Ultrasonic Movement Detector

8/4/2019 Ultrasonic Movement Detector

1/17

G R - 1 7

D E B A J Y O T I A C H A R Y A

A S I T K U . S A H O O

A M A R E S H P A T T A N A I K

P R A C H I P A R I M I T A

P R A D H A N

&

R A S H M I R A N J A N P A N D A

8 / 1 6 / 2 0 1 1

The protector

Ultrasonic Motion

Detector


2/17

ULTRA N C V NT DETECTOR

GENERAL DESCRIPTION


3/17

You will find many uses for this movement detector. It

is

built around a matched pair of ceramic transducers,

which convert movement energy to electrical energy

and vice versa. The operating frequency of the pair is

40 KHZ. Any movement in the scanned by the pair of

transducers will detected and a 6V pulse produced. In

this kit the pulse turned on a LED. J1 pads are providedto take this pulse to add-on circuits where it may be

used to turn on BUZZER , RELAY etc. A PCB mounted

switch (S1) can be used to switch between an

automatic reset after the detector has been triggered

or to stay triggered. The unit will work reliably up to

five meters after proper calibration.

TECHNICAL SPECIFICATION


4/17

WORKING VOLTAGE - 9 TO 12V DC

OPERATING CURRENT - 100MA

TRANSDUCERS FREQUENCY - 40KHZ

SENSITIVITY - ADJYSTABLE

RANGE - 4 TO 6 METTERS

CONTACT RATING - 230 VAC/1000W

CIRCUIT EXPLANATION

Two NAND Schmidt trigger circuits are connected as a

multivibrator circuit , which delivers approximate

square wave pulses to the transmitter unit, the

frequency can range from about 11 kHz to 55 kHz and

is controlled by 50k preset.

The receiver uses a similar transducer to receive

the signals that are reflected back to it. The electrical

signals produced by it are then amplified by transistor

T3. The op-amp IC1 that also references the negative

picks of the signal to a predetermined pc level further

amplifies them. The output of IC1 converted to the DC

in a pick detector and then taken to the non inverting

input of IC2, the feedback circuit on this op-amp can be


5/17

adjusted by the sensitivity preset to control there is no

change in incoming signal level IC2 quickly adjusts to a

steady high output.

Sound waves reflected by different objects arrive

at the receiver in different phases, if they are in phase

they add to create a larger signal. If they are out of

phase they cancel to give a smaller signal. As an object

moves towards or away from the Rx unit by a smaller

distance (about 1 cm) it causes the receiver signal to a

cycle through a high/low cycle. It is this change from in-

phase to out-of phase, which triggers the unit. The

steady high output of IC2 is pulled down causing the

NAND get output to go high. The high turns on the

Darlington arrangement of transistors, which turns on

the LED. This 6V signal is available at pads 1 and 2

where it can be taken to manage other devices such as

relays, buzzers opto couplers etc.


6/17


7/17


8/17

PART (COMPONENTS) EXPLANATION

1.ULTRASONIC SENSOR


9/17

The ultrasonic sensor for the air which is made by the

Nippon Ceramic company. This sensor separates into

the two kinds for the transmitter and the receiver. For

the transmitter, it is T40-16 and for the receiver, it is

R40-16. T shows the thing for the transmitter and R

shows the thing for the receiver. 40 shows the

resonant frequency of the ultrasonic. (40kHz) 16 shows

the diameter of the sensor. The one of the terminal is

connected with the case, when grounding; the terminal

on the side of the case should be used. More

information please refers Data sheet of ULTRASONIC

SENSOR.

2.LM741The LM741 series are general-purpose operational

amplifiers which feature improved performance

over industry standards like the LM709. The

amplifiers offer many features, which make there

application nearly foolproof: overload protection

on the input and output, no latch-up when the

common mode range is exceeded, as well as

freedom from oscillations.


