[EE] Homemade anti-static mats?
Matthew Miller
I'm looking for a way to cover plastic tables with an anti-static surface. I
need a solution that that is cheap, and if it is cheap enough I don't mind
if it only stands up to one year of high school student abuse. :) I have
considered paper or cardboard, but that is a little less durable that I
would like. Has anyone heard of using linoleum (with the underside facing
up) as an anti-static surface?
I have priced commercial anti-static mats and to buy the number that I need
would blow my budget... Does anyone have ideas or suggestions?
Thanks. Matthew
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Tony Smith
>
> I'm looking for a way to cover plastic tables with an
> anti-static surface. I need a solution that that is cheap,
> and if it is cheap enough I don't mind if it only stands up
> to one year of high school student abuse. :) I have
> considered paper or cardboard, but that is a little less
> durable that I would like. Has anyone heard of using linoleum
> (with the underside facing
> up) as an anti-static surface?
>
> I have priced commercial anti-static mats and to buy the
> number that I need would blow my budget... Does anyone have
> ideas or suggestions?
>
> Thanks. Matthew
Dunno about lino.
Sheet metal? (Might be $$)
Wood? Thin ply or MDF?
Table cloth sprayed with that anti-static stuff? A bolt of cloth (cotton,
linen) would be cheap & you can teach the kids to sew while you're at it.
Put elastic at the edges, like fitted sheets.
Doesn't totally solve your problem as you still need to connect the cover to
earth.
Tony
Olin Lathrop
> I'm looking for a way to cover plastic tables with an anti-static
> surface. I need a solution that that is cheap, and if it is cheap
> enough I don't mind if it only stands up to one year of high school
> student abuse.
I haven't tried this, but how about cover the table with aluminum foil
first, then mount a thin layer for hardboard (sometimes referred to by one
manufacturer's tradename "masonite"). Most wood products allow enough
leakage at normal room humidity that they don't accumulate static charge.
Tie the aluminum foil layer underneath to ground, but make sure the students
can't come in direct contact with this ground. The hardboard will insulate
anything on the table from this ground for all practical purposes except
picking up static.
Again, I haven't tried this, but have observed wood to generally not
accumulate static.
******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014. #1 PIC
consultant in 2004 program year. http://www.embedinc.com/products
Jinx
> facing up) as an anti-static surface?
Says here that lino is anti-static
http://www.hgtv.com/hgtv/dc_floors_other/article/0,1793,HGTV_3413_4426626,00
.html
Other sites say that anti-static isn't necessarily the same as
giving protection from ESD. For example "anti-static" often
refers to dust and bacteria repelling. It may not also mean
that lino or vinyl is conductive enough to be anti-static in
your context
This glossary of ESD flooring may give you some ideas
http://www.staticsmart.com/esd-static-control-articles/esd_flooring_glossary
.php
Is it possible to -
Use carpet and weave a few strands of bare wire into it ?
Or put a few studs or pop rivets through it, connecting to
chicken mesh or aluminium foil (eg the tough damp course
stuff that builders use) on the underside ?
Have good discharge flooring at the entrances to the room ?
Bob Axtell
> Hi everyone,
>
> I'm looking for a way to cover plastic tables with an anti-static surface. I
> need a solution that that is cheap, and if it is cheap enough I don't mind
> if it only stands up to one year of high school student abuse. :) I have
> considered paper or cardboard, but that is a little less durable that I
> would like. Has anyone heard of using linoleum (with the underside facing
> up) as an anti-static surface?
>
> I have priced commercial anti-static mats and to buy the number that I need
> would blow my budget... Does anyone have ideas or suggestions?
>
> Thanks. Matthew
>
>
spray it on the surface, and it will last
until it has turned to dust, about one day.
Cling Free is designed for women to prevent clothes from "clinging" due
to static charge. It works good,
but it might not be sold anymore in the US.
--Bob
Bob Blick
> Cling Free is designed for women to prevent clothes from "clinging" due
> to static charge. It works good,
Been using women's products again? How naughty of you!
Jack Smith
them across the surface. Doesn't last too long, a day or so, but quite
inexpensive.
