Tire Pressure Monitoring System Through GSM Authors SALAMAT SHAH Cu-168-2011 HAKEEM ULLAH Cu-187-2011 AMMAR ALI SHAH Cu-643-2011 FAIZ ALI KHAN Cu-149- 2011 IMRAN KHAN Cu- 609-2011 Supervisor: 1
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Tire Pressure Monitoring System Through GSM
Authors
SALAMAT SHAH Cu-168-2011HAKEEM ULLAH Cu-187-2011AMMAR ALI SHAH Cu-643-2011FAIZ ALI KHAN Cu-149-2011IMRAN KHAN Cu-609-2011
Supervisor:
Engr.Ibrar UllahAsstt. Prof.
DEPARTMENT OF ELECTRICAL ENGINEERINGCECOS University of IT and Emerging Sciences Hayatabad Peshawar
June, 2015
1
Tire Pressure Monitoring System Through GSM
Author
Salamat Shah Cu-168-2011Hakeem Ullah Cu-187-2011Ammar Ali Shah Cu-643-2011Faiz Ali Khan Cu-149-2011Imran Khan Cu-609-2011
A thesis submitted in partial fulfillment of the requirements for the degree of
B.Sc. Electrical Engineering
Thesis Supervisor
Engr.Ibrar UllahAsstt. Prof.
Electrical Engineering Department
Signature:-------------------
DEPARTMENT OF ELECTRICAL ENGINEERINGCECOS University of IT and Emerging Sciences Hayatabad Peshawar
June 2015
2
ABSTRACT
Correct tire pressure is a critical factor in the safe operation and efficiency of a motor vehicle. Over inflated tires often result in accidents, reduce fuel mileage and less than optimal vehicle performance as well as vehicle safety. A tire pressure monitoring system (TPMS) monitors air pressure in the tires of a motor vehicle, by generating a signal indicative of the tire pressure in each of the tire, to increase the vehicle efficiency and safety. Present work is based on the design of the tire pressure monitoring system which includes pressure sensors, an RF-communication unit, signal processing unit and display unit. To sense the changes in inflation pressure, a diaphragm based pressure sensor is designed to be used in pressure measurement of the tube. The inflation pressure is transmitted to the receiver side using ISM (Industrial, Scientific and Medical) band at 433.92MHz. The pressure sensor was tested at room temperature as well as at elevated temperature of 33°C - 70°C. Finally, the collected data is analyzed and displayed.
Keywords: TPMS, Automotive safety, Pressure Sensor, Microcontroller, RF communication, ISM band, ASK.
3
UNDERTAKING
We certify that research work titled “Tire Pressure Monitoring System through GSM” is our own
work. The work has not been presented elsewhere for assessment. Where material has been used
from other sources it has been properly acknowledged / referred.
Salamat Shah Cu-168-2011 __________________
Hakeem Ullah Cu-187-2011 ________-_________
Ammar Ali Shah Cu-643-2011 _________________
Faiz Ali Khan Cu-149-2011 __________________
Imran Khan Cu-609-2011 __________________
4
ACKNOWLEDGEMENT
We would like to thank Engr. Ibrar Ullah, Engr. Naveed Jan, Mr. Zahid sarwar, and
Col(R).Ashfaq Ahmad (Chairman EED) for their guidance and support throughout
our Bachelor program. We would like to specially thank again Engr. Ibrar Ullah for
giving us the freedom of thought and expression while performing our project and
thesis. We owe our sincere and heartfelt regards to our Mom, Dad, Brothers and
sisters, who always supported and guided us. Without them, we would not have come so
far. We also take this opportunity to thank our other family members and cousins
who helped us in completing this project and friends for their invaluable support and
cooperation. In last we would like to thank Mr. Muhammad Khan, Mr. Mubasir shah,
Mr. Saif Ur rehman, Dr. Riaz Ali shah, Dr. Asghar Ali shah and Mr. Kamran khan for
their help in completing this project.
5
TABLE OF CONTENTS
Abstract ...........................................................................................………...3
Undertaking......................................................................................................4
Acknowledgement............................................................................................5
List of Figures..................................................................................................8
List of Tables....................................................................................................9
Symbols..........................................................................................................10
Chapter I: Introduction...............................................................................11
1.1 TPMS concept..........................................................................................12
1.21 Types of TPMS.......................................................................................12
1.3 Statement of the Problem.........................................................................14
1.4 Objectives.................................................................................................14
1.5 Market scope ...........................................................................................15
Chapter II: 2.1Overview of TPMS…………………………………….......16
2.11 General operation of TPMS....................................................................16
2.4 Hardware and software concept of TPMS................................................21
2.5 TPMS functionality..................................................................................23
Chapter III: components used and Power sources.....................................26
3.1 MPX4115.................................................................................................27
3.2 Variable resistor........................................................................................31
3.3 Zigbee.......................................................................................................34
3.4 LCD 16*2.................................................................................................42
6
3.5 ADC.........................................................................................................43
3.6 Microcontroller.........................................................................................45
3.7 GSM module............................................................................................48
3.8 Power sources...........................................................................................50
3.82 Power consumption in TPMS.................................................................51
3.9Tyre losses.................................................................................................54
Chapter IV: 4.1 source code.........................................................................57
4.2 Flow chart.................................................................................................57
Conclusion......................................................................................................67
Future work....................................................................................................68
References......................................................................................................69
Abbreviation...................................................................................................71
7
List of Figures
Topic Page
1.50Market value 15
2.11 Schematic Diagram 18
2.32.1 Main Architecture available in market 20
2.52 RF Transmitter 24
3.1 Mpx4115 28
3.11 Sensor output voltage and absolute 30
Pressure
3.2 Variable resistors 31
3.3 Zigbee working 35
3.32 Zigbee network 36
3.33 Hype cycle for zigbee 38
3.34 Hype cycle for zigbee 39
3.36 Zigbee 41
4.3 LCD 16*2 42
3.6 Microcontroller 48
3.61 Microcontroller 49
3.7 Gsm sim900 48
3.9 Cross-section of a tyre 56
8
List of TablesTopics Page
1.21 Comparison B\T direct and indirect 14
3.1 Parameters 28
3.11 Pressure Vs sensor voltage 29
3.2 Model selection 32
3.21 Electrical specification 32
3.25 Values Vs tolerance 33
3.26 Load life 34
3.27 Power dreading curve 34
3.31 Zigbee and other technologies 40
3.35 Wireless communication standards 40
3.5 Microcontroller parameter and test 44
3.81 Power supply 51
3.84 Percentage of power consumption 52
3.84 Datagram 54
9
List of Symbols
V Voltage
Vin Input voltage
fin Input frequency
Vref Reference voltage
Rin Input resistance
Cref Reference capacitance
ΩOhm
10
CHAPTER 1
1.1 INTRODUCTION:
Every year, many accidents occurred and for certain cases, accidents are caused by Under-
inflated Tyres. Under-inflated tyres could promote to problems such as blowouts decreased tyre
life, and handling. Due to this awareness of the importance of tyre pressure, US government has
introduced Transportation Recall Enhancement Accountability and Documentation (TREAD)
Act (www.nhtsa.gov, February 2010). This act requires all Passenger cars, van, and light trucks
to include low tyre pressure warning systems as standard equipment. The National Highway
Traffic Safety Administration (NHTSA) Oversees the TREAD Act and has expressed an interest
in extending the legislation to other types of vehicle. As a result, NHTSA established Federal
Motor Vehicle Safety Standard which requires the installation of tyre pressure monitoring
systems (TPMS’s) that warn the drivers when a tyre is significantly under-inflated (25% of the
right pressure).The significant of running the tyres at the specified pressure helps provide proper
vehicle handling (thus, reducing the chance of accident). The right pressure for a vehicle is well-
stated on the tyre information label or tyre placard located on a door edge or door jamb, or inside
the glove-box door. The label also Lists maximum load and tire size (including spare).
