Temperature Monitoring System Final

1. INTRODUCTION This project explains about a simple low cost circuit which can be mainly used in large scale industries to detect the high temperature and take immediate measures. This circuit is used to sense the temperature at a place. It indicates the temperature on the LCD with the help of microcontroller. This circuit makes use of LM35 which is a 3 pin centigrade temperature sensor IC. It directly senses the temperature and sends the data to the controller. The block diagram of temperature monitoring system consists of temperature sensor, ADC, microcontroller and LCD. LM35 is used as temperature sensor it senses the temperature. The output of Temperature sensor is in the form of analog signal. ADC0804 is used to convert this analog signal to digital. The output of ADC is given to the Microcontroller. The output of controller will be displayed on the LCD The complete project is built around the 8051 micro controller. PCB Wizard Schematic generation software is employed to prepare the schematic for development of project. Hardware is built according to schematic prepared by soldering each component on the general purpose PCB. Source code is developed using Keil micro vision software. µVision is an IDE (Integrated Development Environment) that helps you write, compile, and debug embedded programs. The written source code is dumped into the microcontroller IC using a Programmer. To dump the code into microcontroller micro C Flash software is used.

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BLOCK DIAGRAM

TEMPERATURE SENSOR 8051

LCD DISPLAY

MICRO CONTROLLER

ADC0804

Figure 1.1: Block diagram of temperature monitoring system 1.1 DESCRIPTION: The block diagram of temperature monitoring system consists of temperature sensor, ADC, microcontroller and LCD. LM35 is used as temperature sensor it senses the temperature. The output of Temperature sensor is in the form of analog signal. ADC0804 is used to convert this analog signal to digital. The output of ADC is given to the Microcontroller. The output of controller will be displayed on the LCD.

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SCHEMATIC

Figure 1.2: Schematic of temperature monitoring system

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2. HARDWARE DESCRIPTION 2.1 REGULATED POWERSUPPLY: A variable regulated power supply, also called a variable bench power supply, is one where you can continuously adjust the output voltage to your requirements. Varying the output of the power supply is the recommended way to test a project after having double checked parts placement against circuit drawings and the parts placement guide. This type of regulation is ideal for having a simple variable bench power supply. Actually this is quite important because one of the first projects a hobbyist should undertake is the construction of a variable regulated power supply. While a dedicated supply is quite handy e.g. 5V or 12V, it's much handier to have a variable supply on hand, especially for testing. Most digital logic circuits and processors need a 5 volt power supply. To use these parts we need to build a regulated 5 volt source. Usually you start with an unregulated power supply ranging from 9 volts to 24 volts DC (A 12 volt power supply is included with the Beginner Kit and the Microcontroller Beginner Kit.). To make a 5 volt power supply, we use a LM7805 voltage regulator IC (Integrated Circuit). The IC is shown below CIRCUIT FEATURES Brief description of operation: Gives out well regulated +5V output, output current capability of 100 mA Circuit protection: Built-in overheating protection shuts down output when regulator IC gets too hot Circuit complexity: Very simple and easy to build Circuit performance: Very stable +5V output voltage, reliable operation

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Availability of components: Easy to get, uses only very common basic components Design testing: Based on datasheet example circuit, I have used this circuit successfully as part of many electronics projects Applications: Part of electronics devices, small laboratory power supply Power supply voltage: Unregulated DC 8-18V power supply Power supply current: Needed output current + 5 mA Component costs: Few dollars for the electronics components + the input transformer cost

BLOCK DIAGRAM:

Figure 2.1: Block diagram of power supply

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POWER SUPPLY CIRCUIT DIAGRAM:

Figure 2.2: Circuit diagram of power supply

POWER SUPPLY REQUIREMENTS:

Figure 2.3: Power Supply Requirements 2.1.1 POWER SUPPLY CIRCUIT DESCRIPTION: Above is the circuit of a basic unregulated dc power supply. A bridge rectifier D1 to D4 rectifies the ac from the transformer secondary, which may also be a block rectifier such as WO4 or even four individual diodes such as 1N4004 types. (See later re rectifier ratings).

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The principal advantage of a bridge rectifier is you do not need a centre tap on the secondary of the transformer. A further but significant advantage is that the ripple frequency at the output is twice the line frequency (i.e. 50 Hz or 60 Hz) and makes filtering somewhat easier. As a design example consider we wanted a small unregulated bench supply for our projects. Here we will go for a voltage of about 12 - 13V at a maximum output current (IL) of 500ma (0.5A). Maximum ripple will be 2.5% and load regulation is 5%. Now the RMS secondary voltage (primary is whatever is consistent with your area) for our power transformer T1 must be our desired output Vo PLUS the voltage drops across D2 and D4 (2 * 0.7V) divided by 1.414. This means that Vsec = [13V + 1.4V] / 1.414 which equals about 10.2V. Depending on the VA rating of your transformer, the secondary voltage will vary considerably in accordance with the applied load. The secondary voltage on a transformer advertised as say 20VA will be much greater if the secondary is only lightly loaded. If we accept the 2.5% ripple as adequate for our purposes then at 13V this becomes 13 * 0.025 = 0.325 Vrms. The peak to peak value is 2.828 times this value. Vrip = 0.325V X 2.828 = 0.92 V and this value is required to calculate the value of C1. Also required for this calculation is the time interval for charging pulses. If you are on a 60Hz system it it 1/ (2 * 60) = 0.008333 which is 8.33 milliseconds. For a 50Hz system it is 0.01 sec or 10 milliseconds. Remember the tolerance of the type of capacitor used here is very loose. The important thing to be aware of is the voltage rating should be at least 13V X 1.414 or 18.33. Here you would use at least the standard 25V or higher (absolutely not 16V).With our rectifier diodes or bridge they should have a PIV rating of 2.828 times the Vsec or at least 29V. Don't search for this rating because it doesn't exist. Use the next highest standard or even higher. The 7

