Microwave Motion Detector
Published: Mon, 5 Dec 2016
CHAPTER NO: 1
MICROWAVE MOTION DETECTOR (MMD)
“The Microwave Motion Detector (MMD) is a true microwave Doppler transmitter and receiver, solves difficult detection problems easily with the microwave motion detector, senses any moving body – be it a person, animal, car, bicycle or extra-terrestrial.”
1.2 WHY MICROWAVE MOTION DETECTOR:
Understanding basic home security best practices could mean the difference between keeping your home safe and becoming the victim of a break-in. Start protecting your home better by exploring our Home Security Basics section which provides a good foundation of knowledge on everything from security cameras to outdoor lighting options that help prevent break-ins before they happen. I the light of above detail we have a requirement of autonomous microwave motion detector to prevent our assets from terrorism and any other type damage or robbery.
1.3 PROJECT GOAL:
The major goal of this project is to design an autonomous Motion Detection setup, that will be able to sense the motion of any moving object (person, car bicycle or extra-terrestrial) in the designated area or designated range.
In our project we have used different type of small size electronics (Diodes, Transistors, FETs, Resistor, Capacitors and Operational Amplifiers) to complete the setup and to make a smart and precise design of MMD.
1.4 PRINCIPLE OF MICROWAVE MOTION DETECTOR:
The system emits microwave energy that completely fills its area of detection, much like ultrasonic sensors. A Gunn diode emits energy in the x-range, similar in effect to Doppler frequency shifts. Any disturbance caused by movement within the field of detection may activate the alarm system/Buzzer. Despite fears held by many, these sensors do not adversely affect humans and pacemakers.
Ø True microwave Doppler shift operation
Ø Unaffected by heat, light, sound, humidity or temperature
Ø A real microwave transmitter/receiver – runs at 1 GHz
Ø Runs on 9 to 15 volts DC – ideal for car burglar alarms
Ø DC Voltage, (+9V to +15V).
Ø Oscilloscope DC 2 to 200MHz to monitor the transmitted signal of oscillator and observe waveform of different stages of Microwave Motion Detector.
Ø BNC plug to BNC plug cable 75 Ohms, 1 Meter
1.7 APPLICATIONS OF MMD:
The chief applications for MMD have been given bellow.
Ø Detection of unauthorized entry in our home, Offices and other restricted buildings.
Ø Detection of moving object which triggers a Camera to record subsequent events or to operate a Buzzer/Alarm, LED, Laser Diode etc.
Ø This relatively inexpensive and the MMD can easily be used in a variety of science projects, robots and other useful devices.
1.8 BREIF HISTORY OF MOTION DETECTION:
Motion can be detected by measuring change in speed or vector of an objector objects in field of view. This can be achieved either by mechanical devices that physically, interact with the field or by electronic devices that quantify and measures changes in the given environment.
1.9 PREVIOUS METHODS OF MOTION DETECTION:
Different methods of motion detection were used in past. These are given bellow. Some methods have been obsolete. Some methods are still in used.
1.9.1 MECHANICAL DEVICES:
A tripwire is a simple form of motion detector. When an object steps into the tripwire s sensory field (i.e, trips the wire), then a simple sound device might alert to the user.
1.9.2 ELECTRONIC DEVICES:
The principal methods by which motion can be electronically identified are optical detection an acoustical detection. Infrared light or laser technologies may be used for optical detection. Microwaves are one of the best tools for motion detection.
CHAPTER NO: 2
DOPPLER THEORY AND RADIATION PATTERN
2.1 DOPPLER THEORY:
The operation of the MMD is based on a physical theory known as the “Doppler Effect”. In its simplest form the Doppler theory states that as sound, light or even radio waves are reflected back by a moving object, the frequency of these waves will be different from the frequency when the object is stationary. As the object moves away the frequency will decrease and if the object moves toward you, the frequency will increase. This effect is demonstrated very visibly (or should we say audibly) by a train whistle passing you. This change in frequency is due to the waves being either stretched or compressed as they leave the moving object. Compressing the waves closer will have the effect of increasing the perceived frequency while stretching the waves will cause the frequency to appear lower. This is obviously not the place for an in depth discussion of Doppler theory Just be aware that it is the basis for the operation of the MMD. In fact, with an oscilloscope you can actually see this frequency change at U1 pin 10.