Underinflated tyres wear on the outsides of the tread. Also, the tyres flex excessively which
produces extra heat and more rapid Wear. Over inflation causes the center of the tread to wear.
The tyre cannot flex normally And this puts stress on the sidewalls and plies. It is not convenient
to frequently check the tyre pressure using pressure gauge. For Long journey, tyre pressure may
vary from time to time due to load, road irregularities, and temperature. Hence, one could not
possibly know the condition of the tyre and that had Caused many tyre blowouts especially for
heavy trucks. Hence, TPMS is introduced. TPMS is an electronic system that observes and
monitors the air pressure. Certain TPMS also monitors the temperature of the automobile tyre.
The system alerts the driver of the vehicle of the air pressure inside the tyres by displaying the
real pressure or just a warning light. Some of the car manufacturers already installed their own
TPMS on their vehicles.
11
1.2 TPMS concepts
In this section, the types of TPMS and their functionality are presented. Also, their advantages and disadvantages along with the applications of TPMS are discussed.
1.21 Types of TPMS
Based on the method of measuring air pressure and sending that information to the driver of the vehicle, tire pressure monitoring systems are broadly classified into two types, namely, direct and indirect.
1) Direct TPMS:
Direct TPMS calculates the pressure drop based on actual pressure measurements through physical pressure sensors installed with each tire. The data can then be transmitted to the vehicle’s electronic control unit (ECU) to instantly inform the driver. The capabilities of Direct TPMS can always be extended by employing additional components, such as microcontrollers (MCUs) and radio Frequency (RF) devices.
2) Indirect TPMS: Indirect TPMS, as the name suggests measures the air pressure indirectly and
most of the existing systems are based on wheel speed measurements. It detects under-inflation by using the speed sensors located in the anti-lock braking System (ABS) to compare wheel rotating speeds making use of the fact that an under-Inflated tire has a slightly smaller diameter, thus it rotates at a different rate from properly inflated tires. But the disadvantage of indirect TPMS is that the vehicle has to be in motion. Also the vehicle driver cannot keep track of the individual tire pressures. Further if all four tires lose the same amount of air, then the relative Change will be zero limiting the effective functionality of the TPMS to only three Tires.
12
Table 1.21
Comparison between Direct and Indirect TPMSDirect TPMS Indirect TPMS
Instant alert when pressure drops below preset level.
Alerts only when any single tire loses pressure.
Heavy load does not affect ‘alert’. Won’t indicate to driver which tire is low.
No ‘alert’ if all tires are losing pressure over time at the same rate.
Won’t ‘alert’ in time to prevent tire damage especially if heavily loaded.
Alerts when pressure drops 25%.
Can also provide incremental pressure measurements.
Alerts only when pressure drops > 30%.
13
1.3 Problem statement:
The problems that we faced are:
To minimize the size of entire circuit that can be fixed with a tire To use such a battery whose life time is maximum Transmission of the data through a wireless communication GSM module location and its use
1.4 Goal of the Project:
The goal of our project is to design such a system which can reduce daily occurring accidents all
Over the world. The main goal of this project is:
To increase handling capacity
To increase fuel efficiency
To increase tire life
To minimize daily occurring accidents
1.5 Market scope:
14
From 2004 in America all public vehicles will have TPMS to ensure safety. Thus most of
Country has developed TPMS in their public vehicles, so there is a lot of opportunity to
make a progress in developing TPMS. The figure below show the market opportunity
200011%
200421%
200726%
201442%
Sales
fig 1.50
Category 1 Category 2 Category 3 Category 40
20
40
60
80
100
120
Chart Title
Axis Title
Table 1.5
Chapter II
15
OVERVIEW OF TPMS
2.1 INTRODUCTION
This chapter will discuss the previous inventions of TPMS. It will include direct TPMS, indirect
TPMS, and self-power operation
. 2.11 GENERAL OPERATION OF TRADITIONAL TPMS
An automobile tyre pressure monitoring system and tyre identification method includes a
transmitting and detection unit provided on each tyre, as well as a receiving and display unit that
includes a receiving unit, a main control unit and a display unit. A plug-in encoding memory is
plugged into the receiving and display unit. One fixed identification (ID) code, which is the same as
that for the encoding memory, is provided for each transmitting and detection unit. When the power
is on, the receiving and display unit reads the ID code in each transmitting and detection unit. When
the power is on, the receiving and display unit reads the ID code in each Plug-in encoding memory
plugged into the socket of the display unit, and saves the information on the corresponding
relationships between ID codes saved in memories and tyre identity. The receiving and display unit
reads the ID codes in it, and determines whether these codes are identical with those in the memories.
If the signal is valid, the receiving and display unit compares the corresponding relationships,
determines which tyre the detection unit is transmitting the signal, and displays the information about
pressure and Temperature in corresponding display areas. As shown in Figure 2.11, an automobile
tyre pressure monitoring system generally consists of a transmitting and detection unit 92 and a
receiving and display unit 91, which there upon comprises display unit 9101, receiving unit 9102 and
receiving antenna 9103.The left side of Figure 2.1 is a front sketch diagram of the display unit, i.e.,
the screen that is displayed on the automobile instrument panel. The display unit 91901 of an
ordinary automobile includes four data display areas 91011, which display the parameters of the four
tyres respectively. The broken lines in Figure 2.1 represent the correlations between the display area
91011 and the respective tyres.
16
fig 2.11
Schematic diagram of general operation of a direct TPMS
The operation process is as follows: The sensor in the transmitting and detection Unit 92
converts variation of the tyre pressure into electric parameters which vary accordingly to
electronic component induction. Then, the electric parameters are processed By a MCU in the
transmitting and detection unit into digital code signals. After identification of the ID of the
digital code signals in this unit (used to distinguish it from other units) is completed, these code
signals are transmitted via a carrier frequency by a transmitter. The original data is recovered
after the radio signals are received and demodulated by the receiver antenna 9103. Then, after
being processed by the MCU of receiving and display unit, the data is displayed on the
17
corresponding tyre data area of the user’s interface by the display screen installed in the vehicle.
In this way, the driver can clearly know the pressure in each tyre. When the received data shows
the pressure in the tyre lower or higher than the set limit, the MCU will show an alarm icon on
the display screen. The driver can then take appropriate action for the tyre according to the data
of tyre pressure shown so as to ensure safe driving. This data is also processed to the GSM
module which Alert the user by sending a message to the user, if he is not currently present in
vehicle.
Fig 2.11.2
Direct tire pressure monitoring systems offer the following Features:
Measure and display tire air pressure with accuracy able to detect under
Inflation conditions of less than 25% of the recommended cold inflation pressure.
Measure and display tire air temperature.
Locate tire involved in pressure defect (optional).
React to fast and slow leaks (<5secs) for early warning.
Warn for punctures.
18
Alert for proper tire maintenance.
can monitor spare tire pressure.
can monitor tire pressure when stationary and deliver key information to the driver.
2.2 Fixed encoding method: The correlation between ID code in the MCU memory of the
receiving and display unit and the tire identification information are fixed at the factory. The
same ID code is also fixed in the MCU memory of the transmitting and detecting unit and is
marked on the surface of the transmitting and detection unit. During the installation, the
transmitting and detection units are installed on the corresponding tyres in accordance with the
marks and no change is allowed during application. This method is quite simple and its
shortcoming is that wrong installation is not allowed. Otherwise, identification confusion may
arise. Meanwhile, if a transmission unit is damaged, the user has to go to the manufacturer for
repair or replacement. The transmitting and detecting units must be reinstalled in accordance
with their marked positions when the tyres are rotated.
