Piddling around with more LEDs

Earth's

Your eyes generally try to smooth out the flicker. The beat frequencies between two displays at different refresh rates causes that mechanism to fail. Try forcing both monitors to the same vertical rate.

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Duh! Ya think? The question is *WHY?*

They are (when I can see the beat). That's the whole point. If the monitors were driven by separate cards I could understand it.

Why did he commit to 1000 before seeing a sample?

No, I don't ask for engineering samples when I buy strings of Christmas lights from Home Depot.

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Sorry, i am not all that deep into the neurophysics of vision, i do electrical engineering primarily.

I would have expected the driver to normally synchronize them rather than maximize each refresh rate. Maybe something is funny about the driver configuration. Maybe a rabid gamer set it up?

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I'm not getting through. It's one card, one system, two monitors, set up identically. Where is the beat coming from?

Not possible. It's my work system (I went to LCD long ago). There is no setting other than 60, 75, or 85Hz (at least at 1280x1024).

That's really weird.

I once had two monitors connected to different PCs running at almost the same rate (the difference was about 10hz in the horizintal rate, so about 0.01hz in the vertical rate) and the beating was clearly visible as a vertical discontinuity (vertical retrace in the other monitor) that slowly migrated up the screen of one of the monitors

I solved the problem by rearranging my desktop to have a pc case between the two monitors.

ultimately it comes down to the rate of the pixel clock in the crtc if they're both phase-locked to the same source (logic suggests that this would be the case) then it should be possible to phase-lock the horizontal, and vertical scans also by using the same base pixel clock, horizontal total and vertical total settings.

doing that requires that the maker of the video driver exposes the CRTC registers to the OS and that you get in behind the scenes and tweak them. (In windows this means special software or editing the registry, in linux it's xvidtune and adding modelines to the /etc/x11/xorg.conf file)

not easly, may or may not be possible.

if it were me I'd (after investigating and rejecting a software based fix) get a 600mmx600mm piece of .4mm steel sheet (eg pc case side panel) and wedge that between the monitors and see if it helps, if it only helps a little I'd try two, mu-metal, or thicker.

seing as it's at work I'd complain to my immediate boss, IT, and or HR, that's it's causing "stress"

G >Why did he commit to 1000 before seeing a sample?

KRW > No, I don't ask for engineering KRW > samples when I buy strings of KRW > Christmas lights from Home Depot.

$150 smackers worth? 1000 lights? Did you see them in the store? Usually you can plug them in before purchase. Even Wal Mart lets you do that.

That's exactly what I'm seeing, except on one system, one card, same setup.

That would be too far away to make the monitors useful. The *real* solution is to replace the (at least) decade old monitors with LCD monitors. I'm workign on it. ;-)

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...or just set them to very different frequencies. ...though if I look I can still see the beat.

Steel isn't likely to do anything, though mu-metal might. I don't have a handy source for that much mu-metal though.

I have. I shame the boss every time he comes into my cube. ;-) The whole system is junk but this is a very bad time to spend any money.

On the reel.

Five reels, 200 per.

How about a couple pieces of steel with foam board between them? It would still be under a half inch thick. I've had decent results with a single layer of steel in a wood rack with four monitors, but you could put several layers between monitors. Also, the electromagnetic field is near the back of the case, so the steel doesn't have to reach the front of the monitor case to be effective. You just need to keep the yokes from interacting so it should run from the rear to around 3/4 of the depth Broadcast monitors are usually in steel cases and no mu-metal. They are stacked in all sorts of combinations with no problems

for an example, but I have bought 20" * 30" sheets it at 'Dollar Tree' for a dollar a sheet.

The steel I used was from scrapped equipment cases.

Did you ask them to light them up for you to see?

As for mu-metal - many oscilloscopes have sleeves of that around their CRTs. My father asks me to let him have those whenever I find occaision to dump an O-scope.

One thing to watch for - bending mu-metal (or similar ones) can change their permeability at low Gauss, and will have a high rate of changes being downward. After bending, mu-metal needs to be annealed (heated past the Curie temperature and cooled at some slow rate afterwards).

Meanwhile, if weight is not a concern and the metal sheet is allowed to be flat, I suspect 1/4 inch plate steel is not that much less effective than a usual thickness of mu-metal and probably cheaper. Same for a few layers of sheet steel - and that can even be bent into shapes.

- Don Klipstein ( snipped-for-privacy@misty.com)

Thin steel will work, especially if it is layered with separators. I've done it a lot of times. Old computer cases can be cut with a shear, or sawn apart so you don't even need to buy the steel. Some monitors have metal shielding around the bell of the CRT to keep the AC lines from causing problems, so all you have to do is isolate the electromagnetic fields of the yokes. Scopes are electrostatic deflection devices, and are a lot more sensitive to stray fields.

I might try that. We have some steel laying around, though most of it is parts for our cases. ;-) Hmm, if I make the lashup ugly enough I'll get the boss' attention, again. ;-)

Nope. The HomeDespot here is pretty lame. Lowes is much better but they had no LED strings this year. Perhaps I now know why. I just bought another 10 strings of incandescent lights for a buck-a-string, though I coudn't find any clear.

If you 'really' want his attention, cut up the cover from his computer. Unless his computer is an 'Etch-A-Sketch'. ;-)

I usually see them at Dollar Tree, but not this year. A few years ago I bought a pile of sets of 50 white bulbs for 50 cents each.

Yeah, these are strings of 100. The latest ten strings were a buck each. I bought twenty strings right before Christmas for $1.50/100. They had red, green, blue, and mixed but no clear. Next year I'll do blue.