Customer: small,
volunteer-run hackerspace for underprivileged high school students in a shared
access building
Problems
A small, volunteer-run hackerspace for underprivileged high school students
needed an electronic proximity key based building access control system to manage
access to the building. To reduce costs, and to provide a learning opportunity
for high school students, the hackerspace wanted to design and build a custom solution
instead of hiring professionals to install one.
Workshop director: Wants to increase
open hours without increasing personal time involved by providing trained adult
volunteers access to the building without the director present. The director didn’t
want to provide volunteers with a copy of building keys to avoid the risk of
losing keys and having to replace all building locks. Director also wants a record
of which volunteers have accessed the building in case equipment is damaged/missing
when director isn’t present.
Volunteers: Want to be able
to get into the workshop when the director isn’t present, but doesn’t want to carry
building keys to avoid risk of losing keys and having to replace building locks.
Process:
User-centered design techniques were used to research, plan, design, and
build a custom electronic key card access control system. I led a team of 3-6
high school students that installed wiring, RFID readers, replaced door locks,
and wrote Arduino software program.
I defined the overall vision and wrote a functional spec that with
prioritized list of features & scenarios after interviewing stakeholders
and researching competitive landscape of professional proximity key access
control systems from companies such HID and DoorKing and Arduino and RFID based
hobbyist DIY projects.
Through interviews with hackerspace director and board of directors, I understood
their need to expand the open hours by providing access to trained volunteers
without providing them a copy of building keys. Being a nonprofit,
volunteer-run organization, the hackerspace needed a low-cost, low-maintenance,
and secure solution.
Product:
The custom electronic proximity key based building access control
system was successfully built performed at 99.99% uptime for 2 years until hackerspace
closure. The total system was built for ~$400 in parts, a fraction of the installation
and hardware cost of professional solutions.
Components used:
•Arduino Mega 2560 microcontroller
•Open Access v3.0 I/O shield
•2x RFID card reader (Mifare 13.56MHz)
•2x electric door lock (fail-secure)
•Integrated Open Access Control open-source firmware
System Features:
•Reads ID of RFID tags at either of 2 doors
•Authenticates RFID tag against a list of allowed users, unknown RFID
tags are ignored
•Unlocks the corresponding electric door lock for 3 seconds when
allowed RFID tag is detected
•Saves log of access attempts with success or failure
•Door stays locked in case of system failure, and traditional key still
unlocks door
•Target 99.9% uptime (8 hrs downtime/year)
•Users can use regional transit card (ORCA card) as ID instead of
carrying additional RFID card
•Stays working during power outages using uninterruptible power supply
•Same hardware also supports future capabilities that can be enabled by
software: Remote unlock of door over the web, view access logs over the web,
“moving mode” that temporarily keeps door unlocked
To increase reliability and uptime, the following decisions was made:
•Arduino microcontroller was used instead of PC to increase reliability
and to lower costs.
•To reduce risk of vandalism to RFID card reader, RFID reader was
mounted on the interior. Reader could still identify RFID tags placed on the
other side of the door.
To minimize costs, commodity hardware was used:
•Utilized metal housing from discarded satellite TV box
•Utilized commodity modem uninterruptible power supply
•Used speaker wire for high current (500mA) electric door locks, while
Cat5 ethernet cable was used for RFID card reader signaling.