2.3 DIRECT TPMS
This part will explain the present invention of direct TPMS. Basic principle is still the same but
every invention uses different approach to realize the application. Some inventions used different
materials, and some used different circuit.
2.31 Air Pressure Monitoring System of Vehicle Tire and Identification Method ofVehicle Tire by Wei and Hongling
This invention adopts encoding plug-in technology and converts the identification issue caused
by tyre transposition and tyre replacement into the issue of resetting the ID code. Thus, it
provides a simple and effective technological solution for tyre re-identification. Because of the
adoption of plug-in method, the operation is easy and reliable. The invention adopts the encoding
technology, reads the ID code in the plug-in Encoding memory via input/output (I/O) rather than
via radio signals. Consequently, it avoids the problem of low frequency (LF) signal in LF wake-
19
up being disturbed in transmitting by the electromagnetic noise in the automobile and essentially
solves the disturbance problem.
2.32 Tyre Pressure Monitoring (TPM) System by Laurens and Kill
This invention explains a typical TPM system specifically intended for automotive use. It serves
as a reference to design a real-world system based on various microchips products. A TPM
system primarily monitors the internal temperature and pressure of an automobile’s tyre. There is
a variety of system approaches to follow, although this one is a rather comprehensive auto-
location system. An auto-location system can dynamically detect the position of a specific
sensor, which is useful when tyres are rotated. The heart of the TPM system is the
Sensor/Transmitter (S/TX) device and it is based on Microchip’s rfPIC12F675.
The main architectures of TPMS that are on the market or in development are shown
Figure2.32
20
2.4 Hardware and software concepts of TPMS:
The hardware components that are embedded into the TPMS module both interior and
exterior to the tire and the software required to implement the necessary operations
are listed in this section.
2.41 With the tire:
The TPMS tire module has both hardware and software components embedded
inside it. The hardware components include pressure sensors, microcontroller
unit (MCU), an ultra- high frequency (UHF) transmitter (zigbee) along with a
crystal, battery and an antenna. Any programmable MCU with a low-power sleep
mode Proves to be very useful for battery-powered TPMS. Proper design of the
antenna ensures sufficient RF power essential for reliable reception of signal from the
tire. The software used for TPMS has to perform the following three vital tasks:
Measure
Process data
Transmit
The tire module derives power from a lithium coin cell battery which has a typical
capacity of 250-300mAh. Therefore an extremely efficient algorithm is required
to provide the 7-10 year lifetime for a TPMS. The efficiency of this software program
or algorithm is related to timing and prior to designing the system the following
questions have to be considered.
21
i. Will the receiver display pressure of each tire, or just indicate a low pressure
warning?
ii. How often are pressure and temperature data measured and transmitted?
iii. Does the system always measure both pressure and temperature or is one
measured more often than the other?
iv. How many bits of data are in each data frame? The shorter the data frame the
lesser battery energy is consumed by the transmitter.
v. What happens when the pressure gets low? For efficient transmission of data to
the receiver in a noisy environment, warning signal may have to be sent several times.
2.42 Recover:
The TPMS components present inside the car, module also consists of both
hardware and software features. A receiver module consists Of a UHF receiver
(zigbee), a central antenna, and an interface to the rest of the car. higher end systems
might include distributed receiver antenna at each wheel well enabling the tires to
transmit at a lower power. The electronics inside the receiver work on the basis of
signal received by the Antenna. The stronger the power of the signal delivered by the
antenna, the easier will be the work of the electronics. The highest-end systems
include an LF signal initiator in each wheel well along with an LF receiver on the
tire module. Such a design allows the central body controller to send a signal to a
single tire, thus asking for a transmission from that tire only and eliminating data
collision issues. Automatic tire location is also efficiently managed in such systems.
The system's usefulness could also be enhanced by using the LF initiator to send
data to the tire module—anything from new low-pressure thresholds to
instructions for completely reprogramming the MCU .If the TPMS systems use the
same central receiver then efficient communication protocols would be required.
Most RKE systems use amplitude shift keying (ASK) modulation, which works
22
well for stationary transmitters such as a key fob. But the data coming from the
rotating tire are not as reliable as those from a key fob. Therefore to increase
reliability of data, TPMS uses frequency shift keying (FSK). Thus receivers that can
receive and demodulate both ASK and FSK seem to be the best choice. With respect
to software, many automobiles with RKE systems should require only a software
upgrade at the body controller to enable them to accommodate a TPMS. There
receiver should be reconfigured to alternate between ASK and FSK modulation so
that it can receive signals from both the TPMS and RKE systems. One option is
to always default to ASK so that existing RKE transmitters don't have to be
modified. The TPMS modules transmit a wake-up tone to the receiver, which the
receiver takes as a cue to reconfigure itself for FSK modulation. Once the TPMS
data are received, the receiver goes back to ASK. In order to make sure that the car
battery does not drain during long periods of inactivity, it is important to program an
efficient algorithm that allows there reiver to oscillate periodically between sleep and
receive modes
2.5 TPMS functionality:
This section explains the functionality of TPMS module and discusses the two main
components of TPMS module i.e. transmitter and receiver.
2.51 TPMS Transmitter:
Currently, external SAW or PLL based UHF transmitters are used as TPMS
transmitters. The TPMS transmitter module is based on low battery consumption
and thus the components within must have minimum current requirements and use
very little energy. Typical active operating current is approximately 1 to 5 mA and
100 nA during stand-by mode .Electronically, the TPMS module functionality lies in
translating the coded input from each wheel, into the receiver module to display the
pressure level. Figure 3.6 depicts its functionality. Typically the data format is sent at
9600 bps and Manchester encoded using FSK/ASK modulation. With a reference
quartz oscillator of 13.56MHz, the PLL can be able to generate 315, 433, 868 MHz
23
carriers. Testing of the TPMS transmitter module involves checking the signal
power level, frequency deviation (FSK), burst measurement (ASK), and
demodulation of ASK/FSK signal. A low frequency wakeup signal of about 125 KHz
is needed by the transmitter to wake-up the microcontroller in order to generate
continuous RF transmission.
2.52 RF generator:
The RF generator (zigbee) as shown in Figure 3.6 is used to modulate the carrier
signal and create an output for the TPMS receiver. TPMS RF bands are typically
315MHz in the United States/Japan and 433/868 MHz in Europe. To test the
receiver module, signal generators which can generate ASK/FSK signals are required
to simulate the signal.
Fig 2.522.53 TPMS Receiver:
24
The goal of any radio receiver is to extract and detect selectively a desired signal
from the electromagnetic spectrum. This selectivity in the presence of a plethora of
interfering signals and noise is the fundamental attribute that drives many of the
tradeoffs inherent in radio design. Radio receivers must often be able to detect
signal powers as small as femto watt while rejecting a multitude of other signals that
may be twelve orders of magnitude larger .The design of wireless receivers is a
complex, multi-faceted subject that has a fascinating history. Few of the early
receiver architectures are
Microcontroller
Zigbee
Display Unit
GSM module
25
Chapter 3
Components used and power sources:
Main components used in Tire Pressure Monitoring System are:
Pressure Sensor (MPX4115)
Crystal for clock generation
Variable resistor
Capacitor
Voltage Regulator
Resistors
Microcontroller
LCD 16*2
GSM Module
Zigbee
ADC(analogue to digital converter)
3.1 Pressure Sensor (MPX4115)
26
Integrated Silicon Pressure Sensor Altimeter Barometer Pressure Sensor On-Chip Signal
Conditioned, Temperature Compensated and Calibrated The MPX4115 series is designed to
sense absolute air pressure in an altimeter or barometer (BAP) applications Free scale’s BAP
sensor integrates on-chip, bipolar op amp circuitry and thin film resistor networks to provide
high level analog output signal and temperature compensation. The small form factor and high
reliability of on chip integration makes the Free scale BAP sensor a logical and economical
choice for application designers.
