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Electronic Door Lock


The Eugene Maker Space is in need of an electronic door locking mechanism. This will make key management really simple because every key holder will have their own separate key that can be revoked at any time. Clif was working on a USB key based system at one point in time. There are other possibilities as well such as RFID or smart cards. We should build a good system for the space and log all relevant information about it here.

Example Systems:
Similar but with an iPhone:
Similar but with analog distance sensor and plays cute tones:

This one uses a VCR worm gear assembly for running the dead bolt, which actually pushes the door latch in!
Text message powered, with different type of deadbolt.
RFID with door strike.

Feature list

  • Authentication possibilities: USB serial Number, RFID, Keypad, Email, Texting, or Webpage.
    Checks with something like a radius server, credentials could be something you have and/or something you know.
    Keypads could have a pizio beeper or speaker/mike for audio.
  • Uses servos or actuator that can also be turned by a key? This is a tradeoff.
    Has door closed Mag switch, to prevent bolt from being thrown at the wrong time.
    Also an electric door strike, so one can be "buzzed" in when the knob is locked.
  • Has ethernet , possibly with PoE and a DC battery charger for a small Gell Cell on the door.
    Monitors wall power and battery voltage, use simple trickle charger maybe with cutoff FET.
    Probably a 6V system, make sure servo and door strike are 6V.
  • The MCU board has a sleep mode,
    and Flash so a small number of codes can be DL into it that will work if the Radius system can't be reached.
  • Use the watchdog timer for robustness. Log it if we were bit. wink
  • Red/Green/Yellow lit push buttons on inside and outside. Red is Locked, Yellow is in transit or authenticating, Green is Unlocked. Inside button is on deadbolt cover, and could also be on PWM for pretty fade effects. Inside light blinks slowly if wall power is out, fast 25% DC if battery is low. Blinks Yellow if jammed.
  • Outside hooded keypad for privacy and waterproofing.


Optionally, when leaving; Close door, authenticate, and press button to lock, (default is unlock). This logs you out of the space.

Roll the (Optional) alarm system terminal into it. Which consists of a 4x4 keypad, backlit LCD and blinky LEDs.

Initially use ethernet, then later when we build a CAN or LIN network, and swap the controller for a lessor one that does just one of those. The first controller can become the CAN/LIN to ethernet bridge. Use headers like found in a PC for disk / reset / power leds etc... for connections to the MCU board. Later just slide the wires onto the new controller. Could use the Teensy++ 2.0 for a LIN node, but it doesn’t have CAN. Might be awkward for audio.

Door should have a door closer so that if it is unlocked and "Buzzed" open but no one enters, it can be relocked automatically. There may be a security camera near the door but on a separate system.

MCU board resources:

Feature Resource Netduino Plus mbed - LPC1768
USB Master for USB fob auth USB Master    
Ethernet NIC to network NIC    
Outside Button w/RG LED 3DIO Int?    
Inside Button with RG LED 3DIO, 2PWM?    
Deadbolt Servo 1PWM    
Servo jam current sensor 1 ADC    
Electric door strike 1DO    
Door closed mag Switch 1DI    
Monitor power and battery 1DI, 1ADC    
Battery charger 1PWM    
Power conservation Sleep mode    
Local auth code storage Data Flash    
RFID reader?      
Optional inside 4x4 keypad 8 DIO    
Optional outside 3x4 keypad +3 DIO    
Optional Beepers/Speakers 1PWM Ea.    
Optional inside LCD/LEDs 8 +4-5DIO    
LCD backlight control 1PWM    
Optional Audio IO 1ADC, 1PWM    
Totals: 9+11+12=32, 32-19+1=14DIO, 2-5PWM, 2-3ADC = 22 + serial

Sample BOM and Costing

Vendor Part number Description Price Quantity Extended Shipping Subtotal   mbed NXP LPC1768 dev board $59.00 1 $59.00 $4.95 $63.95 1058 Power HD Standard Servo 3001HB $9.95 1 $9.95 $1.00 $10.95 DH970 Thomas & Betts DH970 Carlon Electric Door Strike $16.10 1 $16.10 $3.00 $19.10 RR-1C543122 Delux USB Waterproof Connector $14.95 1 $14.95 $2.00 $16.95 77413 Recessed-Mount Magnetic Contact Sensor Switch $1.61 1 $1.61 $7.99 $9.60 7113 Surface Mount Magnetic Contact Switch $1.25 1 $1.25 $1.00 $2.25 MAX6957ANI+ LED DRIVER / GPIO, CONSTANT CURRENT, DIP-28 $7.19 2 $14.38 $1.00 $15.38 14N8135 CAT5/CAT5E RJ45 MODULAR JACK 8POS 1 PORT $0.47 2 $0.94 $1.00 $1.94 553-1480-ND CONN STARJACK 1PORT 10BASE-T $4.15 1 $4.15 $1.00 $5.15
    Red / Green LEDs Common Anode $0.50 2 $1.00 $1.00 $2.00
Batteries Plus   6V Gell Cell $0.00 0 $0.00 $0.00 $0.00
Junk Box   7-9V DC wall bug $0.00 1 $0.00 $0.00 $0.00 COM-08653 Keypad - 12 Button $3.95 0 $0.00 $0.00 $0.00 BAS009 Sealed Membrane 4X4 button pad with sticker $4.50 0 $0.00 $0.00 $0.00
Radio Shack 273-073 Piezo transducer $1.99 1 $1.99 $0.00 $1.99   USB Adapter - USB A Female to USB B Male 4 Pin Mini $2.77 1 $2.77 $1.00 $3.77
Avnet Express A22L-TW Omron Lighted round pushbutton Op+Case $5.53 2 $11.06 $3.00 $14.06
Avnet Express A22L-10M Omron Lighted round pushbutton SPST switch $13.54 2 $27.08 $3.00 $30.08
      $0.00 0 $0.00 $0.00 $0.00
      $0.00 0 $0.00 $0.00 $0.00
      $0.00 0 $0.00 $0.00 $0.00
      $0.00 0 $0.00 $0.00 $0.00
SubTotals         $166.23 $30.94 $197.17
Total Cost         $197.17    


Here are links to various useful parts.

RFID readers: Smart USB FOBs: Servos: Vertical Deadbolts: Door Strikes: Maglocks: Waterproof USB: Pushbutton Switches: Hooded Keypads:

Door / Window Sensors: -- RickO - 2011-10-18

-- ClifCox - 15 Nov 2011
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Topic revision: r6 - 15 Nov 2011, ClifCox

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