Another phenomenon associated with waves is called the Doppler Effect. Imagine standing near a train track, and a train approaches you with its whistle blowing. The pitch of sound waves is associated with the frequency of the wave: the higher the pitch, the higher the frequency.
Thus, as the train approaches the frequency of the sound wave you hear is higher, and as it recedes the frequency is lower. This can be pictured by the following diagram.
In this ‘: 2.1 the circles represent, as viewed from above, the crests of adjacent waves. Thus, if you are standing to the right, with the wave source moving towards you, more waves reach you per second, which means that the frequency you hear is higher.
Conversely, if you stand to the left, with the wave source moving away from you, fewer waves reach you per second and the frequency you hear is lower.
2.2 TYPICAL RADIATION PATTERN.
The microwave motion detector circuit radiates the microwave frequency from an omni directional antenna so the radiation pattern for the electromagnetic waves is given as under.
2.3 RADIATION SAFETY
Microwave radiation from the module is well below established safety standards for general public environment, like ANSI C95.1-1991 of USA and NRPB-G11 of United Kingdom.
The module is an electrostatic sensitive device (ESD). Precautions shall be observed for handling and assembly. Use the circuit module in an electromagnetic interference free environment to avoid errors in detection.
2.5 FUNCTIONAL IMPROVEMENT:
The module can be improved to calculate the speed of the moving object. This can also be used to find the direction of the moving object; some additional circuitry is required for these functions.
CHAPTER NO: 3
HARDWARE DESIGN OF MICROWAVE MOTION DETECTOR
In this section it has been tried to cover hardware related topics of MMD. That is given below separately.
3.1 MMD BLOCK DIAGRAM:
The block diagram of the MMD has been shown in the following
The detail of block diagram has been shown in the following section.
3.2 BLOCK DIAGRAM BRIEF DESCRIPTION:
The MMD consists of eight (08) major blocks.
Ø Power supply unit
Ø Buffer amplifier
Ø Band pass amplifier
Ø Output Drive Amplifier
Ø Signal indicator/ Interfacing circuitry
3.2.1 Power Supply Unit:
This unit provides required supply voltages for several circuit stages. Source required for the operation of this circuit is from +9v to +15v dc. It is responsible of biasing for all stages of the system. We can use dc battery or built in power supply for this system. This property of the system made it portable device for motion detection.
This section of the circuit produces the frequency approximately 1Ghz.Crystal oscillator is used to generate the required frequency. choice of this oscillator is due to its compact size , low cast and availability of the this component in the market.
The microwave RF energy that is developed by the oscillator is radiated in an omni-directional pattern from the antenna. Then the redirected waves are also received by the same antenna.
Received frequency is mixed with the transmitted frequency.
3.2.5 Buffer Amplifier:
Frequency generated by the mixer is amplified and buffered in this section of the circuit.
3.2.6 Band Pass Amplifier:
Frequency filtered by the mixer is amplified and buffered in this section of the circuit. The band of frequencies passed from the stage is between 10Hz to 40Hz.
3.2.7 Output Drive Amplifier:
This amplifier drives the output stage.
3.2.8 Signal Indicator/Interfacing circuits:
The detected motion is indicated in the form of an LED glow or it can be interfaced with an interfacing signal that could be some alarm system, camera etc.
3.3 MMD CIRCUIT DIAGRAM:
The circuit diagram has been generated in Protell / P-CAD.
