Picture of Keyless Entry / Arduino
                                                                                 Keyless Entry System

 Enter the correct code into the keypad and the servo will unlock the door. Enter the incorrect code and Sorry you stay out. 
There was a couple of stipulations i wanted in my Keyless Entry system:

  1. Helper Light. A light that would come on whenever a key was pressed. Then off after the preset time limit.
  2. An override switch so the servo could be operated without the keypad. 
  3. Some indication that the pass code entered was correct or not.
  4. Powered by a wall charger.
  5. Be able to operate manually during a power outage
With these stipulations i started out to build. 

The Keypad works on a matrix system. Pressing any key will involve 2 wires.
Example if you press number 8 it will effect the wire ROW3 and CLO2. By this the micro controller can determine what key was pressed with only 7 wires from the keypad.
 While this keypad schematic is not correct to this build the theory is still the same. 
This build does not use the external resistors. It takes advantage of the internal pullup resistors in the Atmega328.

Keypad in Arduino Playground.

Step 1: What we are going to need

Picture of What we are going to need
                            Parts and Pieces

  • Atmega328P-UP Bootloaded
  • 28 Pin socket
  • 16Mhz Crystal
  • 22pF caps ( 2 )
  • LM317 voltage regulator
  • LM7805 Voltage regulator
  • 10uF Caps ( 2 )
  • #104 Caps ( 2 )
  • 220R Resistor
  • 1K Resistor
  • 470R Resistor
  • 10K Resistor
  • LED of your choice
  • Tact Switch
  • 5mm Power Connector
  • 2 pin female header
  • 16 Pin Female header
  • Perf Board 70mm x 90mm
  • Flat wire strips 2 wire   4 wire   7 wire  1' long
  • Servo

I would call this a intermittent build as there is several sub build components.

iceng2 years ago
Nice instructable good pass code device work.
Now I can point to a good project when this comes up as a question every year.

I would add a missed the code counter that penalized the key-er after 5 or 7 bad
entries in a series :)

WWC (author)  iceng2 years ago
Wow your fast,also.

Thanks for the comment.
What would the action be for to many incorrect entries? Siren and flashing light?
iceng WWC2 years ago
I had a circuit penalty device to protect a bicycle that electrified the seat with
a modified Tesla circuit.
It never found commercial interests :(
WWC (author)  iceng2 years ago
Huh wonder why, ha.

Good idea tho, i think a piezo or similar would be appropriate in this case.
iceng WWC2 years ago
Generally a 5 Minute lock out penalty is sufficient to discourage code breakers.
MicMofMou2 years ago
Looks quite awesome. Would this also work with codes longer than 4 digits? Say, 9 or 10 digits, for instance?
WWC (author)  MicMofMou2 years ago
Hi thanks for looking and the kind words.
While i have not tried it, i would say so. I don't see why not.