Painless static discharge - Page 1
Forum section: electronics / beginners

author: pdxw
author_rank: Newbie
timestamp: September 24, 2016, 03:11:43 am
content: Hi all,I'm physically disabled with cerebral palsy. Thus I use a power wheelchair. For those of you who don't know, carpets are the bane of wheelchair users' existence. It would be nice to find an apartment that lacked carpet, but very few of those exist. It generates a lot of static electricity, and (more specific to wheelchairs) a lot of stuff gets tracked in. Think mud and other debris.But my post today is due to the first of these two problems.Just going from room to room, it generates quite a charge. I am getting sick and tired of getting zapped (almost) every time I touch my computer (an iMac) or external hard drive (which has a similar metal case.) I even had to replace Apple's standard wired keyboard with one made mostly of plastic, because even THAT would zap me quite regularly.I have tried those anti-static things that drag against the ground, as one might attach to their vehicle. For some reason, it never works for me.The carpet is your standard carpet. I am parked on a standard chair mat, as one might buy in any office store. I should also note that my tires (all 6 of them) are solid-core rubber. No pneumatic tires here.What can I do to safely and PAINLESSLY discharge the static? Wearing an anti-static strap would be inconvenient (and I wouldn't know where to clip it.So I searched for some answers.Some people, combating the ever-popular metal doorknob, have suggested a half dollar coin—touching the knob with the coin first before grabbing the knob. In that application, would I simply tap the hard drive (or the iMac) with the coin, and then proceed as usual?I could train myself to do that, I think.But, looking elsewhere, people suggested things such as this:https://www.amazon.com/Aulyn-Car-Elimination-Discharger-Anti-Static/dp/B00S4W0CFO/ref=pd_day0_263_3?ie=UTF8&pd_rd_i=B00S4W0CG8&pd_rd_r=9S676DN923CQCYKGWD1B&pd_rd_w=3MSJy&pd_rd_wg=wujz8&refRID=9S676DN923CQCYKGWD1B&th=1Would such a thing work?Is the basic idea that I grab the keychain and touch the device with it first? And if so, would I have to hold it by the keyring end while the other end touches the device? Most of the advice I have found deals specifically with preventing damage to internal components while installing them, etc. which is something I will never personally do because I lack physical dexterity. That's why I'm asking you.Or is there something else I can do?Thanks!

author: helius
author_rank: Super Contributor
timestamp: September 24, 2016, 03:29:19 am
content: The static discharge you feel is high in voltage ("tension"), but low in available charge. If you were to spread out the flow of charges to a large area of the skin, it would become painless as the number of charges impinging on each nerve would be less. This is the principle behind using a coin to touch a surface: your skin is pressed against both faces of the coin making a large area contact.It might be better to prevent the static buildup to begin with. I'm not surprised that the dragging cables didn't work, since they rely on the ground having some conductivity. When you try to discharge static electricity through an insulator like carpet, nothing happens. But what will work is using sharp points sticking into the air, as found on lightning preventors and air ionizers. When an object has these points, the electric field strength nearby is great enough to break down the air and form a corona that streams the static charge away. Maybe there are easy ways to attach lots of points to a wheelchair: metallic fringe strips like they make for parade floats? As the static charge increases, the fringe will lift up and spread out, making lots of points.You can also just wrap a wire around the metal frame and touch it to a grounded point (like the case of an appliance) at the desk before touching your equipment.

author: Towz
author_rank: Contributor
timestamp: September 24, 2016, 03:45:42 am
content: So the suggested keychain is basically a way to discharge yourself via a bigger surface area (the shock will be distributed in a larger skin area so it will feel less intense) and (I assume) via a series resistor between you and the surface you are about to touch (reducing the current). So it should work! Of course, the keychain is ment for you to touch a door knob or a metalic desk or something similar with it. For component handling the usual practice is to wear an antistatic wristwrap/wristband that continiously discharges to mains earth.

author: Brumby
author_rank: Unknown
timestamp: September 24, 2016, 04:12:04 am
content: I, too, can vouch for the concept of using a metal object that you are holding to take the 'hit' - again, for the same reason of spreading the current flow over a MUCH larger area than the pinpoint of the discharge. You will feelnothing.Once you are discharged, it is safe to touch the device - until you build up another charge.When approaching door knobs (and other metallic objects) I used to grab my keys and let one of those take the hit. Once I was in an office and someone sitting 10 feet away turned and asked me "What was THAT?" when I had a discharge that not only jumped several millimetres with a vibrant blue flash, but emitted a "crack" that was rather loud. Using my key, I felt absolutely nothing - aside from a little surprise at how impressive the display was.

author: andtfoot
author_rank: Unknown
timestamp: September 24, 2016, 04:42:26 am
content: The chairs at work seem to generate static like crazy. I've gotten into the habit of touching things with the back of my hand (knuckles mainly)first to discharge the static; it doesn't really hurt that way.

author: pdxw
author_rank: Newbie
timestamp: September 24, 2016, 04:51:24 am
content: Quote from: Brumby on September 24, 2016, 04:12:04 amCheers, mate! Since, in my case, I'm talking about computer equipment, is it safe to assume that the case is protecting the much more delicate components within? If the discharge COULD potentially be as impressive as you describe, that wouldn't put the equipment in even more danger, would it?