I bought the Cling-Free spray three or four years ago to spray on the
tires of my automobile. The particular tires on it were highly
non-conductive and would build up large amounts of "wheel static" that
totally wiped out AM radio reception when traveling on the interstate
system at reasonable speed. Touching the brake pedal would discharge the
voltage potential out for a few minutes until it built up again. In any
event, spraying the tire sidewalls with cling-free worked, but had to be
repeated every day or two. (In the old days, you could get carbon powder
and inject it via the valve stem.) The next set of tires were by a
different manufacturer and the problem went away.
Jack
Olin Lathrop
> I bought the Cling-Free spray three or four years ago to spray on the
> tires of my automobile. The particular tires on it were highly
> non-conductive and would build up large amounts of "wheel static" that
> totally wiped out AM radio reception when traveling on the interstate
> system at reasonable speed. Touching the brake pedal would discharge the
> voltage potential out for a few minutes until it built up again.
Huh? Why would touching the brake pedal have anything to do with
discharging static buildup between the car and the ground? The insulation
of the tires between the road and the car frame should still be there
whether the brake is applied or not, unless of course you have Fred
Flinstone brakes. I think something totally different was going on than you
think.
******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014. #1 PIC
consultant in 2004 program year. http://www.embedinc.com/products
David VanHorn
Cheap, antistatic, and very serviceable.
Jack Smith
static. I believe the actual insulating junction might be the front
wheel bearings that ride on a thin film of grease and do not have
metal-to-metal contact whilst the wheel is spinning. You can read about
it in the older editions (1950's and 1960's) of the ARRL Mobile Handbook
for example.
Touching the brakes make a connection between the car body and the tire
in this case through the brake pads which have enough conductivity to
discharge the build up.
When raining the problem would not occur as there would be enough of a
leakage path to discharge the car body to ground. Even going through a
puddle would provide leakage until the water dried off.
I observed this consistently for two years until the new tires were
installed, and I had chats with the Volvo dealer about it and they all
agreed that it did happen and thought there was an old service bulletin
about it for earlier models but couldn't find it.
Jack
Olin Lathrop
> Not so. It's well known phenomenon called "wheel static" or tire
> static. I believe the actual insulating junction might be the front
> wheel bearings that ride on a thin film of grease and do not have
> metal-to-metal contact whilst the wheel is spinning.
Hmm, sounds a bit implausible that significant static can be built up
accross a thin layer of grease with moving metal parts on both sides, but
maybe. However then you said:
> I observed this consistently for two years until the new tires were
> installed,
Then why would new tires fix the problem if the static buildup is in the
bearing, not accross the tire insulating the chassis from the ground?
Jack Smith
if I describe it a better explanation can be found.
The vehicle in question was a 1996 Volvo 850R high boost turbo that I
purchased new. The tires were 17" low profile, and I don't recall the
brand name that was installed as the OEM.
In normal city traffic, AM radio reception was fine, as it was stop and
go traffic with lots of application of the brakes and never hitting a
very high speed. When cruising along the interstate I noticed the
background noise would increase slowly, over the space of a few minutes.
The background noise could best be described as broadband hash, no
discernible tonal frequency to it. It was strong enough to cover up
stations that were at a moderate distance. I would guess something like
20 dB desensitization but I did not make formal desense measurements.
One of my thoughts was alternator noise, so to test that I put the
transmission into neutral and turned the engine off and coasted down the
interstate at 60 MPH for a brief distance. No change in the noise level.
Another test for alternator-related noise I conducted was to put the
transmission into neutral and vary the engine RPM to see if the noise
level or sound varied with the RPM. I could detect no change. Turning
the headlights on/off and other accessories on/off made no difference.
When driving on wet pavement, no noise. This was only a dry pavement
issue. On many trips (I was working in Northern NJ on a long term
consulting contract at the time, so I was driving from the DC area to NJ
several times a month) I would go from rain to clear skies and the noise
always acted the same -- it would start to build up as the road and the
car dried out. Or, in the other direction, it would quickly cease when
the rain started or I drove onto wet pavement.
Touching the brake pedal cleared the noise up for a few minutes, but it
would gradually build back up again until I touched the brake pedal
again or it rained or I ran into wet pavement.
I found that spraying the tires with the cling-free did greatly reduce
the noise level for a day or two and then it returned.
