antistaticequipment
I have a 23" x 60" metal work table…the kind that restaurants use for prep work. I'm using it as my computer table & electronics workstation.
I want to make the surface non-conductive in the cheapest way.
I've seen cheap neoprene mats and more expensive mats with grounding wires.
An expensive example out there:
Static Control Work surface mat
What are some cheap alternatives to cover a large area? Can I get something from the hardware store? Rubber shelf liners?
Natural Bristol brushes such as horse hair generate less static electricity. There are some Nylon brushes designed to reduce ESD, but a general purpose nylon brush can cause ESD damage.
ESD damage is a cumulative effect. While there are occasional catastrophic effect that destroy device immediately, most ESD damage shortens the live of the device rather then causing it to fail immediately.
Can static shocks occur from grounded and ungrounded metals?
Yes. A large ungrounded object still has capacitance. If there is a higher density of electrons on you than on the object, the electrons on you will feel repulsion from the other electrons on you and want to jump to the object where they will have more room to spread out. (Same goes in reverse if there are more electrons on the object.)
Eventually if people keep transferring electrons to the large object, then the electrons will build up on the object until they push back as much as the electrons on you, and there will be no spark. The bigger the object, the more electrons it takes to "fill" it up to having the same density of electrons as there are on you. Grounding an object connects it to the earth, which is the biggest object around and so represents a practically infinite sized holder of electrons. You can keep charging yourself up and then discharging to the earth and never make a practical dent in its charge density.
How do you prevent getting zapped when everything around you is metal and glass floors?
You can either...
Prevent yourself from accumulating a different density of charge relative to the metal building.
a. Wear a pair of diamond soled shoes. Because this material much closer to glass on the Triboelectric Series, you will accumulate less charge while walking compared to the rubber soled shoes you are likely using now. Alternately, you can cover the soles of your existing shoes with a rich red acrylic coat.
b. Keep yourself electrically connected to the metal at all times, possibly using a wrist strap that is tied into an overhead Pantograph system on the ceiling.
c. Increase the humidity in the air inside the building, possibly by installing a large fountain or waterfall in the center of the atrium area. The humidity will help excess charge bleed off your body and therefore prevent you from accumulating enough to cause a spark between you and the metal.
Prevent any charge you have already accumulated from making a spark and "zapping" you.
a. Buy a conductive arc flash protective suit and wear it whenever you are in the building. The zap between your body and the metal is just a smaller version of the arcs that linemen and electricians deal with everyday, and this suit will keep the arc between the metal and the suit rather than your skin, so you should not feel it. Be sure to get the suit inspected and certified frequently.
b. Get a hot stick. Anytime you approach a metal shelving unit, use the hot stick to equalize the charge between your body and the metal before touching it. There is still charge flowing between your body and the metal, but the high resistance slows that flow by reducing the current to levels that should not hurt.
c. Evacuate the air inside the building. With no air, there would be no gas to ionize and therefore no arc to zap you. This would require hermetically sealing the building envelope and using a large pump to remove the air and maintain the vacuum. This might also require structural modifications as the forces generated by the external air pressure on the building surfaces can be quite large.
What is the worst case scenario if I unbound the metal structure from mains earth? (Not contacts, nor lighting rods, just make sure to leave the metal book shelves ungrounded), will the user still get shocked?
People would still get shocked until the metal was charged up. Once the metal was charged, it would still zap people who had not yet been charged themselves by walking on the floor yet. It would probably make sense to divide the building into a dozen or more zones of increasing charge, each completely electrically isolated from the others. The zone near the entrance would have the least amount of charge to accommodate people first entering the building who have not accumulated any charge yet from walking on the glass floors. The zone farthest from the entrance would be at full charge and would hold the physics textbooks.
Best Answer
While it is risky, if done properly, can provide an ESD safe place to work. Since you live on the beach near LA, this may be of no importance. Humidity above 60% or so makes ESD protection somewhat redundant. I'd get a sheet of 3 or 6mm plywood for the top (full sheet, not pieces which will let the table show through). An overhang of 2-3 inches on all sides is best, but will require a thicker sheet. The sides of the table top can be covered with heavy duty wide insulation tape.
Make sure no live wires are below the table. A simple stand to hold the power points can be made using wooden batons (1"x1") and fixed to the sides or rear, so all live wires are well above the table top. Do not skimp on safety.
My wooden shelf constructed with 1"x0.5" batons is behind the table and holds all my gear, and a wooden stand with power sockets and wire spools, tape rolls, multimeter probes, is attached to the table side. Makes it all very handy, and safe. I work at a metal table with 3/4" blockboard top.
edit: pics you requested
The curtains are a hazard, but it's simply too dusty in India. Definitely not recommended. [Almost all are brick houses in India, so hopefully only me and my room will burn in case of fire]
The full setup. table is 3'x2', always wish it was at least a foot wider. Rear shelf is 40" wide, 10" deep (fitted inside unused doorway). Bottom steel shelves hold multimeters, magnifying glasses soldering accessories, pliers wire cutters etc.
There is a fuse on the left, and another fuse where this strip attaches to the wall socket. Wiring is very heavy gauge (4 square mm).
Shelves lined with cardboard, but no cardboard under laptop. Keeps it very cool. The batons are 1"x0.5" shorea robusta... extremely strong, and dirt cheap.
As you can see, I do not throw away any packaging... ever :(
two 12W LED bulbs fitted on the top of the near edge of the table, so no shadows under my fingers while working. Also, 2' away from the curtains.
Can there be a fire? yes. Never leave the workplace unattended. Always switch off everything when not in the room. Do not sleep at work.