Similarly we are still using DOS, mainly for CAD but still find it useful for the occasional bit of buchery :-))
We bought a load of new DOS 6.22 a few years ago, gradually using them up as the floppies fail....
Peter
-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:
Thank you, I had the impression that you were talking about a whole house system. I assume that the room unit will be regulated as load could vary widely. If not you could have problems which don't occur with equipment which comes with its own wall wart designed for that particular apparatus.
-- Don Kelly dhky@shawcross.ca remove the X to answer ----------------------------
"Don Kelly" wrote in news:cp8Dh.1090652$R63.576131@pd7urf1no:
Yes, as I said (in other posts), regulation of 5V and 12V busses would be done. I doubt they'd have to be done independently. Devices that want other voltages or very clean supplies would also have their own regulation.
The only specifically new part of the idea is the elimination of warts and the waste associated with them, acheived by standardising buss voltages and polarity, ideally positive centre pin as that's become a dominant standard now. Things like ground loops and noisy signal lines can all be cured by current good practise.
The idea is not in conflict with many good practises, if any, it's only the adherence to bad ones that perpetuates problems. Most successful hardware protocols are those that were established before counterproductive conventions could trouble them. This one could still succeed because of the increasing number of small low-volt devices. A sprawling mains buss is awkward and dangerous, and a few house fires will dramatically hammer home the truth of this false economy to a public that will then buy eagerly from whoever is making a safer alternative.
They are useful, up to a point. They don't exhibit a great tolerance to spikes as we found out, and it is difficult to assess their performance in-circuit.
If the source impedance is very low then they are definitely the weakest part of the protection chain.
Interesting that in each case (3 separate failures) the actual failure mode was identical, the body blew open and red-hot parts went like shrapnel through the equipment cabinet, that was the most worrying part.
The 620V charger is at:
Peter
-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:
of
MOVs that vaporize or explode are grossly undersized for the task. MOVs must become conductive (shunt) and remain functional. MOVs have tremendous tolerance for transients. But MOV manufacturers also provide charts that relate current, length of transient, and number of transient to life expectancy.
How does an MOV fail? Its threshold voltage degrades by 10%. Vaporization occurs when the MOV operates on curves that are far off the chart - well beyond what the manufacturer intended. Vaporization (one shot usage) occurs where MOVs are grossly undersized such as in many power strip protectors. Vaporization promotes sales among the naive.
VI curves for MOVs obviously make them poor for transient protection across an electrolytic. Again, look at how they work. Voltage increases significantly as the current increases. But electrolytic capacitors have a narrow region between operational voltage and destructive voltage.
Protection for the electrolytic is part of an integrated system that includes series mode protection such as EMI/RFI filters and other parts. This integrated protection makes appliances so resilient that a 120 volt appliance will even withstand a short 600 volt spike without damage. Are larger spikes occurring? Then those much be earthed back at the building entrance so that the transient does not overwhelm protection inside all electronics.
Can we put additional shunt mode protection across electrolytics? Well, first the current size (not voltage) and time of that transient must be determined. Again, functions defined by the series mode filters, et al currently installed. To obtain effective protection in the narrow range between operational voltage and destructive voltage, components such as Transzorbs or overvoltage crowbars should be considered.
Meanwhile, learn the VI curves and life expectancy curves for MOVs. And notice the absolute maximum ratings. The exploding MOV must be well outside those maximum rating - a violation of manufacturer's specs.
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