With absolutely no other changes in the automobile conditions, I had all
four tires replaced when the tread had worn down. The new tires were a
different make than the OEM tires. With the new tires the noise had
vanished and never returned.
During the time the Volvo had the original tires, I had them rotated a
couple times so they had been removed and reinstalled on different
wheels. No change in the noise level.
The only explanation that I could come up with that matched my
observations was the the car body was being electrostatically charged,
and the noise was caused by discharges across small gaps and that the
original tires had better insulating properties than the replacements so
that the static charge did not have a chance to build up to the level
that it would produce noise, and that the wheel bearings were acting as
an insulator that was bridged when I touched the brake pedal. (I imagine
the brake pads had copper woven into them. Or, they might have even been
sintered metallic pads.)
So there it is. This was 100% repeatable under the conditions I
described. I no longer have the Volvo so I can't conduct new tests, but
I have a very good recollection of the problem and the tests I made at
the time to pin it down.
Jack
David VanHorn
charged up.
I can't believe the wheel is insulated from the frame in any real sense. WAY
too much structural things going on there. But the surface of the pads, a
fraction of an inch from that spinning metal disk, seems wimshurst-ish to
me.
That, or it could be discharges of the car's static through the tires, but
that wouldn't explain stopping on brake contact.
David VanHorn
> Huh? Why would touching the brake pedal have anything to do with
> discharging static buildup between the car and the ground? The insulation
> of the tires between the road and the car frame should still be there
> whether the brake is applied or not, unless of course you have Fred
> Flinstone brakes. I think something totally different was going on than
> you
> think.
Sounds pretty squirrely to me too..
I've measured about 6000V buildup on my truck, against a gas pump body.
Funny thing, nobody seems to worry about that, but your CELLPHONE!! Oh my!
Russell McMahon
> surface. I
> need a solution that that is cheap, and if it is cheap enough I
> don't mind
> if it only stands up to one year of high school student abuse. :)
> I have priced commercial anti-static mats and to buy the number that
> I need
> would blow my budget... Does anyone have ideas or suggestions?
Butyl rubber sheet, used for industrial pond liners and roof
waterproofing amongst other things, can be your friend. Conductivity
is imparted (AFAIK) by the amount of carbon that is included to
control colouring and hence is variable between brands and types. In
almost all cases conductivity seems to be good enough to be entirely
adequate for anti-static mat use. Worst problem is that many version
have very low conductivity to the extent that the surface is usefully
conductive when eg a circuit board is placed on it - you need to place
an insulator under PCBs and anything else that doesn't appreciate
being placed on a conductor. For personnel safety purposes such
sheeting probably constitutes a conductive surface and may be a safety
hazard in some cases.
I have used Butyl rubber sheet for this purpose for many years and
apart from the occasional "conductive incident" have found it
extremely useful. As a bonus it is used here as cover sheets for other
material from the same bulk supplier and the cover sheets are sold at
a very substantial discount from their normal price. As well as making
anti static mats this sheet works well as playhouse roofing ;-).
Even at roofing material prices the cost is well below that of
'proper" as mats, and when sold as used packing sheets it is vastly
cheaper.
The material is robust enough to last indefinitely when subject to
high school student abuse. The greatest disadvantage is that some
versions smell extremely rubbery for a considerable period.
Conductivity "per square" can be assessed by sticking two multimeter
probes into the rubber and measuring resistance. This is typically
hundreds to thousands of ohms per square. Note that even when
resistance is so high that it is essentially unmeasusrable the sheet
may still be adequately effective for ESD protection purposes.
Totally different solution - spray or paint surfaces with conductive
metal spray. Nickel works well but tends to be expensive. "Cold zinc"
galvanising spray or paint may be cheaper. May not be appropriate for
your purposes. I use nickel spray to adapt plastic boxes/trays for
component storage.
Russell McMahon
alan smith
Matthew Miller <nami...@naxs.net> wrote: Hi everyone,
Thanks. Matthew
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William Chops
bare sheet of plywood sprayed occasionally with anti-static spray.
BillW
Alan B. Pearce
You can certainly get anti-static lino, as used on the elevated floor tiles
in computer rooms - which I take it means it is ESD type. I know that at my
previous employer we had work benches surfaced with it.