The Sign Says "Occupied"

By Alan

Ever feel like you are being watched? Increasingly, this is true, since security cameras, traffic cameras, monitoring systems, and other kinds of video are in more and more locations. But, if you consider the definition of watching being something other than just visual pictures, you have lots of other things observing you. Motion detectors, audio detection, radar systems, all "watch" you to see if you trigger their programming.

We often never really think about the sophistication of designing automatic things that react to you. There are sensors to figure out the proximity of a person, either by infra-red lights, noise, or motion. Lots of ways to determine if a human (or at least an upright, warm, moving body) actually is nearby. Oh, the infra-red sensors know you are there. <click>

But, that's where people make a mistake. Hollywood movie science would let you believe that the sensor is on or off, and that's all that's needed. They think that the sensor is everything. They forget that you actually need to add some logic to the problem. There are tiny little controllers that use logic with the sensors to perform the behavior you need. It's not as simple as you might think.

For example, take the ultramodern public bathroom, where you have things "watching" you, even though there are no video cameras. Anything with the word automatic in their names stresses their ability to perceive if they were supposed to do something because someone was there, or wasn't there, or just arriving, or just leaving. But, they aren't just simple on/off devices. Let's look at each one with its unique behavior:

• The room lights come on as soon as you arrive, and wait patiently a short while until after you leave to shut off again.
• The room fragrance-erizer thingy, waits until after you are long gone, and shoot deodorizer into the now empty bathroom.
• The automatic soap dispenser waits until you hold your hand under it for a long enough time, before it spits out liquid soap.
• The water faucet reacts to hands held under it, turning on immediately, and lingering slightly after hands are removed.
• The paper towel dispenser dispenses a sheet as quickly as you can wave at it, but it doesn't react when someone walks in front of it (well, hopefully).
• The problem posed by the toilet is the most difficult. It has to determine that someone was seated, has gotten up, and has moved some distance away before flushing, not just leaning forward reaching for the toilet paper.

Imagine if the digital programmer got the sensor logic switched around.

• The lights require you to keep moving, because as soon as you stop, they turn off.
• The fragrancer-erizer thingy waits until you stand in front of it for several seconds then zaps that extraordinary deodorizer at you.
• The soap dispenser blasts soap every single time your hand gets near it.
• The sink only runs water for the first second your hands are under it, and you have to leave and come back before you get more.
• The towel dispenser doesn't give you a paper towel until after you stop waving your hand in front of it.
• The toilet flushes continuously while you are near it.

Literally all of the examples here could happen. The sensors are capable of seeing when someone arrives, stays there, leaves, and when someone isn't there at all. The logic just has to be right, too.

It's the simple things that are actually harder to do than you might believe.

Comments

[Helen]

So... You are saying that there is a REASON that the toilet flushes as soon as I get near it?

Actually, I prefer old fashioned sinks. The sink at our local movie theatre does NOT go on immediately. Sometimes I move my hand underneath. Nothing. Eventually it does turn on, but I don't know why.

[katdish]

Those automatic towel dispenser thingys? Oh, man! Kids love those. They'll use up 3 times what they need just to see the paper spit out.