Remote Entry Via Android And Launchpad

[MarkoeZ] had an issue with keys breaking off in his door lock, and while normal people might try to simply replace the lock all together, [MarkoeZ] decided to do it the “Hackaday” way by adding a bluetooth lock to his door. His door is already setup where someone can walk up to it, page an internal intercom and have someone buzz you in. From the inside the intercom was modded with a TI Launchpad with a “deal extreme” bluetooth module and relay.

Access is granted by the use of an android phone running “BT_Serial_Tester” which is a simple app that allows you to send characters over bluetooth. Just enter a pin, grab the door before the buzzer times out, and you’re in! A starting point for the MSP code and schematics are available on his blog. Join us after the break for a quick demonstration video.


8 thoughts on “Remote Entry Via Android And Launchpad

      1. I was thinking more along the lines of someone who wanted to show this kid how incredibly insecure this really is… Breaking in with prybar = obvious and sure to get you caught. Breaking in with bluetooth = take his plasma TV and get away with it ;)

  1. Very nice. I love these electronic locks – having spent a couple hundred bucks for having the door opened after forgetting the key.
    There are two things, which have prevented me from building my own though: 1. at least here in Germany insurance doesn’t pay if your lock is not officially approved and 2. what do I do if my homemade lock breaks/ is out of power? Forcing my door open would result in about 1000 bucks of damage.

    1. Super-capacitor, or a 6-volt Pb-Ca (lead-calcium) battery back-up. I recommend the latter.

      The circuitry to charge, monitor, and maintain the battery is very common. Virtually every emergency exit sign in the civilized world has one embedded, and there are numerous designs out there. My advice would be to find a building about to be demolished, and then ‘liberate’ the signs before the wrecking ball hits.

      The batteries themselves are about $15-20 US, so maybe €10-15; I’d recommend buying new, since they have a limited life span.

      The Bluetooth circuitry itself should not draw much current. For example, the Roving Networks RN-41 module with which I’ve been tinkering only draws about eight milliamps during low-power sniff mode (and that’s at 3.3V, the battery is 6V, so even after regulation, it’s still a small amount of current). I haven’t tried the sleep modes yet, but I’d wager the current can be dialed down further.

      Given that the battery is usually rated at about four ampere-hours, it should still have plenty of power left after several hours of power outage to open the door. If you’re worried it won’t be enough power, simply use a higher-rated battery. :)

      I just took a quick glance at the HC-06 module, and it appears that it draws 40 milliamps in normal operation, and less than one milliamp during sleep. I’m not sure if that includes a low-power ‘sniff’ mode as the RN-41 does, but those currents can be used as a design guideline, I suppose. :?

  2. Thanks for the replies and mostly positive feedback guys!

    About security:
    Indeed in it’s current installation its not super secure. You’d still need to know the pairing code and unlock code, or software to crack those.

    But it is only the door into the common area, my personal space is still locked with an old fashioned, but better quality, key lock.

    If i were to use this on an actual home door, i’d use a more complicated access code, and some kind of encryption for the sent code to prevent interception.

    Still, pretty nice gadget :)


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