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Made by Monkeys

ZAP! Another ESD Casualty

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Rob Spiegel
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One static charge after another
Rob Spiegel   6/5/2013 4:31:34 PM
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I can't tell you how many Made by Monkeys and Sherlock Ohms postings have involved static electricity. A lot. Static electricity has been the culprit in tons of design stories. Do you have any of your own stories that involve static charges?

Charles Murray
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Re: One static charge after another
Charles Murray   6/5/2013 6:55:58 PM
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Littelfuse would love to hear these stories.

nichollr
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Iron
Re: One static charge after another
nichollr   6/6/2013 10:15:14 AM
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I've noticed at our local Walmart that as I push some of the carts, I get a static discharge through my hands.  It's really uncomfortable.  Have other's noticed this same problem?

g-whiz
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Gold
Painful excersize
g-whiz   6/6/2013 3:34:39 PM
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I had my earphones plugged into a (grounded) audio distribution system mounted on the treadmills at the local gym (so we could select and hear television audio from various overhead monitors). I was electrically isolated, in intimate contact with a hard rubber belt, moving and rubbing against another surface. I felt a periodic sharp pain in my head while walking. As a static charge built up on me, the thousands of volts eventually had enough pressure to jump the gap between the grounded earphones and my ear canal. I didn't hear it beacuse the audio was louder, but I sure felt it. It took me a few moments to analyse what was going on. On my next visit, I grounded myself to the treadmill handrail using a standard ESD wrist strap/wire. Problem went away. No wonder noboby was listening to the TVs at the treadmill station. I told manangement and they bought a bag of wired wrist straps for their clients to use.

Rob Spiegel
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Re: Painful excersize
Rob Spiegel   6/7/2013 5:52:59 PM
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Hey, g-wiz, this would make a good Sherlock Ohms posting. Could you send it along with a bit more detail -- to fill out the length -- and include a short two- to four-sentence bio?

You can send it to rob.spiegel@ubm.com

Larry M
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Re: Painful excersize
Larry M   6/13/2013 8:58:42 AM
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g-whiz wrote: " I was electrically isolated, in intimate contact with a hard rubber belt, moving and rubbing against another surface."

The other name for this particular apparatus is "Van de Graff generator." They can generate up to 5 million volts. See the Wikipedia article for more details.

 

 

econobiker
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Iron
Re: One static charge after another
econobiker   6/10/2013 2:16:35 PM
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nichollr wrote:

"I've noticed at our local Walmart that as I push some of the carts, I get a static discharge through my hands.  It's really uncomfortable.  Have other's noticed this same problem?"

Often you will see some versions of  shopping carts with a discharge strap or small chain hanging down rubbing the ground.  This also seems to be a greater problem with the newer plastic carts than the older metal carts... There has been alot of info about this problem with a specific retailer which you can find by searching: Wal-mart shopping cart static electricity shock.

J. Williams
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Re: One static charge after another
J. Williams   6/17/2013 5:34:42 PM
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Yes, the carts at my local Sam's Club replicate four little Van De Graaf generators with the wire basket and frame working as a top load.  The whack I get from the cart is quite startling.

tekochip
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Re: One static charge after another
tekochip   8/8/2014 4:29:45 PM
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One night after a flight I was pushing the aircraft back and when the towbar got close to the nose gear I drew a good 1" spark and a dandy SNAP.


J. Williams
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Re: One static charge after another
J. Williams   8/8/2014 6:16:20 PM
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That was most likely due to the static charge built up on the skin of your aircraft just from airflow.  Rotary wing aircraft are particularly susceptible to this issue.  Don't they always have you ground the skin before you put fuel in your plane?  I'm not a pilot, but I have spent more than a few hours coming and going off of vaious flight lines, usually hauling a ruck. 

tekochip
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Re: One static charge after another
tekochip   8/8/2014 7:16:28 PM
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All true, you have to ground the aircraft before fueling.  Imagine a spark like that being drawn from the fuel hose into an empty tank.

BobKoblish
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Bronze
Re: One static charge after another
BobKoblish   9/8/2014 11:18:23 AM
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I've experienced this just walking across an epoxy-painted concrete floor in tennis shoes.

TJ McDermott
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Re: One static charge after another
TJ McDermott   6/5/2013 11:36:43 PM
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Rob, I have to thank you for the good idea.  I've two to write now.

