IR based Door Protection Circuit

Some Pictures on this page might not be visible . If  so , please Download here.

        [Click here if Problem in Downloading]

Objective:

Ø This is an Infrared based Brocken beam alarm to protect doors and entry passages.

Ø  It gives a loud alarm when somebody crosses the Invisible Infrared barrier.

Ø  It can protect the doors both day and night.

List of components:

Ø IR LED

Ø R1  1KΩ

Ø VR1 is Variable 3kΩ

Ø Green LED

Ø Red LED

Ø IR Receiver

Ø R   1K Ω

Ø Transistor  C945

Ø Buzzer

Ø 9 v Battery

Theory:

Ø  This circuit is very important in defense system and house protection.

Ø  It warns that there will be a danger so we can prepare about this danger.

Ø  The circuit uses Infrared diodes to emit continuous IR rays which are not pulsed as in the case of remote handsets.

Ø  The IR Receiver is used as a light sensor.

Circuit diagram:

Working:

Ø The negative side of IR Receiver is connected to the positive rail through VR1 and the positive end is connected to the Green LED to indicate standby mode.

Ø This receiver conducts when IR light strikes on it and current flow in throw receiver.

Ø All voltages are drop across resistor.

Ø There is insufficient voltage in the base of transistor to conduct it.

Ø The green LED is ON that indicates the supply.

Ø If any object comes to center of transmitter and receiver the IR beam interrupt and the conduction in receiver is stopped.

Ø The current that was flowing through variable resistor will also stop.

Ø So there is no voltage drop across variable resistor.

Ø All the voltages are available at the base of transistor T2.

Ø The transistor will conduct and current will flow in transistor.

Ø The buzzer and red LED will be ON.

Result:

Without variable resistor it is very difficult to operate this circuit.

VR1 adjust the base bias of T2 to keep the buzzer off in the standby mode.

Precaution:

Ø  Do not operate at AC supply.

Ø  Do not short circuit

Ø  IR transmitter and IR receiver must be keep in align.

Ø  Fix IR LEDs on one side of the entry and the IR Receiver on the opposite side.

Future enhancement:

Ø  We can use this circuit in industry as a product counter by using puls counter in place of buzzer.

Ø  We can use SCR (Silicon controlled rectifier) to keep permanent ON the buzzer (if object will be removed) in place of C945 transistor.

Ø  We can use large buzzer that operates in AC supply by using relay.

Conclusion:

Ø  When a person crosses the IR beam, IR Receiver turns 0FF and green LED turn OFF.

Ø  Buzzer produces a sound and red LED turn ON.

/////////////////////////////////////////////////////////////////////// //////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////// //////////////////////////////////////////////////////////////////////