Introduction: Arduino - ACCESS CODE PROTECTED 4 CHANNEL RELAY With 4x4 Keypad

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 make…

Hello world! This code is made to put a access code/password protection on your "dangerous" machines in the garage/workplace (For example). To protect your kids from the danger that might lurk in your garage, without the code power cannot be turned on. Hide it in a box that you can lock, put it on the wall and add a little safety to your garage. Of course it can be used to turn on/off anything! Very simple but i'm sure it is useful for many of you.

Usage of the Device.

Pressing: * will turn off everything and go back into NoAccess mode.

A turns on/off relay 1

B turns on/off relay 2

C turns on/off relay 3

D turns on/off relay 4

Default code is: 3241

Follow the next step for the schematic code & Parts list.


The red led is to notify you that nobody can turn on/off machines. You could reverse this and switch it to pin 10 where the green light is to notify that the devices are still able to be put on by anyone, so the red led warns you the power is still on. While in NoAcces state the Green Led notifys you everything is safe! (Just an idea)

Step 1: Schematic Code & Parts List.

Wire it up like the Schematic and it should work after uploading the code.

If not...

You need the following Librarys.



Parts list:

  1. Arduino uno, I used the RobotDyn uno.
  2. 4 Channel Relay.
  3. 4x4 Keypad
  4. Jumper wire set MM/FF/MF
  5. buzzer.
  6. 2 x Leds / 1 green / 1 red.

Good luck!