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Duane Benson
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Maybe...
Duane Benson   8/13/2014 1:38:09 PM
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You might not actually be connected to ground. You have DC going from the power supply to the notebook. Depending on how the power supply is isolated or not isolated, grounded or not grounded, there may not be a direct connection to an earth ground.

Max The Magnificent
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Max The Magnificent   8/13/2014 1:41:43 PM
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@Duane: You might not actually be connected to ground.

I'm not wearing my smiley face -- how can I determine if I am or am not...?

Duane Benson
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Duane Benson   8/13/2014 1:51:10 PM
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Just to be sure, I ran it past a couple of my ESD experts here.

Connect your ohm meter between the ground wire you have coming out of that USB cable, and the ground pin on the AC power plug (with the AC power cord unplugged). If it's less than 1 ohm, you're good to go.

Max The Magnificent
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Max The Magnificent   8/13/2014 1:55:34 PM
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@Duane: Just to be sure, I ran it past a couple of my ESD experts here [...] if it's less than 1 ohm, you're good to go.

Potential Happy Dance -- I'll check thsi as soon as I get home this evening an report back in the morning...

mhrackin
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mhrackin   8/13/2014 3:45:57 PM
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I don't know what flavor notepad you are using, but I have a number of Lenovo Thinkpad power supplies on my desk right now, and i noticed that they have a TWO-WIRE UNGROUNDED (and unpolarized) AC plug.  I also have some ancient Dell ones with 3-wire cords.  Obviously, there's no point in ohming out the Thinkpad ones as there is NO input ground.  The Dells do have the ground continuous (1.2 ohms) to the shell of the DC power plug.  However, these are REALLY old (from XP PCs) so your results may differ.

Max The Magnificent
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Max The Magnificent   8/13/2014 3:55:44 PM
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@mhrackin: ...and i noticed that they have a TWO-WIRE UNGROUNDED (and unpolarized) AC plug.

1,000 curses-- you are of course 100% correct -- in fact Ivan came bouncing into my office about 30 minutes ago saying the same thing -- and as soon as he said it I remembered that my notepad also has a 2-pin power plug.


Bummer ... watch this space...

David Ashton
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David Ashton   8/13/2014 6:14:31 PM
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@Max...sorry to rain on your parade (or pee on your fire) but I would say 100% of all the brick type laptop and other power supplies I have ever taken apart (and there have been a few) have been switching types with the output isolated from the mains.

A mini-tower desktop computer might be different - those power supplies usually have a connection between the mains earth and the case of the PC....but I am not sure whether this will extend to the USB shield, I will check mine when I can.

Your solution might be to just switch your power supply off rather than unplugging it.  Of course you should also check if the power supply ground goes all the way through to the output.

The best solution would be to get a mains cable with a proper 3-pin plug,  cut the IEC end off (preferably while it is NOT plugged in :-), strip it back a bit, and cut off and insulate the white and black wires (which is what I think you have in the US) leaving the green earth wire only - and connect that to your anti-static mat.  This does assume you have a spare power outlet where you are working, and that G the G does not want to use said outlet while you are electronicking...

PS to avoid the white and black wires shorting, cut them off different lengths.  Then get some pliers and pull the insulation so you don't have wire ends sticking out.  Then insulate them with tape.   As the Irish would say....To be sure...to be sure...

Max The Magnificent
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Max The Magnificent   8/14/2014 10:14:38 AM
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@David: ...The best solution would be to get a mains cable with a proper 3-pin plug,  cut the...

This is what I was planning on doing (except using plugs that are designed for you to wire up yourself) until Wnderer suggested using the existing banana plugs on the wristbands/mats along with these $7 ground plug adapters.

Max The Magnificent
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Max The Magnificent   8/14/2014 10:16:31 AM
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@David: ...The best solution would be to get a mains cable with a proper 3-pin plug,  cut the...

One possible problem with this approach is that if you cut the banana plug off the lead, you might lose the 1M Ohm resistor (these are sometimes mounted in the babana plug itself) -- that's another reason why Wnderer's solution is favorite.

David Ashton
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David Ashton   8/14/2014 6:16:12 PM
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@Max... "One possible problem with this approach is that if you cut the banana plug off the lead, you might lose the 1M Ohm resistor "

You do like to make life difficult.  Modify the mains lead as above, and put a banana socket on the green wire to plug your wrist strap / grounding mat into.  

Maybe you misunderstood me...I meant to use an IEC mains lead, such as you would plug into the back of a PC....and cut the IEC plug off??

In any case, I'd agree that Wnderer's gadget is a much better solution....

Max The Magnificent
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Max The Magnificent   8/15/2014 10:16:18 AM
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@David: Maybe you misunderstood me...

It's your Australian accent...

