5 ms·

Something I learned not long ago on this site: low quality/too long HDMI cables can make some monitors go black when the user stands or sits on a certain kind o

by seri4l 4y ago

Something I learned not long ago on this site: low quality/too long HDMI cables can make some monitors go black when the user stands or sits on a certain kind of office chair. [1] [2] Apparently it's a known issue at Dell: [3] >Surprisingly, we have also seen this issue connected to gas lift office chairs. When people stand or sit on gas lift chairs, they can generate an EMI spike which is picked up on the video cables, causing a loss of sync. If you have users complaining about displays randomly flickering it could actually be connected to people sitting on gas lift chairs. Again swapping video cables, especially for ones with magnetic ferrite ring on the cable, can eliminate this problem. There is even a white paper about this issue. [1] https://www.youtube.com/watch?v=voW5kEI7JKE https://www.youtube.com/watch?v=voW5kEI7JKE [2] https://www.youtube.com/watch?v=D6pY4t0k1hk https://www.youtube.com/watch?v=D6pY4t0k1hk [3] https://support.displaylink.com/knowledgebase/articles/738618-display-intermittently-blanking-flickering-or-los https://support.displaylink.com/knowledgebase/articles/73861...

AriedK 4y ago
This is an issue at our office. We have some cheaper LG monitors that flicker when someone stands up from his gas spring chair. The Dell monitors we have don’t suffer this issue. A paper on the issue: https://www.emcesd.com/pdf/uesd99-w.pdf https://www.emcesd.com/pdf/uesd99-w.pdf Apparently a dangling bag of coins can cause similar issues, but haven’t encountered that so far.
- exmadscientist 4y ago
  > Apparently a dangling bag of coins can cause similar issues A dangling bag of coins is a famous cheap EMC test for products. All of this sounds like monitor vendors cheaped out on their EMC and need to have their ESD and Immunity certifications reevaluated.... Or maybe it's just the fact that they were dumb enough to ship an I²C interface over a cable as part of the industry spec. Never ship I²C off-board or this kind of crap happens.
  - jacquesm 4y ago
    My own favorite trick was to put a 1st gen cellphone near the device and call it, or to fire a piezo based gas lighter with the shroud removed against device ground. This was for devices that stood a very good chance of being deployed in a hostile environment so being able to withstand that kind of interference wasn't a luxury.
    - exmadscientist 4y ago
      The grill igniter is actually my favorite too. I may or may not have a drawer full of them... who carries coins anymore these days?
      - wellokthen2 4y ago
      - aaaaaaaaata 4y ago
        Canadians. British?
  - 411111111111111 4y ago
    Why are the monitor vendors at fault when the cables have the poor shielding? We don't know who produced these cables nor where they came from. I'd wager it's mostly an issue with cheaper products, and you often don't get any cables if you're buying a cheap monitor, so they're likely from a third party.
    - exmadscientist 4y ago
      > Why are the monitor vendors at fault when the cables have the poor shielding? Because part of hardware engineering is making devices that function even in poor environments, and that tolerate foreseeable misuse. (This is a major part of medical device development, for example.) Cable shielding is always iffy on consumer-grade cables. If other vendors can produce monitors that tolerate its absence, because that seems to be reasonably common!, then if you can't, your products will be seen as inferior. Exactly as is happening here.
- stn8188 4y ago
  Thanks for linking Doug Smith's website, he has some excellent EMC/EMI info for us hardware engineers.
  - hyperdimension 4y ago
    Also Henry Ott's website, which unfortunately went down recently as he retired, but luckily can still be found on the Internet Archive.
trinovantes 4y ago
I'm using a Steelcase Leap chair which does use a gas cylinder This might explain why one of my monitors with a 2m long HDMI cable every so often fails to turn on after waking up from sleep mode
tobyhinloopen 4y ago
This happens to me all the time! I thought I was crazy.
annoyingnoob 4y ago
I moved to fiber based cables to solve this. Expensive but work great.
jrockway 4y ago
That solves a lifelong mystery for me. I have twice had monitors that blink off right when I shift position or get up from my desk. I can tell it's caused by me moving, but I can never reproduce it. When it first started happening, I would aggressively shake the monitor cables and nothing happened. But I never considered that it could be my chair.
- breakfastduck 4y ago
  Exactly the same for me, this is mind blowing. I've spent many frustrated minutes trying to identify if me moving was causing a cable to be pulled or such!
skhameneh 4y ago
I put ferrite rings on a ton of stuff to reduce interference, so much I questioned how reasonable it was to do so. Thank you for providing additional confirmation bias for the things I do. On the subject of interference, this is why a good amount of shop equipment doesn't use USB. Especially for vinyl cutters, serial/RS-232 tend to have less issues than USB. USB tends to be more sensitive to the static buildup caused by moving and cutting vinyl.
sveiss 4y ago
Hah, thank you, that explains a mystery! I had a motherboard (an ASUS ROG Strix B550-E) that would frequently freeze when I stood up from my chair. I always figured it was something to do with static electricity discharging when I stood up, but no amount of fiddling with grounding helped. An EMI pulse from the gas lift getting picked up somewhere insufficiently shielded would explain it. Interestingly, I also have a Steelcase Leap chair, as mentioned by someone else in this thread; maybe the gas lift they use is particularly prone to this? Other people also complained about freezes with this motherboard model, so perhaps the combination was particularly bad.
redcodenl 4y ago
This happened to us at work: https://twitter.com/royvanrijn/status/1214162400666103808 https://twitter.com/royvanrijn/status/1214162400666103808
mckirk 4y ago
Holy crap, this is amazing. I've wondered about this a lot when it kept happening, and so far my most likely seeming theory had been 'static discharge through the carpet', or something like that... But the chair generating an EMI pulse? Hilarious
madaxe_again 4y ago
Similar but different: I have a 200m Ethernet run (PoE repeater midway), outdoors, FTP, going to a mast atop a hill. There’s lightning protection etc. on the circuit. It’s worked fine for several years. Last week, we had a huge electrical storm - and every time lightning flashed within 8km, the switch at the cabin would reboot. Unplugged, stuck a scope on the Ethernet cable - and lo and behold, 30V+ flashes every time lightning struck anywhere even remotely nearby. The cable is acting like a great big antenna.
- gnu8 4y ago
  Have you looked at shielded twisted pair or optical fiber for that run? I have a similar project planned but at the moment I’m not looking forward to trenching the cable into the ground so it hasn’t moved forward yet.
  - madaxe_again 4y ago
    I didn’t trench mine as I anticipated it might not be the ideal solution… plus it goes up a 45 degree hill, threads past cliffs, etc. - ran it inside a little 10mm slitted duct, at least, to protect it from friction, UV, and curious teeth. I need it to be able to deliver PoE, which is why I went for Ethernet - but yeah, probably going to replace it with STP, although not sure that’s going to stop lightning induction in the earth/shielding. Other option is splashing out for SWA STP, which should definitely do the job. For the other run, where I don’t need power, I’m using 802.11n with a pair of Yagis to go about a kilometre. No problems except the usual headaches around layers and discovery a Wi-Fi bridge provides.
TheSpiceIsLife 4y ago
Thanks for posting this. It hadn't occurred to me that cheap and excessively long HDMI cable might be a contributing factor to my AV receiver playing up. I've replaced the cable with a much shorter one with built in ferrites both ends and haven't noticed the problems I was having.

