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Apartment Keyless Entry

Page history last edited by Stephen M. 13 years, 11 months ago

I moved into a new apartment at the beginning of the summer.  My roommate (A CompSci major named Shane) and I were simply too lazy to be bothered with keys so we improvised a keyless entry system for our apartment from electronics components that I had had in my collection at the apartment.


The upstairs door is locked with a deadbolt that I rigged to be actuated with a servo.  The servo is triggered when a valid RFID card is present at the detector, if the button out side (to lock), or if the button inside is pressed (to lock or unlock).


The downstairs door can be unlocked by pressing the unlock button on the console next to the upstairs door.  I rigged a circuit to listen in to the doorbell (pressed downstairs) and interpret patterns using the Arduino.  This would allow the upstairs console to unlock the downstairs door when a specific rhythm is entered in on the doorbell.


All coding and controlling was done using the Arduino microcontroller and was interpreted by Shane and I based on samples of code found online written by people doing similar things with arduinos and doors.



On the left, the console that allows entry to the first floor door.  The button on the left allows talking to whomever is on my stoop.  The second button allows listening to the stoop and the third button allows entry to whomever is on the stoop.  All of the buttons are momentary on switches that can be spoofed for my purposed by activating a transistor using the Arduino.  On the right is the deadbolt, the red wire is what is temporarily holding the motor to the deadbolt.  Everything that I modified needs to be completely reversible for the sakes of our security deposits.


The first step was to breadboard the circuit to test the coding, after that was accomplished we determined where the LED's were to be placed and how many were to be used.



I happened to have a project box or two lying around that I cut to shape using a jewelers saw and a power drill, when completed, the box will be held in place on the door using only the mounting hardware from the deadbolt itself (in no way marring the door).



On the left, the dry fit of all of the components in the door box.  The small board on the right holds the resistors needed for the LED's and switch.  The green and red LEDs will be visible within the room.  On the right the box has been installed for testing, the red wires leading off to the right allow for the the LEDs embedded in the peephole to show the lock status from the outside.



Backing up, the whole door can be seen.  The LED's embedded in the peephole can be seen and the blue (ethernet) wire will soon be routed to the right and looping back over the door to connect the door box to the arduino.  On the right is a picture of the circuit board and speaker on the door console.



Shifting outside the door for a moment the box that connects the intercom to the rest of the apartment buildings system (5 other apartments) can be seen on the wall.  This is what we will tap in to.



I replaced the metal box with another project box (again sawed apart to adapt as needed) and we pulled the cables need through the wall using a coat hanger.  On the right can be seen the RFID reader ready to be boxed up after wiring.  This location was perfect because it provided a via for the wires and an inconspicuous location for the rather large RFID antenna.



Buttoned up nobody would no anything devious had taken place here aside from an innocuous black button.  Aside from the color difference, the box looks perfectly in place on the wall.



The small board that bridges the gap between the arduino and the intercom box is the isolator board.  This makes use of photocouplers to jump a digital signal across a gap of electrical isolation.  The grounds and current on both sides are kept separate.  The optoisolators are packaged with transistors that make them easy to interface with the arduinos.  One of the isolators listens to the speaker line and notifies the arduino whenever the doorbell is ringing.  The other send a signal to its isolated transistor to close the circuit and allow entry to whomever properly keyed in the code.  An elegant solution that allows for complete functionality of the intercom as usual while allowing greater capabilities to those who are in on the joke.



In these two pictures the arduino is shown as connected to the RFID, intercom, and servo circuits.  The small switch allows for disconnection of the RFID reader for security purposes and to allow upload to the board (which is disabled when signal on the Rx pin is present).  At this point all systems are completely operational.


Since the last picture was taken, all of the systems have been packed up and everything is working.  The arduino on the wall is still rather conspicuous but at least it is located on the inside of the door.


The RFID chips used vary in size from the wallet variety down to 25mm diameter disks than can be hidden in anything (clothes, shoes, sub-dermal implantation) and allow for discrete and impressively illusionary entry.  The code to enter the lower floor can be anything that we want to program it to.


I will be uploading a commented code shortly.

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