This is a complete design circuit for a complete ultrasonic transceiver used in a variety of pulse/echo-ranging applications. Here’s the figure of the circuit;
In this circuit, the LM1812 transmits a burst of oscillations with transducer X1. Then, using the same X1, listens for a return echo. If an echo of sufficient amplitude is received, the LM1812 detector produces a pulse (pin 16) of about the same width as the original burst. The closer the reflecting object, the earlier the return echo. Using the values and parts shown, the circuit has a range of about 4 inches to 30 feet. L6 resonates at 50 to 60 kHz, with the 500-pF capacitance of X1. L1 is tuned to this frequency by watching for maximum echo sensitivity with a scope at pin 1. [Circuit diagram source: National Semiconductor Application Notes and Seekic.com]
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