Hard power cycle question 1

[davekuch]

I work for an OEM that manufactures machinery for the plastics industry. I have an application where I must use an industrial PC on my machine. The way we'd like the machine to operate is that the PC will have power removed from it everytime the machine disconnect is turned off. We have selected a PC with a hard switch (not the ATX style power supply) - so when power is turned back on, the PC will re-boot.

I know nobody at Microsoft will recommend this method - but it's the best for our machine.

Does anybody have experience with Windows 2000 vs. XP in a situation like this?

Any suggestions for a situation like this?

Thank you in advance...

 

[MikeHalloran]

DOS is the last OS that doesn't get all confabulated on abrupt removal of power. It runs at lightning speed on today's procesors.

No doubt you _must_ have the fancy graphical interface, for 'marketing reasons'.

Given that, I'd be inclined to go with Linux or XP, and hide a small UPS in the machine to store enough energy for a graceful shutdown.

[ Others report great success with Linux. I, personally, have managed to acquire an assortment of machines with unsupported video cards, sound systems, modems, etc., so installing Linux requires a lot of hardware substitutions and repeated install attempts and/or arcane shell script modifications. Once installed, it seems much more solid than any Windows version ever. ]



Mike Halloran
Pembroke Pines, FL, USA

 

[automatic2]

Depends. On powerloss, the equipment should fall into a default (safe) state. You don't want a independently powered controller trying to make adjustments, which contradicts the safe state.

In our plant of 20 extruders, I implemented a custom monitor system which continuously reported the status of support services, water temps/flows, chiller press/temps, air pressures, etc. That systems was run on UPS because of the valuable info. Equipment dependant controllers however fell with the equipment into it's default (power removed) state.

 

[analogkid2digitalman]

Would this be of use:

Use a UPS that notifies the PC to do an orderly shutdown when it detects loss of power- this is quite common nowdays.

Yes, the backup battery will get a workout, but not fully discharged, and the PC will have a clean shutdown.

If not, at least use a high quality surge supressor to protect the PC from the transient when everything gets powered up and down.

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[davekuch]

We actually tried a UPS in the past - but had problems with it not turning on properly after the shutdown (the UPS, not the PC). Does anybody know of an industrial UPS that can handle hot temperatures? We design for 50 deg C.

A UPS is an option, but not the most accepted by our customers. They'll take it if we force the issue though...

 

[MikeHalloran]

I've worked on products that had a UPS built in, and the power fail detect circuits gave unending trouble, so I have some appreciation of the difficulty of making an industrial UPS, or of even properly testing one.

Other options?

Windows caches a lot of critical information in memory, and does a lot of disk swapping in order to implement virtual memory. Abrupt removal of power leaves important files open and in an undefined state on the hard drive. If you could turn off all of the cacheing and virtual memory stuff, it would be relatively immune to power failures, and I'd guess at least an order of magnitude slower. I'm not sure that civilians can actually do such a thing. MS sells an embedded version of Windows, though so far as I know it's intended for stuff like PDAs that don't really ever get turned off.

I get the impression, though I'm not sure, that you _can_ configure Linux to do that, i.e. cache nothing and use only physical memory. Yes, it would also be slow.

You could investigate other operating systems, e.g. QNX, which is alleged to be highly configurable, fast, robust enough for industrial use, and all that rot.

If your user interface is stable and not horribly complex, you could duplicate or approximate its appearance and functionality on top of a simpler OS, or no OS at all. This requires a programmer with different skills than the common WinWizard.



Mike Halloran
Pembroke Pines, FL, USA

 

[ScottyUK]

Many of the solid state MMI terminals use Windows CE in the background - this seems fairly immune to power cycling, although if someone knows better then I won't argue with them.


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