Features
• 1.5% Maximum Error over 0to 85
• Ideally suited for Microprocessor or Microcontroller-Based Systems
• Available in Absolute, Differential and Gauge Configurations
• Durable Epoxy Unibody Element
• Easy-to-Use Chip Carrier Option
Typical Applications
• Altimeter
• Barometer
27
ORDERING INFORMATION(1)
Device Options Case No. MPX Series Order
Marking
Basic Element Absolute, Element Only
Case 867-08 MPX4115A MPX4115A
Ported Elements
Absolute, Ported Case 867B-04 MPX4115AP MPX4115AP
Absolute, Stove Pipe Port
Case 867E-03 MPX4115AS MPX4115A
Absolute, Axial Port
Case 867F-03 MPX4115ASX MPX4115A
Table 3.10
Fig 3.1
Parametric Symbol Value Unit
Overpressure(2) (P1 > P2) Pmax 400 kPa
Burst Pressure(2) (P1 > P2) Pburst 1000 kPa
Storage Temperature Tstg -40to +125 C
Operating Temperature TA -40to +125 C
Maximum ratings
Table 3.1
28
3.11 Pressure sensor:
A pressure sensor senses the pressure and generates a voltage proportional to the
pressure. The pressure sensor MPX4115 produced by Motorola which can
measure pressure in the range 20kPa to 400kPa is used here. The power supply
voltage range of this sensor is 4.64V to 5.36V and it operates in the temperature
range -40°C to125°C. The pressure sensor is an 8 pin device with pins 1,5,6,7 and 8
being the internal device connections (NC). Pins 2 and 3 serve as the power supply
and ground respectively while pin 4 generates a voltage Vout proportional to the
pressure, which is interfaced to the PIC’s ADC. The diagram for interfacing the
pressure sensor to the PIC is shown in Figure 4.4.In order to take experimental data,
the pressure sensor is fitted inside an air filled closure or portable air tank to ensure
that required amount of pressure can be applied as desired by the user. The readings
for output voltage versus absolute pressure for different supply voltages are recorded
and plotted in excel and the calibration curves for the pressure sensor were
obtained. It is observed that the curves are linear and parametric for different supply
voltages and pressures. The datasheet of MPXH6400AC6T1 reveals that its transfer
function is of the form shown in equation 4.2.
Vout aP b
29
Table 3.11
Fig 3.11
30
Pressure (kPa) Sensor voltage (V)
100 1.15
120 1.38
140 1.6
160 1.86
180 2.1
200 2.35
220 2.6
240 2.89
260 3.08
280 3.32
300 3.59
320 3.82
340 4.05
360 4.29
380 4.54
400 4.78
3.2 Variable resistor:
Bulk Metal® Foil Technology Ultra High Precision Trimming Potentiometers, 1/4" Square, RJ26 Style,
Designed to Meet or Exceed The Requirements of MIL-PRF-39035, Char. H with a Smooth and
Unidirectional Output
Setting stability: 0.1 % typical; 0.5 % maximum, DSS
Power rating: 0.25 W at + 85 °C
Resistance range: 5 to 10 k
Tolerance: ± 5 %, ± 10 %
Electrostatic discharge (ESD) at least to 25 kV
Terminal finish: gold plated (tin/lead finish is available on request)
Temperature coefficient of resistance (TCR):± 10 ppm/°C. (- 55 °C to + 150 °C ref. at + 25 °C);through the wiper
(3); ± 25 ppm/°C (see table 2 for low values)
A smooth and unidirectional resistance with lead screw adjustment
Load life stability: 0.1 % typical R, 1.0 % maximum R under full rated power at + 85 °C for 10 000 h
Settability: 0.05 % typical; 0.1 % maximum
Introduction:
Vishay Foil Resistors’ (VFR) precision trimmers have the Bulk Metal® Foil resistive element
which possesses a unique inherent temperature and load life stability. Plus, their advanced
virtually back lash-free adjustment mechanism makes them easy to set quickly and accurately
and keeps the setting exactly on target
Fig 3.2
31
Table 3.2TABLE 1 - MODEL SELECTIONMODEL TERMINATION STYLE AVERAGE WEIGHT (g) POWER RATING at + 85 °C AMBIENT NO. OF TURNS
1240W-edge mount, top adjust
0.4 0.25 W 21 ± 2X-edge mount, side adjustP-horizontal mount, side adjust
Table 3.21TABLE 2 - 1240 (RJ26) SERIES
ELECTRICAL SPECIFICATIONSTemperature Coefficient of Resistance (TCR) 50 to 10 k
± 10 ppm/°C maximum (- 55 °C to + 150 °C,+ 25 °C ref.)End-to-end (2)
Temperature Coefficient of Resistance 5, 10 and 20 ± 20 ppm/°CThrough the wiper (3) ± 25 ppm/°CStabilityLoad life at 10 000 hEnd-to-end (2)
0.1 % typical R1.0 % maximum R (under full rated power of0.25 W at + 85 °C)
Power Rating (4) 0.25 W at + 85 °CSettability 0.05 % typical;
0.1 % maximumSetting Stability 0.1 % typical;
0.5 % maximumContact ResistanceVariation - CRV (noise) (5)
3 typical;10 maximum
Hop-off 0.25 % typical;1.0 % maximum
High-Frequency OperationRise time Inductance Capacitance
1.0 ns without ringing0.08 µH typical0.5 pF typical
Operating Temperature Range - 55 °C to + 150 °C
Table 3.22TABLE 3 - VALUES VS. TOLERANCES
STANDARD RESISTANCE VALUES(in )
STANDARD TOLERANCE
5, 10 ± 10 %
20, 50, 100, 200, 500, 1K, 2K, 5K, 10K ± 5 %
32
TABLE 3 - VALUES VS. TOLERANCESSTANDARD RESISTANCE VALUES(in )
STANDARD TOLERANCE
5, 10 ± 10 %
20, 50, 100, 200, 500, 1K, 2K, 5K, 10K ± 5 %
Table 3.23
Table 3.24
33
FIGURE 3 - 1240W 10 kLOAD LIFE, 20 UNITS,
10 000 h at 0.25 W, + 85 °C (Wiper at CW)+ 2000
+ 1500
+ 1000
+ 500
0
- 500
- 1000
- 1500
- 20000 2000 4000 6000 8000 10 000
Time (h)
FIGURE 2 - POWER DERATING CURVE
+ 85 °C+ 100
+ 75
+ 50
+ 25
0- 75 - 50 - 25 0 + 25 + 50 + 75 + 100 + 125 + 150 + 175
Ambient Temperature °C
3.3 Zigbee:Introduction
Zigbee is the most popular industry wireless mesh networking standard for connecting sensors,
instrumentation and control systems. Zigbee, a specification for communication in a wireless
personal area network (WPAN), has been called the "Internet of things." Theoretically, your
Zigbee-enabled coffee maker can communicate with your Zigbee-enabled toaster. Zigbee is an
open, global, packet-based protocol designed to provide an easy-to-use architecture for secure,
reliable, low power wireless networks. Zigbee and IEEE 802.15.4 are low data rate wireless
networking standards that can eliminate the costly and damage prone wiring in industrial control
applications. Flow or process control equipment can be place anywhere and still communicate
with the rest of the system. It can also be moved, since the network doesn't care about the
physical location of a sensor, pump or valve. The Zigbee RF4CE standard enhances the IEEE
802.15.4 standard by providing a simple networking layer and standard application profiles that
can be used to create interoperable multi-vendor consumer electronic solutions.
