Restroom hacks
Datadog built an office bathroom-availability monitor to reduce contention without compromising privacy or existing door functionality. Raspberry Pi 2 devices, GPIO-connected sensors, and simple Unix tools provided a low-maintenance way to report whether bathrooms were occupied. The project showed that the hardest parts were adapting to varied real-world hardware, mounting sensors cleanly, and dealing with unreliable Wi-Fi—not writing software. ## Project Goals - Avoid intrusive monitoring: - No cameras or sensors that could feel invasive. - Provide reliable occupancy information with minimal false positives and negatives. - Use door-lock status where possible as the occupancy signal. - Avoid interfering with existing locks and doors. - Keep devices secure, professional-looking, easy to maintain, and remotely updateable. - Treat the project as a fun hardware experiment. ## Adapting to Different Bathrooms - Bathrooms differed significantly in: - Lock styles, including push-button handles and rotary stall locks. - Number of rooms or stalls. - Availability and location of power outlets. - Wi-Fi quality, especially near concrete walls and older electrical equipment. - These variations required different sensor designs rather than one universal installation. ## Raspberry Pi and Sensor Hardware - Raspberry Pi 2 Model Bs served as the project’s controllers because they: - Ran Linux. - Supported Wi-Fi and SSH administration. - Were compact enough to conceal. - The team used several sensor types: - Magnetic reed switches for detecting door position. - Pin switches for detecting sliding stall-lock positions. - Photoresistors were purchased as a possible way to detect darkness but were not needed in the MVP. - For push-button locks, reed switches detected whether the door was open or closed. Although this could theoretically misreport a closed but unoccupied bathroom, it worked reliably in practice. - Stall-lock sensors were hidden inside hollow metal panels. Automotive-style pin switches were mounted using simple carved wooden blocks that contacted the sliding lock without obstructing it. - Wiring was concealed in wiremolding, with Raspberry Pis placed inside outlet boxes where possible. ## GPIO and Unix-Based Monitoring - Raspberry Pi GPIO pins were accessed through files in `/sys/class/gpio/`. - A Python script read sensor values and translated them into bathroom availability. - Configuration handled differences between normally open and normally closed sensors. - The service was exposed through `tcpserver` and managed with `daemontools`. - A basic command-line client could query status with Netcat, for example: ```sh nc 11.bathrooms.datadog-internal.com 50 ``` ## Making Availability Easy to Use - Employees could check status from the command line. - Some added bathroom availability to TextBar. - Datadog dashboards displayed bathroom status throughout the New York office. - The implementation required very little code; most effort went into sensor selection, physical installation, and network troubleshooting. The project demonstrates that inexpensive, hackable hardware combined with simple Linux tools can solve a practical office problem. For similar systems, prioritize non-intrusive sensors, flexible installation designs, and secure remote management; the resulting software can remain remarkably small.
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