PIC Projects
TFT Clock and Thermometer
WiFi, Ethernet
Doorbell with SD / EEPROM
SD FAT16/32 for .bmp
LCD TFT Egg Timer
LCD TFT Oscilloscope
SD Talking Clock
SD Sound Recorder,
    FAT32 wav Player
LED Thermometer
LED Egg Timer
LCD Egg Timer

Frequency Counters
100KHz For PC
1MHz For PC
8 Digits LED 50 MHz
Scope Screen Display
LCD Module 10MHz
6MHz for Android
USB PIC18F2550
USB TFT display BMP
USB DS18B20 Sensor
USB Thermometer
USB Counter
USB Meter
USB Oscilloscope
USB Input-Output
USB 16x2 LCD

COM & LPT Ports
MCP3201 on LPT
Serial TFT Text
Serial Inputs Outputs
Serial Port LCD
Analogue Signal to LPT
MCP3201 on Serial Port
Serial Thermometer
Analogue Signal to Serial
LCD Display on LPT
Serial Thermostat

Water Softener
HP Stream 7 docking
3.7V to 5V
Solar Charger

Infrared Decoder
PIC Music

Code Lock
Code Lock with LCD
HOME MOBILE Technical Tips


Electronic code lock with the ability to rewrite the entry code. Can be used for entrance door, car door or a locker. Any 4 digits number can be used (the digit 0 is not used). Using microcontroller PIC16F628A programmed with the downloadable assembly and C source code. To change the 4 digits code press 'code change' switch, the LED will indicate ready state, press the 4 new digits, the LED will switch off. The code changing switch has to be mounted in a hidden area. There is a max 5 seconds delay between pressing any two digits, after the 5 seconds delay the 4 digits code has to be re-entered. The 4 digits are stored in the chip's EEPROM, so the numbers are retained when the power is off.

Software includes PIC code. You are free to use the circuit diagram and the software with no

Circuit Description
See also Technical Tips

78L05 is the regulator for the IC. The 12V supply is for the relay, you can use 24V relay and supply voltage.
Key pad can be any matrix switches. The on resistance 1K max.
The digit 0 is not used.

The EEPROM retains the code when the power is off.
330K resistor determine the microcontroller frequency, increasing the value will decrease the frequency hence increasing the 5 seconds delay.


Comments and questions

Copy the number from the picture It stops net-robots from adding comments.

02.05.2017 - 23:05
Comment: LCD

03.02.2017 - 09:50
Name: shehryar
Comment: plz contac the mobile number

16.01.2017 - 17:20
Name: Agbolade amos
Comment: this circuit didn't work

29.09.2013 - 06:12
Name: alimog
Comment: CODE LOCK with LCD

29.09.2013 - 06:12
Name: alimog
Comment: CODE LOCK with LCD

29.09.2013 - 06:12
Name: alimog
Comment: CODE LOCK with LCD

29.09.2013 - 06:10
Name: alimog
Comment: CODE LOCK with LCD

17.09.2013 - 06:59