current rating should be at least twice the load current maximum i.e. 2 X 0.5A or 1A. A good type to use would be 1N4004, 1N4006 or 1N4008 types. These are rated 1 Amp at 400PIV, 600PIV and 1000PIV respectively. Always be on the lookout for the higher voltage ones when they are on special. TRANSFORMER RATING: In our example above we were taking 0.5A out of the Vsec of 10V. The VA required is 10 X 0.5A = 5VA. This is a small PCB mount transformer available in Australia and probably elsewhere. This would be an absolute minimum and if you anticipated drawing the maximum current all the time then go to a higher VA rating. The two capacitors in the primary side are small value types and if you don't know precisely and I mean precisely what you are doing then OMIT them. Their loss won't cause you heartache or terrible problems. The fuse F1 must be able to carry the primary current but blow under excessive current; in this case we use the formula from the diagram. Here N = 240V / 10V or perhaps 120V / 10V. The fuse calculates in the first instance to [ 2 X 0.5A ] / [240 / 10] or .04A or 40 ma. In the second case .08A or 80 ma. The difficulty here is to find suitable fuses of that low a current and voltage rating. In practice you use the closest you can get (often 100 ma). Don't take that too literal and use 1A or 5A fuses. 2.1.2 LM 7805: DESCRIPTION: The LM7804 series of three terminal positive regulators are available in the TO-220/D-PAK package and with several fixed output voltages, making them useful in a wide range of applications. Each type employs internal current limiting, thermal shut down and safe operating area protection, making it essentially indestructible. If adequate heat sinking is provided, they can deliver 8

over 1A output current. Although designed primarily as fixed voltage regulators, these devices can be used with external components to obtain adjustable voltages and currents.

Figure 2.4 General view of Regulator FEATURES: • Output Current up to 1A • Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V • Thermal Overload Protection • Short Circuit Protection • Output Transistor Safe Operating Area Protection WORKING: Voltage regulator limits the voltage that passes through it. Each regulator has a voltage rating; For example, the 7805 IC (these regulators are often considered to be ICs) is a 5-volt voltage regulator. What that means is that no matter how many volts you put into it, it will output only 5 volts. This means that you can connect a 9-volt battery, a 12-volt power supply, or virtually anything else that's over 5 volts, and have the 7805 give you a nice supply of 5 volts out. There are also 7812 (12-volt) and 7815 (15-volt) threepin regulators in common use. The pin-out for a three pin voltage regulator is as follows: 1.Voltage-in 2.Ground 3.Voltage out

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For example, with a 9-volt battery, you'd connect the positive end to pin 1 and the negative (or ground) end to pin 2. A 7805 would then give you +5 volts on pin 3.Voltage regulators are simple and useful. There are only two important drawbacks to them: First, the input voltage must be higher than the output voltage. For example, you cannot give a 7805 only 2 or 3 volts and expect it to give you 5 volts in return. Generally, the input voltage must be at least 2 volts higher than the desired output voltage, so a 7805 would require about 7 volts to work properly. The other problem: The excess voltage is dissipated as heat. At low voltages (such as using a 9-volt battery with a 7805), this is not a problem. At higher voltages, however, it becomes a very real problem and you must have some way of controlling the temperature so you don't melt your regulator. This is why most voltage regulators have a metal plate with a hole in it; That plate is intended for attaching a heat sink to-Do not confuse three-pin voltage regulators with a device known as a TRIAC (short for triode AC switch). It is easy to associate them with each other, since they look similar (both have three pins) and they both regulate power. However, the 78XX types of regulators are used for regulating DC current, while TRIACs are used for AC current. 2.1.3 LIGHT EMITTING DIODE (LED): LED's are special diodes that emit light when connected in a circuit. They are frequently used as "pilot" lights in electronic appliances to indicate whether the circuit is closed or not. A clear (or often colored) epoxy case enclosed the heart of an LED, the semi-conductor chip.

Figure 2.5 LED View

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Figure 2.6 LED Symbol

LED’s must be connected the correct way round, the diagram may be labeled a or + for anode and k or - for cathode. The negative side of an LED lead is indicated in two ways:

Figure 2.7 LED Internal View 1) By the flat side of the bulb. 2) By the shorter of the two wires extending from the LED. If you can see inside the LED the cathode is the larger electrode (but this is not an official identification method). The negative lead should be connected to the negative terminal of a battery. LED's operate at relative low voltages between about 1 and 4 volts, and draw currents between about 10 and 40 mille amperes. Voltages and currents substantially about these values can melt a LED chip. The most important part of light emitting diode (LED) is the semi-conductor chip located in the center of the bulb as shown below. The chip has two regions separated by a junction. The p region is dominated by positive electric charges, and the n region is dominated by negative electric charges. The junction acts as a barrier to the flow of electrons between the p and n regions. Only when sufficient voltage is applied to the semi-conductor chip, can the current flow and the electron cross the junction into the p region? In the absence of the large enough electric potential difference (voltage) across the LED leads, the junction presents an electric potential barrier to the flow of electrons.

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2.2 General Description of LM35: The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in ˚ Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centi-grade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±1⁄4˚C t room temperature and ±3⁄4˚C over a full −55 to +150˚C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM35’s low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies, or with plus and minus supplies. As it draws only 60 µA from its supply, it has very low self-heating, less than 0.1˚C in still air. The LM35 is rated to operate over a −55˚ to +150˚C temperature range, while the LM35C is rated for a −40˚ to +110˚C range (−10˚ with improved accuracy). The LM35 series is available pack-aged in hermetic TO-46 transistor packages, w LM35C, LM35CA, and LM35D are also available plastic TO-92 transistor package. The LM35D is al able in an 8-lead surface mount small outline package plastic TO-220 package. 2.2.1 Features: •

Calibrated directly in ˚ Celsius (Centigrade)

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Linear + 10.0 mV/˚C scale factor

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0.5˚C accuracy guarantee able (at +25˚C)

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Rated for full −55˚ to +150˚C range

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Suitable for remote applications

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Low cost due to wafer-level trimming

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Operates from 4 to 30 volts

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Less than 60 µA current drain