Rob Spiegel
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Re: One static charge after another
Rob Spiegel   6/11/2013 9:46:31 PM
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Thanks TJ. I look forward to seeing them.

3drob
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Re: One static charge after another
3drob   6/6/2013 1:07:52 PM
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Years ago I worked with a SW engineer who just couldn't (or wouldn't) take ESD seriously.  One of his habits that drove me up the wall was he would put an IC on his plastic notebook and just slide the chip around in a circle on the notebook (a good way to zap the chip).

We could never get him to wear ESD straps. The final straw was when he walked into a lab I was working in.  We had operational equipment set up on an ESD safe bench with the covers off.  He walked over to one of my modules and touched an accessible board.  I heard the zap from over 10' away.  He destroyed the module.  He also found new opportunities elsewhere not long after (probably unrelated to the ESD event).

It amazes me how so many people (many smart Engineers) just don't understand how little static electricity it takes to destroy electronics.  Probably because often the induced failures are not catastrophic (the device will even appear to continue to work).  Many of the real failures are manifest as weird or mysterious problems that cannot be pinned down.  Because they don't see a ZAP and then a truly dead device, they assume they've done no real damage.   I'll continue to be paranoid and minimize such problems.

Ralphy Boy
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Platinum
Re: One static charge after another
Ralphy Boy   6/6/2013 10:55:01 PM
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Yeah 3drob... We get that too sometimes. I've been told by one EE that he's never zapped a board... 'Yet' is what I replied.

We have below 1% humidity in the dryrooms and an over active air exchange in one of those creates a bit of a breeze too. We do a good job of maintaining boot straps, wrist straps, ESD Lab coats as SOP in those... and we still get the occasional fire, so far though those always seem to be non-static events. Friction; go figure.

dbues
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Gold
Re: One static charge after another
dbues   6/7/2013 6:43:58 AM
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3drob, I know what you mean.  We had a guy years back that used to flick his cigarette ashes into our chassis.  Drove QA nuts!!!  He's the same guy that designed everything with discrete J-K flip flops.

 

Everybody assumed he was a genius because all his designs worked, but nobody understood them.  Luckily for me, he left before I had to debug anything he designed.

Rob Spiegel
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Re: One static charge after another
Rob Spiegel   6/7/2013 5:56:12 PM
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Hey, 3Drob,

I'd like to use this story as a Made by Monkeys blog. 

You can send it along to rob.spiegel@ubm.com

Thanks.

JimT@Future-Product-Innovations
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I guess not every company focuses on ESD
JimT@Future-Product-Innovations   6/6/2013 9:01:40 AM
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Dwight, you write very well – great article.  Your descriptions of 'back then' vs today are hauntingly familiar to me as I was right there with you both times.  The various companies I've served over the years learned the same lessons you've described, and ESD prevention has steadily gained prominence to become a standard initiative in the electronics industry. But because of that, I am very surprised the new camera you bought suffered a catastrophic failure from an ESD shock.  It seemed to me that EVERYBODY was designing for prevention these days.

William K.
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Platinum
Re: I guess not every company focuses on ESD
William K.   6/6/2013 9:32:44 AM
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Unfortunately adequate ESD protection does not add to the "features" of a product, and it's lack will not be obvious until after the product is purchased and used a bit. And the very short warranty period has expired. So a bargain thing will usually have inadequate protection.

Of course, the story sounds like a really large charge was delivered, probably far beyond the typical one that a minimal system would be protected against.

dbues
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Gold
Re: I guess not every company focuses on ESD
dbues   6/7/2013 6:45:16 AM
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JimT, thanks for the feedback!!!  Comes from having an English teacher for a Mom....

etmax
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Gold
Modern ESD Testing
etmax   6/6/2013 9:29:39 AM
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Remarkable, I would have thought that with modern products and the amount of ESD testing that is supposed to be done that this would be a thing of the past. I've been involved in product development for the last 30 years and we zap thing repeatedly (30 times in development and then in compliance testing another 30) with 8kV positive and negative to all metal accessible parts and we don't even see a reset let alone damage. I wonder what went wrong here?

