I know I'm not the first person to ask this question, but I haven't found a good answer for the Diecimila yet. Can it be ran directly from car voltages? 11.5 to 13.5v?
I'm working on a keypad to unlock my car. I was spoiled by my old Lincoln, and my new Caliber doesn't have one. It's about half-way there now. When I started, it would accept a five button sequence, and then evaluate it for being correct or incorrect. No, actually, when I started, it was a game of Simon. (Thank you Gian Pablo Villamil) But then I removed the flashing lights and the random generator and the locked it on a five digit code.
But the problem was, it still evaluated the five button sequence. That is, if I press a button, and then you enter the correct 5 buttons, it's going to stop on your 4th, and tell you it's wrong. I needed to make a sliding array. So I did and it works. This way if the code was, 12345, I could push 54312345 and it would still take the code. Also, I had to implement a timeout feature. Because before, if I entered 1234, and then the next day you pressed 5, it would unlock. Now it times out after 4 seconds of the last key pressed and resets the input array.
So I'm close. Now I need to implement the extra unlock when you press one more key after the correct code, and the lock feature if you press the last two key together at any time.
I'm excited because this is my first psuedo-original project (I did start with someone else's source) that I'm not just reproducing someone else's project.
Ok, back on track, can I power it straight from the car or should I put it on a nice 5v or 9v regulator?
the diecimila already have an integrated voltage regulator, but at 12v people say it heats quite a lot. I would suggest you to put a diode and cut it to perhaps 9-10 volts before plugging it into the arduino. It will waste a bit of power but with a car battery, I think it's better then risking to damage the diecimila's 5v regulator.
Just recently I realized that a "cigarette lighter" cell phone charger generally has a bucking switch circuit that will supply 5V - often from up to 24V.
I can't recommend it at this point since I have not used it myself. But I see no reason what it wouldn't work.
If a 5V one was used, I'm not sure if you can get away with going through the Arduino's regulator or if you need to power the Arduino directly with it.
Heh. Building a keyfob controlled door-lock-and-immobilizer myself. For tests I've been plugging in directly (via the cigarette lighter). Using a Freeduino, which has the larger (TO-5?) voltage regulator. Doesn't seem to get that warm, not so far. I may attach a heat sink to it for safety, tho.
I'd be interested in seeing how you chose to drive the auto relays.
ok, so what it LOOKS like I'll do is power it off of a 12v to USB port (5v adapter) and I'll explain why.
I need this setup to be as small as possible, since I plan on embedding IN my door. So I think I'll go with the Arduino Nano, which is really small. If I power the Nano with 5v on the usb plug, I can get 3.3v off of it to power my keyfob. Also, if I keep the usb end on the cable (the end not inside my door), (somewhere inconspicuous) I can plug it into my laptop and change software (or just the combination code in the software) easily without pulling my door apart.
Echoing my thoughts there. I'm using a Decimilla so I can hook up a USB cable while the unit is still in the car, and tweak the software. Right now looking at sticking the whole mess behind a custom faceplate where the radio would usually sit.
Well, I finished the software tonight. It takes the combination and unlocks, will do an extra unlock if the correct code is followed by a '3' within 4 seconds, and will lock when the last two are pressed together at any time. Oh, and I fixed the debounce so it actually works now.
By 'lock' and 'unlock' I mean 'light green LED' or 'light red LED'.