3.4 PARTS LISTS:
3.4.1 CAPACITORS LIST:
0.01 uF Disk capacitor (marked .01 or 103 or 10nf)
C3, C8, C15, C18
0.1 uF disk capacitor (marked .1 or 104)
C11, C12, C20
2.0 pF. or 2.2 pf. disk capacitor
22 pF. disk capacitor
1.0 uF electrolytic capacitor
10.0 uF electrolytic capacitor
C1, C2, C9, C10, C13, C14
220 uF electrolytic capacitor
1000 uF electrolytic capacitor
3.4.2 RESISTORS LIST:
220 Ohm (red-red brown)
470 Ohm (yellow-violet-brown)
1K Ohm (brown-black-red)
R6, R7, R11, R20
4.7K Ohm (yellow-violet-red)
10K Ohm (brown-black-orange)
R4, R14, R16, R19, R21
47K Ohm (yellow-violet-orange)
100K Ohm (brown-black-yellow)
R5, R17, R18
470K Ohm (yellow-violet-yellow)
1 Mega Ohm (brown-black-green)
3.4.3 SEMICONDUCTORS LIST:
Diode 1SS99 (clear glass body with black and blue bands)
Diode 1N4148 (glass body with single black band)
2N3904 NPN transistor
2SC2498 or 2570 NPN UHF transistor
BS170 FET transistor
3.4.4 HARDWARE AND MISCELLANEOUS LIST:
MMD Printed Circuit Board
Connector 6 Pin
Connector 2 Pin
3.5 MMD PARTS LAYOUT & COMPOMENT STUFFING
3.6 CONSTRUCTION OF THE MMD CIRCUIT:
The following steps have been taken for the construction of the MMD main circuit in the light of the PCB layout given in the previous ‘: 3.3
3.6.1 Check off each step as understood and completed. Examine the parts layout diagram for parts location on the PC board. In all steps, “install” means to carefully insert the part into the correct hole, solder the leads to the PC board and trim away the excess lead wire.
3.6.2 Use good soldering techniques – let your soldering iron tip heat each connection wire enough so that the wire itself and PC board circuit trace BOTH become hot enough to melt the applied solder. The solder should flow smoothly around the lead wire and PC board trace.
3.6.3 Orient the circuit board as shown in parts layout diagram.
3.6.4 Install the LED, with the longer lead towards potentiometer R8. Leave the leads about 3/4” long if you are using the MMD case.
3.6.5 Install sensitivity control R8, 10K potentiometer. R8 acts as a “volume” control, adjusting the level of Doppler shift signal being applied to amplifier and switching portions of the MMD.
3.6.6 Install J1, 6 pin connector.
3.6.7 Install C1, 10uF electrolytic capacitor. Electrolytic capacitors are polarized and must be installed correctly. Usually PC layouts will show where the + lead should go while the capacitor itself will usually indicate the – lead. In any case, be sure you observe correct polarity.
3.6.8 Install Q2, 2N3904. Orient the flat side of the transistors as shown on parts layout diagram. Q2 has an interesting function, being connected as a zener diode! The reversed biased base-emitter junction on a silicon transistor behaves as a low power zener diode with a breakdown voltage in the 6 to 8 volt range.
3.6.9 Install Q1, 2N3904 Orient the flat side as shown. Q1 acts as a power supply filter and regulator for the op-amp IC chip, U1.
3.6.10 Install R1, 470 Ohm (yellow-violet-brown).
3.6.11 Install Q8, BS170 and orient the flat side as shown.Q8 is a power transistor.
3.6.12 MOSFET that controls the external load you connect to your MD3.
3.6.13 MOSFET is used since, as the load is turned on and off, a regular bipolar transistor will cause the MD3 to “see” itself. This is due to the diode switching action in a bipolar transistor’s base-emitter junction. 10. Install C20, .1uF capacitor (marked .1 or 104). 2.3 Power supply (General Purpose) Circuit Operation.
In the above ‘: 3.4 a preview of the main PCB have been shown. In this preview the portable battery has also been shown.
3.7 POWER SUPPLY CIRCUIT:
The supply is provided by using a transformer with output 20v+20V, 2A leading to a distributed power supply circuit (for general purpose supply) that provides outputs +15V,-15v, +12V, +9V connected to 50Hz, 220 VAC supply mains.
The power supply circuit consists of bridge rectifier that provides +20v and -20v with 2A ratings.