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Low self-heating, 0.08˚C in still air

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Nonlinearity only ±1⁄4˚C typical

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Low impedance output, 0.1 Ω for 1 mA load

Figure 2.8 Bottom View of LM35 2.2.2 Applications The LM35 can be applied easily in the same way as other integratedcircuit temperature sensors. It can be glued or cemented to a surface and its temperature will be within about 0.01˚C of the surface temperature. This presumes that the ambient air temperature is almost the same as the surface temperature; if the air temperature were much higher or lower than the surface temperature, the actual temperature of the LM35 die would be at an intermediate temperature between the surface temperature and the air temperature. This is especially true for the TO-92 plastic package, where the copper leads are the principal thermal path to carry heat into the device, so its temperature might be closer to the air temperature than to the surface temperature. To minimize this problem, be sure that the wiring to the LM35, as it leaves the device, is held at the same temperature as the surface of interest. The easiest way to do this is to cover up these wires with a bead of epoxy which will insure that the leads and wires are all at the same temperature as the surface, and that the LM35 die’s temperature will not be affected by the air temperature. The TO-46 metal package can also be soldered to a metal surface or pipe without damage. Of course, in that case the V− terminal of the circuit will be grounded to that metal. Alternatively, the LM35 can be mounted inside a sealed-end metal tube, and can then be dipped into a bath or screwed into a threaded hole in a tank. As with any IC, the LM35 and accompanying wiring and circuits must be kept insulated and dry, to avoid leakage and corrosion. This is especially true if the circuit may operate at cold temperatures where condensation can occur. Printed-circuit coatings and varnishes such as Hum seal and epoxy paints or dips are often used to insure

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that moisture cannot corrode the LM35 or its connections. These devices are sometimes soldered to a small light-weight heat fin, to decrease the thermal time constant and speed up the response in slowly-moving air. On the other hand, a small thermal mass may be added to the sensor, to give the steadiest reading despite small deviations in the air temperature. 2.3 General Description for ADC: The ADC0804 are CMOS 8-bit successive approximation A/D converters that use a differential potentiometric ladder—similar to the 256R products. These converters are designed to allow operation with the NSC800 and INS8080A derivative control bus with TRI-STATE output latches directly driving the data bus. These A/Ds appear like memory locations or I/O ports to the microprocessor and no interfacing logic is needed. Differential analog voltage inputs allow increasing the common-mode rejection and offsetting the analog zero input voltage value. In addition, the voltage reference input can be adjusted to allow encoding any smaller analog voltage span to the full 8 bits of resolution. Features: •

Compatible with 8080 µP derivatives—no interfacing logic needed access time - 135 ns

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Easy interface to all microprocessors, or operates “stand alone”

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Differential analog voltage inputs

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Logic inputs and outputs meet both MOS and TTL voltage level specifications

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Works with 2.5V (LM336) voltage reference

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On-chip clock generator

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0V to 5V analog input voltage range with single 5V supply

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No zero adjust required

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0.3" standard width 20-pin DIP package

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20-pin molded chip carrier or small outline package

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Operates ratio metrically or with 5 VDC, 2.5 VDC, or analog span adjusted voltage reference

Figure 2.9 Pin Description of Adc0804

2.4 MICROCONTROLLER AT89S52: The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8k bytes of in-system programmable Flash memory. The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard 80C51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications. The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89S52 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 interrupt system to continue functioning. The Power-down mode saves the

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RAM con- tents but freezes the oscillator, disabling all other chip functions until the next interrupt or hardware reset. 2.4.1 FEATURES: •

• COMPATIBLE WITH MCS-51®

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PRODUCTS

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• 8K BYTES OF IN-SYSTEM PROGRAMMABLE (ISP) FLASH MEMORY

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– ENDURANCE: 1000 WRITE/ERASE CYCLES

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• 4.0V TO 5.5V OPERATING RANGE

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• FULLY STATIC OPERATION: 0 HZ TO 33 MHZ

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• THREE-LEVEL PROGRAM MEMORY LOCK

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• 256 X 8-BIT INTERNAL RAM

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• 32 PROGRAMMABLE I/O LINES

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• THREE 16-BIT TIMER/COUNTERS

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• EIGHT INTERRUPT SOURCES

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• FULL DUPLEX UART SERIAL CHANNEL

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• LOW-POWER IDLE AND POWER-DOWN MODES

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• INTERRUPT RECOVERY FROM POWER-DOWN MODE

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• WATCHDOG TIMER

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• DUAL DATA POINTER

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• POWER-OFF FLAG

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PIN CONFIGURATION: • •

Figure 2.10 Pin Description of 8051 Microcontroller

2.4.2 Pin Description: VCC: Supply voltage. GND: Ground. Port 0: Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high-impedance inputs. Port 0 can also be configured to be the 17

multiplexed low-order address/data bus during accesses to external program and data memory. In this mode, P0 has internal pull-ups. Port 0 also receives the code bytes during Flash programming and outputs the code bytes during program verification. External pull-ups are required during program verification. Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups. In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external count input (P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively, as shown in the following table. Port 1 also receives the low-order address bytes during Flash programming and verification

Table 2.1 Port 1 Pins Functions Port 2: Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current 18

(IIL) because of the internal pull-ups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that uses 16-bit addresses (MOVX @ DPTR). In this application, Port 2 uses strong internal pull-ups when emitting 1s. During accesses to external data memory that uses 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the high-order address bits and some control signals during Flash programming and verification. Port 3: Port 3 is an 8-bit bidirectional I/O port with internal pullups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pullups. Port 3 also serves the functions of various special features of the AT89S52, as shown in the following table. Port 3 also receives some control signals for Flash pro-gramming and verification.

Table 2.2 Port 3 Pins Functions RST:

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Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device. This pin drives High for 96 oscillator periods after the Watchdog times out. The DISRTO bit in SFR AUXR (address 8EH) can be used to disable this feature. In the default state of bit DISRTO, the RESET HIGH out feature is enabled.

