Arduino Project: How to Make an RGB LED Combination Door Lock

Posted: April 26, 2013 by yevaanderson in Phys II Projects

By Evie Anderson and Tatiana Coverdell

Purpose of the Project:

The purpose of this project was to design a RGB combination door lock, which would allow a person to unlock a door via an electric door strike using the correct color combination code.  To do this, the following items were needed:

  • An electric door strike
  • A locking door handle
  • An Arduino or compatible clone
  • 1 TIP120 transistor
  • 1 1N4001 diode
  • 10 1N4148 diodes
  • 4 2n2222 transistors
  • 1 Monome style keypad
  • 1 Keypad PC board
  • 8 RGB LEDs
  • 1 7805 voltage regulator
  • 4 100 ohm resistors
  • 2 150 ohm resistors
  • 8 1 kohm resistors
  • 1 AD5206 digital potentiometer
  • 1 electrical box
  • 1 wall plate

Using these materials, we needed to build a board in which we could solder the LEDs and wires connecting the board, Arduino, and breadboard.


The board that we used for our keypad with the LEDs and Diodes soldered on. Then we prepared to solder our wires to the board.

The code was then to be run through the Arduino, which would light up different colors in the LEDs.


Once all of our wiring was completed correctly, the two rows of LEDs alternated through different color combinations.

An electric door strike would be attached to the board and installed in a door so that when the correct color combination was set up and applied, the door strike would unlock the door, allowing access into the room.


An electric door strike installed in the door frame.


A drawing of the the over all set up including the keypad, Arduino, and door strike.









We accessed a website: in order to get the supplies list and instructions to build our combination door lock.  After we ordered all the parts that were on the list provided by the website we began our soldering process once we cut the PC board.  The PC board for the LEDs was designed to have 16 LEDs so we had to cut it in half.  Although the instructions on the website were not clearly stated, we learned that the board needs to be cut parallel to the lines on the side of the board with the white circular circuits for the LEDs.  Then we began soldering the diodes, LEDs, and wires.  During this part of our process we learned that in order to properly solder, you have to first tin the tip of the soldering iron with solder and then heat the wire that you want to solder before using any solder.  When all of our soldering was completed we began the wiring process.  After trying the wiring once we learned that a crucial part was missing from the list—the digital potentiometer.  When that part arrived we had to rewire everything twice before we were able to get 6 of the LEDs to work.  At this point we found that using more breadboards makes the wiring easier since there is a little more space to keep all the different segments separate.  We ended up using 3 breadboards, each of which was approximately 2 ½” x 3 ½”.


The schematic used to wire the Arduino, door strike, and keypad together.

There are detailed written instructions on the website that correlate with each part of the schematic.  We found that a basic understanding of all of the symbols on the schematic was necessary before we could successfully wire anything.  Also, if you follow the instructions on the above website you will need to know that “pot” stands for the digital potentiometer (AD5206 on the schematic).  After wiring and rewiring 3 times we were finally rewarded by the pulsing, glowing sight of 8 RGB LEDs.


An all red color combination.


Purple and Blue combination


Red and Green

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