ESD safety

[Doodski]

Has anyone tried to ESD protect a standard office chair? I have a Sidiz T50 in my study and I often get loud crackling through my iLoud monitors when I get up and then a shock from the next metal thing I touch - this has been enough to condition me to be wary of metal door handles regardless of my location.

I know that ESD office chairs are a thing. Has anyone tried to ESD proof a standard chair? I happy with my T50 in all other respects and loathed to replace it with something else without attempting to fix the ESD issue.

I was thinking of purchasing some 'Faraday' tape and attaching is to some strategic locations on the chair and then grounding it using an ESD wrist strap.

There are ESD safe floor coatings, fabric coatings, clothing coatings etc. All discharge the ES at a safe rate.

 

[DonH56]

Most major electronic suppliers have sections on ESD control (Allied, Arrow, Digikey, Mouser, etc.) as well as lab material supply houses (don't have a list of them in mind). What works for your chair depends somewhat in its construction. Our lab chairs had a short metal chain dangling down from the chair's central support shaft (metal) to connect to the treated lab floor; it also works if you have an ESD floor mat. The chair's cushions came in a couple of types: one was treated with a spray that you renewed once a year or so, and the others had conductive material woven into the chair's seat cloth. There were chains/wires/strips of metal tying seat, arms, and support shaft together to drain to that dangling grounding chain.

In the past, with a standard office chair, I had some success by using an ESD floor mat grounded to the wall outlet (via the usual 1 M resistor), and attaching a small (gauge) wire to the base of the chair to contact the floor, screwed to the chair's support shaft, and continuing up to the seat where I just glued a bare segment of wire to the cushion. I left a large loop to allow the chair to move up and down and turn, but of course every now and then one my my boys would grab and spin the chair so I'd have to replace the wire to the seat. The wire was one long piece since the chair had a plastic cover over the support shaft, making it harder to just tap it at the top and bottom.

 

[Speedskater]

So I went up in the attic and found two catalogs:

Techni-tool. They have a section on "Static Protection"

https://www.techni-tool.com/

Zack Electronics
There 1999 print catalog had 17 pages on Static Control and Clean Rooms. But I can't find that section on-line.

Zack Electronics - Audio, Video, Wire, Components, Cable, Connectors & Datacom Professionals

Zack Electronics is a leading West Coast distributor specializing in wire, cables, connectors, and installation solutions for audio, video, broadcast, and datacom professionals.

www.zackelectronics.com

 

[Berwhale]

Electrostatic charges come into existence when 2 non conductive materials are rubbed together of pulled apart.
That charge can't go anywhere when walking on carpets or something with isolation between feet and ground.
That charge can accumulate on the body (which is conductive).
Once you touch something that is grounded (other potential) the electrons will find a way though your body to the ground potential.
Spark flies and you can feel a jolt if enough electrons leave your body at once.

Your non ESD chair has isolating materials, isolating feet and and the floor, most likely, is also non conductive.
Riding/sliding on the floor = friction = charge building up. Getting on/off the chair or 'reseating' is friction = charge building up.
Touch something grounded and it flows away.

So... to get your chair to become ESD safe requires a slightly conductive (ESD) floor.
Wheels that are conductive (like car tires are)
Cloth on the chair that has wires in it or materials that conduct charges and do not create much when there is friction.

What you could do is wear an ESD wristband while on the chair that is tied (via a 1M resistor which usually is the wristband) which is connected to safety ground.
Once you got of the chair take it off or disconnect and you should have no charge to speak of.
Walk with friction on a carpet and its there again.

Thanks, yes I have a basic understanding of the principles. I have the chair (and myself) on a cotton rug which I have attached to earth via an ESD strap connected to a nearby central heating radiator (the copper piping of my radiator system being bonded to earth in several places). I've also made up an 'ESD solution' of water mixed with fabric conditioner and isopropyl alcohol. I have sprayed this on the rug and the chair. This does help, but it needs reapplying every few days and it's not an ideal solution (pun intended!)

 

[Berwhale]

There are ESD safe floor coatings, fabric coatings, clothing coatings etc. All discharge the ES at a safe rate.

Yes, I have researched this and attempted to replicate with my cheap ESD solution.