David Ashton
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David Ashton   8/15/2014 7:27:39 PM
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@Max..."It's your Australian accent"      When I phone my mom in England she says "oh, you sound so Australian".  I told this to my mates at work and they could not stop laughing.

But then I have taught my workmates some useful Afrikaans words,,,like

Bliksem - loosely equates to "Bastard" but probably not as strong

Snaaks - very strange

Vrot (pronounced Frot) - literally "rotten", but can be applied to anything bad

antedeluvian
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antedeluvian   8/15/2014 9:38:59 PM
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David

..."It's your Australian accent"      When I phone my mom in England she says "oh, you sound so Australian".

Thanks for the segue into my favourite story. Let me say (for the readers) that like in any country the accent of the spoken language (English in the case of Rhodesia/Zimbabwe) fills a spectrum. In Zimbabwe the range is from very close to the Queen's English (which I suspect David uses) to a middling South African accent. The South African accent in its extreme can be as harsh or evn harsher than a broad Australian accent. My accent, for several possible reasons including the fact that I lived in South Africa for 13 years, tends strongly to the South African.

When I first got to Canada there was no internet as we know it, and I wanted some data on some IC or another. I phoned the company in California, requested that the data be mailed to me and proceeded to give my address, ending with the usual flourish- "Ontario, Canada". "Oh," said the lady I was speaking to, "that explains your accent!"

zeeglen
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zeeglen   8/15/2014 10:35:09 PM
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@ antedeluvian "Ontario, Canada". "Oh," said the lady I was speaking to, "that explains your accent!"

South African accent mistaken for Canadian? LOL! Some accents are more readily identifiable; I once met a young lady from Scotland (she was an HP sales Engineer back before the word "Agilent" was even a gleam in a marketeer's eye) with a most beautiful Scottish accent that was a pleasure to hear.

Even though I no longer say "Eh?", after having lived in Texas USA for the last 17 years I still get asked "Are you Canadian?"  I can't hear any difference between the way I talk and my native-born colleagues, other than one with a very pronounced Texas drawl. And contrary to myth, Canadians never did refer to that rock band as "Zed Zed Top".

David Ashton
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David Ashton   8/16/2014 2:09:52 AM
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@Zeeglen... " I once met a young lady from Scotland....with a most beautiful Scottish accent that was a pleasure to hear."

When I worked for an international airlines telecomms company in Harare (Zimbabwe) there was a lass in our Nice (France) office who used to sent me messages to phone through to her mom who lived in Harare. (This was way pre-internet.)   The first time I did this I fell in love with her mom over the phone....she had the most beautiful southern Irish accent.  I never met her but it was always a pleasure to phone her to pass the messages on.

David Ashton
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David Ashton   8/16/2014 12:53:48 AM
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@Antedeluvian..." the Queen's English (which I suspect David uses)..."

If I wrote to the Queen I think she'd be happy, but if I went and spoke to her I don't think she'd consider me one of her subjects.  Even though I am... 

There is actually a sample of me speaking here (I was testing Max's geiger counter) so you can judge for yourself :-)

I once rang a guy in Australia whom I had never spoken to before,  After he'd spoken for about 10 seconds I said "You're from Zimbabwe, aren't you?"  Astonished, he admitted he was....but I find the Zimbabwe accent very distinctive.

antedeluvian
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antedeluvian   8/16/2014 10:38:00 AM
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David

There is actually a sample of me speaking here (I was testing Max's geiger counter) so you can judge for yourself :-)

Your accent is broader than I imagined.

There is a sample of me speaking here. I must admit I cringe at the sound of my own voice.

Max The Magnificent
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Max The Magnificent   8/18/2014 9:22:11 AM
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@antedeluvian: "Oh," said the lady I was speaking to, "that explains your accent!"

LOL

So, out of all the "English accents" -- British English, American English, South African English, Australian English, Scottish English, Irish English... which do you find most pleasing to the ear?

antedeluvian
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antedeluvian   8/18/2014 9:23:54 AM
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max

So, out of all the "English accents" -- British English, American English, South African English, Australian English... which do you find most pleasing to the ear?


A light Irish lilt begorrah, or even Welsh, look you.

Max The Magnificent
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Max The Magnificent   8/18/2014 10:20:20 AM
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@Antedeluvian: A light Irish lilt begorrah, or even Welsh, look you.

Have you ever heard a "Geordie" accent from the Tyneside area of England -- pretty close to the boarder between England and Scotland in the scheme of things -- I love that accent -- to me it always sounds a bit like they are singing (plus they have a great sense of humor).

antedeluvian
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antedeluvian   8/18/2014 11:32:25 AM
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Max

 to me it always sounds a bit like they are singing (plus they have a great sense of humor).

