Super Simple SONAR

Thomas Scarborough’s electronics design have been popular. Here, therefore, is a “super simple” SONAR (designed by him).

SONAR stands for SOund NAvigation Ranging. It is a technique which is used to determine the distance and direction of objects by acoustic means — usually in water, but also in air. The SONAR described here has the most basic functionality — it simply reports the existence of an object up to a few metres’/yards’ distance. It would, for example, shriek when a reversing vehicle approached a wall (X1 and X2 would be mounted just far enough apart NOT to shriek until the vehicle was near the wall). Or X1 and X2 would be mounted on opposite sides of a closed door — thus the circuit would shriek when the door was open. Or X1 and/or X2 could be placed underneath an item, to shriek when the item was lifted.

OBSERVATION: The circuit relies on acoustic feedback. IC1 is a sensitive amplifier. Both X1 and X2 are piezo sounders (discs, mounted in plastic housings) without internal electronics. X1 functions as a “microphone”, X2 as a “speaker”. Ideally, X1 and X2 will be identical, to encourage feedback at their resonant frequencies. Piezo tweeters may also be used, although these are expensive. C2 determines gain (amplification). First try the circuit without C2. If C2 is, say, 10μ, the circuit’s sensitivity will be greatly increased. C3 is necessary to limit output current. The circuit would ideally be run off a 12V DC plugpack power supply. You may click on the circuit to enlarge it. Click on the “Electronics” category top left to follow the electronics trail on this blog.

NOTE: You may re-publish this design, on condition that you acknowledge the designer (Thomas Scarborough) and this blog (

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