JimT@Future-Product-Innovations
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Re: Modern ESD Testing
JimT@Future-Product-Innovations   6/6/2013 9:58:42 AM
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Exactly – 8kV – repeatedly.  Read William K's response to my original post, (making the same point you made here) William's response is logical – it's about a fast buck, and no repeat business.

etmax
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Re: Modern ESD Testing
etmax   6/6/2013 10:16:12 PM
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Hi Jim,


I read William K's reply and his point really suggests that as consumers we should only buy CE marked products which actually MUST go through this testing to be allowed to apply the logo. That way the shonky operators cease to sell products and we all benefit. The purpose of the CE mark was to lift product quality to a minimum standard deemed necessary for the application. In the EU it's enforced and placing a CE mark without complying results in fines and worse a need to remove the mark. Designing for ESD places some real challenges on the designer adding great skills and improving employment prospects (at least where it's mandatory :-) ).

Frank Karkota
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Iron
ESD discharge
Frank Karkota   6/6/2013 10:43:08 AM
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Before you completely give up on the camera, try something:

Remove the batteries for a week or two and then replace them.  The microcontroller may have jumped to a nonvalid program location.  It may be jumping around in the program.  Once the internal capacitor discharges, it will reset.  I have had that happen with cameras and other comsumer products.  

dbues
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Gold
Re: ESD discharge
dbues   6/7/2013 6:40:30 AM
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Thanks for the tip, Frank.  I'm trying it now.

dbues
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Gold
Re: ESD discharge
dbues   7/1/2013 8:50:11 AM
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Frank,

Good idea to pull the batteries.  Didn't work, though.  Not sure what the right way would be to discharge the alleged capacitor.  I might try to remove the batteries and then short the DC + and - together.  Otherwise, I'll have to take a look inside.

Dwight

profgroove
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Iron
ESD
profgroove   6/6/2013 2:13:13 PM
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We had an ESD problem with Si wafer fork robot.  Not only did the computer occasionally re-boot, but spark damage occurred on wafers withdrawn and/or inserted into their plastic cassettes.  The solution:  Isolate the fork and connect to ground through a giga Ohm resistor.

John E
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Silver
Re: One static charge after another
John E   6/7/2013 6:25:48 PM
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I once worked for a contract ICT test house developing test programs and fixtures.  Our test head (HP3065) and debug bench was in a "static controled" room with a disapative carpet.  One day durring the winter, I walked accros that rug, reached down into the empty patch bay of the test head and drew a 1" arc to one of the test card connections; it hurt like heck and I jumped back.  I immediatley grabed the diagnostics fixture, and found that we had a dead analog card.  It took two day of down time for HP to find the problem and get us a replacement card.  So much for the anti static carpet.  We got a lot more serious about wrist staps after we learned that we could not rely on the carpet any more.

Cadman-LT
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Everyone
Cadman-LT   6/17/2013 5:03:35 AM
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I would have to guess that almost everyone has had this happen to them at some point in time. I sure have.

rhayashi
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Silver
ZAPPED!
rhayashi   8/7/2014 7:29:15 PM
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I had a Medical instrument the was reported to reboot in a Swedish operating room that had very bad static charge issues. We could not duplicate the problem with a local unit, so the aquired the Swedish unit. I could not get it to fail with my sparky stick. The only clue was it happened when it was set for full volume. The volume control was for a anoying vacume level warbler sound. (so I always set it to minimun) I finnaly tried it at full volume. As it turns out the volume control pot set at maximum allowed a spark into the A/D which latched up the CPU, While a low volume setting sent the spark into ground.

BobKoblish
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Bronze
ESD zapping terminals
BobKoblish   9/8/2014 2:03:07 PM
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Some decades ago we computerized the admissions department at a series of entertainment venues. The initial installations were in coastal Florida, where the humidity was high and we had no problems.

At a newer site in New Jersey the installation was in the cold weather and the terminals were resetting at random. We eventually figured out that the tellers' uniforms were rubbing up a static charge as they shifted on their stools, then the terminal would get zapped as they touched it to process the next patron. The fix was to install a conductive plastic cover over the seat cushion. We also removed the rubber tips from the stools' metal legs so that the stool would ground itself to the masonry floor.

In retrospect, attaching a length of sash chain to the bottom rung of the stool might have worked as well to ground the legs. But it might have created a tripping hazard.

 

 

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