The benefits of this technology go far beyond, Zigbee applications include:
_ Home and office automation
_ Industrial automation
_ Medical monitoring
_ Low-power sensors
_ HVAC control
_ Plus many other control and monitoring uses
34
Fig 3.3
Zigbee targets the application domain of low power, low duty cycle and low data rate
requirement devices. Figure below shows the example of a Zigbee network.
35
Zigbee NetworkFigure 3.32:
Zigbee is poised to become the global control/sensor network standard. It has been designed to
provide the following features:
– Low power consumption, simply implemented
– Users expect batteries to last many months to years
– Bluetooth has many different modes and states depending upon your
latency and power requirements such as sniff, park, hold, active,
etc.; Zigbee/IEEE 802.15.4 has active (transmit/receive) or sleep
– Even mains powered equipment needs to be conscious of energy.
Zigbee devices will be more ecological than its predecessors saving
Megawatts at it full deployment.
36
Low cost (device, installation, maintenance)
Low cost to the users means low device cost, low installation cost and low maintenance. Zigbee
devices allow batteries to last up to years using primary cells (low cost) without any chargers
(low cost and easy installation). Zigbee simplicity allows for inherent configuration and
redundancy of network devices provides low maintenance.
High density of nodes per network
Zigbee use of the IEEE 802.15.4 PHY and MAC allows networks to handle any number of
devices. This attribute is critical for massive sensor arrays and control networks.
Simple protocol, global implementation
Zigbee protocol code stack is estimated to be about 1/4th of Bluetooth’s or 802.11’s. Simplicity
is essential to cost, interoperability, and maintenance. The IEEE 802.15.4 PHY adopted by
Zigbee has been designed for the 868 MHz band in Europe, the915 MHz band in N America,
Australia, etc.; and the 2.4 GHz band is now recognized to be a global band accepted in almost
all countries.
Wireless Communication
All wireless communication systems have the following components:
_ Transmitter
_ Receiver
_ Antennas
_ Path between the transmitter and the receiver
37
In short, the transmitter feeds a signal of encoded data modulated into RF waves into the
antenna. The antenna radiates the signal through the air where it is picked up by the antenna of
the receiver. The receiver demodulates the RF waves back into the encoded data stream sent by
the transmitter.
Fig 3.33
38
Fig 3.34
Zigbee and other technologies:
39
Table 3.31
Fig 3.35
40
Fig 3.36
41
3.4 LCD 16*2:
Introduction
Alphanumeric displays are used in a wide range of applications, including palmtop computers,
word processors, photocopiers, point of sale terminals, medical instruments, cellular phones, etc.
The 16 x 2 intelligent alphanumeric dot matrix display is capable of displaying 224 different
characters and symbols. A full list of the characters and symbols is printed on pages 7/8 (note
these symbols can vary between brand of LCD used). This booklet provides all the technical
specifications for connecting the unit, which requires a single power supply (+5V).
Fig 3.4
42
3.5 Analogue to digital converter:
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS
CONVERTER SPECIFICATIONS V+ = 5V, TA = 25o
C and fCLK = 640kHz, Unless Otherwise SpecifiedTotal Unadjusted Error
1/ADC0803 V /2 Adjusted for Correct Full Scale Reading - -
2LSB
REF
ADC0804 VREF/2 = 2.500V - - 1 LSB
VREF/2 Input Resistance Input Resistance at Pin 9 1.0 1.3 - kΩAnalog Input Voltage Range (Note 3) GND-0.05 - (V+) + 0.05 V
DC Common-Mode Rejection Over Analog Input Voltage Range - 1
/16 1
/8 LSBPower Supply Sensitivity V+ = 5V 10% Over Allowed Input Voltage -
1/16
1/8 LSB
Range
CONVERTER SPECIFICATIONS V+ = 5V, 0oC to 70
oC and fCLK = 640kHz, Unless Otherwise Specified
Total Unadjusted Error
1/ADC0803 V /2 Adjusted for Correct Full Scale Reading - -
2LSB
REF
ADC0804 VREF/2 = 2.500V - - 1 LSB
VREF/2 Input Resistance Input Resistance at Pin 9 1.0 1.3 - kΩAnalog Input Voltage Range (Note 3) GND-0.05 - (V+) + 0.05 V
DC Common-Mode Rejection Over Analog Input Voltage Range - 1
/8 1
/4 LSBPower Supply Sensitivity V+ = 5V 10% Over Allowed Input Voltage -
1/16
1/8 LSB
Range
AC TIMING SPECIFICATIONS V+ = 5V, and TA 25o
C, Unless Otherwise Specified
Clock Frequency, fCLK V+ = 6V (Note 4) 100 640 1280 kHzV+ = 5V 100 640 800 kHz
Clock Periods per Conversion (Note 5), 62 - 73 Clocks/ConvtCONV
Conversion Rate In Free-Running Mode, CR tied to with = 0V, fCLK = 640kHz - - 8888 Conv/sINTR WR CSWidth of Input (Start Pulse Width), = 0V (Note 6) 100 - - nsWR CStW(WR)I
Access Time (Delay from Falling Edge of CL = 100pF (Use Bus Driver IC for Larger CL) - 135 200 nsRD to Output Data Valid), tACCThree-State Control (Delay from Rising CL = 10pF, RL= 10K - 125 250 nsEdge of RD to Hl-Z State), t1H, t0H (See Three-State Test Circuits)Delay from Falling Edge of to Reset of - 300 450 nsWRINTR, tWI, tRIInput Capacitance of Logic Control Inputs, - 5 - pFC
IN
Three-State Output Capacitance (Data - 5 - pF
43
8-Bit, Microprocessor-Compatible, A/DConvertersThe ADC080X family are CMOS 8-Bit, successive-approximation A/D converters which use a modified
potentiometric ladder and are designed to operate with the8080A control bus via three-state outputs. These convertersappear to the processor as memory locations or I/O ports,and hence no interfacing logic is required.
The differential analog voltage input has good common-
mode-rejection and permits offsetting the analog zero-input-voltage value. In addition, the voltage reference input can beadjusted to allow encoding any smaller analog voltage spanto the full 8 bits of resolution.
