Completely Analog Ultrasonic Range Finder

Discussion in 'The Projects Forum' started by simply_me, May 6, 2010.

  1. simply_me

    Thread Starter Member

    May 6, 2010

    I'm trying to design an ultrasonic range finder using only analog components and that its range will exceed 2m. So far I've designed the Wien Bridge (40Khz), bandpass amplifier, and a sinusoidal to rectangular wave form converter. So what I have in mind is-- The oscillator generates a sinusoidal wave sends it to the bandpass amplifier and from there one input goes to the transmitter and the other goes to the sine to rectangle converter. Now, I'll use a time delay circuit to pulse the rectangular wave (with a delay of about 12ms-- distance/speed of sound--4m/(343m/s), from there i thought to use a comparator to turn the receiver on to wait for a reading. Does anyone know how I can turn the receiver on for just 12ms? On the other side I'll have the sinusoidal wave pulsed all the time. At the receiver end, once it's turned on I want to put a threshold op-amp (not sure on how to implement it, but I'll do some research) and from there to amplifier. Once I have the output voltage readings, I'll use something similar to a voltmeter to read the distance (i.e. just a needle w/distance marks after doing manual measurements). Does that sound a reasonable design? Does anyone can point me to how to go about turning the receiver on/off every ~12ms?
    Someone suggested to me to use frequency sweep and frequency to voltage converter instead of the above approach, but the only problem is that I don't know how to do a frequency sweep in analog or find any example circuit.
    I'll be happy to hear any input/different approach you might have.

    Thank you,

  2. beenthere

    Retired Moderator

    Apr 20, 2004