PIC Projects
OBDII Tacho, Diagnostic app
TFT Clock and Thermometer
WiFi, Ethernet
Doorbell with SD / EEPROM
SD FAT16/32 for .bmp
TFT Timer
TFT Oscilloscope
SD Talking Clock
SD Sound Recorder,
    FAT32 wav Player
LED Thermometer
LED Timer
LCD 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 Ports
Serial TFT Text
Serial Inputs Outputs
Serial Port LCD
MCP3201 on Serial Port
Serial Thermometer
Analogue Signal to Serial
Serial Thermostat

MCP3201 on LPT
Analogue Signal to LPT
LCD Display on LPT
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. The LCD simplify the interaction by the user. Any 4 digits number can be used. Pressing the right code activates the relay for 2 seconds. Not pressing any key for more than 30 seconds resets the display. Using microcontroller PIC16F870. To change the 4 digits code press 'New Code' pushbutton. The pushbutton has to be mounted in an area not accessible to the public. The 4 digits are stored in the chip's EEPROM, so the numbers are retained when the power is off.
You are free to use the circuit diagram and the software with no limitations.

Circuit Description
See also Technical Tips

Supply 12 to 24V for the relay, 5V for the PIC is from 78L05 voltage regulator.
The NO contact of the relay is connected to the door electric latch.
Key pad can be any matrix switches.

All transistors are BC237 or equivalent.
LCD module is 1 line 16 characters. It has 14 way connector, 10 connections are used, 4 bits data bus is selected. There is a big selection of LCD modules, and they are very similar in characteristics i.e. DM1601, ACM1601.
Contrast pot must be set because in one end of the pot it is totally dimmed.
New Code pushbutton is for entering new 4 digits code.


Comments and questions

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

14.09.2017 - 18:33
Name: Joe
Comment: This is a great project. It is possible to publish a program with a 5-number code? I would be glad. HJS

21.05.2017 - 22:01
Name: Moty
Comment: Try downloading the software to a PC or another computer.

21.05.2017 - 12:07
Name: saheed
Comment: how can I get code please? my e-mail address: mustech05@gmail.com

11.01.2017 - 19:45
Name: Agbolade Oluwole
Comment: Thanks alots

08.12.2015 - 21:08
Name: Easir
Comment: thanks...

15.06.2015 - 07:00
Name: Absee.
Comment: Yes its very interesting and thanks. I would be very pleased if you could illustrate a door lock circuit with Rf card and smart phone reader.Once again thanks a lot. Hoping to see more advanced circuits from your site. Absee from Maldives. abseekudabe@gmail.com

23.05.2015 - 17:48
Comment: PLES.