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Infrared beam barrier/ proximity
P N Click here for Circuit Diagram.
This circuit can be used as an Infrared
beam barrier as well as a proximity detector.
The circuit uses the very popular Sharp IR module (Vishay
module can also be used). The
pin nos. shown in the circuit are for the Sharp &
VIshay modules. For other modules please refer to their respective
The receiver consists of a 555 timer IC working as an
oscillator at about 38Khz (also works from 36kHz to
40kHz) which has to be adjusted using
the 10K preset. The duty cycle of the IR beam is about
10%. This allows us to pass more current through the
LEDS thus achieving a longer range.
The receiver uses a sharp IR module. When the IR beam
from the transmitter falls on the IR module, the output
is activated which activates the relay and de-activated
when the beam is obstructed. The relay contacts can
be used to turn ON/OFF alarms, lights etc. The
10K preset should be adjusted until the receiver detects
the IR beam.
can also be used as a proximity sensor, i.e to detect
objects in front of the device without obstructing a
IR beam. For this the LEDs should be pointed in the
same direction as the IR module and at the same level.
The suggested arrangement is shown in the circuit diagram.
The LEDs should be properly covered with a reflective
material like glass or aluminum foils on the sides to
avoid the spreading of the IR beam and to get
a sharp focus of the beam.
When there is nothing in front of them, the IR beam
is not reflected onto the module and hence the circuit
is not activated. When an object comes near the device,
the IR light from the LEDs is reflected by the object
onto the module and hence the circuit gets activated.
If there still a lot
of mis-triggering, use a 1uF or higher capacitor instead
of the 0.47uF.
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