Abstract:
The circuit may be used to automatically switch on a light at the entrance gate to the premises at night by sensing the presence of a person. In addition, it sounds an alarm to signify the presence of a person. Here we are using an IR Led as the transmitting unit and the TSOP as receiving unit. A monostable, multivibrator circuit is used for the purpose of getting time delay accordingly. Lamp is switched on only for a short interval to save electricity.
PRINCIPLE
In addition, it sounds an alarm to signify the presence of a person. Here we are using an IR Led as the transmitting unit and the TSOP as receiving unit. A monostable, multivibrator circuit is used for the purpose of getting time delay accordingly. Monostable multivibrator often called a one shot multivibrator is a pulse generating circuit in which the duration of this pulse is determined by the RC network connected externally to the 555 timer. In a stable or standby state, the output of the circuit is approximately zero or a logic-low level. When external trigger pulse is applied output is forced to go high (» VCC). The monostable circuit has only one stable state (output low) hence the name monostable. Astable Multivibrator is a two stage switching circuit in which the output of the first stage is fed to the input of the second stage and vice versa. The outputs of both the stages are complementary.
This free running multivibrator generates square wave without any external triggering pulse. The circuit has two stable states and switches back and forth from one state to another, remaining in each state for a time depending upon the discharging of the capacitive circuit. Lamp is switched on only for a short interval to save electricity. An LDR based circuit is used to switch on the bulb at night only. The buzzer is connected such that it functions whenever the IR beam is interrupted.
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