INTRODUCTIONThisreport paper analyses a small sensor unit and analogy amplifier which ispositioned at the when of a racing car to monitor the pressure of the tire. Thetemperature of the whole system will arise up to 300oC during racingsince the unit will be close to the brake system.

The optimum time of operationshould be 180 min for the unit during the race while the total operating periodin a season is a maximum of 500 hours. This extensive cooling unit will not bepossible due to the weight and space reasons. The materials and technologiesthat are needed for this unit include pressure sensor, temperature sensor, RFmodule, Digital-to-Analog converter, microcontroller, analogueinstrumentation amplifier, display device, timer, and LED indicator. LITERATURE REVIEWThe operation ofthe sensor unit will majorly deal with the measurement of temperature,pressure, and timer. This sensor should have detailed features in order forthem to efficiently operate within the required guidelines, thesecharacteristics include the ability to withstand a temperature of 300oC,ability to operate for a duration of 180 minutes during the race, and abilityto have a lifespan of more than 500 hours while operating.

ComponentsThe analoguecomponents and semiconductor technologies that are needed to ensure safeoperation include the pressure sensor, temperature sensor, RF module,Digital-to-Analog converter, microcontroller, analogueinstrumentation amplifier, the display device, timer, and LED indicator 1. These materials andtechnologies of semiconductor that are required for the design of the system ofwheel pressure monitoring are discussed below:  PressuresensorThis sensor willbe used in determining the pressure of the wheels of the car. From input to theoutput, a sensor may possess numerous stages of conversion before it generatesthe electric signal.

The pressure imposed in the tire will lead to alterationin strain in the diaphragm which will lead to a deflection. This will lead togeneral variations in the strain gauge’s resistance attached to the diaphragm.The variations in the resistance will lead to unbalance in the circuit ofStrain Gauge Bridge leading to variations in the output voltage in the circuitof the bridge 2. The type ofpressure sensor that can be used in this design is a piezoresistive pressuresensor which is a monolithic, wafer fabricated solid-state sensor by the use ofsilicon processing. Since piezoresistive pressure sensors are wafer fabricated,more than 200 sensors can be produced in a single wafer. Figure 1: Circuit diagramof a pressure sensor 3The pressuresensor above function by measuring the changes in the resistance whichultimately represent variations in the pressure of the wheel. Every resistor inthe pressure sensor either stretches or compresses. TemperaturesensorThis is a gadget whichmay be utilized in detecting and measuring hotness and coolness and changes itinto an electrical signal.

The temperature sensor that can be used on thewheels of this racing car is the LM35 series which has a temperature range of-550C to +1200C. This temperature sensor consists of extensive signalprocessing circuitry contained in the similar package as the sensors and forthe sensor IC of temperature the compensation circuit is not needed 4. Figure 2: Temperature sensor,LM35 5The supply ofpower of the temperature sensor above needs 5.5V and it has three terminals ofa material which performs its function depending on the temperature to varyresistance. When there is a rise in voltage, the temperature will also rise.Temperature sensors connected directly to microprocessor input hence has theability to reliably and directly communicate with the microprocessor. Thesensor unit can effectively communicate with processors that are of low costwithout the requirement of analogue to digital converter.

 6. AnalogInstrumentation amplifier (AD8237)The criteria ofselection for the instrumentation amplifier for this design include low inputoffset voltage, low input bias current, and low-frequency noise. There is the necessityfor the noise’s frequency to be as low as possible which is estimated as 10 Hzto 0.1Hz because the sensor output is similar.  7. Figure 3: Representationof analogue instrumentation amplifier 7AnalogDigital Converter (ADC)An analogue todigital converter is a device that is involved in the conversion of analoguesignals such as temperature and pressure signals into the digital signal whichis then fed to the microcontroller. The microcontroller can only interpret adigital signal, therefore, there is need of converting these analogue signalsof temperature and pressure into digital signals by the ADC before being fedinto the microcontroller.  The otherdevices such as the display device, LED indicator, and RF module are devices thatare digital which only interpret the number which as zero and one 8.

MicrocontrollerThemicrocontroller is involved in accepting data from the analogue to digitalconverter, manipulating the data and then produce the required results in thisdesign of wheel pressure monitoring system. In this case, the input devicesinclude the timers, pressure sensors, and temperature sensors and then sendssignals to different components which include the display device, RF module,and LED indicator 9. RFModuleRF module is anabbreviation of radio frequency module and is a minute electronic device whichis used for receiving and transmitting radio signals between two devices. TheRF module received data concerning pressure and temperature from the sensorsthrough the microcontroller and then transmit these signals to the displaydevice and LED indicator where necessary steps will be performed. Figure 4: RF Module 10This wirelesscommunication is made possible through radio frequency communication or throughoptical communication 10. TimerFor this design ofthe wheel pressure monitoring system, there is need to in-cooperate a timerwhich will be involved in the counting of minutes during the period in whichthe racing car is in operation. Counting of time for this design is criticalsince there is need of informing the driver of the maximum time of operation ofthe car during a particular race which has been set to be 180 minutes for anygiven race 11. DisplayDeviceA typical systemof tire-pressure monitoring integrates numerous functions.

