Week 4 Combination Lock


I want to create a combination that allows me to push desired button in the desired order to unlock a green LED.


3 buttons to control red and green button. Red button means still lock but more step needed, Green button means unlock.

  • How it works: You have to push the 1st button to trigger the 2nd button, then push the second button to unlock the green LED. (Like a step-by-step unlock process)

Problem (solved):

The problem is that I cannot release buttons. Once I push the first one I have to hold it to while pushing the second one to make it work. My original intention is once I push the button even I release it the button will still work.


  1. Arduino UNO R3 x 1
  2. Breadboard x 1
  3. Buttons x 3
  4. Red LED x 3
  5. Green LED x 1
  6. 220Ω Resistors x 3
  7. Wires

Connection Diagram:


Github Link: https://github.com/jiany457/PCom/blob/master/CombinationLock/version1/version1.ino


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