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Old 02-20-2017, 03:38 PM
 
Location: Sun City West, Arizona
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Just wanted to put it out there that the other day when I touched my land-line telephone's answering machine button and there was that static electricity, it fried the answering machine functions.
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Old 02-20-2017, 04:29 PM
 
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LOL... you are not alone. I once killed a mouse. I could see the spark go through the gap between the front two buttons and that was the end of the mouse.
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Old 02-21-2017, 04:49 PM
 
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Very bad device design. You'd think the designers are aware of static. And the risks are easily handled in good design.

Sigh....
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Old 02-26-2017, 08:13 AM
 
Location: The 719
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The newer consumer electronics get, the smaller and faster they get, thus more prone to esd damage, not less.

I suppose shielding can be built into the design of user interface, but why do manufacturers of sensitive electronics go to such great lengths to assemble and test esd prone devices with wrist straps, esd matting, flooring, footwear, packaging, etc?

When you see, feel, hear an esd shock, you're dealing with 3500 and higher voltages. Sensitive electronics is damaged at as little as 100 volts and even less for some.

Cell phones, for example do pretty well.

We are the static generators. We create the charge. Even though we are pretty good conductors of electricity, we are what they call isolated conductors, due to clothing, shoes, etc.

Due to Ansi/Esd s20.20 -2014, you need to wear a wrist strap when working in an esd work station while seated, and you need to have esd footwear in conjunction with esd flooring while standing or walking about an esd workstation.

It's near impossible to create this environment everywhere you might encounter these consumer products. Humidifiers help, esd spray can be used on carpet and flooring, but who doesn't walk around with non-esd rubber soled shoes?

It's a tough situation. Ionizers are industrial and commercial fixes for neutralizing charges from isolated conductors and insulators by pumping + and - ions into the air but are only good to about 5 to 8 feet.

There's a product out there called a versastat which can be used around computers, copy machines, etc. They might entail standing on a conductive mat. Maybe having a "touch me here first" pad near your more expensive devices would do the trick.

It's been said having a bunch of house plants around, well watered ones helps knock the potential for an esd event down.

Last edited by McGowdog; 02-26-2017 at 08:48 AM..
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Old 02-26-2017, 08:44 AM
 
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^ you must not be aware of the difference between working on a device internally versus using an assembled device. Yes, internally, you use an anti-static strap because the static protections are bypassed.

Good design uses a variety of approaches to avoid static damage, such as foil liners and opto-isolaters. These aren't effective until a device is assembled and sealed. Manufacturing and repair are totally different activities.

Please keep in mind that manufacturing and repair are different activities from consumer use.
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Old 02-26-2017, 09:03 AM
 
Location: The 719
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You must not know the difference between a 3500 volt static event, which can occur anywhere and anytime, and an esd event on an assembly floor.

You telling me that a computer couldn't incur damage right through the keyboard? A lot of shielding on consumer devices are for FCC regulations, they are not necessarily a guarantee of a Faraday cage.

Just having devices assembled is no guarantee of esd protection. Layers of protection at an esd workstation are recommended.

Technology has surely improved the protection of these devices, but I'd think you'd have a hard time denying electronics have goten smaller and faster, and thus more prone to electrical overstress, tribocharge damage, etc.

For example, some components and devices incur damage without a direct hit. Just merely being in the presence of a disharge field can cause damage in an adjacent component, of course it would probably have to be fairly close and not shielded.

I'm going off of statistics and experience here as an engineer with esd training and esd auditing from about 2002 to 2010.

It's been a while for me since I've been that field, but here's some of my ramblings on the topic from the past, from a more commercial perspective as you would say...

Quote:
Originally Posted by McGowdog View Post
We are typically isolated conductors when we walk around. We are very good conductors, but we're isolated from ground when we're walking around on an insulative floor (a static conductive or dissipative floor, that's between about 25000 ohms or 2.5e4 ohms and 1 gig ohm 1e6 ohms for static conductive or 1000 meg ohms or 1e9 ohms for static dissipative per ansi/esd s20.20-2007) with our typically insulative shoes on. What generates ESD is mere tribocharge or contact and separation of dissimilar materials.

We only feel electrostatic discharge when the potential or voltage gets to above 3,000 to 3,500 volts. HollyT, when you got blasted with that ESD charge that other people heard... and maybe even saw, you probably got nailed with 15,000+ volts... or we could say you nailed earth with that energy.

