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Proximity detector circuit

A very simple ultrasonic proximity detector circuit can be constructed using few external electronic components . As you can see in the circuit diagram shown here, this proximity detector circuit require some external components and is very easy to build. The R4 ( 100k ohms potentiometer ) sets the current fed to the buzzer ( sounder) . The potentiometer must be adjusted to a sounder point where the buzzer begins to sound .
The Q1 transistor is coupled to the positive side of the sounder , and its output is fed to a voltage doubler circuit .The base of Q2 transistor is driven by the output of voltage doubler circuit , which activate the relay . As long as the buzzer sounder produce an audible sound , the relay stays energized .

If an solid object is moved in close proximity to the front of the buzzer , the relays drops out .
This simple ultrasonic proximity circuit described here needs to be powered from an 12 volts DC power supply , so you will need to use an 12 volts electronic relay .

ultrasonic proximity detector circuit diagram


am intrested in circuit designing, i would like to design this circuit using basic components only that the lebel is not clear

C1,C2=0.1uF; C3=0.22uF; R1,R2=2.2k; R3=220k;R4=100k;Q1=2n3994,Q2=2n2222;D1,D2=1n914,D3= 1N4002.

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