 

Well here they actually are singing. Now I am going to have Lindisfarne's "Fog On The Tyne" as an ear-worm for the rest of the day.

Measurement.Blues
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Measurement.Blues   8/20/2014 8:32:53 AM
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All this talk of accents.

I was born in Brooklyn but moved to New England (north of Boston) at age 13. Some people in New England say I still sounds like a NYer, but those in NY say I sound like I'm from New England.

A man without two cities.

Max The Magnificent
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Max The Magnificent   8/21/2014 9:58:32 AM
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@MeasurementBlues: A man without two cities.

But you'll always have the memory of bagels to see you through the hard times...

studleylee
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studleylee   8/21/2014 4:13:53 PM
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You just put it into a known state.....

I still keep a A/D converter I bought from Analog Devices that cost me $100 in 1984. I zapped it. Now it's a reminder. -Lee

zeeglen
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zeeglen   8/21/2014 4:34:29 PM
@studleylee I still keep a A/D converter I bought from Analog Devices that cost me $100 in 1984. I zapped it.

An engineering lab actually had a carpeted floor.  Was supposed to be anti-ESD carpet, but the installer got it wrong, and it had to be sprayed weekly with some kind of chemical.  Back then we did not have heel straps or wrist straps.

Anyway, on a cold dry winter day in the Great White North, a colleague had just installed the 1st of 10 samples of his brand new ASIC into the socket.  It was in a ceramic package with a metal top. We fired the board up, then we wondered how warm the ASIC was running.  My friend reached out to feel it - I said "Static!" but it was too late.  We could hear the 'snap' of a strong ESD discharge.

He said "It's not very hot."  Then a few seconds later "But it sure is getting hot now!"

One down, nine to go.

Max The Magnificent
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Max The Magnificent   8/21/2014 5:15:56 PM
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@zeeglen: "It's not very hot."  Then a few seconds later "But it sure is getting hot now!"

I can so imagine this scene...

zeeglen
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zeeglen   8/21/2014 10:30:38 PM
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@Max I can so imagine this scene...

Well, the boss was not around and I don't know if he ever found out.  We were in the habit of touching the rack metalwork before touching boards, but my colleague forgot this one time.

Max The Magnificent
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Max The Magnificent   8/29/2014 9:45:00 AM
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@zeeglen: We were in the habit of touching the rack metalwork before touching boards...

I gort into that habit years ago -- and I often do it automatically -- maybe touching the case of my power supply -- even if I'm already wearing an ESD wristband.

antedeluvian
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antedeluvian   8/15/2014 10:33:53 PM
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David

But then I have taught my workmates some useful Afrikaans words,,,like

Why don't we play "Ag Pleez Deddy" for the nice folks to experience whatvyou are talking about

Here is Jeremy Taylor explaining his song and this is the complete original

David Ashton
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David Ashton   8/16/2014 12:57:23 AM
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Love it!  I know the song, but the video of him explaining how he came to write it was interesting!

I should explain that I am an English-born Zimbabwean, but I learned Afrikaans after being ridiculed in a history class at school for not being able to pronounce "Bezuidenhout" a well know Afrikaans surname (it's "Ber-zayden-hote", but I said something like "Ber-zewden-howt" causing the whole class to crack up.  Later I worked on a South-African island for a year and got almost fluent..

Max The Magnificent
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Max The Magnificent   8/18/2014 9:25:56 AM
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@David: ...after being ridiculed in a history class at school for not being able to pronounce "Bezuidenhout"...

I'm not surprised -- shame on you LOL

 

Duane Benson
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Duane Benson   8/13/2014 1:54:46 PM
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In most US wall sockets, the screw that holds the outlet plate on is grounded. If that's the case, you could just connect to that screw for your earth ground.

Max The Magnificent
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Max The Magnificent   8/13/2014 1:57:42 PM
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@Duane: In most US wall sockets, the screw that holds the outlet plate on is grounded. If that's the case, you could just connect to that screw for your earth ground.

But they I still have the probem that the wall socket is quite a way from the table -- unless I attach a loong piece of wire -- and I don;t fancy attaching and detaching that wire each time I want to play with my electronics...

Crusty1
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Crusty1   8/13/2014 2:28:15 PM
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Hi Max : I get over stretching the colied cable of the wristband by having a multiple socket strip, on a lead from the wall socket, in England these are very cheap from Ikea. The soldering Iron and powers supply go into two of the free sockests leaving me with two other sockets for wristband and antistatic mat.

This approach any use?

Max The Magnificent
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Max The Magnificent   8/13/2014 2:34:55 PM
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@Crusty: I get over stretching the colied cable of the wristband by having a multiple socket strip...