ALE/PROG: Address Latch Enable (ALE) is an output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming.

In normal operation, ALE is

emitted at a constant rate of 1/6 the oscillator frequency and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external data memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode. Weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode. PSEN: Program Store Enable (PSEN) is the read strobe to external program memory. When the AT89S52 is executing code from external pro-gram memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory. Program Store Enable (PSEN) is the read strobe to external program memory. When the AT89S52 is executing code from external pro- gram memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory. Note, however, that if lock bit 1 is programmed, EA w internally latched on reset. EA should be strapped to VCC

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for internal programming. This pin also receives the 12-volt programming enable age (VPP) during Flash programming. XTAL1: Input to the inverting oscillator amplifier and input internal clock operating circuit.

XTAL2: Output from the inverting oscillator amplifier. Special Function Registers: A map of the on-chip memory area called the Special Function Register (SFR) space is. Note that not all of the addresses are occupied, and unoccupied addresses may not be implemented on the chip. Read accesses to these addresses will in general return random data, and write accesses will have an indeterminate effect. User software should not write 1s to these unlisted locations, since they may be used in future products to invoke new features. In that case, the reset or inactive values of the new bits will always be 0. Timer 2 Registers: Control and status bits are contained in registers T2CON (shown in Table 2) and T2MOD (shown in Table 3) for Timer 2. The register pair (RCAP2H, RCAP2L) are the Capture/Reload registers for Timer 2 in 16-bit capture mode or 16-bit auto-reload mode. Interrupt Registers: The individual interrupt enable bits are in the IE register. Two priorities can be set for each of the six interrupt sources in the IP register. Dual Data Pointer Registers: To facilitate accessing both internal and external data memory, two banks of 16-bit Data Pointer Registers are provided: DP0 at SFR address locations 82H-83H and DP1 at 84H-85H. Bit DPS = 0 in SFR AUXR1 selects DP0 and

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DPS = 1 selects DP1. The user should always initialize the DPS bit to the appropriate value before accessing the respective Data Pointer Register. Power off Flag: The Power off Flag (POF) is located at bit 4 (PCON.4) in the PCON SFR. POF is set to “1” during power up. It can be set and rest under software control and is not affected by reset.

Memory Organization: MCS-51 devices have a separate address space for Program and Data Memory. Up to 64K bytes each of external Program and Data Memory can be addressed. Program Memory: If the EA pin is connected to GND, all program fetches are directed to external memory. On the AT89S52, if EA is connected to VCC, program fetches to addresses 0000H through 1FFFH are directed to internal memory and fetches to addresses 2000H through FFFFH are to external memory. Data Memory: The AT89S52 implements 256 bytes of on-chip RAM. The upper 128 bytes occupy a parallel address space to the Special Function Registers. This means that the upper 128 bytes have the same addresses as the SFR space but are physically separate from SFR space. When an instruction accesses an internal location above address 7FH, the address mode used in the instruction specifies whether the CPU accesses the upper 128 bytes of RAM or the SFR space. Instructions which use direct addressing access of the SFR space. For example, the following direct addressing instruction accesses the SFR at location 0A0H (which is P2). MOV 0A0H, #data:

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Instructions that use indirect addressing access the upper 128 bytes of RAM. For example, the following indirect addressing instruction, where R0 contains 0A0H, accesses the data byte at address 0A0H, rather than P2 (whose address is 0A0H). MOV @R0, #data: Note that stack operations are examples of indirect addressing, so the upper 128 bytes of data RAM are available as stack space.

Watchdog Timer: (One-time Enabled with Reset-out) The WDT is intended as a recovery method in situations where the CPU may be subjected to software upsets. The WDT consists of a 13-bit counter and the Watchdog Timer Reset (WDTRST) SFR. The WDT is defaulted to disable from exiting reset. To enable the WDT, a user must write 01EH and 0E1H in sequence to the WDTRST register (SFR location 0A6H). When the WDT is enabled, it will increment every machine cycle while the oscillator is running. The WDT timeout period is dependent on the external clock frequency. There is no way to disable the WDT except through reset (either hardware reset or WDT over-flow reset). When WDT overflows, it will drive an output RESET HIGH pulse at the RST pin. Using the WDT: To enable the WDT, a user must write 01EH and 0E1H in sequence to the WDTRST register (SFR location 0A6H). When the WDT is enabled, the user needs to service it by writing 01EH and 0E1H to WDTRST to avoid a WDT over-flow. The 13-bit counter overflows when it reaches 8191 (1FFFH), and this will reset the device. When the WDT is enabled, it will increment every machine cycle while the oscillator is running. This means the user must reset the WDT at least every 8191 machine cycles. To reset the WDT the user must write 01EH and 0E1H to WDTRST. WDTRST is a write-only register. The WDT counter cannot be read or written. When WDT overflows, it will 23

generate an output RESET pulse at the RST pin. The RESET pulse duration is 96xTOSC, where TOSC=1/FOSC. To make the best use of the WDT, it should be serviced in those sections of code that will periodically be executed within the time required to prevent a WDT reset. WDT during Power-down and Idle In Power-down mode the oscillator stops, which means the WDT also stops. While in Power-down mode, the user does not need to service the WDT. There are two methods of exiting Power-down mode: by a hardware reset or via a level-activated external interrupt which is enabled prior to entering Powerdown mode. When Power-down is exited with hardware reset, servicing the WDT should occur as it normally does whenever the AT89S52 is reset. Exiting Power-down with an interrupt is significantly different. The interrupt is held low long enough for the oscillator to stabilize. When the interrupt is brought high, the interrupt is serviced. To prevent the WDT from resetting the device while the interrupt pin is held low, the WDT is not started until the interrupt is pulled high. It is suggested that the WDT be reset during the interrupt service for the interrupt used to exit Power-down mode. To ensure that the WDT does not overflow within a few states of exiting Power-down, it is best to reset the WDT just before entering Power-down mode. Before going into the IDLE mode, the WDIDLE bit in SFR AUXR is used to determine whether the WDT continues to count if enabled. The WDT keeps counting during IDLE (WDIDLE bit = 0) as the default state. To prevent the WDT from resetting the AT89S52 while in IDLE mode, the user should always set up a timer that will periodically exit IDLE, service the WDT, and reenter IDLE mode. With WDIDLE bit enabled, the WDT will stop to count in IDLE mode and resumes the count upon exit from IDLE. UART: The UART in the AT89S52 operates the same way as the UART in the AT89C51 and AT89C52. For further information on the UART operation, refer to the ATMEL Web site (http://www.atmel.com). From the home page, select ‘Products’, then ‘8051-Architecture Flash Microcontroller’, then ‘Product Overview’. Timer 0 and 1: 24

