Posted by Circuits Arena on Saturday, 15 November 2014
Ultrasonic Proximity Sensor Circuit Using Transducer is the artlcle explaining Ultrasonic Proximity Sensor Circuit This circuit designed to provide a very high gain for the reflected faint ultrasonic frequency sig...
Ultrasonic Proximity Sensor Circuit
This circuit designed to provide a very high gain for the
reflected faint ultrasonic frequency signals detected by the ultrasonic
transducer and Its working on frequency of 40khz.
This circuit can be used in
exhibitions to switch on prerecorded audio/video messages automatically
when a visitor evincing interest in a product comes near an exhibited
product.
- The above figure shows the transmitter circuit and comprises CMOS timer IC 7555 (IC1)
configured as an astable multivibrator, which may be tuned to the
frequency of the ultrasonic piezoceramic transmitter’s resonant
frequency of around 40 kHz using preset VR1.
- The pair of
transistors T1 and T2 is used for driving and buffering the transducer
while it draws spikes of current from IC1 circuit to sustain
oscillations and thereby avoids any damage.
- The receiver
front-end (below fig) is designed to provide a very high gain for the
reflected faint ultrasonic frequency signals detected by the ultrasonic
transducer.
- The amplifiers built around N1 and N2, respectively,
provide AC voltage gain of around 80 each.
- For higher efficiency, you may use single
op-amps such as CA3130 or CA3140.
- When
a visitor pauses before a sistor R10 is used to meet this requirement.
The filter also helps to bypass brief bursts of ambient noise in the
ultrasonic range.
- The third stage comprising N3 works as a comparator to
provide a triggering pulse when a visitor stops by. This pulse can be
used to trigger a timer or a monostable, whose output may then be used
to switch on the audio/video message concerning the product for a
predetermined period.
- When somebody comes in front of the
ultrasonic piezoceramic transducer pair, the status LED (LED1) glows
because of the signal reflected from the body of the visitor.
- The
circuit can be assembled on any general-purpose PCB. The transmitter
and the receiver should be aligned such that the transmitted ultrasonic
signal is optimally received by the receiver after reflection.
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