Ultrasound Detector with 567PLL and LM386 ICs

Posted on Aug 6, 2012

The bat ultrasounds are picked up by the microphone SPKR1 and go through two stages of amplification at Q1 and Q2. Separately, a tunable (R12) single frequency is produced by the LM567 oscillator U1. The LM567 is a tone decoder but here its input is grounded and its voltage controlled oscillator is used as a precision oscillator.

Ultrasound Detector with 567PLL and LM386 ICs
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The oscillator frequency is given by f = 1/(1.1*C4*(R10 + R12)) = 1/(1.1*0.0022*10-6*(4.7 + [0-50])*103) = [88-7.5] khz The two signals are mixed at Q3 to produce both a signal in the audio range and higher frequencies that are the

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