Ultrasonic Radar For A Home PC System

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and even themselves on their PC screen. Just to impress a
neighbour or friend is reason enough to build your own ultrasonic radar
station.

Similar to that of a Polaroid, ultrasonic transducers are used in this
type of radar. A rangefinder emits a brief pulse of high frequency sound
that produces an echo when it hits an object. This echo returns to the
emitter where the time delay is measured and thus the result is displayed.
The Polaroid rangefinder is composed of two different parts. The transducer
(Fig. 1) acts as a microphone and a speaker. It emits an ultrasonic pulse
then waits for the echo to return. The ranging board is the second part
(Fig. 2). This board provides the high voltages required for the transducer,
sensitive amplifiers, and control logic. Since R1 is variable it controls
the sensitivity of the echo detector. A stepper motor rotates the
transducer to get a 360o field of view. For entire assembly see Figure 3.

An Experimenter is hooked up to ...

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per second, the distance based on the speed of
sound (1100 feet per second). With a program called DISTANCE.BAS the exact
speed of sound can be calculated according to the local weather conditions.

The stepper motor is used to rotate the radar so it can scan 360o
around the room. An ordinary DC motor would not do for such a project. The
rotation must coincide with the emissions and the receptions of the echoes.
In a DC motor the armature rotates and the brushes connect successive
commuter bars to windings to provide the torque. The speed of this motor
depends heavily on how much load there is and how much voltage is applied.

A stepper motor has different wires to each winding. ...

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