Driving 1,000 computer monitors?

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How?

Actually, what jargon should I use to search for circuits to build.


The background is that I do work for a community group that re-uses old
computers and we currently have premises in an arts centre. Our "rent"
is basically technical knowledge and assistance to support vqarious
"artistic" projects.

This one comes out a project that will be a wall of computer monitors
(db15 plug driven) all showing the same image, so my understanding says
that we are going to need an amplifier and splitters or
splitter-amplifier, preferrably with the least number of stages.

Hence, my question for assistance in what jargon I should plug into
search engines.

This is basically for the mathematics of costing the construction of the
video splitters, etc.

TIA.

Re: Driving 1,000 computer monitors?


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   The proper term is "Video Distribution Amplifier"  There are plenty
of commercial units, as well as chips designed for this application.
The biggest problem will be cable lengths causing roll off of higher
frequencies.  National. maxim and others make suitable chips for the
project.

--
Link to my "Computers for disabled Veterans" project website deleted
after threats were telephoned to my church.

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Re: Driving 1,000 computer monitors?


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I've seen something like this using TV sets? video monitors? at a
shopping centre, only they formed 1 *BIG* picture. I'd suggest it'd be
cheaper/easier to use TV's and you'd get the same result.

John Mackesy

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Umm, this is "art", you know, here today, gone tomorrow, faster than a
movie set. so, there is no/absolute minimal budget. (hmm, anyone know of
a movie set that needs something like this).

And since we pass on computer monitors, they are "free", plus, the local
supplier of "TVs" has just soiled his pants on supplying reliable goods
(only 3 out of 20 worked - of course artist didn't test on delivery did he).

So, we have said we can give them to him, one way trip, absolutely no
returns will be considered for any reason. This is a future project, so
we can pass on our surplus.



Re: Driving 1,000 computer monitors?



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You never know in a big city like Syd-na-nee :) Know a guy who built a 24:1
pulley system for special fx - gun shots, falling off bikes, etc

Re: Driving 1,000 computer monitors?



"Terry Collins"
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** Are you serious ?????

***1000***  monitors  ???

The average monitor draws circa 0.5 amps rms from the supply -  so 1000 of
them means 500 amps !!!!!!!!

Even with 3-phase that load is 170 amps per phase  -  with no neutral
current cancellation  !!!!!!!

Monitors have large switch on surges too -  circa 50 amps peak EACH  !!!!





..........   Phil





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He is.

Yep, one of our number has already done this dance, but as I said, it is
all just mathematics, HIS.

And we have already had the first discussion session with him and
pointed out that he will need to do a lot of calculations on electricity
demands, weight and the scaffolding to support it, plus make sure the
floor will support it (and no I don't think that your or my welding
skills are good enough to make a scaffold), etc, etc,

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Well, this is where we can advise him about staging the switch on, but
did you mean 5 amp?

Now, the good news is that the hall in which he wants to do it has at
least 6 three phase outlets and he knows he has to check circuit
numbers, plus he has already asked the site electrician to come and talk
to him.

I hope it is in winter, then the concrete mausoleum will not need the 12
radiant heaters is has for this space {:-)

Re: Driving 1,000 computer monitors?



"FruitLoop"
"Phil Allison"

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** You must be a mug electrician as well as a fruit loop.

The rms value of the neutral current when the load wholly electronic is
1.73 ( sqrt 3  ) times the phase currents.

The is simply no cancellation in the neutral.





...........  Phil




Re: Driving 1,000 computer monitors?



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neutral
neutral


Na , Im a rocket scientist , more interesting than a lowlife electrician

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What about the 120 degree phase seperation . Also I have seen 3 phase power
single phase systems with the neutral fully floating and not connected . For
this to work a balanced 3 phase load is required + a common star point
connection on a transformer . So go root your boot a neutral isnt even
required .

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"FruitLoop"   =  one king size, moronic pig


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 **  Must be one of them former Nazi types  -  eh  ???



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**  No point even trying to inform this anencephalic POS about anythig.

   Wanna bet the anonymous cretin is an apprentice ???




..........  Phil







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And your normal , hahahahahahahahahaha

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Yep even a modern day apprentice is smarter than you phillis .
Hahahahahahaha

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Re: Driving 1,000 computer monitors?