We also have the data centre floor coated with it at my work - it's not my cheap stuff though

 

[Berwhale]

In the past, with a standard office chair, I had some success by using an ESD floor mat grounded to the wall outlet (via the usual 1 M resistor), and attaching a small (gauge) wire to the base of the chair to contact the floor, screwed to the chair's support shaft, and continuing up to the seat where I just glued a bare segment of wire to the cushion. I left a large loop to allow the chair to move up and down and turn, but of course every now and then one my my boys would grab and spin the chair so I'd have to replace the wire to the seat. The wire was one long piece since the chair had a plastic cover over the support shaft, making it harder to just tap it at the top and bottom.

Thanks, this is exactly what I was thinking of. I have a grounded mains outlet about 2 feet from the stem of my office chair. I can buy a UK 1M grounding plug and wire the chair straight to it.

 

[Doodski]

Thanks, this is exactly what I was thinking of. I have a grounded mains outlet about 2 feet from the stem of my office chair. I can buy a UK 1M grounding plug and wire the chair straight to it.

After all this ESD safe stuff is in place remember to moisturize the arms and hands and wear a ESD approved lab coat and always strap in. ESD is insidious.

 

[Berwhale]

After all this ESD safe stuff is in place remember to moisturize the arms and hands and wear a ESD approved lab coat and always strap in. ESD is insidious.

I'm not sure what my work colleagues would make of that on a Webex!

I have purchased an 'anti-static' mat designed for PC assembly...

https://www.amazon.co.uk/dp/B00009XT3H

It's much cheaper than a similar sized one designed for electronic assembly/repair and I have some doubts about it's efficacy*, but I thought it was worth a go. The mat will replace the PU leather desk pad I had under my mouse and keyboard previously.

I should add that i've been building and repairing PCs for 35 years, both professionally and at home. I was a certified IBM Professional Server Expert in my youth and worked on many servers worth over $100,000. I've never had a issue with static before or needed to use an ESD strap or desk pad, although I would make sure touch something grounded (like a rack in a data centre) before tinkering with something really expensive like swapping out $50k of RAM, perhaps i've just been lucky

*I measured the resistance of the mat surface using my little Wavetek multimeter. It was infinite no matter how close I put the probes together on the surface of the mat, but i'm conscious that this might not be the right tool for the job (for reference, the measured resistance between my hands was around 5MΩ). However, the resistance of the blue cable which is used to connect the mat to earth was 0.98MΩ which is suspiciously close to the 1MΩ in an earth bonding plug for a mains socket. So i'm guessing that the blue wire has a resistor in one of the ends and maybe this thing has been designed to work. We shall see!

 

[Berwhale]

So after a day sitting at my desk with the anti-static pad installed, i've not had any re-occurrence of the issues (crackling through my monitors or shocks off door handles). I am cautiously optimistic that the mat has helped.

 

[Doodski]

So after a day sitting at my desk with the anti-static pad installed, i've not had any re-occurrence of the issues (crackling through my monitors or shocks off door handles). I am cautiously optimistic that the mat has helped.

To be ESD aware is to never let your guard down.

 

[Berwhale]

So this problem returned after I rebuilt my study and installed my standing desk. I really didn't like the look or feel of the anti-static PC mat I linked to above and it didn't fit well on my new desk. So i've been using a wrist strap turned inside out and put over the arm of my chair to ground myself as I get up. The strap was grounded to a nearby heating radiator tail (all water pipes are earth bonded in the UK) and this has worked well as long as I remember to tough the strap as I get up - however, having my chair attached to a radiator is somewhat annoying.

Looking for a better solution, I found this wrist support ESD mat on Amazon. The company that sell the mat specialise in suppling industrial ESD kit, so I was hopeful that the mat would work as advertised. The mat turned up today and it's working well. It came with a 2m long blue earthing lead, rather than the short black on shown on the Amazon listing, but this suits me as the longer cable can more than accommodate full actuation of my standing desk. Here's the mat in action...

Obviously I still need to remember to touch the mat to discharge myself, but that's a lot easier with the mat sat in front of me

 

[egellings]

I have a small metal touch pad plate on my audio equipment rack, and this is connected to earth ground through a 2.2 meg resistor. I walk up to the rack, touch the pad first, and then proceed to operate the equipment. My understanding is that the average human body acts like about a 150pF single plate capacitor, and it doesn't take much to bleed that amount of charge down. The 2.2meg series resistor limits the inrush current (to your fingers!) so there's no unpleasant shock.