Need Help with Ultrasonic receiving circuit

Discussion in 'General Electronics Chat' started by vivek1925, May 14, 2010.

  1. vivek1925

    Thread Starter New Member

    May 12, 2010
    11
    0
    Hey, I have my project on Ultrasonic transducer and receiver circuit. I have already built my transmitter circuit using the 555 timer to give out 40khz.

    But with the receiver, I have a two stage active amplifier LM386 which actually amplifies the signal and i also have a comparator and a delay circuit attached to my amplifiers in order to tune the signal.

    This is the point where i cannot understand:confused: in order to receive the signal is it necessary to have the delay and the comparator circuit connected or just continue with th Flip flop toggle switch.

    If anyone can help me out with any ideas please help me as I am stuck at this position.
     
  2. kingdano

    Member

    Apr 14, 2010
    377
    19
    guarantee people will want to see schematics and code of what you have so far...

    just figured id save someone else the post.
     
  3. vivek1925

    Thread Starter New Member

    May 12, 2010
    11
    0
    Hey Kingdano , this attaachment shows three parts . the second part with q3 amplifier is where i find a problem.. whether to have the circuit or not . The third part is the toggle .

    I want to clarify if I can skip the Q3 and the delay and carry in with the toggle instead.

    thnks anyways
     
  4. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Look at the datasheet for the LM386 power amplifier.
    It shows an important resistor in series with an important capacitor from its output to ground. This prevents it from oscillating at a high frequency.
    A supply bypass capacitor must be used at each one. This prevents motorboating and oscillation.
    For a gain of 200, a capacitor is supposed to connect between pin1 and pin8 instead of your piece of wire.
    The LM386 is a noisy power amplifier. You should have used a low noise opamp instead.
     
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  5. vivek1925

    Thread Starter New Member

    May 12, 2010
    11
    0
    yeah checked with a 0.1uf capacitor in order to have a gain of 200:). this amplifier started to saturate therefore in order to eliminate the noise i have an another stage of amplifier to actually concentrate on the transmitted signal.

    But i am not sure how the waveform if that pin 5 of stage 3 amplifier should look like as I am not sure whether i am getting my tunning correct with the potentiometer or should i need a input signal of 40khz from the transmitter in order to check Q3 amplifier.
     
  6. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Any amplifier clips when its output swing gets too close to the power supply rails. Simply turn down the volume control to eliminate clipping.
     
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