This is a remote control circuit using ultrasonic signals. The Ultrasonic Remote Control Circuit is built around IC1 (NE 555). IC1 astable operating system is a multi-vibrator in the output of the amplifier IC1 is 40KHz.The complementary pair of transistors (Q1 and Q2) and transmitted by the ultrasonic transmitter K1. Switch S1 is used to activate the transmitter.
Note:
- switch S1 can be a push button switch.
- The preset R16 can be used to adjust the sensitivity of the receiver.
- The frequency of the ultrasonic signal can be varied by adjusting the preset R17.Adjust it for optimum performance.
The receiver uses an ultrasonic transducer sensor (K2) to detect the ultrasonic signals. When an ultrasonic signal is falling on the sensor, which produces a voltage signal proportional to its output. This weak signal is amplified by the two-stage amplifier circuit comprising transistors Q3 and output amplifier Q4.The is rectified by the diodes D3 and D4.The rectified signal is given to the inverting input of operational amplifier is connected as a comparator. When ever there is an ultrasonic signal that falls on the receiver, the output of the comparator activates the transistors Q5 and Q6 to drive the relay. Thus the load connected through the relay can be changed. The diode D5 is used as a freewheeling diode.
