Infra-red Receiver


This very simple
infra-red receiver is intended to form an infra-red remote control
system with the simple infra-red transmitter described in this site. The
system does not use any kind of coding or decoding, but the carrier of
the transmitter is modified in a simple manner to provide a constant
switching signal. Since the receive module, IC1, switches from low to
high (in the quiescent state, the output is high) when the carrier is
received for more than 200 milliseconds, the carrier is transmitted in
the form of short pulse trains. This results in a pulse at the output of
the receiver that has a duty cycle which is just larger than 12.5%. The
carrier frequency used in the system is 36 kHz, so that the output
frequency of IC1 is 281.25 Hz.

Circuit diagram:

Infra Red Receiver Circuit

Infra-Red Receiver Circuit Diagram

This signal is rectified with a time constant that is long enough to
ensure good smoothing, so that darlington T1 is open for as long as the
received signal lasts. A drawback of this simple system is that it may
pick up signals transmitted by another infra-red (RC5) controller. In
this case, only the envelopes of the pulse trains would appear at the
output of T1. This effect may, of course, be used intentionally. For
instance, the receiver may be used to drive an SLB0587 dimmer. Practice
has shown that the setting of the SLB0587 is not affected by the RC5
pulses. The receiver draws a current of about 0.5 mA.

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