Custom Car Door Keypad


[Michael] has a keypad in his previous car’s door and he missed it enough to hack one into his Dodge Caliber. He bought a Ford keypad and mounted it inside his door with some custom electronics. He started with an Arduino nano to receive and authenticate button presses. This then splices into wires in the door that control the door lock. The program has a 5-digit code to unlock the door, but simply pressing 1 twice will lock the doors. He also implemented a lockout feature to prevent people from brute-forcing the combination. Although it isn’t wireless, it’s significantly simpler.

[thanks Michael]

25 thoughts on “Custom Car Door Keypad

  1. this doesn’t make a whole lot of sense to me. most cars nowadays have keyfobs at the very least, and most have unlocking systems where you dont even need to push a button to unlock the car – they automatically unlock when your key comes into proximity with the door.
    i appreciate the craftiness, but is it useful? thats a resounding no.

  2. This would have been useful to me the other day. For the first time in the 8 years I’ve owned my Impreza, I managed to lock the keys in the car. My wife had to bring me the spare set. I really could have used a keypad option.

    As it is, I had to make a copy and tape it up under the bottom side of my desk at work, just in case I screw up again.

  3. Having never owned a Ford before, I didn’t see the value in an external keypad – till now. [nubie] is right – lock the keys in the car at the beach, the game, wherever you’d rather not carry ’em with you.

    besides, it’s a great hack anyway – it looks great and the attention to detail makes it look like it’s not a ‘hack’.

  4. Problem is he bought a dodge. Second thing is he owned a ford. And as posted above, most cars know when you’re in range and unlock automagically. Fail? I think so. More speshul would be to tap into this and unlock the door on its own. if the keys are in the car, it’d unlock for you anyway. Rite?

  5. “if the keys are in the car, it’d unlock for you anyway. Rite?”

    How do you propose to tell the car that its -you- and not someone else trying to steal your car?

    In fact, how do you tell the car anything. Your magical proximity key is locked inside.

  6. He’s done an awesome job. I’d like to have a touch key entry system. I’ve locked my keys in the car a few times — especially when I’m in a hurry on the way to the fire station. It’s happened enough that I keep a spare entry key with my bunker gear. On the other hand, an add-on like that would be something I’d worry would make the car harder to sell. Tough call.

  7. Hey guys, I’m glad that most of you like my project! I did try and make it look as factory as possible.

    @life2death: I know that there are cars now that will unlock automatically with the key, I wouldn’t say most, though. I only know one person that has a car that does that. Also, I paid several thousand dollars less for my car. I’m a cheap/poor student afterall.

    Besides, the keypad isn’t really about getting into my car easier or faster. I definately use my keyless entry (keyfob) alot more than my keypad. It’s purpose is to let me into my car when I *don’t* have my keys on me. If they’re in the house and I’m not, or if I ever locked my keys in. I could easily add rfid, infrared, some kind of wireless like the iFob, or whatever to this. It’s easily expandable, but really all I want is to get into my car without keys. (or chips, or fobs, or remotes, or cards, or anything)

    My source code is available on the site and the board is available at BatchPCB. If it’s not exactly the way you want, it’s all there to make it what you want.

  8. Good job, looks good, too bad the buttons look plasticy and cheap lol (maybe look at changeing them later on with custom ones, maybe brushed aluminium etc?).

    As for the ideas of locking your keys in the car when down the beach etc, that is the stupidest idea ever! Imagine someone sneeks a peak at you doing this as they walk past, or you brag to somone you know who tells other people etc. Then the next time you do such a thing, someone breaks your window, takes the keys and shuts off the alarm and a free car they have. Try explaining to your insurance why your keys were in the car. They would NEVER pay out in such a circumstance cos the car got stolen from your negligence!

  9. oh, give me a break. It’s not like you’re going to leave the keys laying on top of the dash, and a note that says “Look for keys here!”

    It’s easy enough to lock the doors with the remote, arming the alarm (assuming you have one), toss the keys under the seat or in the dash, and then shut the door. Unless someone is staring at you, they’re not going to go “Oh look, he actually didn’t use his keys to lock the door from outside the car!”

    Not to mention, a thief is less likely to steal a car with a car alarm (again, if you have one) than a car sitting right next to it without one.

    Of course, you can always just park next to a car that’s far more likely to be stolen :) Here’s a list:

  10. Yeah, there’s no alarm at all on my car. Having a cheap car (arguably having a Dodge car right now) maybe helps me out. Notice that unlocking with the keypad looks exactly like pressing the inside unlock button to the car, and I didn’t have to disable any security before I did this.

  11. @mike

    That bit of info is actually kinda interesting. My van has an alarm, and using the interior unlock switch will set off the alarm if it is active. In fact, the car will NOT start, even if you have the correct key/fob, while the alarm is going off. So…if I were to perform this interesting hack, I wouldn’t be well served to activate the alarm, since the keypad would let me in, but set off the alarm as well.

  12. @kevin: it’s all pretty well covered in the forums. If I had to make another one, it would probably cost about $200. I spend about $450 on it, but I went through a few revisions and had alot of parts that didn’t get used in the final implementation.

    @-7-: it can still be brute forced, but it just takes longer. One could easily make the code longer, exponentially increasing the time it would take. Again, the fact that I have Dodge’s cheapest vehicle probably makes me less of a target.

  13. I wish I’d had this on my Blazer a year ago. We were leaving the therapy center at the local hospital (my 10 yo son is autistic) and my son got locked in the running SUV with my wife and I outside. The doors lock automatically when the ignition is started, and we couldn’t get in to our son. We had to wait 10 minutes for the tow service to come out and unlock our truck while our son was having a melt-down. We keep spare keys stashed on the truck now, but I’ll never forget the fear, and tears, of my wife and son.

  14. @andar_b: for something like that, i’d just wire the “unlock” and “lock” signal to a spare alarm keyfob instead of direct to the door locks. you could wire the keyfob to the power in the door and build a power supply so you never need to worry about changing the battery and it would work just as seemlessly as the original poster while retaining your security.

  15. Had this option on my ’92 mercury grand marquis (think police cruiser). also had large sound system in it – lots of space in trunk for subs… anyways. i always used the keypad – it was a five digit code, then press another button and the rest fo the doors unloacked, press another and the trunk popped open. i’d toss my keys in a small container in my trunk and lock it up. when i came back, i’d just enter the code, pop the trunk, grab keys and go. if anyone got in, they wouldn’t find the keys under the seat or dash, and never suspect an old geezer’s car could pump out 140 dB..

  16. This is the one thing that I have to have on a car. I was hiking in the upper pennisula of Michigan way off the beaten path, there lying on the trail was a rusty set of General Motors keys. All I could do was thank FORD for having the keyless entry system as my keys were locked in my trunk! If you are an outdoor person keyless keypad is the only way to go. Canoeing swimming how good are the fobs going to work on the bottom of some riverbed?

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