03-01-2013, 12:54 PM
UltraSonic Radar
[attachment=46319]
General Description
This is a very interesting project with many practical
applications in security and alarm systems for homes,
shops and cars. It consists of a set of ultrasonic receiver
and transmitter which operate at the same frequency.
When something moves in the area covered by the circuit
the circuit’s fine balance is disturbed and the alarm is
triggered. The circuit is very sensitive and can be
adjusted to reset itself automatically or to stay triggered
till it is reset manually after an alarm.
How it Works
As it has already been stated the circuit consists of an ultrasonic transmitter and a receiver both of which work at
the same frequency. They use ultrasonic piezoelectric transducers as output and input devices respectively and
their frequency of operation is determined by the particular devices in use.
The transmitter is built around two NAND gates of the four found in IC3 which are used here wired as inverters and
in the particular circuit they form a multivibrator the output of which drives the transducer. The trimmer P2 adjusts
the output frequency of the transmitter and for greater efficiency it should be made the same as the frequency of
resonance of the transducers in use. The receiver similarly uses a transducer to receive the signals that are
reflected back to it the output of which is amplified by the transistor TR3, and IC1 which is a 741 op-amp. The
output of IC1 is taken to the non inverting input of IC2 the amplification factor of which is adjusted by means of P1.
The circuit is adjusted in such a way as to stay in balance as long as the input frequency is the same as the output
frequency of the transmitter. If there is some movement in the area covered by the ultrasonic emission the signal
that is reflected back to the receiver becomes distorted and the circuit is thrown out of balance. The output of IC2
changes abruptly and the Schmitt trigger circuit which is built around the remaining two gates in IC3 is triggered.
This drives the output transistors TR1,2 which in turn give a signal to the alarm system or if there is a relay
connected to the circuit, in series with the collector of TR1, it becomes activated. The circuit works from 9-12 VDC
and can be used with batteries or a power supply.
Construction
First of all let us consider a few basics in building electronic circuits on a printed circuit board. The board is made of
a thin insulating material clad with a thin layer of conductive copper that is shaped in such a way as to form the
necessary conductors between the various components of the circuit. The use of a properly designed printed circuit
board is very desirable as it speeds construction up considerably and reduces the possibility of making errors.
Smart Kit boards also come pre-drilled and with the outline of the components and their identification printed on the
component side to make construction easier. To protect the board during storage from oxidation and assure it gets
to you in perfect condition the copper is tinned during manufacturing and covered with a special varnish that
protects it from getting oxidised and also makes soldering easier. Soldering the components to the board is the
only way to build your circuit and from the way you do it depends greatly your success or failure. This work is not
very difficult and if you stick to a few rules you should have no problems. The soldering iron that you use must be
light and its power should not exceed the 25 Watts. The tip should be fine and must be kept clean at all times. For
this purpose come very handy specially made sponges that are kept wet and from time to time you can wipe the
hot tip on them to remove all the residues that tend to accumulate on it. DO NOT file or sandpaper a dirty or worn
out tip. If the tip cannot be cleaned, replace it. There are many different types of solder in the market and you
should choose a good quality one that contains the necessary flux in its core, to assure a perfect joint every time.
DO NOT use soldering flux apart from that which is already included in your solder. Too much flux can cause many
problems and is one of the main causes of circuit malfunction.
[attachment=46319]
General Description
This is a very interesting project with many practical
applications in security and alarm systems for homes,
shops and cars. It consists of a set of ultrasonic receiver
and transmitter which operate at the same frequency.
When something moves in the area covered by the circuit
the circuit’s fine balance is disturbed and the alarm is
triggered. The circuit is very sensitive and can be
adjusted to reset itself automatically or to stay triggered
till it is reset manually after an alarm.
How it Works
As it has already been stated the circuit consists of an ultrasonic transmitter and a receiver both of which work at
the same frequency. They use ultrasonic piezoelectric transducers as output and input devices respectively and
their frequency of operation is determined by the particular devices in use.
The transmitter is built around two NAND gates of the four found in IC3 which are used here wired as inverters and
in the particular circuit they form a multivibrator the output of which drives the transducer. The trimmer P2 adjusts
the output frequency of the transmitter and for greater efficiency it should be made the same as the frequency of
resonance of the transducers in use. The receiver similarly uses a transducer to receive the signals that are
reflected back to it the output of which is amplified by the transistor TR3, and IC1 which is a 741 op-amp. The
output of IC1 is taken to the non inverting input of IC2 the amplification factor of which is adjusted by means of P1.
The circuit is adjusted in such a way as to stay in balance as long as the input frequency is the same as the output
frequency of the transmitter. If there is some movement in the area covered by the ultrasonic emission the signal
that is reflected back to the receiver becomes distorted and the circuit is thrown out of balance. The output of IC2
changes abruptly and the Schmitt trigger circuit which is built around the remaining two gates in IC3 is triggered.
This drives the output transistors TR1,2 which in turn give a signal to the alarm system or if there is a relay
connected to the circuit, in series with the collector of TR1, it becomes activated. The circuit works from 9-12 VDC
and can be used with batteries or a power supply.
Construction
First of all let us consider a few basics in building electronic circuits on a printed circuit board. The board is made of
a thin insulating material clad with a thin layer of conductive copper that is shaped in such a way as to form the
necessary conductors between the various components of the circuit. The use of a properly designed printed circuit
board is very desirable as it speeds construction up considerably and reduces the possibility of making errors.
Smart Kit boards also come pre-drilled and with the outline of the components and their identification printed on the
component side to make construction easier. To protect the board during storage from oxidation and assure it gets
to you in perfect condition the copper is tinned during manufacturing and covered with a special varnish that
protects it from getting oxidised and also makes soldering easier. Soldering the components to the board is the
only way to build your circuit and from the way you do it depends greatly your success or failure. This work is not
very difficult and if you stick to a few rules you should have no problems. The soldering iron that you use must be
light and its power should not exceed the 25 Watts. The tip should be fine and must be kept clean at all times. For
this purpose come very handy specially made sponges that are kept wet and from time to time you can wipe the
hot tip on them to remove all the residues that tend to accumulate on it. DO NOT file or sandpaper a dirty or worn
out tip. If the tip cannot be cleaned, replace it. There are many different types of solder in the market and you
should choose a good quality one that contains the necessary flux in its core, to assure a perfect joint every time.
DO NOT use soldering flux apart from that which is already included in your solder. Too much flux can cause many
problems and is one of the main causes of circuit malfunction.