[Techtalk] OT but I'm desperate.... Windows....!

[L J Laubenheimer]

Maria Blackmore wrote:
> On Thu, 17 Oct 2002, Alvin Goats wrote:
> 
>> ? wrote: 
>>>It is true that a monitor is usually the most power hungry component of a
>>>computer, however it is drawing its power from the mains, so doesn't
>>>affect the computer
> 
>>To some extent that is true. However, as I recall from an earlier
>>message, all of your hardware is running off of one outlet. The power is
>>shared between outlets, so a power consuming object on one plug is
>>sapping some power from the other plug.
> 
> Uhm
> 
> no.  sorry.  I think not.

I think so.[1]

Power is in Watts(volt-amps)==Voltage(V) x Current(amp), *not* Volts!  You are 
neglecting the variable half of the equation.  Several devices on one circuit 
are said to be "in parallel", therefore the voltage stays constant, and the 
available current is shared between them.

AC Power supplies are rated in terms of Watts.  "Watt refers to a
time-averaged power flow.  In AC circuits, Power flow varies as a sine
function.  The "root-mean-square" rate of flow is approximately 65% of the
maximum flow."[2]

>>This can still lead to a brown out type condition (before tripping
>>circuit breakers/blowing fueses).
> 
> If the voltage drop caused by additional load on the same circuit is
> sufficient to cause problems, then I would suggest that the house wiring
> needs to be looked at in some depth.

The problem isn't voltage, it's current.  The voltage is regulated by the utility.

If you have a 15 amp circuit powering 2 outlets, and those outlets are trying 
to suck 20 amps of draw combined, something loses, and a brownout condition 
can occur before circuit breakers trip.  Computers, for some reason, are 
sensitive to brownout conditions, in spite of their converting (AC to DC) 
power supplies.  That is why line conditioners are used in most datacenters.

> Mains voltage is very well regulated, and has a lot of oompf behind it to
> back it up.  The voltage drop across properly installed cables when
> addition load is applied should be pretty much negligible, and the voltage
> droop caused by the additional load should be easily corrected by
> regulating transformers after a short delay.

But that doesn't say anything about current, which is what is restricted in 
household circuits.

> The time period that the mains voltage droops for doesn't matter anyway,
> since if the power supply is correctly regulating its output rails then it
> should have no effect, in fact a well designed power supply should be able
> to cope with no power coming into it at all for at least half a cycle of
> 50 Hz or 60 Hz, usually much more (the hold over time).  Power supplies
> should be able to cope over a range of voltages at least as far apart as
> 100 and 120 V or 220 and 240V.  I believe (though I'm probably wrong) that
> the acceptable range of voltages to find on a mains outlet in the USA is
> 90-130V, and in the UK/europe 210-250.  There is a percentage range
> defined, though I can't remember it off hand.

If your power supply isn't getting the amperage it needs to convert, it starts 
flaking out.  Talking about voltage alone tells nothing.[1]

> As to the original problem, if it crashes every time you go to print, I
> would be rather suspicious.  Though the error pasted in another email
> would seem to suggest that windows is experiencing its equivalent of a
> kernel panic.

I would suspect: bad/unstable power supply (possibly due to current 
availability problems.), dying cpu, flaky printer port/printer riser.

				Linda

[1] Strongly recommended reading (these are nice tutorials!): 
http://www.electronics2000.com/basics/basics.html - a basic tutorial on 
electricity and http://www.electronics2000.com/basics/basics2.html, which 
covers basic circuits.  More advanced tutorials can be found off of 
http://www.electronics2000.com/page2.html, but get the basics down first.
[2] http://newton.dep.anl.gov/askasci/phy00/phy00205.htm
-- 
Linda J Laubenheimer - UNIX Geek, Sysadmin, Bibliophile and Iconoclast
http://www.modusvarious.com/ - consultants available
http://www.laubenheimer.net/ - personal demo site
http://www.geocities.com/laubenheimer/ - web design gaffes (I wouldn't
disgrace a real ISP with these) and rants about bad design.