Temperature sensorsand pressure sensors in every wheel of the racing car determine pressure andtemperature at intervals that are regular. The information gotten from thesesensors are sent by the signal of radio-frequency to an electric control unitwhich is located inside the racing car. This electric control unit isresponsible for analysing the data gotten through the radio-frequency signalfrom the temperature and pressure sensors. Initiators interrogate sensors arerequired to find out possible warnings rapidly and to make sure the informationthat is accurate is transmitted 12. Figure 5: Display Device 12The display showsthe data of the quantity of pressure and temperature as determined by thepressure and temperature sensors. If the temperature of the wheels is above 300oC,the temperature sensor will detect this rise in temperature and send the datato the display device which is located inside the racing car where the drivercan observe it. When the pressure of the wheels is below the level that isallowable, the pressure sensor will convey the information through the RFmodule to the electric control unit where the pressure drop value will be showed.The driver of the car can simply note the drop in pressure value and may make adecision to increase the stop racing before the wheels could cause an accident 13.

LEDIndicatorThe LED indicatorwill be used to show a warning in case the information received from thepressure sensor shows that the wheels’ pressure has dropped beneath a givenlevel which can be disastrous to the car. The LED indicator is coupled to themicroprocessor such that it will only become active when the temperature goesabove 300oC or pressure of the wheels reduces to 14psi or below. TheLED indicator play a major role in monitoring the pressure and temperature ofthe wheel of the racing car by alerting the driver in case critical temperatureand pressure is reached. The remedy can either be to slow down the car and addpressure in the tyres or stop applying the breaks on the wheels to reduce the temperature 11. Figure 6: LED Indicator 14SOLUTIONEVALUATIONThe wheel pressuremeasuring system is an important unit that plays a critical role in the safetyapplication of the racing cars.

From the components discussed above whichinclude the microcontroller, the display unit, temperature sensor, RF module,timer, and instrumentation amplifier are the major components that are neededfor this design of wheel pressure monitoring system 15. The block diagramof the design after the incorporation of the components discussed above is asshown in the figure below: Figure 7: Block diagramof wheel pressure monitoring system 15Typeof Materials used in making the Pressure UnitThe operation ofcomponents and made of semi-conductor has been reported at temperatures ofapproximately +700oC on a high end and as low as -270oC. Thematerial used for making the outer section of the pressure sensor was SiCMOSFET which has an operational temperature of up to +650oC. However,it has been reported that temperature above +650oC will lead to degradationof mechanical performance of the pressure sensor.

The Si MOSFET hightemperature sensors as developed by the use of piezoresistive and capacitivesensing technology 14. OperationPrinciple and Architecture of SiC MOSFETThis section dealswith the fabrication process, materials and components used in designing a hightemperature sensor made of SiC MOSFET. Figure 8: Si MOSFETpressure sensorWhen externalpressure is applied, the SiC MOSFET diaphragm deflects over the dopantsegregated region over the gate on the NiSi. The bending and deflection has aunique impact since it increases the value of capacitance between the substrateand diaphragm. Through the modification of the thickness of the diaphragm aswell as the radius, one can attain pressure of touch point and depth which willresult in variations in the value of capacitance 15.

 Sensorfabrication The pressuresensor discussed in this section is based on the piezoresistive pressure sensorbased on silicon on insulator wafers. The first step is to acquire 400 ?m waferthen designing a pattern layer of approximately 0.34?m on the top layer of thewafer. The passive layers of SiC are deposited by LPCVD.

The MOSFET ohmiccontact is fabricated using self-aligned silicide process. The MOSFETmultilayer films are sputtered and patterned using lift-off to form electrodesand metal interconnects. The component Ni is introduced in this step torepresent the multilayer electrode 13. DISCUSSIONPressuresensor DesignThe wheel pressuremeasuring system is an important unit that plays a critical role in the safetyapplication of the racing cars.

The system contains the microcontroller, thedisplay unit, temperature sensor, RF module, timer, and instrumentation amplifier.The sensor is a strained gauge and a circular diaphragm type sensor joined onthe opposite diaphragm’s face which was taken as the pressure of reference andthe other section joined to the valve of input pressure. The strain gauge isbased on the principles of piezoresistive such that strain gauge’s resistancewill show a variation. The detailed circuit diagram of the wheel pressuremonitoring system is as shown in the figure below: Figure 8: Circuit diagramof the wheel pressure monitoring system 16Operationof the Pressure Monitoring SystemThe sensor unit ofthis monitoring will be located at the circular diaphragm of the wheels witheach unit in the four wheels joined together by the microcontroller. Thetemperature and pressure sensors are a strain gauge and circular diaphragmsensor type joined on the opposite diaphragm’s face which was taken as thepressure of reference and the other section joined to the valve of inputpressure.

