Linked by Eugenia Loli on Mon 9th Oct 2006 01:31 UTC
QNX Most people haven't heard of QNX Software, though they've likely come in contact with it. The real-time operating system is used where software failure can lead to catastrophic consequences, even death - from high-speed trains to air traffic control towers to highway toll systems. It's also used in more than 100 different types of cars on the road.
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RE[3]: great stuff
by monkeyhead on Mon 9th Oct 2006 15:22 UTC in reply to "RE: great stuff"
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I can't imagine an elavator in a large building that didn't use a microcontroller or PLC.

How do you get your electromechanically controlled elevator to look at 10 requests from 10 different floors for up or down direction and schedule them appropriately with hardwired relays?

I'm sure it's possible with lots and lots of boolean simplification and cabinets full of hundreds of relays, but each relay is a mechanical failure point, and the project would be ridiculously expensive. I can buy 3 or 4 relays for the same price as a cheap PLC that can emulate thousands of relays.

Reply Parent Score: 3

RE[4]: great stuff
by JonathanBThompson on Mon 9th Oct 2006 18:05 in reply to "RE[3]: great stuff"
JonathanBThompson Member since:

Certainly PLC's are used, and certainly there's a microcontroller in them: but they're also certainly not running anything more than a very simple embedded bit of software in a very tight loop.

Yes, PLC's simplify things immensely, and can often make things much cheaper once things start getting complicated and allow things to be reprogrammed as needed, but they don't require even anything as complicated as QNX, or as much RAM: they've been around and used before QNX was around, in such places as car factories. PLC's have a minimum amount of memory, only as much as is required to hold the current state of all the I/O hardware and the limited number of timers and such, because they don't need anymore than that.

Put in the original context of "I wouldn't use an elevator with anything else" even with the more sophisticated elevators (how many use QNX?) causes options to be extremely limited.

FYI, yes, I've programmed PLC's in industry.

Reply Parent Score: 1

RE[5]: great stuff
by Sphinx on Fri 13th Oct 2006 16:46 in reply to "RE[4]: great stuff"
Sphinx Member since:

What is your building control system/application written in? Building I work in is centrally controlled, from the vents to the window shades to the elevators to the escalators to the moving sidewalks to surveillance... there is only 5 flights of stairs and I do usually use them just for my health but if someone were to say, "QNX or nothing", then I would take it to mean nothing is perfectly acceptable which would include those antiques.

Reply Parent Score: 1