author: pdxw
author_rank: Newbie
timestamp: September 24, 2016, 04:53:33 am
content: Quote from: andtfoot on September 24, 2016, 04:42:26 amWow...that never even crossed my mind. I'll have to try that. Thanks!

author: edpalmer42
author_rank: Super Contributor
timestamp: September 24, 2016, 05:05:17 am
content: You need something like this:https://www.startech.com/Computer-Parts/System-Build/Anti-Static/24x27in-Beige-Desktop-Anti-Static-Mat~M3013You put your computer, printer, keyboard, whatever on it and then touch the mat before you touch the device. You can also get smaller ones that sit on your desk. Same idea. There's a resistor in the cable that allows the static to be dissipated in a fraction of a second, but still slows it down enough that you don't feel it.You could make your own by using any lump of metal and a ground cord with a resistor in the cord.Of course, you could use a standard anti-static mat that you use for soldering, but they are designed for high heat and tend to be more expensive.Ed

author: fivefish
author_rank: Frequent Contributor
timestamp: September 24, 2016, 06:13:15 am
content: Why not drag a light metal chain under your power wheelchair? (I know trucks carrying flammable liquids/gasoline have this to prevent static buildup.)Don't know if it will make a difference, but maybe worth a try?

author: SeanB
author_rank: Super Contributor
timestamp: September 24, 2016, 06:25:50 am
content: Simplest fix is to get the carpet professionally cleaned, using a wet extractor. In the water tank you add fabric softener as per the instructions for washing use ( typically 2 capfuls into the tank) so you get the softener solution all over the carpet as a rinse. That will safely dissipate all the static for a considerable time, and then the wheelchair can be fixed by simply wiping the wheel rubbers with a cloth which has had the same softener solution applied to it. Fabric softener is designed to dissipate static charge in clothes and does the same here.Carpet cleaning companies do this as a special anti static service, but do not tell you the special ingredient is regular liquid fabric softener.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 24, 2016, 07:06:46 am
content: Maybe one of those wireless antistatic wrist straps could work if they are well made.So you tough metallic things with the strap first and dissipate the charge slower through the internal resistor. Kind of a improved version of the key-chain suggested above.

author: Brumby
author_rank: Unknown
timestamp: September 24, 2016, 07:45:31 am
content: Quote from: pdxw on September 24, 2016, 04:51:24 amTo be safe, it might be better to discharge to something other than the computer ... but the idea of the dissipative anti-static mat is probably a much better approach, especially for something in a set position.The idea with the key is portable and can be used immediately it is required, practically anywhere and everywhere, where preparation is not possible. Your situation with the computer is different.

author: ChunkyPastaSauce
author_rank: Unknown
timestamp: September 24, 2016, 08:05:54 am
content: Another thing to consider maybe increasing humidity in work room if you can.You may also be charging from sitting in the chair rather than rolling (clothes rubbing against seating materials, dragging against plastic side wheel etc), so maybe try fabric softener on clothing or different clothing material. You might also try anti-static coating on the entire chair (commercial products for that, or fabric softener diluted with water and alcohol) particularly on plastics, rubbers, coated metals.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 24, 2016, 11:41:13 am
content: Quote from: pdxw on September 24, 2016, 04:53:33 amwork fine if contact area is large. back of hand skin is thinner for normal people. if you touch a point, you should get bigger tinggling sensation. the advice is sound for people with thicker back hand skin or for testing mains voltage presence (if you dont have anything else better of course, though still not advisable). btw, normal people will get the same tinggling sensation if they touch anything floating smps case, not just you, and esp me if something hit my back hand/finger skin. i remember the worst case is on a carpet yes in a ballroom.

author: amyk
author_rank: Super Contributor
timestamp: September 24, 2016, 03:21:10 pm
content: Quote from: Brumby on September 24, 2016, 04:12:04 amI use the metal wristband of my watch for the same purpose. I've seen ~5mm strong blue sparks on particularly dry days. As a rule of thumb, the dieelectric strength of air is 3kV/mm, so that was approximately 15kV

author: BobsURuncle
author_rank: Regular Contributor
timestamp: September 24, 2016, 03:22:38 pm
content: My car likes to give me a good poke when I touch the handle. In the winter I just got into the habit of first touching with knuckles or the back of my hand to the car door to remove the charge. That is a painless approach as opposed to discharging through the fingertips.

author: pdxw
author_rank: Newbie
timestamp: September 24, 2016, 08:25:20 pm
content: Quote from: Brumby on September 24, 2016, 07:45:31 amI notice it has a grounding cord with an alligator clip. Would I have to attach it to something, or is it (as the item's description would lead me to believe) the material itself that dissipates the static?If I do need to clip it to something for the mat to work, where is best?Thanks again!

author: Zero999
author_rank: Super Contributor
timestamp: September 24, 2016, 08:40:26 pm
content: Try using some carbon loaded paint on the wheels? That may help prevent it from becoming charged in the first place.

author: Brumby
author_rank: Unknown
timestamp: September 24, 2016, 10:53:13 pm
content: Quote from: pdxw on September 24, 2016, 08:25:20 pmAttach the clip to something earthed and make sure your hands come into contact with the mat before any earthed metalwork. The mat will drain the charge pretty quickly - but not as quick as the 'zap', which is instantaneous.