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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 datasheets.
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.
The circuit
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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