Description.
Now a days we are using lots of remote controls based on
different working principles like radio frequency, infra red etc... Here I am
introducing a new type of remote control based on ultra sonic sound .
The transmitter part of the circuit is build around IC1(NE
555).The IC1 is wired as an astable multi vibrator operating at 40KHz.The output
of IC1 is amplifier the complementary pair of transistors ( Q1 & Q2) and
transmitted by the ultrasonic transmitter K1.The push button switch S1 is used
the activate the transmitter.
The receiver uses an ultrasonic sensor transducer (K2) to
sense the ultrasonic signals. When an ultrasonic signal is falling on the
sensor, it produces a proportional voltage signal at its output. This weak
signal is amplified by the two stage amplifier circuit comprising of
transistors Q3 and Q4.The output of the amplifier is rectified by the diodes D3
& D4.The rectified signal is given to the inverting input of the opamp
which is wired as a comparator. Whenever there is an ultrasonic signal falling
on the receiver, the output of the comparator activates the transistors Q5
& Q6 to drive the relay. In this way the load connected via the relay can
be switched.
Circuit Diagram
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