Features:
• 80C48 and 80C80/85 Bus Compatible - No Interfacing Logic Required
• Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . .<100µs
• Easy Interface to Most Microprocessors
• Will Operate in a “Stand Alone” Mode
• Differential Analog Voltage Inputs
• Works with Band gap Voltage References
• TTL Compatible Inputs and Outputs
• On-Chip Clock Generator
• Analog Voltage Input Range(Single + 5V Supply) . . . . . . . . . . . . . . . . . . . . . . 0V to 5V• No Zero-Adjust Required• 80C48 and 80C80/85 Bus Compatible - No InterfacingLogic Required
Buffers), COUT
Table 3.5
3.6 Microcontroller AT89S51:
Features:• Compatible with MCS®-51 Products •• 4K Bytes of In-System Programmable (ISP) Flash Memory
– Endurance: 10,000 Write/Erase Cycles
• 4.0V to 5.5V Operating Range
• Fully Static Operation: 0 Hz to 33 MHz
• Three-level Program Memory Lock
• 128 x 8-bit Internal RAM
• 32 Programmable I/O Lines
• Two 16-bit Timer/Counters
• Six Interrupt Sources
• Full Duplex UART Serial Channel
• Low-power Idle and Power-down Modes
• Interrupt Recovery from Power-down Mode
• Watchdog Timer
• Dual Data Pointer
44
• Power-off Flag
• Fast Programming Time
• Flexible ISP Programming (Byte and Page Mode)
• Green (Pb/Halide-free) Packaging Option
Description
The AT89S51 is a low-power, high-performance CMOS 8-bit microcontroller with 4K bytes of
In-System Programmable Flash memory. The device is manufactured using Atmel’s high-density
nonvolatile memory technology and is compatible with the Indus-try-standard 80C51 instruction
set and pin out. The on-chip Flash allows the program memory to be reprogrammed in-system or
by a conventional nonvolatile memory pro-grammar. By combining a versatile 8-bit CPU with
In-System Programmable Flash on a monolithic chip, the Atmel AT89S51 is a powerful
microcontroller which provides a highly-flexible and cost-effective solution to many embedded
control applications. The AT89S51 provides the following standard features: 4K bytes of
Flash,128 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, two 16-bit
timer/counters, a five-vector two-level interrupt architecture, a full duplex serial port, on-chip
oscillator, and clock circuitry. In addition, the AT89S51 is designed with static logic for
operation down to zero frequency and supports two software selectable power saving modes. The
Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and system to
continue functioning. The Power-down mode saves the RAM con-tents but freezes the oscillator,
disabling all other chip functions until the next external interrupt or hardware reset.
Fig 3.6
45
Fig 3.61
46
P1.0 1 40 VCCP1.1 2 39 P0.0 (AD0)P1.2 3 38 P0.1 (AD1)P1.3 4 37 P0.2 (AD2)P1.4 5 36 P0.3 (AD3)
(MOSI) P1.5 6 35 P0.4 (AD4)(MISO) P1.6 7 34 P0.5 (AD5)(SCK) P1.7 8 33 P0.6 (AD6)
RST 9 32 P0.7 (AD7)(RXD) P3.0 10 31 EA/VPP(TXD) P3.1 11 30 ALE/PROG
P3.2 12 29(INT0) PSEN
P3.3 13 28 P2.7 (A15)(INT1)(T0) P3.4 14 27 P2.6 (A14)(T1) P3.5 15 26 P2.5 (A13)
P3.6 16 25 P2.4 (A12)(WR)
P3.7 17 24 P2.3 (A11)(RD)
XTAL2 18 23 P2.2 (A10)XTAL1 19 22 P2.1 (A9)
GND 20 21 P2.0 (A8)
47
3.7 SIM900GSM/GPRS Module
The SIM900 is a complete Quad-band GSM/GPRS solution in a SMT module which
can be embedded in the customer applications. Featuring an industry-standard interface,
the SIM900 delivers GSM/GPRS 850/900/1800/1900MHz performance for voice,
SMS, Data, and Fax in a small form factor and with low power consumption. With a
tiny configuration of 24mm x 24mm x 3 mm, SIM900 can fit almost all the space
requirements in your M2M application, especially for slim and compact demand of
design.SIM900 is designed with a very powerful single-chip processor integrating
AMR926EJ-S core Quad - band GSM/GPRS module with a size of
24mmx24mmx3mm SMT type suit for customer application An embedded Powerful
TCP/IP protocol stack
Based upon mature and field-proven platform, backed up by our support service, from
definition to design and production
Fig 3.7
48
General features
Quad-Band 850/ 900/ 1800/ 1900 MHz GPRS multi-slot class 10/8GPRS mobile station class B Compliant to GSM phase 2/2+– Class 4 (2 W @850/ 900 MHz) – Class 1 (1 W @ 1800/1900MHz) Dimensions: 24* 24 * 3 mm Weight: 3.4g Control via AT commands (GSM 07.07, 07.05 and SIMCOM enhanced AT Commands) SIM application toolkit Supply voltage range 3.4 ... 4.5 V Low power consumption Operation temperature: -30 °C to +80 °C
Specifications for dataGPRS class 10: max. 85.6 kbps(downlink)PBCCH support
Coding schemes CS 1, 2, 3, 4
CSD up to 14.4 kbps
USSD
Non transparent modePPP-stack
Pin Assignment
Fig 3.71
49
3.8 Power sources for TPMS:
This section deals with the power sources for TPMS, functionality of transmitter and
receiver in TPMS, current consumption in TPMS along with the methods to
minimize power consumption in TPMS and RFID tags. This also discusses in detail the
commonly employed TPMS strategies, some of the related energy harvesting techniques
and helps to provide an insight into the losses in tires and their impact on the read range
of RFID tags embedded inside the tires.
3.81 Power sources for TPMS
The most widely used power sources for direct TPMS are Lithium (Li) - ion primary
batteries. Even though other alternatives such as inductive coupled power schemes
have been developed, due to higher overall system costs they could not replace
batteries successfully. Li–ion coin cells exhibit an excellent energy-density versus
weight ratio with an open-circuit voltage of about 3-3.6 V as well as an
extended operating temperature range [12]. The three types of Li-ion batteries that have
been used for TPMS applications are
Polycarbonate monoflouride (BR type).
Manganese dioxide (CR type).
Thionyl chloride (ER type).
However due to superior high temperature performance, better durability and lower
weight the BR and CR types of batteries are more often used. A few basic
requirements for TPMS power supplies are listed in Table 3.81 [12].
50
Table 3.81: Requirements for TPMS power supplies.
Requirements for power supply (battery) Specifications
Lifetime 10 years (87600 hours)
Operating temperature -40°C ±125°C
Voltage range 2V-3.6 V
Pulse current 8-10 mA
Duty cycle (run mode) 1:500-1:1000
Self-discharge Less than or equal to 1% per year
Vibration robustness Continuous (5-2000Hz)
Acceleration robustness Max. 1500-2000g
Humidity 5-95%
No coin cell battery can provide enough energy to power the TPMS continuously for a
lifetime of 10 years. Therefore, the needed battery capacity strongly depends on the
application program, temperature profile, transmission power level and
ASIC specifications. Usually coin cells of the type 2450 (24 mm diameter and 5 mm
height)
3.82 Current consumption in a TPMS module:
This section discusses the battery–based TPMS and the development towards a
reduced current consumption through intelligent low-power management technique.
The amount of current consumed by the TPMS module determines the size, weight,
cost, and life time of the battery that is being used as the power source. The percentage
of current consumed by different processes of a battery-based TPMS module is
illustrated in Figure
51
Fig 3.82
: Percentage of current consumed by different processes of a battery-based TPMS
.
It can be seen from Figure 3.1 that specific modes such as power-down current (leakage
currents), motion detection, CPU execution and RF transmission consume largest
amounts of current. These modes are discussed in the following sections.
52
3.83 RF transmission:
The RF transmitter in general modulates the data provided by the microchip,
amplifies the signal and sends it out via the RF antenna. There are two possible
methods to reduce current consumption during RF transmission. One power saving
option is to utilize higher data rates and therefore shorter transmission times. The
second power saving option is given by the definition of so-called intelligent
datagram. A typical datagram of a current TPMS module is illustrated in Table 3.2
[12].The pressure is measured at periodic intervals and compared with the
previous stored value. If the difference in pressures is zero, then only the ID is
transmitted according to the datagram. The datagram that has to be transmitted can
be reduced to a minimum of three bytes if there is no difference between the
measured values, which results in about 25% of current saved.
3.84 CPU execution:
The amount of current consumed by CPU execution is about 11% of the total
current consumed by the TPMS module itself. A fast processor such as a
single instruction cycle CPU is required so as to minimize the cycle time and in turn
the current consumption. Also, an optimization of the software according to the
used hardware components could significantly reduce the overall current
consumption.