3.7.1 BLOCK DIAGRAM OF POWER SUPPLY CIRCUIT:
The block diagram of the power supply unit has been shown in the following ‘:
3.7.2 SCHEMATIC DIAGRAM OF POWER SUPPLY CIRCUIT:
In the following a circuit diagram of general purpose power supply has been shown in the ‘: 3.6. The circuit diagram has been designed in the Protel Software.
3.7.3 POWER SUPPLY ASSEMBLED PCB:
The preview of the assembled power supply unit has been shown in the ‘: 3.7.
3.8 ALTERNATE PORTABLE POWER SUPPLY:
An alternate supply can be used instead of a self made supply we can use a +9 Volt Battery to power up the circuit. In this circuit battery is used for simplicity.
In the remote area or the area where AC power source is not available we are required to used this portable battery for a short period of time because the life of this battery is to short for proper working of MMD for a long period.
CHAPTER NO: 4
ASSEMBLY INSTRUCTIONS AND USER MANUAL
4.1 ASSEMBLY INSTRUCTIONS FOR THE MMD:
After the stuFfing of PCB test the Microwave motion detector PCB on your workbench for the verification of the design and reliability of components used in the stuFfing of PCB. If the testing is assured to be perfect now it is the time to assemble the PCB of microwave motion detector in a casing.
There are three parts of the Assembly of the microwave motion detector.
Ø Composites Box
Ø Power Supply PCB
Ø Microwave Motion Detector PCB
Ø Power ON/OFF switch
Ø Motion indicator LED (Green LED)
This box is made of fiber (Composites material).
4.2.1 POWER SUPPLY PCB:
In the following ‘: 4.2 assembled Power supply unit has been shown.
4.2.2 MOTION DETECTOR PCB:
In the following ‘: 4.2 assembled Main MMD PCB has been shown.
Assemble the box in the following steps.
Ø Mount the power supply PCB on the bottom of the box
Ø Mount the Microwave Motion Detector PCB in the box
Ø Mount the power switch on the box
Ø Mount the indicator LED on the box at the last.
Ø Final assembly is shown inn the ‘.
In the following ‘: 4.3 assembled MMD system has been shown. The MMD has been shown in the working conditions in a room, means it is sensing the movement of a moving body and giving its response of motion sensing by glowing up the LED.
4.3 INSTRUCTION MANUAL:
A switch is placed in the path of DC power so that the power can be saved in the time when the device is not in use. Turn off the switch after using the device and turn it on before using this device. The green light will glow automatically for approximately 5 seconds soon after turning on the device. This indication is not for a moving object but this light glows as a function of turning on the device.
The Microwave motion detector is operated in the case where a moving object is needed to sense. In our design the circuit antenna is arranged in the position that it can sense a motion within the range of 2 meters approximately. When an object is moved within this range the motion is sensed by the design and a green light blinks on the panel of the box. This is an indication for the moving object. It can sense another motion approximately 10 seconds after the first motion is sensed. For better sensitivity this device may be used in the electromagnetic interference free environment so that the waves cannot interfere in the produced frequency of the device. Also it must be operated in the vibration free environment so that its antenna must be in static condition if it is in the vibration itself it will sense the motion when nothing is in moving condition, it is due the motion of its own antenna that the frequency is transmitted and received itself by the moving antenna and the green light on the panel keeps on glowing that is an operator fault and can be rectified by placing the device on a balanced plane surface.
A special care for the Microwave Motion detector is that operate the circuit in the box and never use the PCB alone because this PCB needs special care for the electrostatic charge. An external supply port may be given in the box so that a regulated DC power can also be applied externally to the device. For external power be careful about the polarity of the given DC power.
CHAPTER NO: 5
OPERATION OF MICROWAVE MOTION DETECTOR
5.1 WORKING PRINCPAL OF MICROWAVE MOVEMENT DETECTOR:
Microwave generating and receiving module generates and transmits a microwave signal which is reflected by a moving target and received back by the module. The module comprises a disc-form Shottky diode or Gunn diode acting as both oscillator and mixer and forming part of micro strip circuitry and signal processing circuitry which processes the reflected signal to extract relevant target information. The signal processing circuitry can be physically displaced from the module and connected to it by a coaxial line. By operating the diode in the diplex mode the requisite target information can be provided for with a compact construction.
