KeyPad Combination Lock

Introduction

If you want to make an electronic lock, using a KeyPad is the obvious way. There's one of these in the Espruino Ultimate kit, but see the KeyPad page to see where you can buy them.

You'll Need

• One Espruino Board
• A KeyPad

Wiring Up

Just plug the Key Pad in to B2,B3,B4,B5,B6,B7,B8 and B9 (they're one long row of pins) so that as the KeyPad is facing you, the wire nearest D goes to B2, and the wire nearest * goes to B9. There are no real requirements for the pins you can use, but if you use different pins then you'll have to change the software below.

Software

The first step is to respond when a button is pressed. Connect to the Espruino, copy and paste this into the right-hand window, and click the Send to Espruino button:

function onKey(key) {
  console.log("123A456B789C*0#D"[key]);
}

require("KeyPad").connect([B2,B3,B4,B5],[B6,B7,B8,B9], onKey);

Note that we can't paste this into the left-hand side initially, because it uses the KeyPad module which the Web IDE needs to be able to load off the internet for you.

Now, when you press a key, that character will be output on the screen.

The next step is to check each digit in turn against out combination. Copy and paste the following into the right-hand side and click Send to Espruino:

var code = "B59";
var digit = 0;

function setLocked(isLocked) {
  // output red or green depending on whether we're locked or not
  digitalWrite([LED1,LED2,LED3], isLocked ? 0b100 : 0b010);
  // then two seconds later turn it off
  setTimeout(function() {
    digitalWrite([LED1,LED2,LED3], 0);
  }, 2000);
}

function onKey(key) {
  var ch = "123A456B789C*0#D"[key];
  // check against our code
  if (ch == code[digit]) {
    digit++; // go to next digit
    if (digit >= code.length) {
      console.log("We're at the end of the code - unlock!");
      setLocked(false);
      // and go to the begining of the code again
      digit = 0;
    } else {
      console.log("Digit correct - next digit!");
    }
  } else {
    console.log("Wrong! Go back to the start");
    setLocked(true);
    digit = 0;
  }
}

require("KeyPad").connect([B2,B3,B4,B5],[B6,B7,B8,B9], onKey);

And we're done! Press B...5...9 and the green LED will light for 2 seconds, but if you press any other characters in any other combination then the red LED will light.

Next Steps

The next thing to do might be to operate some kind of lock when the combination was entered. To do this, just change the setLocked function. For instance you could plug a Servo Motor into pin B13 and replace setLocked with the following:

function setLocked(isLocked) {
  // output red or green depending on whether we're locked or not
  digitalWrite([LED1,LED2,LED3], isLocked ? 0b100 : 0b010);
  // then two seconds later turn it off
  setTimeout(function() {
    digitalWrite([LED1,LED2,LED3], 0);
  }, 2000);
  // Now operate a servo motor - give it 1 second of pulses (50 * 20ms) to move it to the new location
  var servoPos = isLocked ? 0 : 1;
  var servoPulses = 0;
  var interval = setInterval(function() {
    digitalPulse(B13, 1, 1+servoPos);
    servoPulses++;
    if (servoPulses>50) clearInterval(interval);
  }, 20);
}