance value. And vice versa when in the dark or under dim light, the disk material containing only the number of free electrons in a relatively very small, so the value is very high resistance material, so the alarm can work.
Bel (speaker) functions as an alarm sound producer.

EQUIPMENT AND MATERIALS REQUIRED

List of components used
R1 = 2 K 2
R2 = 4 K 7
R3 = 1 K
R4 = 2 K 2
R5 = 1 K
C = 150?F / 12 VDC
TR = BC178
SCR: 3328 Type SS or 3D FIR
LDR: Type ORP 12
Buzzer: 6VDC
SWITCH: S = SPDT Switches
BATTERIES: 6VDC


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