10/17


11/17

ASSEMBLY INSTRUCTION

The most important thing is to make sure the

ultrasonic transmitter (Tx) and receiver (Rx) units are

put into there correct position on the small circuit

board. If they are mixed up then damage to the

receiver unit will probably result, the transmitter is

marked with a T. The receiver is marked with an R.

To make soldering easier (and not heat the Tx/Rx units)

gently scrape the leads of each unit before soldering.

The second most important thing is to connect the

earth/case, Rx sensor pin (it is the pin which is

connected to the metal case) to earth pad of the To

RX pads on the main circuit board. The earth pad is

the top pad. The polarity of the Tx unit is not importantin this circuit; it can be connected either way around.

The circuit is very sensitive. Separate the two wires

going to the ultrasonic units to prevent electrical

crosstalk between them. If you want to locate the units


12/17

more than 1-2 feets from the main PCB then you

should use co-axial cable to shield the two transducers.

With these points to keep in mind assembly is straight

forward and components may be added to the pcb in

any order. Generally it is best to solder the lowest

height components first such as resistors , diodes and

IC sockets. Then move on to the physically taller

components. Note in particular the polarity of the

electrolytic capacitors, the ICs and diode, as

mentioned clean. The lead of the Tx & Rx units so

soldering is quick and easy. Do not overheat the

ultrasonic units during soldering.


13/17

ASSEMBLY LAYOUT OF MAIN BOARD

ASSEMBLY LAYOUT OF SENSOR BOARD (PCB)


14/17

ADJUSTMENT AND TESTING

The 50K preset must be adjusted so that the

multivibrator oscillates at 40 kHz, then the sensitivity

pot must be adjusted so that the system will reset

quickly and lock on, calibration can be done very easily

by trial and error. First put the switch to self reset

position and the sensitivity pot in the most sensitive

position. Place the preset at the 9 o-clock position. Awave of the hand in front of the Tx/Rx pair may turn on

the LED for about a second. Adjusts the position slights

towards the 10 o-clock position then try again. Move

further away about 2 to 3 yards/meters and try again.

There will be one particular position, which is most

sensitive at about 3 meters. Also simultaneouslyadjusts the sensitivity control as well either one way or

other. No more than 2-3 minutes should be needed to

calibrate the unit in this way.


15/17

If you have a CRO (cathode ray oscilloscope) then youcan very easily do the calibration by displaying the

signal from the Tx pins and directly adjusting the

driving frequency to 40 kHz.

After Calibration you should be able to reliabletriggering of the unit in the 2 to 3 meter range. Up to 5

meter is possible with good calibration.

Note that the unit will not only operate at kHz but it

will also operate but not as well at 20 kHz. Using a CROthis difference can be easily seen but using trial and

error the difference may not be so easy. The correct

position of the trim pot for 40 kHz is that is pointing in

about the 10 o-clock position. The wrong 20 kHz

setting is in the 12 to 1 o-clock position.

Each unit best transmits and receives in a 40-degree

cone spreading out from each unit. Naturally in the

area to be monitored this imaginary cones must


16/17

overlap you cannot have the Tx pointing one way and

the Rx unit pointing the other.

WHAT TO DO IF IT DOES NOTWORK

Poor soldering is the most likely reason that circuit

does not work. Check all solders joints carefully under

a good light. Next check that all components are in

their correct position on the PCB especially diodes,

electrolytic capacitors, and IC. If you put in the Tx/Rx

around the wrong way they have probably been

damaged.

Did you CALIBRATE the transmitter? Check the

transmitter is working. The easiest way to do this is to

use a CRO to check that a DC pulse wave is being fed

into the Tx unit or a portable frequency meter held in

front of the Tx unit.


17/17

NOTE

That this circuit is very sensitive. Even air moving (hot

air rising,wind blowing) will trigger it when the trimpot

is set near the most sensitive position. That is why we

say to set it for your particular need.

Documents

Ultrasonic Movement Detector