by seri4l 4y ago

AriedK 4y ago

This is an issue at our office. We have some cheaper LG monitors that flicker when someone stands up from his gas spring chair. The Dell monitors we have don’t suffer this issue. A paper on the issue: https://www.emcesd.com/pdf/uesd99-w.pdf https://www.emcesd.com/pdf/uesd99-w.pdf Apparently a dangling bag of coins can cause similar issues, but haven’t encountered that so far.

exmadscientist 4y ago
> Apparently a dangling bag of coins can cause similar issues A dangling bag of coins is a famous cheap EMC test for products. All of this sounds like monitor vendors cheaped out on their EMC and need to have their ESD and Immunity certifications reevaluated.... Or maybe it's just the fact that they were dumb enough to ship an I²C interface over a cable as part of the industry spec. Never ship I²C off-board or this kind of crap happens.
- jacquesm 4y ago
  My own favorite trick was to put a 1st gen cellphone near the device and call it, or to fire a piezo based gas lighter with the shroud removed against device ground. This was for devices that stood a very good chance of being deployed in a hostile environment so being able to withstand that kind of interference wasn't a luxury.
  - exmadscientist 4y ago
    The grill igniter is actually my favorite too. I may or may not have a drawer full of them... who carries coins anymore these days?
    - wellokthen2 4y ago
    - aaaaaaaaata 4y ago
      Canadians. British?
- 411111111111111 4y ago
  Why are the monitor vendors at fault when the cables have the poor shielding? We don't know who produced these cables nor where they came from. I'd wager it's mostly an issue with cheaper products, and you often don't get any cables if you're buying a cheap monitor, so they're likely from a third party.
  - exmadscientist 4y ago
    > Why are the monitor vendors at fault when the cables have the poor shielding? Because part of hardware engineering is making devices that function even in poor environments, and that tolerate foreseeable misuse. (This is a major part of medical device development, for example.) Cable shielding is always iffy on consumer-grade cables. If other vendors can produce monitors that tolerate its absence, because that seems to be reasonably common!, then if you can't, your products will be seen as inferior. Exactly as is happening here.
stn8188 4y ago
Thanks for linking Doug Smith's website, he has some excellent EMC/EMI info for us hardware engineers.
- hyperdimension 4y ago
  Also Henry Ott's website, which unfortunately went down recently as he retired, but luckily can still be found on the Internet Archive.