Timer 0 and Timer 1 in the AT89S52 operate the same way as Timer 0 and Timer 1 in the AT89C51 and AT89C52. For further information on the timers’ operation, refer to the ATMEL Web site (http://www.atmel.com). From the home page, select ‘Products’, then ‘8051-Architecture Flash Microcontroller’, then ‘Product Overview’. Timer 2: Timer 2 is a 16-bit Timer/Counter that can operate as either a timer or an event counter. The type of operation is selected by bit C/T2 in the SFR T2CON (shown in Table 2). Timer 2 has three operating modes: capture, auto-reload (up or down counting), and baud rate generator. The modes are selected by bits in T2CON Timer 2 consists of two 8-bit registers, TH2 and TL2. In the Timer function, the TL2 register is incremented every machine cycle. Since a machine cycle consists of 12 oscillator periods, the count rate is 1/12 of the oscillator frequency.

Table 2.3 Timer 2 Operating Modes In the Counter function, the register is incremented in response to a 1-to-0 transition at its corresponding external input pin, T2. In this function, the external input is sampled during S5P2 of every machine cycle. When the samples show a high in one cycle and a low in the next cycle, the count is incremented. The new count value appears in the register during S3P1 of the cycle following the one in which the transition was detected. Since two machine cycles (24 oscillator periods) are required to recognize a 1-to-0 transition, the maximum count rate is 1/24 of the oscillator frequency. To ensure that a given level is sampled at least once before it changes, the level should be held for at least one full machine cycle.

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2.4.3 MICROPROCESSORS Vs MICROCONTROLLERS: Microprocessor has following instructions to perform: 1. Reading instructions or data from program memory ROM. 2. Interpreting the instruction and executing it. 3. Microprocessor Program is a collection of instructions stored in a Nonvolatile memory. 4. Read Data from I/O device 5. Process the input read, as per the instructions read in program memory. NECESSITY OF MICROCONTROLLERS: Microprocessors brought the concept of programmable devices and made many applications of intelligent equipment. Most applications, which do not need large amount of data and program memory, tended to be: Costly:

The microprocessor system had to satisfy the data and program

requirements so, sufficient RAM and ROM are used to satisfy most applications .The peripheral control equipment also had to be satisfied. Therefore, almost all-peripheral chips were used in the design. Because of these additional peripherals cost will be comparatively high. An example: 8085 chip needs: An Address latch for separating address from multiplex address and data.32-KB RAM and 32-KB ROM to be able to satisfy most applications. As also Timer / Counter, Parallel programmable port, Serial port, and Interrupt controller are needed for its efficient applications. In comparison a typical Micro controller 8051 chip has all that the 8051 board has except a reduced memory as follows. 4K bytes of ROM as compared to 32-KB, 128 Bytes of RAM as compared to 32-KB. Bulky: On comparing a board full of chips (Microprocessors) with one chip with all components in it (Micro controller). Debugging: Lots of Micro-processor circuitry and program to debug. In Micro controller there is no Microprocessor circuitry to debug. Slower Development time: As we have observed Microprocessors need a lot of debugging at board level and

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at program level, where as, Micro controller do not have the excessive circuitry and the built-in peripheral chips are easier to program for operation. So peripheral devices like Timer/Counter, Parallel programmable port, Serial Communication Port, Interrupt controller and so on, which were most often used were integrated with the Microprocessor to present the Micro controller RAM and ROM also were integrated in the same chip. The ROM size was anything from 256 bytes to 32Kb or more. RAM was optimized to minimum of 64 bytes to 256 bytes or more.

Typical Microcontroller Features:  8/16/32 CPU  Instruction set rich in I/O & bit operations.  One or more I/O ports.  One or more timer/counters.  One or more interrupt inputs and an interrupt controller  One or more serial communication ports.  Analog to Digital /Digital to Analog converter  One or more PWM output  Network controlled interface

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Figure 2.11 Block diagram of 8051 Microcontroller

2.4.4 Types of memory: The 8051 have three general types of memory. They are on-chip memory, external Code memory and external Ram. On-Chip memory refers to physically existing memory on the micro controller itself. External code memory is the code memory that resides off chip. This is often in the form of an external EPROM. External RAM is the Ram that resides off chip. This often is in the form of standard static RAM or flash RAM. a) Code memory: Code memory is the memory that holds the actual 8051 programs that is to be run. This memory is limited to 64K. Code memory may be found on-