53
Byte Description Comments
1 Synchronization Synchronization bytes for the receiver
2 Synchronization Synchronization bytes for the receiver
3 Identification ID3 Unique 32 bit ID number
4 Identification ID2 Unique 32 bit ID number
5 Identification ID1 Unique 32 bit ID number
6 Identification ID0 Unique 32 bit ID number
7 Pressure Pressure value
8 Temperature Temperature value
9 Diagnostics Status Information
10 Check sum CRC
11 End of message 1-2 bits
Typical Datagram of current TPMS module [12].
Table 3.84
3.9 Tire losses:
This section in general presents information about tires, their composition, properties
of rubber, importance of carbon black and the factors that affect the performance of RFID.
54
3.91 Composition of tires:
Tires are made of vulcanized (i.e. cross-linked polymer chains) rubber and various
reinforcing materials [22]. Natural rubber is considered as the best tire material because it
possesses the following technical strengths [23]:
High green strength, tack and cohesive properties which are essential for
maintaining green tire uniformity and stability during building and shaping
operations.
Excellent adhesion to brass-plated steel cord.
Low hysteresis which imparts low heat generation, which in turn maintains new
tire service integrity and extends retread ability.
Low rolling resistance with enhanced fuel economy.
Excellent snow and ice traction for winter tires and all-season treads.
High resistance to cutting, chipping and tearing.
The black color of tires is due to the use of a very important filler material known as
carbon black. Carbon black is often used as a pigment and reinforcement in rubber
and plastic products [24]. The advantages of carbon black have been known for a long
time as the best material to strengthen tire rubber compounds and to extend tread
life. It also helps in conducting heat away from the tread and belt area of the tire
which in turn reduces thermal damage and increases lifetime of tires [24].Besides
rubber, certain metals like high tensile-strength steel in the form of wires, cords;
belts, etc. along with special alloys such as bronze or brass for coating purposes
form major constituents in tire manufacturing process. Various other additives are
also included in order to increase strength and toughness of tires.
55
3.92 Cross-section of a tire:
The cross section of a tire illustrated in Figure 3.7 helps to understand the position
of RFID tag embedded into the tire along with the dimensions of tire, rubber material,
and thickness of steel. The RFID tag is placed parallel to the outer steel mesh at a
distance that depends on the tire size and ranges from 4 to 8 cm above the inner steel
mesh. The tag may be added to the tire during tire build by itself or encased in a
sandwich of green rubber of a low carbon composition [25]. The thickness of the
sandwich correlates directly to the final read distance since the carbon in the tire rubber
detunes the tag [25].
Fig 3.92
56
Chapter 4
4.1 Source code:
The At89S51 is programmed in C language with the help of MPLAB C18 C
Compiler. After verifying the operation of the microcontroller in the “debug” mode, it is
programmed in the “release” mode and placed on the bread board to evaluate the current
consumption. The circuit connections remain the same except that a separate 4 MHz
crystal is required on the bread board for normal operation of the microcontroller.
Flow chart
57
dataadc equ 35h
org 0
mov p1,#0ffh mov p3,#0ffh mov scon,#50h mov tmod,#20h mov th1,#-3 setb tr1 acall initial
acall initial acall title1 acall delay
acall delay acall delay
acall delay acall delay acall delay
acall delayacall delayacall delayacall delaymov dptr,#cmgf
acall send acall delay acall delete
clr amov sbuf,a
start:jnb ri,start clr ri
mov a,sbuf mov dataadc,a acall disppress //sjmp start acall delay acall delay acall delay acall delay mov a,dataadc cjne a,#48,nxt
acall title3acall sendmsg
mov a,#01h
58
acall comnwrt lcall delaylcd
acall title5
sjmp start
nxt:jnc nxt1
acall title3acall sendmsgmov a,#38h
acall comnwrt lcall delaylcd
acall title5sjmp start
nxt1: sjmp start
initial:mov a,#38h acall comnwrt lcall delaylcd mov a,#0ch acall comnwrt lcall delaylcd mov a,#06h acall comnwrt ret
comnwrt:acall delaylcd mov p2,a clr P3.6 nop nop nop setb p3.7 nop
59
nop nop clr p3.7 ret
datawrt:acall delaylcd mov p2,a setb p3.6 nop nop nop setb p3.7 nop nop nop clr p3.7 ret
lcd_msg:clr a movc a,@a+dptr inc dptr jz lcd_msg9 cjne a,#01h,lcd_msg1 acall comnwrt jmp lcd_msglcd_msg1:cjne a,#7fh,sk sk:jc lcd_msg_data acall comnwrt jmp lcd_msglcd_msg_data:acall datawrt jmp lcd_msglcd_msg9:ret
title1:mov dptr,#message1 acall lcd_msg retmessage1:db 01h,80h,'Pressure:000Psi',00H
title5:mov dptr,#message5 acall lcd_msg retmessage5:db 01h,80h,'Pressure: Psi',00H
title2:mov dptr,#message2
60
acall lcd_msg retmessage2:db 88h,'Psi',00H
title3:mov dptr,#message3 acall lcd_msg retmessage3:db 01h,80h,'Low pressure',00H
disppress:
mov a,#89hacall comnwrtmov dptr,#hundredmov a,dataadcmovc a,@a+dptrmov dptr,#datalcdmovc a,@a+dptracall datawrt
mov a,#8ahacall comnwrtmov dptr,#tensmov a,dataadcmovc a,@a+dptrmov dptr,#datalcdmovc a,@a+dptracall datawrt
mov a,#8bhacall comnwrtmov dptr,#onesmov a,dataadcmovc a,@a+dptrmov dptr,#datalcdmovc a,@a+dptracall datawrt
RET
/*ones:
61
db 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,0,0,1,1,2,2,3,3,4db 4,5,5,6,6,7,7,8,8,9,9,0,0,1,1,2,2,3,3,4,4,5,5,6,6db 7,7,8,8,9,9,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9db 9,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,0,0,1,1db 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,0,0,1,1,2,2,3,3,4db 4,5,5,6,6,7,7,8,8,9,9,0,0,1,1,2,2,3,3,4,4,5,5,6,6db 7,7,8,8,9,9,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9db 9,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,0,0,1,1
tens:db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1db 1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2db 2,2,2,2,2,2,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3db 3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,5,5,5,5db 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,6,6,6,6,6,6,6,6,6db 6,6,6,6,6,6,6,6,6,6,6,7,7,7,7,7,7,7,7,7,7,7,7,7,7db 7,7,7,7,7,7,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8db 8,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,0,0,0,0
hundred:db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1*/
ones:db 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2db 2,2,2,2,2,7,7,8,8,9,9,0,0,1,1,2,2,3,3,4,4,5,5,6,6db 7,7,8,8,9,9,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9db 9,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,0,0,1,1db 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,0,0,1,1,2,2,3,3,4db 4,5,5,6,6,7,7,8,8,9,9,0,0,1,1,2,2,3,3,4,4,5,5,6,6db 7,7,8,8,9,9,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9db 9,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,0,0,1,1
tens:db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2db 2,2,2,2,2,2,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3db 3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,5,5,5,5db 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,6,6,6,6,6,6,6,6,6
62
db 6,6,6,6,6,6,6,6,6,6,6,7,7,7,7,7,7,7,7,7,7,7,7,7,7db 7,7,7,7,7,7,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8db 8,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,0,0,0,0
hundred:db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1
datalcd:db 30h,31h,32h,33h,34h,35h,36h,37h,38h,39h
sendmsg:mov dptr,#cmgsacall send lcall delaylcall delaymov dptr,#prmsgacall send lcall delaylcall delaymov A,#26 Acall send1mov A,#10Acall send1mov A,#13Acall send1ret
send1: mov sbuf,a jnb ti,$ clr ti ret
send:
63
again:clr a movc a,@a+dptr jz zero inc dptr acall delay2 mov sbuf,a jnb ti,$ clr ti sjmp again zero:ret
delete:acall delaymov dptr,#cmgdacall sendacall delayret
cmgf:db 'at+cmgf=1',13,10,0
cmgd:db 'at+cmgd=1,4',13,10,0;;cmgs:;;db 'at+cmgs="03365125140"',13,10,0
cmgs:db 'at+cmgs="03439769445"',13,10,0
prmsg:db 'Warning Low Pressure',13,10,0
delay:mov r3,#10 back51:mov r1,#200 back41:mov r6,#230 djnz r6,$ djnz r1,back41 djnz r3,back51 ret
64
delay2:mov r3,#3 back5:mov r1,#100 back4:mov r6,#100 djnz r6,$ djnz r1,back4 djnz r3,back5 ret
delaylcd:mov r3,#60 back1:mov r1,#25 djnz r1,$ djnz r3,back1 ret
end
/* org 00h mov p1,#0ffh mov p3,#0ffh mov scon,#50h mov tmod,#20h mov th1,#-3 setb tr1 start: mov a,p1 mov sbuf,a jnb ti,$ clr ti acall delay sjmp start
delay:mov r3,#10 back51:mov r1,#200 back41:mov r6,#230 djnz r6,$ djnz r1,back41 djnz r3,back51 ret
65
end */
66
Conclusion:
In this paper we analyzed the chances to utilize TPMS systems for traffic and transportation
management purposes by a unique identification . It was demonstrated that with some reverse
engineering it is possible to fully analyze and decode the packets sent from TPMS sensors and
identify ID address of the sensors. Moreover, it was shown that by using of-the-shelve
components simple eavesdropping hardware platform can be implemented and utilized for
obtaining the sensor data.
