Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!n8emr!uncle!oink!jep
From: jep@oink.UUCP (James E. Prior)
Newsgroups: comp.sys.att
Subject: Re: Screen Power-down switch (Was Re: 3B1 Electric bill!)
Message-ID: <65@oink.UUCP>
Date: 9 Oct 90 01:01:00 GMT
References: <258@ramecs.UUCP> <1454@svin02.info.win.tue.nl> <1556@slimer.UUCP>
Reply-To: jep@oink.UUCP (James E. Prior)
Organization: Random Prime Research Institute  Columbus, Ohio
Lines: 46

In article <1556@slimer.UUCP> mco@slimer.UUCP (Mark C. Otto) writes:
>In article <1454@svin02.info.win.tue.nl> wsinpdb@svin02.info.win.tue.nl (Paul de Bra) writes:
>>In article <258@ramecs.UUCP> car@ramecs.UUCP (Chris Rende) writes:
>>So part of a solution to your problem is to mess with the internals a bit
>>to install a power switch for the screen.
>
>...  I *KNOW* I could save at least
>$10.00 monthly on my electric bill and probably *DOUBLE* the life expectancy
>of my monitor in the process. Yeah. That's the ticket.

Yeah right.  :-|  The monitor doesn't take much power, probably less than an 
amp at 12V.  10W * 24hours/day * 30 days/month yields 7.2kWh a month.  
Unless you're paying more than $1/kWh, you're not going to save anywhere near
$10 a month.  Even if you are using air conditioning, you're not going to 
save $10 a month.  In winter time, electrical power consumption 
contributes to heating you house, albeit, at a higher rate than gas, 
coal, or wood, in any rate reducing the effective rate for using 
electrical appliances in the winter time.  I have the most expensive 
kind of heating: Electrical resistance heating.  I can leave everything 
on in the winter time, and it just doesn't affect my electric bill.  

If you REALLY want to do it anyway, you should consider keeping power 
applied to the filament.  Turning power on and off subjects the filament
and things around it to thermally caused mechanical stress.  Everytime 
you turn your monitor on or off, you subject it to these streses.  
Ever notice how light bulbs _usually_ quit working when turned on?  
It's the damned thermal stress.  Bulbs turned on and left on will last
much longer than one turned on and off.  Unless you only use your screen
once a week, it's not clear that you'll be making the monitor last longer.  
Of course, there is also "wear" on the monitor during its steady on (but
dark) state.  The "wear" from power cycling is considerable.  You'll 
have to weigh these two "wear" factors that I can't quantify for you.  

If you really want to control the monitor power anyway, it's not dificult
to do.  You use a one shot to look at the pixels.  If the one shot doesn't
see any pixels for, oh, about a second, it would turn the monitor off 
with the help of a couple transitors (darlington) and diode (for any 
possible inductive spikes).  You could make this as a module that goes
between the motherboard and the monitor cable.  This way, any changes
made would be reversible, and better yet, no software mods.

You might want to add some tristate buffers that are disabled with the
monitor is turned off, just in case the monitor looks like a short to 
the signals from the motherboard.  

I really don't think it is worth your time and money.  The only reason 
I could think of for doing it is just to demonstrate that it can be done.  

-- 
Jim Prior    jep@oink    osu-cis!n8emr!oink!jep    N8KSM