A microwave movement detector comprising a microwave generating and receiving module for use in generating and transmitting a microwave signal to be intercepted and reflected by a moving target and for receiving the reflected microwave signal from said target, wherein the microwave generating and receiving module comprises micro strip circuitry in combination with a diode acting as both an oscillator and a mixer, said detector further comprising modulating means for modulating the generated microwave signal so that quantitive information as to target range, velocity and direction can be obtained, whereby the detector operates in accordance with a diplex configuration, wherein said detector includes a transmitter for transmitting the modulated generated microwave signal, and wherein the modulating means repetitively switches the transmitter of the microwave generating and receiving module between two frequencies to provide a signal having two spectral lines separated by gaps between the frequencies.
This invention relates to a microwave movement detector particularly although not exclusively for use as an intruder alarm.
An object of the present invention is to provide a microwave movement detector which is sensitive and reliable in operation yet which can be constructed in a simple and inexpensive manner with a conveniently small and compact format.
5.2 GENERAL STUDY RELATED TO THE MMD:
According to one aspect of the invention therefore a microwave movement detector comprises a microwave generating and receiving module for use in generating a transmitted microwave signal to be intercepted by a moving target and for receiving a reflected microwave signal from such target, in which the module comprises microstrip circuitry in combination with a Shottky diode arranged to act both as an oscillator and also as a mixer.
With this arrangement, great operational sensitivity and reliability can be achieved and yet the module can be constructed in a simple and inexpensive manner as a conveniently small and compact device. In one embodiment the module may be in the form of a thin disc having a thickness of, say 0.5 cm, and a diameter which may be as small as about 3 cm.
The said module may be connected to signal processing circuitry responsive to the relationship between the transmitted and reflected signals, for example so as to produce an output whenever target movement is detected, or only so as to produce an output when one or more parameters of such movement (range, velocity, direction) are of a predetermined nature or changes in a predetermined manner. Most conveniently, said signal processing circuitry may be provided in the form of a signal processing module separate from the aforesaid generating and receiving module, and, in accordance with one embodiment, the two modules may be up to 100 m away from each other and interconnected by a simple coaxial or twin cable. The signal processing module may be powered by mains supply, or a 12 V d.c. battery or otherwise as appropriate, and such module may also act to supply operating power to the generating and receiving module.
The output produced by the signal processing module may be utilized for alarm purposes to actuate a separate remote warning bell or siren or buzzer or the like. Alternatively, if desired, the movement detector of the invention may incorporate an alarm module connected to the said signal processing module and arranged to produce modulated warning tone when actuated by said output. Such alarm module may incorporate a stand-by rechargeable battery.
As mentioned above, the detector of the invention may operate in the manner of a simple Doppler detector sensitive only to movement, but preferably the transmitted microwave signal is modulated so that quantitative information as to range, velocity and direction can be obtained, the detector thereby operating in accordance with a diplex configuration. With such diplex configuration, advantageously the requisite information can be obtained with a particularly simple construction.
In accordance with one embodiment of the invention, the diplex, configuration is such that the transmitter is repetitively switched between two frequencies say 3 MHZ apart at X-band to give two discrete spectral lines separated by 3 MHZ . The magnitude of such frequency difference may be decreased with increase in the maximum range to be measured (beyond say 25 m). The reflected signal from a moving target results, after mixing in the Shottky diode, in a reflected signal which is a composite of two Doppler signals sampled sequentially at the modulation rate (say 10 kH Z ). The relative phase of these Doppler signals provides range and velocity sense information, whilst the Doppler beat frequency is proportional to the target velocity relative to the detector. The switching of the transmitter between the two frequencies may be achieved by square-wave modulation of the Shottky diode bias current. With such square-wave modulation particularly simple video circuitry may be used, however sinusoidal modulation may alternatively be used and this allows improved range resolution without reducing the maximum unambiguous range.
