Submitted By
ACHARYA MIRAJ SHAILESHBHAI

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INTRODUCTION
The declining prices of the LCDs. The ability to display number, characters and graphics. This is in contrast with LEDs, which are limited to numbers and few characters. Incorporation of a refreshing controller in to LCD, thereby relieving the CPU to keep displaying the data. Ease of programming for the characters and graphics.
Block Diagram
Block Description:
In this project there are three main blocks
1. Power supply section
2. Controller section(AT89C51)
3. Display section
Power supply section:
• In this section we use step down transformer, capacitor, IC7805, diodes for bridge rectifier.
• Transformer converts230vAC in to 12vAC
• The bridge rectifier converts AC in to DC.
• The capacitors are used for filtering porpoise.
• The IC7805 is used for constant supply of 5v to other section of the circuit.
Controller section:
• In this section we use At89C51 controller IC.
• It has four input output ports such as P0-P3, we use Port-1.
• It has 4KB EPROM & 128B of internal RAM.
• It needs 5V supply for this operation.
• It is the main block or we can say the heart of LCD interfacing.
• Clock & Reset Circuit is in built with the controller section.
Display Section
• We use here 2-line, 16-character LCD.
• It displays 8 characters in one line.
• It needs 5V supply for operation.
Power supply section diagram
AMTEL (AT89C51)
LCD INTERFACING
Circuit description:
Power supply:
• In power supply side we use transformer, bridge rectifier using diodes, capacitors & IC7805.
• Transformer:
• It is used to regulate the output voltage.
• It is the step down 12-0 transformer which converts 230vAC into 12V.
• Its current rating is higher of 500mA.
• It gives 12V AC output.
Bridge rectifier:
• It is made up of 4 IN4007 diodes.
• It is the Full wave bridge rectifier.
• In full wave two diodes conduct.
• It is used to converts the AC Voltage in to DC Voltage.
• The efficiency of the full wave bridge rectifier is 81.2%
Capacitors:
• In the power supply section we use 33pF Electro cyclic Capacitor that is used for filtering.
IC-7805:
It is the voltage regulated IC that gives you a 5V DC output.
• It has three pins.
• The filter is given to the pin no 1 of the IC-7805.
• Pin-2 is connected to ground
• The regulated output is taken at the pin-3
• Its output of 5V DC is given to the different section of the circuit.
Controller Section:
• 5V DC is given to the pin-40 & 31 of the controller IC & pin-20 is connected with the ground.
• Pin-9 is used to reset the ckt.
• Pin-18 & 19 is used for clock circuit.
• Pin-1 to 8 are used as port for the LCD interfacing
• Controller has clock & reset circuit in built. The description of both the circuit is given below.
1. CLOCK CIRCUIT
• Pin-18 &19 is used for clock.
• Capacitors & crystal display are used to form the clock circuitry.
• The crystal frequency range is 1-16 MHz
• Two 33pF capacitors of ceramic disc type are used.
• The equation to calculate the time to execute an instruction is T=C*12d/crystal frequency (C=number of clock pulses)
2. Reset circuit
• Pin-8 is used for reset
• Pin-9 is always high
• It is used to reset the micro controller
• A simple RC circuit is used having resisters, capacitors & Push Button is used to form the reset circuit.
• When push button is pressed the reset pin goes high and microcontroller is reset.
Component List:
Semiconductor devices:
• IC1: AT89C51
• IC2: 5V regulator, BC7805
• LCD: 2-line, 16-character
• Diodes: Silicon Single IN4007
Resisters:
• VRI: 2.2k preset
• R2: 100ohm carbon
• R3: 8.2k carbon
Capacitors:
• C1: 10microF ceramic disc
• C2: 33microF ceramic disc
• C3: 33microF ceramic disc
• C4: 100microF 25V electro cyclic
• C5: 100microF 25V electro cyclic
• 12 MHz Crystal
Other components:
1. 230V to 12-0-12, secondary Transformer
2. IC Zip Socket
3. PCB
4. Push Button
5. Connecting wires
6. Male-Female Socket
Procedure:
First show the circuit diagram of each block.
• Connect the component with the help of circuit diagram
• Load the program in the controller IC
• Connect the LCD with controller IC.
• Connect the 5V Dc supply with the different section of circuit.
• Connect the code wire with the primary winding of the transformer.
• Turn on the switch to give the 230V AC to the transformer with the help of code wire.
• Show the message display on LCD display.
• Switch OFF the supply.
Calculation:
To calculate the time to execute one instruction with the help of following equation:
• T (instruction) =(C*12d)/Crystal Frequency (C=number of clock pulses)
For example:
If C = 1 & Crystal frequency is 12MHz then calculate the time to execute one instruction.
T (instruction) = (C*12d)/Crystal Frequency
= (1*12)/12MHz
=1microSEC
Advantages:
• The declining prices of LCDs.
• Ease of programming for the characters and graphics.
• Incorporation of a refreshing controller in to LCD, thereby relieving the CPU to keep displaying the data.
• The ability to display number, characters and graphics. This is in contrast with LEDs, which are limited to numbers and few characters.
Disadvantage:
• It’s costlier than the seven segment LEDs.
Applications:
• It is used in airport, railway station, hospitals etc.
• It is used in EPABX.
• It is used in telephone exchange.
• It is used in AC.
• It is used in Refrigerator.
• It is used in Software interface.
• It is used in robotics.
Soldering Technique:
1. Soldering iron of 25-30 watts with an iron plated copper tip should be used.
2. Dean in component leads in the copper pads on the PCB before soldering.
3. Iron should be kept in the joint for 2-3 sec only.
4. During this time apply solder on the components leads, PCB over the tip of the solder iron.
5. Don’t use excess solder to arc oil short circuit.
6. Bend the lead of the components properly.
7. The bending angle should be between 20-40 from the base metal