28

chip or off-chip. It is possible to have 4K of code memory on-chip and 60K off chip memory simultaneously. If only off-chip memory is available then there can be 64K of off chip ROM. This is controlled by pin provided as EA b) Internal RAM: The 8051 have a bank of 128 bytes of internal RAM. The internal RAM is found on-chip. So it is the fastest Ram available. And also it is most flexible in terms of reading and writing. Internal Ram is volatile, so when 8051 is reset, this memory is cleared. 128 bytes of internal memory are subdivided. The first 32 bytes are divided into 4 register banks. Each bank contains 8 registers. Internal RAM also contains 128 bits, which are addressed from 20h to 2Fh. These bits are bit addressed i.e. each individual bit of a byte can be addressed by the user. They are numbered 00h to 7Fh. The user may make use of these variables with commands such as SETB and CLR 2.4.5 INTERRUPTS: Interrupts are hardware signals that are used to determine conditions that exist in external and internal circuits. Any interrupt can cause the 8051 to perform a hardware call to an interrupt –handling subroutine that is located at a predetermined absolute address in the program memory. Five interrupts are provided in the 8051. Three of these are generated automatically by the internal operations: Timer flag 0, Timer Flag 1, and the serial port interrupt (RI or TI) Two interrupts are triggered by external signals provided by the circuitry that is connected to the pins INTO 0 and INTO1. The interrupts maybe enable or disabled, given priority or otherwise controlled by altering the bits in the Interrupt Enabled (IE) register, Interrupt Priority (IP) register, and the Timer Control (TCON) register. . These interrupts are mask able i.e. they can be disabled. Reset is a non maskable interrupt which has the highest priority. It is generated when a high is applied to the reset pin. Upon reset, the registers are loaded with the default values. Each interrupt source causes the program to do store the address in PC onto the stack and causes a hardware call to one of the dedicated addresses in the

29

program memory. The appropriate memory locations for each for each interrupt are as follows: Interrupt

Address

RESET

0000

IE0 (External interrupt 0)

0003

TF0 (Timer 0 interrupt)

000B

IE1 (External interrupt 1)

0013

TF1 (Timer 1 interrupt)

001B

SERIAL

0023

Functions of micro controller in main unit are 1.

Sends appropriate commands to ADC to start conversion,

2.

Collects the output of ADC for every 10 sec and stores in buffer,

3.

Sends command to the modem for dialing the base every 80 sec,

4.

Sends data in a serial manner to MODEM,

5.

After data gets transmitted sends command for disconnection.

6.

Sends appropriate information to the display unit as per status of the

communication medium.

2.5 LIQUID CRYSTAL DISPLAY (LCD):

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Figure 2.12 Liquid Crystal Display •

Vcc, at pin 16 controls the background contrast.

•

Vcc, at pin 2 controls the display contrast.

•

Pin 7 - 14 gets input data.

•

Pin 1 and pin 3 controls the brightness of the display.

•

Pin 5, gets a read/write signal.

•

Pin 6, enable signal.

•

Pin 4, data register select.

Figure 2.13 LCD Pins

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Table 2.4 Pin Assignment Interfacing Example - 16 Character x 2 Line LCD 2.5.1 Description: This is the first interfacing example for the Parallel Port. We will start with something simple. This example doesn't use the Bi-directional feature found on newer ports, thus it should work with most, if no all Parallel Ports. It however doesn't show the use of the Status Port as an input. So what are we interfacing? A 16 Character x 2 Line LCD Module to the Parallel Port. These LCD Modules are very common these days, and are quite simple to work with, as all the logic required running them is on board. Schematic:

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Figure 2.14 Schematic of LCD Circuit Description: Above is the quite simple schematic. The LCD panel's Enable and Register Select is connected to the Control Port. The Control Port is an open collector / open drain output. While most Parallel Ports have internal pull-up resistors, there are a few which don't. Therefore by incorporating the two 10K external pull up resistors, the circuit is more portable for a wider range of computers, some of which may have no internal pull up resistors. We make no effort to place the Data bus into reverse direction. Therefore we hard wire the R/W line of the LCD panel, into write mode. This will cause no bus conflicts on the data lines. As a result we cannot read back the LCD's internal Busy Flag which tells us if the LCD has accepted and finished processing the last instruction. This problem is overcome by inserting known delays into our program. The 10k Potentiometer controls the contrast of the LCD panel. Nothing fancy here. As with all the examples, I've left the power supply out. You can use a bench power supply set to 5v or use a onboard +5 regulator. Remember a few de-coupling capacitors, especially if you have trouble with the circuit working properly. The 2 line x 16 character LCD modules are available from a wide range of manufacturers and should all be compatible

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with the HD44780. The one I used to test this circuit was a Power trip PC1602F and an old Philips LTN211F-10 which was extracted from a Poker Machine! The diagram to the right shows the pin numbers for these devices. When viewed from the front, the left pin is pin 14 and the right pin is pin The LCD panel requires a few instructions to be sent, to order to turn on the display and initialize it. This is what the first for loop does. These instructions must be sent to the LCD's Instruction Register which is controlled by the Register Select (Pin 4). When pin 4 is low the instruction register is selected, thus when high the data register must be selected. We connect this to the Parallel Port's Select Printer line which happens to be hardware inverted. Therefore if we write a '1' to bit 3 of the Control Register the Select Printer line goes low. We want to first send instructions to the LCD module. Therefore the Register Select line must be low. As it is hardware inverted, we will want to set bit 3 of the Control Register to '1'. However we don't want to upset any other bits on the Control Port. We achieve this by reading the Control Port and Oaring 0x80 to it. E.g. out port (CONTROL, in port b (CONTROL) | 0x08); this will only set bit 3. After we place a data byte on the data lines, we must then signal to the LCD module to read the data. This is done using the Enable line. Data is clocked into the LCD module on the high to low transition. The Strobe is hardware inverted, thus by setting bit 0 of the Control Register we get a high to low transition on the Strobe line. We then wait for a delay, and return the line to a high state ready for the next byte. After we initialize the LCD Module, we want to send text to it. Characters are sent to the LCD's Data Port, thus we want to clear bit 3. Once again we must only change the one bit, thus we use out port b (CONTROL, in port b(CONTROL) & 0xF7);. Then we set up another for loop to read a byte from the string and send it to the LCD panel. This is repeated for the length of the string.

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The delays should be suitable for most machines. If the LCD panel is not initializing properly, you can try increasing the delays. Likewise if the panel is skipping characters, e.g. Test, 2. On the other hand, if the LCD module is repeating characters e.g. testing then you may have a faulting Enable connection. Check your Enable to Strobe connection.