Actually, that's not a bad idea -- I usually have a couple of these lying around -- but I'm going to check the USB thing first...

mhrackin
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mhrackin   8/13/2014 3:55:43 PM
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Max, the use of the USB and the use of the power strip are NOT mutually exclusive!  It would make sense to use the power strip regardless, just to reduce the excess bending over (although perhaps the exercise is beneficial!). I'd still vote for plugging directly into the U-ground hole rather than depending on the combined continuity of the series chain of alligator clip to USB shield wire to PC USB connector through PC internals to DC ground of power jack to power supply, thence (maybe) to the U-ground of the power cord into the AC outlet!  Far too many points of failure there (and of the most unreliable system element: interconnections!).

elizabethsimon
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elizabethsimon   8/13/2014 4:04:07 PM
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I did something similar when I had to set up on a table that was inconvineiently far from a wall socket. Since I needed a multi lead outlet strip with a long cord to power the equipment, I attached the cable from the antistatic mat to a ground on the outlet strip (which was located on the far side of the table). I then attached the lead from the wrist strap to a banana jack at the grounding point on the antistatic mat (which was on the edge near the front of the table). This minimized the stretching of the wrist strap cord and the whole thing could be moved fairly easily by unplugging the outlet strip from the wall and rolling it (and the cables) inside the antistatic mat.

 

antedeluvian
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Notebook??
antedeluvian   8/13/2014 2:34:46 PM
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Max

I hope I am not alone in noticing that a notebook can run on batteries, in which case you have no ground at all.

Max The Magnificent
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Re: Notebook??
Max The Magnificent   8/13/2014 2:39:47 PM
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@Antedeluvian: I hope I am not alone in noticing that a notebook can run on batteries, in which case you have no ground at all.

True, but I never use it that way -- I always have it plugged in when I'm working on a hobby project.

dt_hayden
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consumer versus industrial
dt_hayden   8/13/2014 2:37:02 PM
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In general, grounding yourself through a piece of (consumer grade) electronic equipment for ESD control seems like a not so good idea.  You are making assumptions about the goodness of that ground and assuming the equipment can withstand discharges into that point.  If you are sure only the wriststrap connection touches the "ground" point, then currents are limited by the resistor in the strap anyway and less of a worry.  If you grab the "ground" to make your connection, you could potentially make a direct discharge at that point. 

Having said that, Tek scopes I have used in the past had a "grounded" banana jack on the front panel which I plugged into for ESD management.  My thinking was since it was industrial gear, Tek designs robust equipment, and the point was probably put there for that purpose, it was fine. 

If you are only dealing with isolated portable gear, I think it is more important to equalize potential to the gear, rather than to ground.  .I have clipped onto grounds of gear in these cases.  In this case, some (all?) soldering ground tips are grounded, so beware when soldering.

Max The Magnificent
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Re: consumer versus industrial
Max The Magnificent   8/13/2014 2:41:38 PM
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@dt_hayden: If you grab the "ground" to make your connection, you could potentially make a direct discharge at that point.

Good point

Wnderer
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power strip and ground plug adapter
Wnderer   8/13/2014 4:07:48 PM
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Get a powerstrip and one of these $7 ground plug adapters. With a power strip you'll have a circuit breaker and switch to help shut down things quickly if there's trouble.



ninja'd by elizabeth

David Ashton
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Re: power strip and ground plug adapter
David Ashton   8/13/2014 6:17:14 PM
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@Wnderer....sorry, only noticed this post after I posted mine above.  Great little gadget, much easier than my idea if you can get them easily.

Wnderer
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Re: power strip and ground plug adapter
Wnderer   8/13/2014 7:46:03 PM
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@David Ashton Great little gadget, much easier than my idea if you can get them easily.


Digikey has them.

 

 

Max The Magnificent
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Re: power strip and ground plug adapter
Max The Magnificent   8/14/2014 10:11:52 AM
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@Wnderer: Get a powerstrip and one of these $7 ground plug adapters.

This is obviously the way to go -- I'm going to order the adapters right now -- Max

zeeglen
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Re: power strip and ground plug adapter
zeeglen   8/14/2014 10:18:01 AM
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A banana plug will fit directly into the outlet ground hole without needing an adapter.  It does help to remove the banana plug plastic insulator sheath, not needed in this application.

Max The Magnificent
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Re: power strip and ground plug adapter
Max The Magnificent   8/14/2014 10:24:24 AM
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@zeglen: A banana plug will fit directly into the outlet ground hole without needing an adapter.

Well, you have to "splay" the end out a bit, and even then it's not a perfect fit -- I think these adapters will do a better job (but they are WAY expensive for what they are)

Sanjib.A
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Re: power strip and ground plug adapter
Sanjib.A   8/24/2014 9:26:38 AM
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Wow!! This is a cool little gadget!! Really appreciate the idea!! The only remaining thing is then to check if the ground point of the socket is "really" connected to ground.

