Adding A Keypad To A Key Card Lock


[Colin Merkel] had a little problem: he was continually forgetting his electronic key card, locking himself out of his own dorm room. Like any normal Hack a Day reader, rather than getting in the habit of always carrying his card, the natural impulse of course is to build this elaborate rig of electronics and duct tape. Right?

The result is an additional keypad that can be used to gain access…not by altering the existing electronic lock, but with a secondary mechanism that operates the inside door handle. An 8-bit PIC microcontroller scans the outside keypad (connected by a thin ribbon cable), and when a correct access code is entered, engages a 12 volt DC motor to turn the handle. It’s a great little writeup that includes a parts list, source code, and explains the process of keypad scanning.

It’s similar to the RFID-based dorm hack we previously posted. By physically operating the handle, most any approach could be used: facial recognition, other biometrics, DDR pad, or whatever inspired lunacy you can dream up.

19 thoughts on “Adding A Keypad To A Key Card Lock

  1. @jc I know, ever since the “read” link has been removed I have had to hunt for it. Could we please have it back? Thanks

    Sms would be neat, i always thought the secret knock would be very insecure, and i really like the usb thumbdrive authentication.

  2. Sorry, I saw that link, and didn’t realize it was the actual article. Probably because of my intense dislike for Instructables (a great idea gone horribly wrong).

    If that’s the lock I think it is, that’s made by a sister company of ours. We make locks for all markets, which have various options for Prox, mag card, keypads, and some which have WiFi and Ethernet access (although the networked locks aren’t intended so much for dorm rooms). We don’t do biometrics yet because they’re somewhat insecure, and don’t lend themselves to the power requirements of universities that only want to replace batteries at most once a year, and preferably every two years.

  3. A friend of mine had a professional system like this. They were having trouble programming in new passwords and I went in to help out. It was similar to this but with a crucial difference. The entire device was mounted on the outside, the screws were on the front, and it was fed the buzzer wire. Once the front was unscrewed you could reset the master password if it took your fancy, or just short the buzzer wire.

    I like how his dormitory is more secure than my friends office was.

  4. This is far from secure. It’s probably MUCH more easy for him to punch in the code than it is to slide his card. Problem is that over time, the key pad will wear thus revealing which numbers are used for the combination. I will be willing to bet you that if he does change his combination, that it’s not frequent enough.

  5. I like the duck tape, I was going to do something similar when I lived in a dorm but the paint on our doors was to old and tape would peal it right off and that meant a fine. would be cool if it could actually lock/unlock the door, not just open the handle. all together not bad.

  6. It’s neat, and for a drunk college student who probably loses everything on him it may work well, but I can’t help thinking something bluetooth related or otherwise accessible via your cell phone would be a better plan. Have your phone, get into your room, easy.

  7. Yes, but a cellphone or anything else except something that you can carry in your head is something you have to have on your person. The point is NOT to have to carry anything to get in. Unless you’re totally trashed, it’s unlikely you’ll forget your PIN.

    Many new cellphones, especially those in Europe and Japan are coming with iClass 13.56Mhz Prox capability built in. Then rather than carrying a card, you can present your cellphone to the lock to get in, make purchases, etc. Kinda neat, kinda scary. Unless you’ve got an additional layer of a PIN or biometric, someone just has to snatch your cellphone to gain access.

    And while I don’t know if anyone has broken the encryption that iClass Prox offers, someone has built a Prox sniffer that’s capable of both 125Khz eProx and 13.56Mhz iClass Prox. Some very rudimentary access control systems use nothing but the very card ID, which is basically the public half of the encryption key. So it’s easy enough to sniff and reproduce eProx and card ID-only iClass stuff.

    @Sklyer, your Arduino system is easy enough to make impractical that it’s not worth bothering with. 8 digit keys with increasing delay times between bad entries will give such a wide number space over such a long period of time that someone is going to see you sitting trying. You’d be better off burying a video cam in the ceiling, or trying a high-voltage pulse approach.

    One thing to remember about access control systems: From MOST people’s perspective, it’s to keep unauthorized people from getting in. But a denial of access attack is pretty effective, too. Don’t want to go to class? Get there first and break the lock on the lecture theater so NO-ONE can get in. Or keep the president of the company out of his office. All sorts of effective mayhem can be committed by keeping authorized people out, instead of just the unauthorized.

  8. @andrew: looks like it just winds for a certain period of time and then stalls once its reached the open position. The handle is spring loaded which allows it to return to the start position when power is removed. Simple and effective.

    If your interested in positioning, it could be done with various types of limit switches or rotary encoders.

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