ay SENG 4315 Embedded Systems Fall 2017 Engineering preject to assess ABET outco

Question

ay SENG 4315 Embedded Systems Fall 2017 Engineering preject to assess ABET outcome E (ability to identify, formulate, and sohve engineering problem). Example We need to design an automatic embedded system that gives indication when the kitchen temperature is more than 95 F. It should also turn on an appropriate device to reduce the kitchen temperature. Identify: (Acknowledging the problem that it exists in domestic and commercial kitchens) Formulate: (Details of what needs to be done to address the problem (sensor, A/D, MC, display) considering the environment in which the solution will work (specification: input temperature)) Solve: (Propose the detail hardware and sofoware that will take care of what needs to be done) Rubric Exemplary (4) Accomplished Developing Beginning Barely Identify problem Clearly identified Identified problem Less clearly identified identified problem Less clearly formulated formulated problem problem Barely Formulate problem Clearly formulated problem Formulated problem oblem Less clearly Barely solved Clearly solved Solved problem Solve problem solved problem 1 problem oblem Submit a paper-based design. Consult section 13.3 of the text book to complete your design

Explanation / Answer

you can use following approch

Hardware Description Whole circuit can be divided into following sections:- (a) Power supply section: The regulated power supply section made with full wave rectifier (with IN 4007 diodes) using voltage regulator IC 7805 and IC 7812 which provide a constant voltage of 5V to the circuit as well as constant 12V to relays. (b) Analog to digital conversion section: Since we have to sense analog parameters i.e. temperature and light hence we have to use any analog to digital converter. We have opted for ADC 0809 as it has 8 channels and is microprocessor compatible ADC which is easily available [3]. It will convert the analog signal of the transducer to digital value with respect to the reference voltage which in our case is 2.5V. This reference voltage is obtained using TL431, which is a programmable shunt voltage reference with output voltage range of 2.5V to 36V and works like zener diode [4]. For the conversion ADC requires a reference frequency which is supplied from 555 IC in the form of astable oscillator. The conversion frequency is kept around 150 kHz. Sensor used for temperature measurement is LM 35 and for light intensity is LDR. LM 35 is calibrated in ºC and is linear in +10 mV/ ºC scale factor with 0.5ºC accuracy [5]. The calibration curve given here with will make the scenario clear. 30 A. Goswami, T. Bezboruah and K.C. Sarma Figure 2: Voltage vs. Temperature Calibration curve. For light intensity we have considered the reference voltage of ADC as standard. In that process 2.5V is considered as full light and 0V is considered as darkness. The light intensity is hence displayed in LCD as the reference voltage itself. (c) Controller section: The analog value is converted to digital value by ADC and is picked up by microcontroller AT89S52 which is a 40pin device. The AT89S52 is a low-power, high-performance CMOS 8-bit microcomputer with 8K bytes of Flash programmable and erasable read only memory (EPROM) [6]. (d) Display section: Since we need to display the data we get from microcontroller a liquid crystal display 44780 LCD is used which is a 2x16 line display [7] [8]. (e) Temperature control section: This section consists of a 12V relay to control hardware to start cooling for maintaining temperature as set by the user. [9] [10]. (f) Light control section: This section consists of another 12V relay to control hardware such an LED to glow at a particular voltage indicating darkness as set by the user. (g) Hardware controlling: Simple push buttons are used to set temperature and light intensity (in form of voltage) as well as to give the time of data transfer to the pc. (h) Data transfer: Displayed data of temperature and light intensity are transferred to RS 232 which is interfaced with microcontroller through MAX232 [11] [12]. Design of An Embedded System For Monitoring 31 Schematic diagram of the system is given below- 26 28 27 12 16 11 13 25 24 23 22 17 14 15 8 18 19 20 21 7 9 6 21 22 23 24 1 2 3 4 5 6 7 8 12 13 14 18 19 20 15 9 (RST) 40 31 5 6 35 34 33 32 555 8 4 7 3 6 2 1 1k 1k 22pf +5V +5V 39 38 37 36 1CD (16 X 1) LINC 1K BC 547 (NPN) RELAY +12V 2K2 D0 D1 D2D3 4 6 11 12 13 14 RS EN +5V T0 T1 T2 T3 10K +5V 10MF A B C EOC OE START 10 Tl431 Vref 2k2 25V I/P1 I/P2 1MF (10K)NTC Lm35 +5V 11 10 RXD TXD 2 3 5 10MF 10MF +Vcc +Vcc + _ + _ 1 3 12 11 4 5 16 2 6 13 14 DB 9 Pin Co BC 547 (NPN) RELAY +12V 2K2 1K 16 M A X 2 3 2 D4 D5 D6 D7 3 2 1 10K 130K +5V 1mf LDR 10k +5V Figure 3: Embedded Control Hardware Circuit --Schematic Diagram. 32 A. Goswami, T. Bezboruah and K.C. Sarma Figure 4.1: Embedded Control Hardware Circuit (Light display). Figure 4.2: Embedded Control Hardware Circuit (Temperature display). Software description Software development for the project consists of two main modules one being the online monitoring and controlling and other offline analysis based on data stored in computer .Presently this paper limits its work on first module keeping second module for future development Software is developed in both C and Assembly language. Algorithm for online monitoring and controlling of temperature: 1. First step is to initialize keys, Interrupt vectors panel and LCD Design of An Embedded System For Monitoring 33 2. Define port P3 of microcontroller ATMEL 89S52 as output port 3. Get data through ADC0809 from two different channels of Temperature and Light Intensity continuously after a fixed interval. 4. Value obtained from different channels converted to appropriate form of display 5. Display the appropriate values of Temperature and Light Intensity in LCD panel in Round Robin pattern 6. Start hardware devices for cooling if sensed temperature is higher than set temperature 7. New value of Temperature can be set using four keys as follows 7.1 Press first key for once to display existing value of temperature set and blink cursor at unit position 7.2 Press second key for increment in unit position 7.3 Press third key for shifting one position left at a time 7.4 Press fourth key for setting new temperature value replacing previous one 8. Start hardware device to glow a light if sensed light intensity is higher than the set value implying darkness. 9. New value of light intensity can be set using four keys as follows 9.1 Press first key twice to display existing value of light intensity set and blink cursor at unit position 9.2 Press second key once for increment in unit position 9.3 Press third key once for shifting one position left at a time 9.4 Press fourth key once for setting new temperature value replacing previous one 10. New value of transfer rate of data to RS232 is set using keypad as follows 10.1 Press first key thrice for display existing value of transfer rate set and blink cursor at unit position 10.2 Press second key for increment in unit position 10.3 Press third key for shifting one position left at a time 10.4 Press fourth key for setting new transfer rate of data to RS232 11. Return to step 3

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