The pressure sensor is used in determining the pressure of the wheelsof the car. From input to the output, a sensor may possess numerous steps ofconversion before it generates an electric signal. The pressure sensor worksconcurrently with the temperature sensor which is a device that is used inmeasuring and detecting coolness and hotness of the wheels’ diaphragm andconverts it into an electrical signal 17. The electricalsignals from the pressure and temperature sensors are then fed to the analogueinstrumentation amplifier whose function is to reduce unwanted noise that mighthave been picked have been picked up by the circuit or by the sensors whileconverting pressure signals and heat signals into electrical signals. Thenoise-free signal from the analogue instrumentation amplifier is then fed intothe analogue to digital converter.

An analogue to digital converter is a devicethat is involved in the conversion of analogue signals such as temperature andpressure signals into the digital signal which is then fed to themicrocontroller 18. This is becausemicrocontroller can only interpret a digital signal, hence there is need ofconverting these analogue signals of pressure and temperature into digitalsignals by the analogue to digital converter before being fed into themicrocontroller. The microcontroller is involved in accepting data from theanalogue to digital converter, manipulating the data and then produce therequired results in this design of wheel pressure monitoring system. Thismicrocontroller takes input from the device it is directing and controls thedevice through conveying signals to diverse components of the device 2.

The RF modulereceived data concerning pressure and temperature from the sensors through themicrocontroller and then transmit these signals to the display device and LEDindicator where necessary steps will be performed. The information gotten fromthese sensors are sent by the signal of radio-frequency to an electric controlunit which is located inside the racing car. When the pressure of the wheels isbeneath the level allowed, the pressure sensor will convey the data through theRF module to the electric control unit where the pressure drop value will bedisplayed. The LED indicator play a major role in monitoring the pressure andtemperature of the wheel of the racing car by alerting the driver in casecritical temperature and pressure is reached 6. ANALYSISThe componentsthat have been used in the design of wheel pressure monitoring system have beenanalysed in Table 1 below with consideration being taken of the component,cost, model, and quantity. Component Model Specification Cost Use Pressure Sensor Piezoresistive pressure sensor 0 to 15 psi $82.

00 This sensor will be used in determining the pressure of the wheels of the car. Temperature Sensor LM35 series Has a range of A temperature -550C to +1200C $75.00 A temperature sensor is a gadget used for detecting and measuring hotness and coolness and changes it into an electrical signal 7 RF Module ASK RF transmitter-receiver Frequency 433MHz or 315MHz $6.79 The RF module received data concerning pressure and temperature from the sensors through the microcontroller and then transmit these signals to the display device and LED indicator where necessary steps will be performed.

Digital-to-Analog converter TLV1572 Analog-to-Digital Converter 12-bit D/A converter $169.00 An analogue to digital converter is a device that is involved in the conversion of analogue signals such as temperature and pressure signals into the digital signal which is then fed to the microcontroller. Microcontroller PIC16C6x/7x 2048 bytes of EPROM, 128 bytes of RAM, and CPU running at 12 MHz $21.99 The microcontroller is involved in accepting data from the analogue to digital converter, manipulating the data and then produce the required results in this design of wheel pressure monitoring system.

Analog instrumentation amplifier MCP602 Model The frequency of about 10 Hz to 0.1 Hz. $50 This device reduces unwanted noise that might have been picked have been picked up by the circuit or by the sensors while converting pressure signals and heat signals into electrical signals 13. Display device TFT LCDs The appropriate size of the display device is 4 inches with the resolution of 800*600.  $4.20 The display shows the data of the quantity of pressure and temperature as determined by the pressure and temperature sensors Timer Digital clock Up to 180 minutes $8.

45 The timer is involved in the calculating of time during the period in which the racing car is in operation. LED indicator HWIP-2FQD The peak wavelength variations are up to + or -10nm and operates at a current of  20mA $17.09 The LED indicator play a major role in monitoring the pressure and temperature of the wheel of the racing car by alerting the driver in case critical temperature and pressure is reached 8.  ConclusionThisreport paper analyses a small sensor unit and analogy amplifier which ispositioned at the when of a racing car to monitor the pressure of the tire. Thematerials and technologies that are needed for this unit include pressuresensor, temperature sensor, RF module, Digital-to-Analog converter,microcontroller, analogue instrumentation amplifier, displaydevice, timer, and LED indicator.

The pressure sensor will be used indetermining the pressure of the wheels of the car. From input to the output, asensor may possess numerous steps of conversion before it generates theelectric signal. The temperature sensor is a used in measuring and detectingcoolness and hotness and converts it into an electrical signal.

The analogueinstrumentation amplifier assists in reducing unwanted noise that might havebeen picked have been picked up by the circuit or by the sensors whileconverting pressure signals and heat signals into electrical signals.

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