Is there a simple reason why elevator floor buttons cannot be reset by a second push of the button?
Update: A comment reminded me of the first time I remember being able to ride on an elevator (at the time there was no elevators in Yreka.) It was at a Little People of America convention in Reno, Nevada (my sister is a little person.) They had installed these nice ramps so that the little people could reach all of the buttons. But for a little tyrant like myself, what this meant was that I could get into the elevator, run up the ramp, quickly press all the buttons and then get off at the next floor. Proceed to the next elevator and repeat. Ah, such fun.
O brave new quantum world!
You make a really interesting point. The only thing I can think of is that if you get into the elevator on the ground floor and press the button for, say, floor 10 then cancel it without picking another floor after the elevator starts moving, it could get confused that it has nowhere to go to. But I guess it could just default back to ground floor in that case – or stop at the next floor anyway. I doubt this would be a difficult issue to overcome.
Kea – that seems like a good reason. But what’s to stop kids pressing every button on the way up. It would be totally annoying to then have to stop at every floor. Which could be avoided if one could cancel the floors again….
I guess rude people in a hurry would be able to cancel all of the stops between where they are and where they need to get to and then intralift fisticuffs could ensue. Grrr.
Anyway, check this.
Yes! What’s to stop kids doing it while the lift is nearing the floor in question?
The boring answer is probably that it would make the dynamics of the lift too complicated: should I speed up now? Oh no, slow down! No, wait – speed up! And kids pressing all the buttons, and then trying to turn them off, might bring the poor lift to tears.
I’m going to go out on a limb and say: no. There is no good reason. There are probably various off-the-cuff reasons, but nothing that couldn’t be overcome by 3 hours of logic and a decent algorithm (at the design stage, mind you — not the pressing-the-button stage!!).
There’s one halfway decent reason, which is that it would increase the complexity of the interface. This isn’t really a good reason, because it could be done with minimal complexity increase, and would convey substantial benefits. However, if you combine this with “If it ain’t broken, don’t fix it”, it’s a fairly good explanation of why we haven’t done it.
Ever read Spider Robinson’s analysis (courtesy of Mickey Finn) of the average bathroom’s inefficiency?
mitsubishi elevators (which I’ve seen in london) have this property (except ou have to press teh button twice quickly to undo it)
In the states, otis is the main elevator maker…. their designs seem to have frozen in the 50’s.
Of course the wave of the future is elevators where you select the floor before you get in the car, and the algorithm optimizes all elevators based all floor requests (cf the mariott marquis in times square)
Clicking an elevator button more than once already has a function: It makes the elevator go faster. Or at least it gives the impatient the illusion that quickly pressing the button many times has some purpose.
But more seriously, the little lights in the buttons can blow out. If a light doesn’t go on when the button is pressed, the first response people are going to have is to press the button a second time. If it still doesn’t light up, they are going to assume the light is out.
I was recently in Iran for a quantum information conference, and the elevator in the hotel did exactly that. I think it’s potential for plutonium enrichment is the sole reason we don’t have it here in the West.
A toggling switch would probably permit inadvertent clears. Why not just a small recessed clear button next to each button? Like your reset button.
As an aside, have you ever walked into an elevator and press your desired button even though it is already lit? Alternatively, have you seen people doing that?
When one measures the state of a button in electronics, one finds that buttons tend to bounce. You can eliminate this in a number of ways. If you don’t mind paying extra for the switch, wires and logic, then you can debounce a SPDT switch by using an SR latch.
An elevator has a lot of floor buttons, so these are probably going to be momentary contact buttons. To debounce buttons like this requires a timing circuit. You look at the status of the button, and ignore changes that don’t last long enough.
Originally elevators were controlled using relay logic circuits. Of course at that time they did not have the brainpower to do debouncing. So only the simplest functions got implemented.
A modern elevator is controlled by a “PLC” circuit. Unfortunately, PLCs are programmed using a language that implements relay logic (but does it with a microprocessor). The overall effect is that programming an elevator to do anything sophisticated is pain in the butt.
But I think that the main reason they’re not programmed to turn a button off is the explanations by Jon and Maverick. People press buttons that are already lit, and the system needs to work even when button lights are out.
I would add that elevators are build to safety, and both design and regulations & testing is conservative.