Security Keypad II
An improved version that can be used on security vaults, Doors with electric latches, Alarms, Safety devices and many other uses. It uses an HITACHI LCD (16x1 or 8x1) and a matrix keypad. The HEX code is available for 16F84A and 16F628. (5/27/2006)
Finally I was able to control an LCD Hitachi display and a 12-key matrix keypad with only one 16F84 or 16F628. In a near future, I will be able to control a full QUERTY-type keyboard and a LCD display. Anyway, this project is an improved version of the Security Keypad/Electronic Code Lock that I made on November 2004.
The function of this Security keypad is similar to the previous version but it have more applications.
The biggest improvement on this projects was the compatibility with the Microchip PIC 16F84 and the 16F628, also the 16x1 or the 8x1 LCD Hitachi can be used. To reduce the cost of this proyect, is possible to remove the LCD and the circuit will work with the beep codes. Basically, the hardware is a mini-terminal controlled by a 16-pin PIC.
As you can see, the 3x4 keypad uses only 4 I/O ports. To determine what key is pressed, I read the discharge time of each capacitor. This is a new technique that I developed since two years ago but finally I was able to test it successfully. The only inconvenience of this method is the reading from the keypad is affected by the voltage of the circuit. Anyway, the circuit needs exactly +5V because the LCD.
The switch labeled as "Toggle" and "Normal" defines the function of the security keypad. With the "Toggle" setting, the "Enable Signal" will toggle each time the correct password is entered. With the "Normal" setting, each time when the correct password is typed, the "Enable signal" will be ON for only four seconds.
Here is how it works:
To enter the code:
Press "#" to enter the code.
The display shows ">".
Input the SIX DIGITS code. Use "*" to cancel it and start again.
If the code is correct, the display with show "Granted!" and the "Enable signal" will be on according the setting on pin 3 (a4).
If the code is incorrect, the display shows "Invalid" and doesn't activate the signal.
To change the code:
Press "*" for three or four seconds until the display shows "Chg Code".
The display will show: ">". Enter the actual code.
If the code entered is correct, the displays asks for the new code. ("New Code"). Enter the new six-digits code.
The display will show: "Repeat!" Enter the new six-digit code again for verificacion purposes. If no display is used, it allows to verify the new code.
The display will show: "Changed!" Now the security terminal is ready to accept the new code.
This is a DEMO version. A commercial version may have more codes. This version will lost the code if it is powered off. The "factory code" is 000000. Everytime when this circuit is powered on, the password is reset to 000000.
Download the HEX file HERE for the 16F84A. The configuration for the PIC is: PWRT ON, OSC RC.
Click HERE for the 16F628. The configuration for the 16F628 is: PWRT ON, OSC INTRC/IO. Use the right-click and choose "Save as...".
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