Max The Magnificent
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Re: power strip and ground plug adapter
Max The Magnificent   8/29/2014 9:47:40 AM
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@Sanjib: Wow!! This is a cool little gadget!! Really appreciate the idea!

It really is, although the ~$7 is a complete rip-off for something that can cost only a fraction of a dollar to make -- but it really does work perfectly for what I want, and it (well, "they" because I bought two) are a one-time buy that should last me the rest of my life ... so what the heck :-)

Max The Magnificent
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Re: power strip and ground plug adapter
Max The Magnificent   8/29/2014 9:49:25 AM
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@Sanjib: The only remaining thing is then to check if the ground point of the socket is "really" connected to ground.

That's true -- you should never take anything for granted.

Max The Magnificent
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Re: power strip and ground plug adapter
Max The Magnificent   9/10/2014 12:53:29 PM
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@Sanjib: Wow!! This is a cool little gadget!!

Just to follow-up to say that these $7 ground plug adapters are GREAT. On the one hand I agree that $7 is a lot of dosh for a small piece of plastic with onely one metal prong -- on the other hand (as I mentioned to zeeglen) they are a one-time buy that will last me the rest of my life.

I was using them last weekend to ground my wristband and antistatic mat -- and they are SO MUCH BETTER than the dorking around I was doing before (happy dance)

Sanjib.A
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Re: power strip and ground plug adapter
Sanjib.A   9/10/2014 10:04:03 PM
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@Max: That is great to hear from you!! Thanks for following-up!!

Max The Magnificent
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Re: power strip and ground plug adapter
Max The Magnificent   10/23/2014 4:47:15 PM
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@Sanjib: That is great to hear from you!! Thanks for following-up!!

As a followup to my followup, I'm delighted to report that I haven't had any more ESD-related problems since I adopted my new procedures (happy dance :-)

mhrackin
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Re: power strip and ground plug adapter
mhrackin   10/23/2014 4:55:53 PM
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@max: that is good to hear! On a possibly related subject: what disappeared from the "most commented" list that allowed the hoary old blog about appliances muttering behind our backs to reappear at the bottom of the list? I could have sworn that there was one at 102....

Max The Magnificent
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Re: power strip and ground plug adapter
Max The Magnificent   10/23/2014 5:19:00 PM
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@mhrackin: On a possibly related subject: what disappeared from the "most commented" list that allowed the hoary old blog about appliances muttering behind our backs to reappear at the bottom of the list?

Why, it's strange you should ask, but by some strange quirk of fate it was this very column.

Sanjib.A
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Re: power strip and ground plug adapter
Sanjib.A   10/24/2014 10:13:01 AM
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@Max: Great to hear that it worked well without any problem. :) Also, it is verified that your kictchen socket is connected to ground/Earth... ;)

Clive
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Re: power strip and ground plug adapter
Clive "Max" Maxfield   10/24/2014 10:25:16 AM
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@Sanjib: Also, it is verified that your kictchen socket is connected to ground/Earth... ;)

Yes -- that was the very first thing I checked LOL

mhrackin
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Re: power strip and ground plug adapter
mhrackin   10/24/2014 3:26:55 PM
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@max: well, in the immortal words often heard on "Laugh-in": Socket to me! Joanne Worley IIRC.... oops! it was Goldie Hawn.

mhrackin
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Re: power strip and ground plug adapter
mhrackin   10/29/2014 12:38:47 PM
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@max: "that was the very first thing I checked"

So what else did you check?  How about your "home away from home" office?  I don't know how recent the building is, but even in very new commercial space, I've found poor grounding practices that can result in significant ground differences between separate branch circuits even in the same room! I recall some recent postings on "Tales from the Cube" (on a sister site) that identified this as root cause of a number of strange occurrences.

Max The Magnificent
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Re: power strip and ground plug adapter
Max The Magnificent   10/29/2014 12:45:46 PM
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@mhrackin: I recall some recent postings on "Tales from the Cube" (on a sister site) that identified this as root cause of a number of strange occurrences.

Hmmm -- the main tower in my office keeps on locking up for no apparent reason -- we've scanned it for malware and viruses --- we've run burn-in software to stress the machine and wee've also run deep memory tests overnight -- nothing shows up. I wonder...

mhrackin
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Re: power strip and ground plug adapter
mhrackin   10/29/2014 12:49:21 PM
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Is it powered by a UPS?  I've had some issues with the UPS monitoring SW doing things like this.

Max The Magnificent
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Re: power strip and ground plug adapter
Max The Magnificent   10/29/2014 12:53:33 PM
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@mhrackin: Is it powered by a UPS?  I've had some issues with the UPS monitoring SW doing things like this.

