Tuesday, January 26, 2016

An Electro-Static Bandaid to Protect Sensitive LCD Displays

After the big East Coast blizzard,  the atmosphere in my ham shack became very dry.  I sit in one of those desk chairs with little plastic wheels.  The shack is carpeted.  So when I roll from operating bench to workbench,  the chair, the carpet, the dry air and I all become a kind of Van de Graaff generator.  Yesterday, my hand brushed against the 16X2 LCD display on my new R2 phasing receiver.  The pretty glowing numerals in that display disappeared in a small spark, never to return.

I swapped out another display I had, so all is well.  But the repair was a pain in the neck, involving the soldering of some 16 LCD pins, so I don't want to do it again.  I consulted with Pete Juliano N6QW who told me that this kind of LCD carnage is quite common in dry environments.  He said he had cured the problem by placing a small piece of Plexiglas in front of his displays. 

This got me thinking about those static protective bags that Digikey uses when shipping many of its components.  Might the material from these bags prevent the loss of another display? 

I retrieved a couple of these bags from the garbage and did a little test:

 First, I rolled across the shack in the chair with a small screw-driver in hand.   At the other end of the shack lies my well-grounded DX-100 transmitter.  I moved the screwdriver close to the metal on-off switch.  SPARK!  It was visible, and quite audible in the AM broadcast receiver nearby. 

Next I taped a small piece of this material over the switch and repeated the ride in the chair.  No spark. Nada.  I repeated this several times and always got the same result.

It appears that the material in the bag helps dissipated the static discharge over a wider area, preventing the spark.  I quickly taped a piece of this material over the two LCD screens in my shack.  It's not pretty, but it is temporary, and cheaper than a humidifier.

I'm not going to try this on the actual screens, but I do think these small pieces of material will help prevent another accidental frying of an LCD display.

Here is the Wiki on anti-static bags: https://en.wikipedia.org/wiki/Antistatic_bag

 And here is the data sheet on the bags that I am using:
http://documents.staticcontrol.com/PDF/Static_Shielding_Bag_1000_Series.pdf
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6 comments:

  1. bminishJanuary 26, 2016 at 5:47 PM

    Slightly off topic, but..

    You can get an anti-static spray designed to treat carpet, upholstered furniture etc. This is a sensible thing to do if one tinkers with electronics and for the average hamshack a bottle will last for many years as it only needs to be applied lightly and infrequently


    For example
    http://ie.rs-online.com/web/p/esd-safe-clean-room-treatments-lotions-dispensers/0182893/

    For cheapskates however, diluted fabric softener sprayed on the carpet and chair will work well for at least a few months but will require much more frequent application than the 'proper stuff'

    73
    Brendan EI6IZ

    ReplyDelete
  2. bminishJanuary 26, 2016 at 5:49 PM

    PS..
    I give my Car seat an occasional squirt in dry summers to stop the 'zap' when getting out on a dry day

    ReplyDelete
  3. AnonymousJanuary 27, 2016 at 7:56 AM

    Wooden laminate flooring in my shack on a leather office chair. Not had problems with bolts of static, but usually touch something at earth potential before constructing anything. On the subject of LCDs - always use connectors here rather than direct soldering. The Leoco brand are inexpensive and use a generic crimp tool for the wiring.

    ReplyDelete
  4. JanNovember 28, 2016 at 6:22 AM

    Hi,

    I think you will be better off with ventilating your shack more often, putting a few potted plants there and a humidifier - even a cut-off plastic bottle filled with water attached to the radiator/heater will do. No need to buy an expensive one.

    It is better solution than taping bags over things - it is not only LCDs that will die if you zap them! Anything CMOS or using MOSFETs (pretty much everything today) is going to be sensitive to this - e.g. your IRF510 linear or the Arduinos in the VFO could be destroyed fairly easily if you zap them.

    73!

    Jan

    ReplyDelete
  5. Dean HutsellNovember 28, 2016 at 11:37 AM

    Bill,

    Thanks again for the reminder. I'm just now setting up my new shack and it has carpet. I'd hate to blow up any new builds.......

    ReplyDelete
  6. Walter AndersonNovember 30, 2016 at 9:13 PM

    Sign from the Radio Gods to stop crossing to the darkside and using those new fangled oscillators!

    ReplyDelete