Arduino - LCD 1602A I2C - PASSWORD PROTECTED DOOR ACCESS With Relay - KY-019

About: Hello world! I make simple & Advanced projects for people who want to learn programming and electronics. Most of my Instructables are about arduino and the wide range of sensors you can use with it. I ma...

Hello world! Today i made a simple code to control a electric strike lock with a Password/ Access Code using a 1 channel relay. I don't have such a lock but i demonstrated it with a lamp attached to the relay. Check the next step for the schematic code & Parts list.

(I know! I wrote access wrong in the video..don't mind the

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Step 1: Schematic, Code & Parts List

You need these following librarys

  • password.h
  • LiquidCrystal_I2C.h
  • Keypad.h

Wire it up like the schematic and it should work after uploading,

if your not seeing anything, try change your I2C Address i will include a Code to scan your address.

You can change this at the line shown below which you can find on line 14 of the code.

  • #define I2C_ADDR 0x27

Most common I2C addresses.

  • PCF8574 = 0x20,
  • PCF8574A = 0x38,
  • PCF8574AT = 0x3F
  • PCF8574T = 0x27

Parts list:

  1. Arduino uno, I used the RobotDyn Uno.
  2. 1 Channel Relay KY-019
  3. Keypad 4x4
  4. LCD 1602 with I2C
  5. Electrical Strike Lock (Not needed to test the code, you will see if relay go's on or off.)

Good luck!



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    6 Discussions


    Question 1 year ago on Step 1

    Where can I get the password.h library? I don't have it and I was unable to find it in the "Manage Libraries" section


    3 years ago

    Very good. I found that the LiquidCrystal_I2C.h library was causing issues with the functions contained within it. I was able to rectify this by installing the NewliquidCrystal_1.3.4 library which can be found here:

    . After that the project worked perfectly. Thanks for the Instructable.


    3 years ago

    This is cool! I made a much simpler version of this with a 6 character combo with 4 numbers. When I want to take it to the next level, I am going to use this Instructable!

    1 reply