It is indeed -- I have a honking big one (although I don't like to boast :-)

mhrackin
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Re: power strip and ground plug adapter
mhrackin   10/29/2014 12:55:18 PM
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Try disconnecting the USB connection to the PC and see if the problem recurs.  I use the 1500VA APC ones in the lab at work.

MeasurementBlues
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Ground? What ground?
MeasurementBlues   8/13/2014 4:58:10 PM
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Having just returned from the EMC Symposium, I'm reminded that there is, as Bruce Archambeault will tell you, there's no such thing as ground except perhaps in this case, for safety.

Too often, we use the term "ground" when we really mean "return" as in current returning to its source. Ground is a reference voltage. Current shuld not flow through a ground wire at all. When it does, you have samety and EMC problems.

Read what Dr. Todd Hubing said last week about "ground" at an EMC fundamentals tutorial.

 

MeasurementBlues
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What ground is actually good for.
MeasurementBlues   8/13/2014 5:01:27 PM
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MeasurementBlues
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Wear the wristband
MeasurementBlues   8/13/2014 5:13:00 PM
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@Max,

The purpose of the wrist band is to provide ahigh-resistance (leakage path) from you to whatever you're working on. So if your circuit is floating and you're connected to the low side of its power supply, you should be OK. If the power supplye is indeed connected to the ground lead of the AC mains, then that's better.

Some years ago, I was installing a new hard drive in my desktop PC. When I powered it up, the power sypply fan came on, but nothing else. I had zapped the motherboard and needed a new one. Since that day, I always wear an ESD wrist strap.

ESD wrist straps whould be part of everyone's EMC troublshooting kit.

zeeglen
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Re: Wear the wristband
zeeglen   8/13/2014 5:24:09 PM
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@Martin So if your circuit is floating and you're connected to the low side of its power supply, you should be OK.

Also a good idea to connect a scope probe ground to a floating circuit as the first connection so that the circuit is no longer floating.  I've zapped MOSFETs by connecting the probe tip to the gate first before the ground.

MeasurementBlues
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Re: Wear the wristband
MeasurementBlues   8/13/2014 5:26:26 PM
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As you surely know, never ever float the scope.

MeasurementBlues
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Braided shield
MeasurementBlues   8/13/2014 5:30:59 PM
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Congratulations Max, you've just created a pigtail, a wonderful source of radiated emissions.

I'll be posting an article to my EDN blog about how those pigtails are evil.

The braided shielding -- shown pulled back from the inner wires, twisted together, and sticking out of the right-hand side



Max The Magnificent
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Re: Braided shield
Max The Magnificent   8/13/2014 5:41:37 PM
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@MeasurementBlues: Congratulations Max, you've just created a pigtail, a wonderful source of radiated emissions.

Thank-you-very-much ... I'll be playing here all week :-)

MeasurementBlues
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Google has found you
MeasurementBlues   8/13/2014 5:36:17 PM
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@Max, I get a Google alert for "electrostatic discharge" and you've been picked up.

MeasurementBlues
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BEWARE: Ground wires can fail
MeasurementBlues   8/14/2014 10:24:50 AM
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@Max,

I just needed to use an ESD wrist strap to work on my wife's computer. The insulation in all four of them failed. I'll write up a piece about it (with photos) and post a link here.

Max The Magnificent
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Re: BEWARE: Ground wires can fail
Max The Magnificent   8/14/2014 10:32:50 AM
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@MeasurementBlues: The insulation in all four of them failed.

The insulation in all for of "what" failed?

MeasurementBlues
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Re: BEWARE: Ground wires can fail
MeasurementBlues   8/14/2014 10:36:48 AM
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Max, I should have been more clear. The insulation on the ground wire of all four of my wrist straps failed, exposing the wire inside. On one of them, the insulation is turning into a kind of black goo. It got all over my hands. On the other three, it just loked like the insulation was stripped away, but I surely didn't do that.

I'll send a link when my article is posted.

Max The Magnificent
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Re: BEWARE: Ground wires can fail
Max The Magnificent   8/14/2014 10:47:29 AM
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@MeasurementBlues: The insulation on the ground wire of all four of my wrist straps failed, exposing the wire inside. On one of them, the insulation is turning into a kind of black goo. It got all over my hands.

Uggh -- remind me not to shake hands with you again.

Are you sure it's goo from the insulation that got all over your hands ... and not goo that was already on your hands being transferred to the insulation?

mhrackin
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Re: BEWARE: Ground wires can fail
mhrackin   8/14/2014 10:57:40 AM
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Maybe he should GOOgle it....

Max The Magnificent
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Re: BEWARE: Ground wires can fail
Max The Magnificent   8/14/2014 11:08:44 AM
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@mhrackin: Maybe he should GOOgle it....

