IR Remote Switch


Imagine the convenience
of selecting TV channels using your remote and then pointing the same
remote to your switchboard to switch on/off the fan or the tubelight.
Here is a simple circuit to remotely switch on/off any electrical device
through a relay using the normal TV/VCR/VCP/VCD remote control unit. It
works up to a distance of about 10 metres. The circuit is built around a
3-pin IR IC receiver (Siemens SFH-506-38 or
equivalent) that can detect 38kHz burst frequency generated by a TV
remote. (This IR receiver module has been covered earlier in many
projects published in this blog.) The output pin of IR sensor goes low
when it detects IR light, triggering the monostable (1-second) built
around timer NE555. The output of the mono toggles the J-K flip flop,
whose Q output drives the relay through SL100 npn transistor (T1).

IR Remote Switch

IR Remote Switch

LED2, LED3, and LED4 are used to display the status of each output stage during circuit operation. Back-EMF
diode D5 is used for protection. Transistor T1 is configured as an
open-collector output device to drive the relay rated at 12V DC. The
circuit draws the power from voltage regulator 7805. Capacitor C5 is
soldered close to the IR sensor’s pins to avoid noise and false
triggering. Capacitor C3 and resistor R3 also avoid false triggering of
monostable NE555. The monostable acts as a 1-second hysterisis unit to
restrict the flip-flop from getting retriggered within one second. To
activate any other 12V logic device, use the output across the relay
coil terminals.


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