3. SOFTWARE DESCRIPTION 3.1 TEST PLAN:

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•

Check the power supply connections

•

Insert smart card in to the smart card reader

•

Check LEDs

•

Check Microcontroller minimum requirements

•

Welcome message will be printed on LCD

•

Consumed units and available units are displayed on LCD

•

A message will be displayed if there is no smart card

3.2 ASSEMBLY LANGUAGE PROGRAM: Software’s used are: 1. Keil software for c programming 2. Express PCB for lay out design 3. Express SCH for schematic design What's New in µVision3? µVision3 adds many new features to the Editor like Text Templates, Quick Function Navigation, Syntax Coloring with brace highlighting Configuration Wizard for dialog based startup and debugger setup. µVision3 is fully compatible to µVision2 and can be used in parallel with µVision2. What is µVision3? µVision3 is an IDE (Integrated Development Environment) that helps you write, compile, and debug embedded programs. It encapsulates the following components: •

A project manager.

•

A make facility.

•

Tool configuration.

•

Editor.

•

A powerful debugger.

To help you get started, several example programs (located in the \C51\Examples, \C251\Examples, \C166\Examples, and \ARM\...\Examples) are provided.

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•

HELLO is a simple program that prints the string "Hello World" using the Serial Interface.

•

MEASURE is a data acquisition system for analog and digital systems.

•

TRAFFIC is a traffic light controller with the RTX Tiny operating system.

•

SIEVE is the SIEVE Benchmark.

•

DHRY is the Dhrystone Benchmark.

•

WHET is the Single-Precision Whetstone Benchmark.

Additional example programs not listed here are provided for each device architecture. Building an Application in µVision2 To build (compile, assemble, and link) an application in µVision2, you must: •

Select Project for example,166\EXAMPLES\HELLO\HELLO.UV2).

•

Select Project - Rebuild all target files or Build target. µVision2 compiles, assembles, and links the files in your project.

Creating Your Own Application in µVision2 To create a new project in µVision2, you must: 1. Select Project - New Project. 2. Select a directory and enter the name of the project file. 3. Select Project - Select Device and select an 8051, 251, or C16x/ST10 device from the Device Database™. 4. Create source files to add to the project. 5. Select Project - Targets, Groups, Files. Add/Files, select Source Group1, and add the source files to the project. 6. Select Project - Options and set the tool options. Note when you select the target device from the Device Database™ all special options are set automatically. You typically only need to configure the memory map of your target hardware. Default memory model settings are optimal for most applications. 7. Select Project - Rebuild all target files or Build target.

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Debugging an Application in µVision2 To debug an application created using µVision2, you must: 1. Select Debug - Start/Stop Debug Session. 2. Use the Step toolbar buttons to single-step through your program. You may enter G, main in the Output Window to execute to the main C function. 3. Open the Serial Window using the Serial #1 button on the toolbar. Debug your program using standard options like Step, Go, Break, and so on. Starting µVision2 and creating a Project µVision2 is a standard Windows application and started by clicking on the program icon. To create a new project file select from the µVision2 menu Project – New Project…. This opens a standard Windows dialog that asks you We suggest that you use a separate folder for each project. You can simply use the icon Create New Folder in this dialog to get a new empty folder. Then select this folder and enter the file name for the new project, i.e. Project1. µVision2 creates a new project file with the name PROJECT1.UV2 which contains a default target and file group name. You can see these names in the Project Window – Files. Now use from the menu Project – Select Device for Target and select a CPU for your project. The Select Device dialog box shows the µVision2 device database. Just select the microcontroller you use. We are using for our examples the Philips 80C51RD+ CPU. This selection sets necessary tool options for the 80C51RD+ device and simplifies in this way the tool Configuration Building Projects and Creating a HEX Files Typical, the tool settings under Options – Target are all you need to start a new application. You may translate all source files and line the application with a click on the Build Target toolbar icon. When you build an application with syntax errors, µVision2 will display errors and warning messages in the Output Window – Build page. A double click on a message line opens the

38

source file on the correct location in a µVision2 editor window. Once you have successfully generated your application you can start debugging. After you have tested your application, it is required to create an Intel HEX file to download the software into an EPROM programmer or simulator. µVision2 creates HEX files with each build process when Create HEX file under Options for Target – Output is enabled. You may start your PROM programming utility after the make process when you specify the program under the option Run User Program #1. CPU Simulation: µVision2 simulates up to 16 Mbytes of memory from which areas can be mapped for read, write, or code execution access. The µVision2 simulator traps and reports illegal memory accesses. In addition to memory mapping, the simulator also provides support for the integrated peripherals of the various 8051 derivatives. The on-chip peripherals of the CPU you have selected are configured from the Device Database selection: You have made when you create your project target. Refer to page 58 for more information about selecting a device. You may select and display the on-chip peripheral components using the Debug menu. You can also change the aspects of each peripheral using the controls in the dialog boxes. Start Debugging: You start the debug mode of µVision2 with the Debug – Start/Stop Debug Session command. Depending on the Options for Target – Debug configuration, µVision2 will load the application program and run the startup code µVision2 saves the editor screen layout and restores the screen layout of the last debug session. If the program execution stops, µVision2 opens an editor window with the source text or shows CPU instructions in the disassembly window. The next executable statement is marked with a yellow arrow. During debugging, most editor features are still available. For example, you can use the find command or correct program errors. Program source text of your application is shown in the same windows. The µVision2 debug mode differs from the edit mode in the following aspects:

39

The “Debug Menu and Debug Commands” described on page 28 are available. The additional debug windows are discussed in the following. The project structure or tool parameters cannot be modified. All build commands are disabled. Disassembly Window: The Disassembly window shows your target program as mixed source and assembly program or just assembly code. A trace history of previously executed instructions may be displayed with Debug – View Trace Records. To enable the trace history, set Debug – Enable/Disable Trace Recording. If you select the Disassembly Window as the active window all program step commands work on CPU instruction level rather than program source lines. You can select a text line and set or modify code breakpoints using toolbar buttons or the context menu commands.