With regard to the Shottky diode, this may be a conventional “barrier injection transit time” device formed from a p + np + construction. Alternatively, a specially fabricated ion-implanted device or an `electron` type Shottky diode may be utilized.
While the utilization of a Shottky diode constitutes an essential feature of the first aspect of the present invention, it has been found that the utilization of a Gunn diode (i.e. a transfer electron diode) may be advantageous in the context of the present invention in the case where microstrip circuitry of diplex configuration (as described above) is also utilized. Thus, and in accordance with a second aspect of the present invention there is provided a microwave movement detector comprising a microwave generating and receiving module for use in generating a transmitted microwave signal to be intercepted by a moving target and for receiving a reflected microwave signal from such target, in which the said module comprises microstrip circuitry in combination with a Gunn diode arranged to act both as an oscillator and as a mixer, said circuitry being of diplex configuration.
Whilst it is anticipated that the present invention will find particular application in the context of an intruder alarm such as a burglar alarm, it is to be understood that the invention is not intended to be restricted to this field of application and the detector of the invention may be utilized for detecting movement of persons or vehicles or any other suitable targets in any suitable environment for any suitable purpose. When utilized as an intruder alarm the said generating and receiving module, due to its possible small size, can be easily and conveniently concealed. Also multiple such modules may be utilized together to enable a large area to be protected. By virtue of the range gate facility, false alarms can be minimized. In the case where the invention is applied to the monitoring of vehicles, a standard Doppler format may be used. Selective monitoring can be achieved by virtue of the direction sense of the detector, and the range gate facility is useful in distinguishing vehicles in a cluttered environment. In the case where the invention is applied to the counting of persons entering or leaving an enclosure, due to the direction sense of the detector it is possible to distinguish between persons entering and leaving.
Due to the use of the Shottky diode in diplex mode in microstrip circuitry, and having regard to the fact that the diode acts both as oscillator and mixer, a particularly simple, inexpensive and compact construction results.
It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiment which are described by way of example only.
5.3 THE MMD “HOW OUR DESIGN WORKS”:
3.2.1 All the RF “magic” is accomplished with Q3 and D1. Q3 is a free running microwave oscillator operating at a frequency of approximately 1.0 GHz. The frequency is determined by the length of the etched strip line and the lead lengths (inductance) of the associated oscillator components.
3.2.2 The microwave RF energy that is developed by the oscillator is radiated in an omni-directional pattern from the antenna. This radiated energy will fill the surrounding area with radio waves. These waves will be reflected back toward the antenna.
3.2.3 Here’s where the Doppler Effect comes in. If within that area there is an object that is moving, the waves that are reflected will either be higher in frequency if the object is moving closer or lower if moving away. The MD3 doesn’t really care which direction; it is only looking for a frequency difference.
3.2.4 The radiated signal and the redirected signal are mixed at diode D1. The difference in the two frequencies provides the input to U1: C pin 10. This frequency (the difference) is in the range of 10 Hz to 40 Hz. U1: C is the amplifier that feeds the sensitivity potentiometer R8.
3.2.5 Transistors Q1 and Q2 function as a very precise voltage regulator providing the proper bias to the amplifiers.
3.2.6 U1: D functions as a band pass filter and amplifier. Buffer amplifier U1: A provides the drive to output transistor Q4.
If we want to extend this project at higher level we are required to interface the MMD circuit output with the extended circuitry with the help of following circuit diagrams.
(THESE TECHENQUES HAS NOT BEEN USED IN OUR PROJECT)
6.1 INTERFACING CIRCUITS:
The MD-3 output transistor provides a pulse when motion is sensed. Here a probably asked question is, “How do I make it do something?” We can interface this circuit with many other circuits; a few examples are given below.
6.1.1 Interfacing with the relay can drive another circuit; it may be a light, a camera, an alarm system etc.
6.1.2 The microwave motion detector circuit can be interfaced with a transistor (PNP or NPN).This transistor act as a relay it can also drive some other circuits; it could be a light or any security system or an automatic door opening system.
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