It might be that I am unusually particular here, but there is nothing (absolutely NOTHING) that upsets me more than dirty toilets. Yes, I know this is the epitome of a pampered-person’s phobia. But I have nightmares — honest, actual, recurring nightmares — about horrible toilets, and I’ll plan my day around avoiding public toilets which are likely to be dirty. So this project appealed to me enormously.

Obi-Wan and the Worst Toilet in Scotland

Automating spotting that things are awry in a toilet cubicle without breaching privacy is really tricky. You can’t use a camera, for obvious reasons. Over at Hackster.io, Mohammad Khairul Alam has come up with a solution: he uses a Raspberry Pi hooked up to Walabot, a 3D imaging sensor (the same sort of thing you might use to find pipes behind studwork if you’re doing DIY) to detect one thing: whether there are any…objects in the toilet cubicle which weren’t there earlier.

From a privacy point of view, this is perfect. The sensor isn’t a camera, and it doesn’t know exactly what it’s looking at: just that there’s a thing where there shouldn’t be.

The Walabot is programmed to understand when the toilet is occupied by sensing above seat level; it’s also looking closer to the floor when the cubicle is empty, for seat-smudges, full bowls, and nasty stuff on the floor. (Writing this post is making me all shuddery. Like I said, I really, really have a problem with this.) Here’s a nice back-of-an-envelope explanation of the logic:

There’s a simple Android app to accompany the setup so you can roll out your own if you have an office with an upsetting toilet.

Learn (much) more over at Hackster — thanks to Md. Khairul Alam for the build!