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4. RESULT In the temperature monitoring system we have used four blocks those are temperature sensor,ADC0804,AT89s52microcontroller,LCD.In this system the first block temperature sensor senses the temperature in the atmosphere in analogue form and then sends this analogue signal to ADC to convert into digital signal.This digital signal is fed to microcontroller through data lines. By using the microcontroller process the data and send it to LCD in the form of ASCIIcode.Finally LCD displays the external temperature in the atmosphere.

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5. CONCLUSION& FUTURE SCOPE: This project explains about a simple low cost circuit which can be mainly used in large scale industries to detect the high temperature and take immediate measures. This circuit is used to sense the temperature at a place. It indicates the temperature on the LCD with the help of microcontroller. This circuit makes use of LM35 which is a 3 pin centigrade temperature sensor IC. It directly senses the temperature and sends the data to the controller. This has been successfully completed under the guidance.

FUTURE SCOPE: In temperature monitoring system we can interface alarm to 8051 microcontroller. By using this interface we can found an alarm sound when temperature increases to certain level.

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6. REFERENCES Books: 1. Muhammad Ali Mazidi, The 8051 Microcontroller and Embedded systems, 2nd Edition. 2. Scott Machenzie, The 8051 Microcontroller. 3. B L Theraja, Electrical Technology. 4. K. Y. Tang, Alternating Current Circuits. 5. Golding and Widdis, Electrical measurements and measuring instruments. 6. Admiralty, Examples in Electrical Calculations. 7. B. W. Williams, Power Electronics. Books from Reference Library. Websites: 1. www.futurlec.com 2. www.wikipedia.org/ADC 0804/Analog-to-digita.htm 3. http://www.electronicsforu.com/efyhome/cover/home.htm 4. http://en.wikipedia.org/wiki/Diode_bridge#column-one 5. http://www.allaboutcircuits.com/vol_6/chpt_5/index.html 6. http://www.beyondlogic.org/serial/serial.htm#1 7. http://geocities.com/SiliconValley/2072/electron.htm 8. http://www.national.com/opf/LM/LM7805C.html#Datasheet

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7. APPENDIX 7.1 SOURCE CODE: #include sbit LCD_RS =

P2^7;

sbit LCD_RW =

P2^6;

sbit LCD_CS =

P2^5;

sfr LCD_DT =

0x80;

sbit READ

=

P3^0;

sbit WRITE

=

P3^3;

sbit INTR

=

P3^2;

void delay(int k) { int l; while(k) { for(l = 0; l<115; l++); k--; } } void command_Lcd(char value) { LCD_DT =

value;

LCD_RS

=

0;

LCD_RW

=

0;

LCD_CS

=

1;

delay(10);

44

LCD_CS

=

0;

delay(10); } void display_lcd(char value) { LCD_DT =

value;

LCD_RS

=

1;

LCD_RW

=

0;

LCD_CS

=

1;

=

0;

delay(10); LCD_CS delay(10); }

void Initialise_Lcd() { command_Lcd(0x38); delay(10); command_Lcd(0x01); delay(10); command_Lcd(0x0e); delay(10); command_Lcd(0x06); delay(10); command_Lcd(0x84); delay(10); } void printl(char *p) { int i; 45

for(i = 0; i
T1 = Value %10;

//123-----> T1 = 3

Temp = Value / 10;

//123-----> Temp = 12

T2 = Temp % 10;

//12-------->T2 = 2 46

Temp = Temp /10;

//12-------->Temp = 1

T3 = Temp ;

//1--------->T3 = 1

command_Lcd(0x84); delay(10);

//change this prompt according to your choice Example Temp:--------> Watch// printl("Temp:"); display_lcd(T3+0x30); display_lcd(T2+0x30); display_lcd(T1+0x30); delay(100); } void main() { Initialise_Lcd(); //change this prompt according to your choice Example WELCOME--------> Watch// printl("WEL COME"); delay(3000); /*

command_Lcd(0xC2); delay(10); printl("HELLO WORLD"); delay(3000); */ command_Lcd(0x01); delay(10); command_Lcd(0x82); delay(10); printl("RANJITH REDDY"); command_Lcd(0xC3); delay(10); 47

printl("06S41A0437"); delay(3000); command_Lcd(0x01); delay(10); command_Lcd(0x83); delay(10); printl("RAVI TEJA"); command_Lcd(0xC3); delay(10); printl("06S41A0411"); delay(3000); command_Lcd(0x01); delay(10); command_Lcd(0x82); delay(10); printl("HARI KRISHNA"); command_Lcd(0xC3); delay(10); printl("06S41A0417"); delay(3000); command_Lcd(0x01); delay(10); command_Lcd(0x84); delay(10); printl("SRIDHAR"); command_Lcd(0xC3); delay(10); printl("06S41A0445"); delay(3000); command_Lcd(0x01); delay(10); while(1) Process(readadc());}

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7.2 LIST OF TABLES

PAGE NO’S

Table 2.1 Port 1 Pins Functions……………………………………...18 Table 2.2 Port 3 Pins Functions……………………………………...19 Table 2.3 Timer 2 Operating Modes………………………………...25 Table 2.4 Pin Assignment……………………………………………31

7.3 LIST OF FIGURES

PAGE NO’S

Figure 1.1: Block diagram of temperature monitoring system…..2 Figure 1.2: Schematic of temperature monitoring system……….3 Figure 2.1: Block diagram of power supply…………………………5 Figure 2.2: Circuit diagram of power supply………………………...6 Figure 2.3: Power Supply Requirements…………………..…………6 Figure 2.4 General view of Regulator…………………………….….9 Figure 2.5 LED View……………………………………………….10 Figure 2.6 LED Symbol…………………………………………….11 Figure 2.7 LED Internal view………………………………………11 Figure 2.8 Bottom View of LM35………………………………….13 Figure 2.9 Pin Description of Adc0804…………………………….15 Figure 2.10 Pin Description of 8051 Microcontroller……………...17 Figure 2.11 Block diagram of 8051 Microcontroller……………….27 Figure 2.12 Liquid Crystal Display………………………………...30 Figure 2.13 LCD Pins………………………………………….……31 Figure 2.14 Schematic of LCD……………………………………..32

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