Miller_Keypad lock with LCD feedback

Keypad lock with LCD feedback

General Description:

     The main goal was to design an embedded system that will unlock a door by entering a code.  A user inputs a 4 digit code into

a 4x4 Matrix keypad which is then checked to the "key" that is stored in memory.  The user has feedback that is displayed on

a 16x2 (col,row) LCD screen.  User input will be displayed on the LCD with stars covering the previous input.  If the incorrect code

is entered the screen does nothing.  If the correct code is entered the screen will display "Open" and a solenoid is activated with a

delay of five seconds for the solenoid to stay active.  When the delay is over the solenoid is deactivated and the LCD will display

"Closed".  I incorporated some functionality into the embedded system and dedicated buttons for certain actions.  The user can

use the 'B' button for a single Backspace and 'C' for an entire Clear of the code to start over.  The user must enter the four digit

code and then press the 'E' key to Enter the desired code.  If you look at the video's below the correct code to enter is 1,2,3,4

which will then activate the solenoid in the following video.

Components Used:

  1. Arduino Uno - "The Brains"
  2. 4x4 Matrix Keypad- "Input"
  3. LCD- "Feedback Input and Output"
  4. 10kΩ Potentiometer- "LCD contrast control"
  5. TIP120 NPN Transistor- "Amplifier for Solenoid"
  6. 6~Volt Solenoid

LCD- Video

Solenoid- Video

Arduino- Code.txt


     The cost analysis of this embedded system is higher than I would like,  but with prototyping the higher price is to be expected.

I believe we could market this basic system for small applications for less than $30 dollars and larger applications would go up in price

based on the type of locking system required.  The higher priced items like the solenoid and LCD display are the bulk of the cost. 

The following list are per item (cheaper in bulk):

  1. LCD Display $15
  2. Matrix Keypad $5
  3. TIP-120 NPN $3
  4. Solenoid $15 to $25 (smaller solenoid)
  5. Arduino Uno $30
  6. ATMega chip only $6

Pending on the application the price would need to be adjusted, but the basics are here for a locking embedded system.


March 29, 2011

      Started interfacing the arduino with the matrix keypad.  Using the serial monitor to interpret the user input from keypad. (2 hrs)

April 4, 2011

      Continuing to interpret the matrix keypad input. (2 hrs)

April 5, 2011

     Continuing to interpret the matrix keypad input. (3 hrs)

April 8, 2011

     Stayed late on Friday afternoon trying to wire up and write to LCD screen.  (5 hrs)

April 9, 2011

     LCD screen is wired up and able to write to it.  Trying to incorporate the keypad input and the LCD

          into one file. (3 Hrs)

April 11, 2011

      Currently have the keypad showing up on the LCD.  Have talked with Jeff Peterson about amplifying

           the high signal from the arduino using either a transistor or a mosfet chip to drive a solenoid.  (2 Hrs)

April 12, 2011

      I have the system working.  When the incorrect key sequence is pressed the system does nothing.

           When the correct sequence is pressed the solenoid retracts. (1 Hr)

April 25, 2011

      Taken pictures of my system and have tried playing with the code to add more functionality. (1 Hr)

April 26, 2011

      Still messing with the code and I think this is ready for demo.  (3 Hrs)


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