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Ring the number, get recognised, enter the premises.


The lease of the space gives us three remotes to open the gate. We're coming up to 20 members now. So we decided to take one remote, mount it in reach of the gate and hook it up to a beagle board with a huawei modem. The idea is: you call the number of the modem, it checks the caller id against a text file, and if it's in there it switches the remote. Best of all: 'just letting it ring one time' doesn't cost money and opens the door. It's democratic because all our members have a cellphone, not all have a smartphone.

Next plans

  • Make a webinterface
  • do something with pgp keys and smartphone.


For more information about the first version of the system, see the events Doorhacking and Doorhack2.7 Since the first system was unstable and damaging to the remote was thought to be harming the remote, a complete redesign was called, with special attention to robustness and proper stable operation.

System architecture

All hardware will be divided in two cases:

  • An old Lantronix Lantronix terminal server 1U mounted in the hackerspace rack
  • A plastic IP65 junction box to be placed in front of the gate


The exception to this division is the USB GSM modem, which will be placed outside the hackerspace rack for reception reasons.

A cat5 UTP cable will connect both boxes.



Circuit of the two printboards together. The switch represents the pin on the beagleboard - which can go 1.8v or 0v. When it is high, the relay does not trigger, when it is low, the relay does trigger.


Lantronix case

Power supply

The original Lantronix PS can be reused. It gives the following outputs on a 6-pin molex:

Pin Number Color Voltage
1 RED +12
2 & 3 BLUE +5
4 & 5 BLACK Ground

Beagle Board

pinout on the beagleboard towards the gate opener:

  • pin 24: white: 1.8V on/off (when high, remote gets "pushed")





The two print boards, from RIGHT to LEFT: power connected to the inverter, connected to the relais steering, connected to the ethernet cable (unclear).

Invert steering

The stripboard contains the following:

  • 5-pin power input connector:
    • blue (5v) (from psu)
    • red (12v) (from psu),
    • black (ground) (from psu),
    • white (1.8v or 0v when relay needs to be closed) (from beagleboard) and
    • orange (1.8v continuous) (from beagleboard).
  • 2x 10k ohm in series
  • a PNP transistor (bc557b)
  • Power output pins towards the next stripboard for steerin the relais:
    • blue (5v)
    • red (12v)
    • white (0v or 1.8v when relay needs to be closed) (inverted steering power) and
    • black (ground)

Steering relay

The stripboard contains the following:

  • 4-pin power input lines
    • blue (5v)
    • red (12v)
    • white (0v or 1.8v when relay needs to be closed) and
    • black (ground)
  • a 1.1K ohm resistor
  • an NPN transistor (bc547b)
  • Power output pins towards the remote
    • pair ground and 0/5V: for steering the relais (brown pair)
      • 5v
      • ground
    • pair ground and 12V continuous: for powering the remote (blue pair)
      • 12v
      • ground

RJ45 output connector to the IP65 case

  • left first RJ45 connector on terminal server acts as output connector
  • Connected to the stripboard
  • the pins on the connector have all been soldered, T568B style.

On the RJ45 connector is present:

  • one pair carrying power to the remote (+12 Volt continuous plus ground)
    • we are using the blue pair for this
  • one pair carrying the signal to the relais (+5 Volt if on, plus ground)
    • we are using the brown pair for this
    • the +5V comes from the PSU but the beagle bord does the switching through pin 24

LED controller

32 leds + controller are present on the case. Connection to the controller is made by 10-pin flatcable. Low-priority, but nice addition to the project.

Door opener tester

Simply a RJ45 male plug with a led attached to the brown pair. To be inserted into the connection of the remote. Allows developing software and hardware and testing the door without actually making the door go open. When the led is on, the remote is pressed.


IP65 Junction box



The stripboard contains the following:

  • Two RJ45 connectors
  • RJ45 connector on the bottom (IN) to receive power & signal
  • Relais
  • Remote
  • Double line male pins, with female connector connected to in ethernet cable
    • currently only the first row is used
    • first brown pair and then blue pair is connected
Pin Usage
1 5v relay steeriong (brown)
2 ground
3 12v remote power (blue)
4 ground
  • Single line pin header with following connections:
Pin Usage
1 & 2 First button
3 & 4 Second button
5 +12V continuous power
6 Ground
7+ Unused



For the gatekeeper python script, see Gatekeeper