My new project: Tact, a simple chat app.

Restroom indicator

Hobby project. 2008

Light sensing, wireless sensor networking, electronics, voltage conversion, mobile power consumption optimizing, intelligent office, Arduino, Dashcode, Python, Javascript


Apply my recent Gadgets and Sensors education to solve an office pain point with a new hardware sensor.

What I did

At the office where I worked at the time, there were few bathrooms and they were often busy. To reduce the required context switching to walk over and check the bathrooms, and augment the office environment with intelligent devices, I designed and built a system that could sense the “busy status” of any number of restrooms by sensing if the light was turned on.

I considered several options to detect the “busy” status of a restroom that would provide relevant info while not having privacy risks. You could detect whether a person is around with various techniques. In the end, a simple light sensor proved to be the most workable solution.

The end result is a complete sensing system that consists of any number of restroom units that sense the status of individual restrooms using a light sensor, and transmit their statuses to a computer.


The hardware was a bit clunky. I also didn’t manage to make the restroom units battery-powered, so they had to be connected to wall sockets. In the end, the system didn’t stay in use for very long.