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Phil's post seems valid to me.

This article mentions the non-balanced neutral problem.

http://www.jmwa.demon.co.uk/EMCLF0010.htm

3 phase balancing works when the loads draw sinusoidal current.  Computer
monitors have bridge rectifiers across the mains input, which charge
capacitors with short pulses of current near the peaks of the sinewave. So
the phases see large amplitude, narrow current pulses - at 120 degree timing
with little neutral cancellation - so the neutral wire is working very hard.

Roger Lascelles



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"Roger Lascelles" <
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**  In any case, the only time the neutral can be left floating in when the
3 phase load is ONE device.

Where multiple, single phase devices constitute the total load, each with
thier own switches, fuses etc it is utterly out of the question.




..........   Phil




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Computer
So
the

Phillis , try it yourself  get a 3 phase load , all independant , roughly
balanced ( like me ) and then connect all the neutrals to create a star
point , but dont connect to a neutral . It WILL work .



Re: Driving 1,000 computer monitors?



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A balanced three Phase load is completely irrelevant to the current topic -
that is 1000 Computer monitors being connected to Mains.
I am afraid that Phil and Roger are quite correct Computer monitors do not
draw Sinusoidal current rather they draw short pulses of current  near the
peak of each Sine wave.
These Pulses on different phases come nowhere close to cancelling each other
out.



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   In fact, large numbers of switching power supplies on a three phase
system require a larger neutral than the same system with a purely
resistive load.  This is due to all the harmonics generated by the power
supplies that have no power factor correction.  A number of fires in
offices and factories occurred when large numbers of switching supplies
were installed, starting about 20 to 25 years ago.

  I had a neutral fire in the breaker box for a CATV headend in 1985 due
to all the harmonics caused by the newer equipment we were installing.

--
Link to my "Computers for disabled Veterans" project website deleted
after threats were telephoned to my church.

We've slightly trimmed the long signature. Click to see the full one.
Re: Driving 1,000 computer monitors?


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You want a video distribution amplifier, and one with the maximum
number of outputs possible. Something like this:
http://www.networktechinc.com/vsplt-pc.html

What you want to do is try to minimise the number of cascaded units. So
if you have one with 10 outputs, you'll need to casacde an array of 3
of these boxes in series to get 1000 outputs. You have to make sure it
can do this at the bandwidth you need.
What resolution and frame rate are you thinking of using?, this may
have a large impact on the number of units you can cascade without
problem.
Shouldn't be too hard if you are using a low-ish resolution and refresh
rate, say 800x600 and <60%Hz.

I designed a system once which drove hundreds of flat screen monitors,
and it could have done thousands, but this was in the digital domain,
direct LCD output.

A commercial solution might be very expensive, so a custom solution
could be the go. You need some triple channel video buffer chips, and
I'm sure there are ones specicially designed for RGB/VGA buffering,
dont' have the details to hand though.

Dave :)


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Thanks. Looking at the $$$ I can see this project being radically
changed. Well, the last one was to have 20 monitors & x speakers
rotating on a clothes line, but it settled for a static wall on TV's {:-).


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This is his problem. We can pass on your comments. Thanks. They are sort
of what we have said. Basically, we have offered to supply 14" & 15"
monitor, so I expect most will be low end resolution anyway. It is just
whether they have the same/compatible resolution, but that is his problem.

If he gives us a spec, then it is simple to build a testing computer
locked at that resolution,

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I don't think it counts as art if you can just buy it.
Actually, I personally would not call the project art as it has a
commercial solution, but then the "art" may be in what is in the video
images.

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And good learning for me. {:-)

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I can hunt around and see what I can find. I don't mind doing a bit of
investigating for amusement, but the materials for trialling will
definitely be funded for this, besides I already have my video splitter
{:-).

OT : Community group at arts centre



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Apologies for the unorthodox method of approaching the subject, but I think
I have met you in the company of Dan, Grant, Mark, et al.

If you are who I think you are, would it be possible to get one of them to
contact me, pls? Perhaps, Grant or Mark? Pls note that I have emailed them
using a new email address.

Thanks.

Re: Driving 1,000 computer monitors?


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This question is really obvious which is probably why no one has asked it,
but why not LCDs? The extra expense might be saved on what sounds like
expensive power considerations and scaffolding.


Michael



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