trinovantes 4y ago

I'm using a Steelcase Leap chair which does use a gas cylinder This might explain why one of my monitors with a 2m long HDMI cable every so often fails to turn on after waking up from sleep mode

tobyhinloopen 4y ago

This happens to me all the time! I thought I was crazy.

annoyingnoob 4y ago

I moved to fiber based cables to solve this. Expensive but work great.

jrockway 4y ago

That solves a lifelong mystery for me. I have twice had monitors that blink off right when I shift position or get up from my desk. I can tell it's caused by me moving, but I can never reproduce it. When it first started happening, I would aggressively shake the monitor cables and nothing happened. But I never considered that it could be my chair.

breakfastduck 4y ago
Exactly the same for me, this is mind blowing. I've spent many frustrated minutes trying to identify if me moving was causing a cable to be pulled or such!

skhameneh 4y ago

I put ferrite rings on a ton of stuff to reduce interference, so much I questioned how reasonable it was to do so. Thank you for providing additional confirmation bias for the things I do. On the subject of interference, this is why a good amount of shop equipment doesn't use USB. Especially for vinyl cutters, serial/RS-232 tend to have less issues than USB. USB tends to be more sensitive to the static buildup caused by moving and cutting vinyl.

sveiss 4y ago

Hah, thank you, that explains a mystery! I had a motherboard (an ASUS ROG Strix B550-E) that would frequently freeze when I stood up from my chair. I always figured it was something to do with static electricity discharging when I stood up, but no amount of fiddling with grounding helped. An EMI pulse from the gas lift getting picked up somewhere insufficiently shielded would explain it. Interestingly, I also have a Steelcase Leap chair, as mentioned by someone else in this thread; maybe the gas lift they use is particularly prone to this? Other people also complained about freezes with this motherboard model, so perhaps the combination was particularly bad.

redcodenl 4y ago

This happened to us at work: https://twitter.com/royvanrijn/status/1214162400666103808 https://twitter.com/royvanrijn/status/1214162400666103808

mckirk 4y ago

Holy crap, this is amazing. I've wondered about this a lot when it kept happening, and so far my most likely seeming theory had been 'static discharge through the carpet', or something like that... But the chair generating an EMI pulse? Hilarious

madaxe_again 4y ago

Similar but different: I have a 200m Ethernet run (PoE repeater midway), outdoors, FTP, going to a mast atop a hill. There’s lightning protection etc. on the circuit. It’s worked fine for several years. Last week, we had a huge electrical storm - and every time lightning flashed within 8km, the switch at the cabin would reboot. Unplugged, stuck a scope on the Ethernet cable - and lo and behold, 30V+ flashes every time lightning struck anywhere even remotely nearby. The cable is acting like a great big antenna.

gnu8 4y ago
Have you looked at shielded twisted pair or optical fiber for that run? I have a similar project planned but at the moment I’m not looking forward to trenching the cable into the ground so it hasn’t moved forward yet.
- madaxe_again 4y ago
  I didn’t trench mine as I anticipated it might not be the ideal solution… plus it goes up a 45 degree hill, threads past cliffs, etc. - ran it inside a little 10mm slitted duct, at least, to protect it from friction, UV, and curious teeth. I need it to be able to deliver PoE, which is why I went for Ethernet - but yeah, probably going to replace it with STP, although not sure that’s going to stop lightning induction in the earth/shielding. Other option is splashing out for SWA STP, which should definitely do the job. For the other run, where I don’t need power, I’m using 802.11n with a pair of Yagis to go about a kilometre. No problems except the usual headaches around layers and discovery a Wi-Fi bridge provides.

TheSpiceIsLife 4y ago

Thanks for posting this. It hadn't occurred to me that cheap and excessively long HDMI cable might be a contributing factor to my AV receiver playing up. I've replaced the cable with a much shorter one with built in ferrites both ends and haven't noticed the problems I was having.