Arrggghh -- go and have another cup of coffee!

mhrackin
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Re: BEWARE: Ground wires can fail
mhrackin   8/14/2014 11:36:15 AM
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you're right as usual....I'm only halfway through mug #3 of the day.  Fresh pot is brewing and should be ready in a few minutes, after I have emptied the mug and my bladder.

Max The Magnificent
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Re: BEWARE: Ground wires can fail
Max The Magnificent   8/14/2014 12:01:31 PM
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@mhrackin: ...after I have emptied the mug and my bladder...

So long as you don't empty the latter into the former, all will be well...

mhrackin
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Re: BEWARE: Ground wires can fail
mhrackin   8/14/2014 12:06:44 PM
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Good suggestion (:)>).  I'll enjoy the next cup with a lunch of sausage and chicken jambalaya, accompanied by the Hank Williams song running through my head.

mhrackin
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Re: BEWARE: Ground wires can fail
mhrackin   8/14/2014 12:21:16 PM
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Damn!  Got down to the cafe, and they decided to NOT make the jambalaya today!  Had to settle for a barbecue sandwich with cole slaw instead..... but the song is still in my head! 

MeasurementBlues
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Re: BEWARE: Ground wires can fail
MeasurementBlues   8/14/2014 3:33:08 PM
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@Max, here's the link to my article ESD wrist-strap insulation decomposes.

Max The Magnificent
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Re: BEWARE: Ground wires can fail
Max The Magnificent   8/14/2014 3:37:27 PM
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@MeasurementBlues: ...here's the link to my article ESD wrist-strap insulation decomposes.

I shall bounce over there immediately to ridicule you some more LOL

seaEE
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What everyone's waiting for
seaEE   8/16/2014 11:29:37 AM
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I think what everyone's waiting for is Wireless ESD.  This would be a wireless method (no wrist or footstrap), of discharging ESD via one of the wireless consortiums that will allow the ESD we build up to power our phone to tablet.  That would be a shocking development!

Put that static to good use!  Conserve static!

zeeglen
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Re: What everyone's waiting for
zeeglen   8/16/2014 4:56:50 PM
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@seaEE I think what everyone's waiting for is Wireless ESD.

Also wireless oscilloscope probes.  No cables hanging everywhere to trip over.  Maybe we could kickstart and get some suckers er, investors interested in both.  Product launch scheduled for next April first.

antedeluvian
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Re: What everyone's waiting for
antedeluvian   8/16/2014 6:09:18 PM
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Glen

Also wireless oscilloscope probes.  No cables hanging everywhere to trip over.  Maybe we could kickstart and get some suckers er, investors interested in both. 

Perhaps not so far fetched . Try this "Trace Signals From Behind Closed Doors"

 

zeeglen
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Re: What everyone's waiting for
zeeglen   8/16/2014 7:02:37 PM
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@Aubrey Perhaps not so far fetched . Try this "Trace Signals From Behind Closed Doors"

Now that is one impressive solution to a practical problem  Missed it first time around.

I still think ESD safety needs wires, seaEE was making a joke.  And 100's of MHz RF bandwidth for wireless scope probes is very unlikely in the near future.  In the far future, maybe.

Max The Magnificent
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Re: What everyone's waiting for
Max The Magnificent   8/18/2014 9:27:52 AM
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@zeeglen: I still think ESD safety needs wires, seaEE was making a joke.

Let's hope he doesn't give up his day job LOL

Reinhardt
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Laptop grounded?
Reinhardt   8/17/2014 12:49:19 AM
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Your idea sounds good a first look, but are you sure our laptop is really grounded? Many laptop PSUs I have seen have only a two pin power plug, no protective earth pin.

And even is the PSU has a real ground connections is this also routed to power ground on the DC side?

 

Max The Magnificent
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Re: Laptop grounded?
Max The Magnificent   8/18/2014 9:30:39 AM
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@Reinhardt: Your idea sounds good a first look, but are you sure our laptop is really grounded? Many laptop PSUs I have seen have only a two pin power plug, no protective earth pin.

If you read the comments below starting from the beginning, you'll see that my suggestion "crashed and burned" for thsi very reason -- it would work with a tower computer with a 3-pin plug and a grounded power supply, but that's not what I've got.

However someone offered a really good solution -- use a power strip with some banana plug to ground adapters, then oplug the banana plugs on the strap & mat inrto ths strip.

William.Biehler_0623
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Re: Laptop grounded?
William.Biehler_0623   8/20/2014 7:22:41 PM
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There are several kits for grounding to an outlet strip. One can be found at the site below.

http://www.stanleysupplyservices.com/static-solutions-sp-101-receptacle-ground-tester-with-wrist-strap-plug/p/479-077

And there are portable mats etc. at the site.

http://www.stanleysupplyservices.com/search.aspx?f=1%3a983


I have some of these in my field service kit along with travel adapters for the different power connectors in countries I travel to.