Putting fabric softeners in the dryer and/or putting fabric softener in the washer do help a bunch. Wearing cotton instead of synthetics and leather instead of rubber helps a bunch. Did you know that rubber can be made to be static dissipative/conductive as well? But what about rubbing against or just making contact with our car seats and carpeting? You can get a small bottle of anti-stat which lasts pretty long, or you can get a fabric softener and mix it about 10:1 water to fabric softner in a spray bottle and spray down your seats and carpet and see if that helps. The fabric softener doesn't last too long and requires frequent sprays.

In your house or inside buildings, humidifiers work great if you can get the humidity up to 30% to even 50%. This may be enough to get the static potential down to well below 3,500 volts. House plants help too. You must keep them properly watered too. For example, you are going to turn a light switch on and get zapped. This is because you are walking on that carpet with you ESD insulative shoes/slippers on and build up a charge and when you touch the grounded screw on the receptacle face plate, you rapidly discharge or neutralize the charge and feel the energy as a shock. This is what I do when the static gets bad, I touch a house plant first, feel a little tingle then touch the light switch, thermometor, door knob, etc.

In Colorado, you ever notice how we have to water our plants twice as much in the very dry winter?

We have different skin types. Lotion certainly helps to make us better conductors. But if we don't have the right footwear on the right flooring surfaces, we're gonna discharge that energy to ground somewhere.

Rules of ESD;
  • You can ground a conductor. If we are that conductor, that may require being bonded or soft grounded to ground via a wrist strap (built in 1 meg ohm resistor or current limiting). We can also be soft grounded via ESD shoes or heel grounders (also with the built in 1 meg ohm resistance that prevents us from going into defib should we get ahold of AC line; I think 0.5 ma is the limit and a person doesn't want to be bonded to ground to less than 500,000 ohms ever) if we're also standing on a floor or surface that is not insulative or have a resistance to ground (RTG) of over 1 Gig ohm or 1.0E9 ohms. [sorry to bore you with industry technical jargon here, but it helps to understand how the industry controls static in that environment.]
  • You sometimes have to deal with isolated conductors; that's people walking on non-ESD surfaces such as at the grocery store (waxed VCT Tile typically), or people walking on a sidewalk (which may have a pretty decent path to ground depending on the moisture in the concrete slab) with insulative shoes.
  • You cannot ground an insulator by bonding it to ground. Balanced ionization is what they use in the industry that's protecting ESD sensitive devices, ordinance/flammables/explosive gasses vapors dusts etc. The best we can practically do with neutralizing charge in our homes is probably using a good humidifier and removing as many sources of high electrostatic tribocharge as possible. Carpet is one of the worst offenders. Someone mentioned how well wood floors are. Although they are not great conductors, they're not the best insulators either and are somewhat low tribocharging. Some carpet claims to be low tribocharging... but what about the padding and the dust beneath them? Folks with insulative footwear walking on typical carpet surfaces can generate 10s of thousands of volts just waiting to discharge somewhere.
Also as someone else mentioned, cotton is great because it absorbs sweat and salt from our bodies and is somewhat static dissipative. Also going barefoot in the home works pretty good.
Here's another post that discussed the more commercial aspects of esd...

http://www.city-data.com/forum/5688115-post12.html

I still don't think it's a bad idea to protect some of your more expensive devices.

Last edited by McGowdog; 02-26-2017 at 09:17 AM..
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Old 02-26-2017, 04:07 PM
 
40,266 posts, read 41,830,220 times
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Quote:
Originally Posted by McGowdog View Post
You telling me that a computer couldn't incur damage right through the keyboard?
The mouse I zapped was corded, nothing happened to the computer. I'm not saying it couldn't of done damage and was actually a bit concerned it did until I tested it with another mouse. Think it was USB mouse.

This was back in about 2004.
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Old 02-26-2017, 08:34 PM
 
Location: Not far from Fairbanks, AK
16,726 posts, read 29,327,585 times
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Since the computer is grounded through the outlet, static electricity from your body is discharged through the computer's case and other ground points throughout the computer, and more than likely it does not damage it (but it can happen). However, if you discharge static electricity on a RAM board contacts when installing it, for example, there is a chance that you can damage it. That's why when working on a computer one should wear a ground strap. But at times a large static discharge can in fact jump across a positive point that is close to a negative grounded point, even if you don't touch anything. For example, when going to turn on a light in your house and you are charged with enough static electricity, sometimes the spark from your finger jumps across before your finger makes contact with the switch. The same for high voltage power lines at a ground transformer, or just a circuit breaker box. In these cases the electricity jumps from the live circuit and hits the nearest ground point, which is you if you are grounded (just like a lightning bolt).

Your dog probably hates static electricity on your hands, too

Last edited by RayinAK; 02-26-2017 at 08:44 PM..
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