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There is lot of ic's that can produce ultrasonic Freq. plus. Is it possible to catch the bounce back and trigger relay? Answered

Is it possible to triggering  a relay by freq. shift or tone? Some of those ant-barking curcuits that use 555's is it possible that they could they be modified for proximity detector use? Could  transmitter  catch the signal or tone on the return  the echo bounce and trigger the relay. Also can some of those Max Bot's run directly to a relay and work? 


i need to detect a crack in a metal for my project, can you help me out with the ultrasonic transducer its cost minimum possible and availability in delhi INDIA

 I don't know what an ant-barking circuit is--let me know?

Anyway, yes, it is possible, but not very easy.  Look up "ultrasonic detection" on the Internet to get some ideas.  You need a microphone that is sensitive to the ultrasonic frequency.  There are ultrasonic "loudspeakers" and microphones that are sensitive at 40 KHz that cost $US 1-2.  You need an amplifier from the microphone to power the relay.  As for measuring the distance, that generally requires a microprocessor.  Check out 
http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf  and the instructable How_to_Make_an_Obstacles_Avoiding_Robot_Arduino_S/

I'm running a sonar system on my laptop - it monitors the environment and detects me moving around, if I stop, it puts the PC into standby in a few seconds. Seems pretty good, with no nuisance events.


Anti-barking, for noisy dogs. Your answer seems to address the question anyway.


 Thanks.  I thought it might be some sort of an insect repellent device.