There are probably several other ways to get ESD safety, but the outlet adapter seems to work for me.

JLBrake
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Re: Laptop grounded?
JLBrake   8/21/2014 3:44:31 PM
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There's lots of stuff going here, but let me try to clarify some things.

 When working on the something like a laptop, there are really two options of grounding for ESD purposes.  

1.  Ground all conductors and dissipative materials (people, product, worksurface, etc) through an electrical ground (third wire).  This is the preferred method for electronics manufactures because the electrical ground is where other equipment (soldering iron, scopes, etc) used in the production environment if grounded, but not always available in "field" applications. 

2. If grounding to the electrical ground is not possible, you can use equipotential bonding. Equipotential bonding connects all conductors and dissipative materials in the environment together.  If you are working on something such as a laptop, you would use an alligator clip to connect the wrist strap to the housing of the laptop. 

Both methods essentially do the same thing in creating an equipotential balance between all items and personnel.  ESD events can only occur when there is a difference in the potential. Note that only conductors and dissipative materials can be grounded, insulators require ionization to control ESD. 

Based on this post we are going to make some samples of a USB to banana jack adaptor to see how this would work.  The adaptor will allow a standard wrist strap to be connected to the USB.

Max The Magnificent
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Re: Laptop grounded?
Max The Magnificent   8/21/2014 5:12:58 PM
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@JLBrake: ...If grounding to the electrical ground is not possible, you can use equipotential bonding....

WONDERFUL point -- I'm kicking myself for not thinking about this.

Max The Magnificent
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Re: Laptop grounded?
Max The Magnificent   8/21/2014 5:14:31 PM
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@JLBrake: Based on this post we are going to make some samples of a USB to banana jack adaptor to see how this would work.  The adaptor will allow a standard wrist strap to be connected to the USB.

You might want to make it a double-banana jack -- that way someone could connect both their wriststrap and their anti-static mat to the same USB plug

zeeglen
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Re: Laptop grounded?
zeeglen   8/21/2014 5:27:10 PM
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@JLBrake you can use equipotential bonding.

When breadboarding it can help to do all your work on a new cookie baking sheet.  The raised edges keep small parts contained within your work area, and since your wrists can rest on the raised edges everything is at the same potential as the worker.  Just be sure to touch the cookie sheet first when starting a session, and maintain contact with the cookie sheet.

Max The Magnificent
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Re: Laptop grounded?
Max The Magnificent   8/29/2014 9:43:37 AM
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@zeeglen: When breadboarding it can help to do all your work on a new cookie baking sheet.  The raised edges keep small parts contained within your work area, and since your wrists can rest on the raised edges everything is at the same potential as the worker.

This is really good advice -- especially for younger people -- I have a young lad in mind (a friend's grandson) who is just starting to play with the Arduino -- his family doesn't have much money, so splashing out on earth straps and pads and those banana-to-power adapters would be out of his range -- also teaching him the discipline to use them correctly would be problamatic -- but the cookie sheet idea woudl be perfect for him -- I'll tell him when I see him next week. 

Max The Magnificent
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Re: Laptop grounded?
Max The Magnificent   9/16/2014 10:39:54 AM
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@JLBrake: Based on this post we are going to make some samples of a USB to banana jack adaptor to see how this would work.  The adaptor will allow a standard wrist strap to be connected to the USB.

Did you ever get around to experimenting with this?

Max The Magnificent
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Interesting ESD Stories
Max The Magnificent   9/17/2014 9:49:55 AM
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I'd love to hear other peoples' ESD stories ... just to reassure me that I'm not alone LOL 

DrQuine
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ESD seasons, geography, and grounding
DrQuine   11/28/2014 12:25:59 PM
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ESD is tricky stuff, not only does it vary seasonally (the classic example of walking across a rug in the winter and then touching a grounded device) but also it varies geographically (Albuquerque, New Mexico is so dry that special precautions must be taken in manufacturing facilities). Regarding a simple home ground, I must say that I'm a little uneasy discharging unwanted high voltages into the moidst of a (presumably) well grounded laptop computer.

Why not plug the banana plug into the grounded third prong (after confirming that the outlet is properly grounded) of an outlet?

Max The Magnificent
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Re: ESD seasons, geography, and grounding
Max The Magnificent   12/1/2014 10:41:21 AM
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@DrQuine: Why not plug the banana plug into the grounded third prong (after confirming that the outlet is properly grounded) of an outlet?

That's essentially what I am now doing with the $7 ground plug adapters that someone recommended in an earlier comment.

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