In this thesis we have implemented tyre pressure monitoring system by using very low power
devices such as zigbee for transmission and sensor which have very little power consumption.
In this project we used Gsm module for the first time in Pakistan which will inform us about the
pressure when we were outside the car or away from our vehicle, for example if we are sitting in
our office and the tyre get inflated so it will inform us by sending a warning message.
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Future work:
In later years, TPMS will most likely be expected to incorporate new and more features owing to the increasing safety standards in automotive industry. This could be achieved in a number of ways like adding more sensors to the TPMS module in order to provide data other than pressure, temperature, etc. or combining different information sources like the integration between RKE and TPMS so as to communicate more effectively with other parts of the vehicle. Moreover, adding wireless capabilities such as Bluetooth to the TPMS would definitely make it simpler than other complicated methods.
As TPMS will become a standard safety feature on all vehicles, it is very important to consider the methods that improve the battery life. Battery less TPMS based on alternatives such as inductive coupling is also being developed so as to conserve battery power. Here the TPMS will be equipped with a central transceiver which handles both transmission and reception of transmitted values and a transponder utilizes power from this transceiver to relay data from the sensors located inside the TPMS module. This method eliminates batteries which were required previously to transmit data from the sensors.
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REFERENCES
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[3] Kais Mnif, “A Smart Tire Pressure Monitoring System,” Sensors Mag., Nov 1, 2001.
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[5] “Tire pressure monitoring system,” Schrader Bridgeport Article, May 2006, pp. 4-6.
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[8] Martin Motz, “Wireless Approach Monitors Tire Pressure,” Microwaves and RF, ED Online ID #5464, March 2003.
[9] W.Stallings, Data and Computer Communications, 7th edition, Prentice-Hall, 2004.
[10] “Three methods of digital signal modulation,” Encyclopaedia Britannica. Retrieved September 05, 2008, from Encyclopaedia Britannica Online http://www.britannica.com/EBchecked/topic/455350/phase-shift-keying
[11] T. Rappaport, Wireless Communications - Principles & Practice, 2nd edition, Prentice-Hall, Upper Saddle River, NJ, 1996.
[12] “Power reduction techniques for ultra-low power solutions,” Virage Logic Corporation, EE Times Mag., January 2007, pp. 27-35.
[13] T. Lange, M. Lohndorf, T. Kvisteroy, “Intelligent Low-Power Management and Concepts for Battery-less Direct Tire Pressure Monitoring Systems (TPMS),” Infineon Technologies AG and SensoNor AS.
[14] Pedro Pachuca and Laurent Gauthier, “Power management alternatives for RF portable devices,” RF Design and Semiconductor Technology, Feb 2006, pp. 28-32.
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[16] “RFID chip to monitor tire pressure,” RFID Journal, vol. 6, issue 7, October 17, 2002.
[17] Paul D. Mitcheson, Tim C. Green, Eric M. Yeatman, Andrew S. Holmes, “Architectures for Vibration-Driven Micropower Generators,” Microelectromechanical Journal, vol. 13, issue 3, June. 2004, pp. 429-440.
[18] Joseph. L. Dvorak, Moving Wearables Into The Mainstream- Communication and Power, Springer US, Part 3, October 24, 2007, pp. 195-229.
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[21] Derek K.Shaeffer and Thomas H.Lee, “The Design and Implementation of Low-Power CMOS Radio Receivers,” Kluwer Academic Publishers.
[22] Takeshi Amari, Nickolas J. Themelis, Iddo K. Wernick, “Resource recovery from used rubber tires,” Science Direct Journal, vol. 25, issue 3, Sep 1999, pp. 179-188.
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[25] “Michelin guidelines for deployment of licensed RFID tag,” Michelin General guideline for tire RFID Journal., pp.1-4.[26] Dr. Patrick King, “Trial by tire,” RFID Journal, April 3, 2006.[27] Dr. Patrick King, “Guest Viewpoint: RFID Violates Packaging Symmetry -What to Do about It,” AIM Global, Nov 16, 2006.[28] S. Basat, K. Lim, I. Kim, M.M. Tentzeris, J. Laskar, “Design and Development of a Miniaturized Embedded UHF RFID Tag for Automotive Tire Applications,” School of ECE, Georgia Institute of Technology, Atlanta.[29] Microchip PIC18FXX2 Data sheet, High-Performance, Enhanced Flash Microcontrollers with 10-Bit A/D. Retrieved September 5, 2008, from Microchip Downloads.http://ww1.microchip.com/downloads/en/DeviceDoc/39564c.pdf[30] Microchip PICDEM 2 Plus Demonstration board user’s guide. Retrieved September 05, 2008, from Microchip Downloads. http://ww1.microchip.com/downloads/en/DeviceDoc/51275d.pdf
[31] Microchip hardware and software development tools. Retrieved September 05, 2008, from Microchip Downloads. http: / / w w1. m icrochip. c o m /downloads/en/UniversityCorner/00136d.pdf
70
List of Abbreviations
TREAD Transportation Recall Enhancement Accountability and Documentation
NHTSA the National Highway Traffic Safety Administration
TPMS Tyre Pressure Monitoring System
MCU Microcontroller Unit
ID Identification
I/O Input/output
LF Low frequency
S/TX Sensor/transmitter
DL Data line
ABS Auto-braking system
IEEE Institute of Electrical and Electronics Engineers
MHz Megahertz
SAW Surface acoustic wave
IDT Interdigital transducer
AC/DC Alternating current/direct current
DC/DC Direct current/direct current
V/F Voltage-to-frequency
F/V Frequency-to-voltage
LED Light-emitting diode
NDT Non-destructive test
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