Password Controlled Home Appliances (Simulation Model)
Why do you need to spend your money with hardware to learn, when free simulation models are available online. Simulation models also allows you to check for the working and logic of the programs. One simulation model that I have worked with is PROTEUS software.
The project below is a simulation model for a password controlled home appliance. When the key 1 is pressed the relay turns on and does the light with a LCD display displaying "Access Granted". For all other values the light is turned off and the LCD display shows "Acess denied".
LIQUID CRYSTAL DISPLAY:
LCD (Liquid Crystal Display) screen is an electronic display module and finds a wide range of application. A 16x2 LCD display is very basic module and is commonly used in various devices and circuits. These modules are preferred over seven segments and other multi segment LEDs. The reasons being: LCDs are economical; easily programmable; have no limitation of displaying special & even custom characters (unlike in seven segments), animations and so on. A 16x2 LCD means it can display 16 characters per line and there are 2 such lines.
In this LCD each character is displayed in 5x7 pixel matrix. This LCD has two registers, namely, Command and Data.The command register stores the command instructions given to the LCD. A command is an instruction given to LCD to do a predefined task like initializing it,
clearing its screen, setting the cursor position, controlling display etc. The data register stores the data to be displayed on the LCD. The data is the ASCII value of the character to be displayed on the LCD.