12 to 23 Counter

The start and end value of Asynchronous (ripple) counter is controlled by and gate or nand gate. Generally
J K flip flop is have active low preset and clear value so we use Nand gate.
This example give an idea to construct an ripple counter with some start point instead of zero.


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Multiple Door Lock with LCD and Keypad using pic16f877A:

A Brief Description:

This project is written in C language and compile in Mikro C compiler. The basic user lock is of 2 Digits.

The input is taken from a 4x3 Keypad (please see the schematic for more information) and Display the user input on a 2x16 LCD. A pin is assigned as output for activating and deactivating the lock. For demonstration I have connected an LED to that pin.


How combination lock works:

1. Turn switch on (5V DC voltage power supply)
2. A message name “Multiple door Lock” will display on LCD at first row,
3. Second row display “Enter Pass:” it asked you to enter password for open doors.
4. In this lock design it has three doors.  These are the code locks to open doors “door1=55, door2=66, door3=77, door1 & door2 = 33”.

5.      If you entered one of the codes in step 4 then press enter key that door will open.  For example, you enter 05 for door 1 it’s then open and close door 1 after 5 seconds.

6.      If codes you entered are not matched one of the code in step 4 then led door is not turn on.

7. If your first attempt failed the message “invalid code’ display on screen.
8. Then you pressed any key to clear and you can try for second attempt.

After you have reached three attempts but you have not entered correct password.  Next Any Keys press alarm will activate for 5 seconds.

Using the Keypad:
Keypad has 12 keys (4x3) starting from 1,2,3,4,5,6,7,8,9,*,0,# (please see the schematic for layout). Numeric keys are used for entering numbers. '*' is used as the Cancel key and '#' is used as the Enter key.

Source Code Available at ELECTRODATA

BATH ALARM

Here is the block diagram, for a bath alarm which will sound an alarm before the water in the bath overflows:

The float sensor consists of a voltage divider with a float switch at the top and a 100 k pull down resistor at the bottom. If the water level rises above a critical level, the float switch closes and the output of this subsystem becomes HIGH, logic 1.                                                                          
The astable, or pulse generator, produces pulses. Its output alternates repeatedly from HIGH to LOW. The float sensor provides a control input to the AND gate. If the control input is LOW, the output of the AND gate remains LOW. However, if the control input goes HIGH, the output of the AND gate starts to produce pulses, alternately HIGH and LOW, following the astable.
The transducer driver is needed to provide enough current to drive the buzzer. When the bath is full, the buzzer pulses ON and OFF.
It is easy to model this system using the system blocks provided by Crocodile Technology ©:

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