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I am a novice to electronics, and I am currently building a wooden workbench. The workbench will have an ESD bench mount and ESD matting over the entire bench.

I now want to have a small fold-out table (one of those cheap ones that you can buy from hardware stores), which has a plastic surface and metal frame/legs, next to the workbench. I will use this table for computer and pen and paper work. If my wrist strap is attached to the ESD bench mount, then is it safe for me to just "wheel" in my chair from one bench to the other, going from doing electronics and/or chemical work on one bench to computational and pen and paper work on the other?

Furthermore, with this setup, is it safe to have a laptop and/or pen and paper on the electronics workbench itself, and to work with that while I do electronics work?

Since the ESD bench mount is attached to the mains, I want to be sure that I'm not doing anything unsafe (both for myself and my electronics). I would greatly appreciate it if people would please take the time to advise me on this.

The Pointer
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2 Answers2

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You said "the ESD bench mount is attached to the mains", which sounds to me like it's directly connected to the ground lead of a power outlet somewhere. Please don't do this! ESD safety equipment usually uses a series resistor between you and the ground, to avoid high currents flowing through your body in case you accidentally touch something that's at a high voltage. Based on this question and its answers, that resistance can be around 1-2.5 MΩ. This answer to the same question explains nicely how that protects you as well as the electronics you work on.

ksadowski
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  • This https://images-na.ssl-images-amazon.com/images/I/41ElKrP%2BrfL.jpg is what I am referring to. I made sure to ask, and was told that it has a 1Mohm resistor built into it. But besides this, I don't think your answer fully addresses my questions. My questions are, in particular, about the safety of working across multiple benches/desks, whilst having a wrist strap attached to the ESD bench mount of the single workbench. – The Pointer Jun 24 '20 at 18:25
  • That's a relief! Good on you for making sure. It's a good thing that the resistor is inside a permanently installed device, I think that's safer than eg. relying on it being a part of a wrist strap. – ksadowski Jun 24 '20 at 18:29
  • I think *both* the ESD bench mount *and* the wrist strap have resistors in them. This is an off-topic question that I was going to ask later: is this still safe? I'm a newbie, so I'm unsure if both having resistors in them changes anything (at least, changes anything detrimentally). – The Pointer Jun 24 '20 at 18:31
  • Yes, wrist straps will typically have a resistor in them as well. The exact resistance in series between you and the ground doesn't matter much, as long as it's not dangerously low. You'll likely have 2 MΩ here (assuming the wrist strap resistor is 1 MΩ), which will discharge your body's static charge in a couple of milliseconds. But it could be 10 MΩ and still be fine, making you "safe to touch" in a matter of tens of milliseconds. – ksadowski Jun 24 '20 at 18:38
  • Oh, ok, thanks for the clarification. Do you know the answer to my question about working across multiple benches/tables? – The Pointer Jun 24 '20 at 18:40
  • I can't think of any other potential dangers, either to you or to the electronics, coming from using multiple benches and a laptop. At first I was worried about the grounding issue (a metal-encased laptop powered by an improper power adapter would carry a tiny risk of presenting a high voltage at the chassis), but that won't be a problem. The only other thing coming to mind is to consider putting the ESD wrist strap hookup somewhere between the two benches, so you can keep yourself attached when switching to the laptop for a moment - it's easy to forget to hook back up in situations like this. – ksadowski Jun 24 '20 at 18:48
  • ... but that's more of an ergonomics issue than safety :) – ksadowski Jun 24 '20 at 18:50
  • The tables will be next to each other, and I will remain attached at all times. I will just "wheel" in my chair from the wooden workbench (which is the one with the ESD mount that I am attached to) to the plastic table (with metal legs/frame). The plastic table does not have any ESD mounting. There isn't something about me using the other table whilst still attached to the ESD strap that will cause me (or my laptop on the table, say) to be electrocuted? – The Pointer Jun 24 '20 at 18:51
  • As I said, that resistance that your ESD protection equipment puts between you and the ground is there to protect you from getting electrocuted by accidental contact with high voltage. While a direct attachment to ground would be dangerous (for the risk of accidentally touching a damaged device or an exposed high-voltage conductor - think of it as using a hairdryer while standing barefoot in a bathtub of salty water, a bit of a russian roulette), that high resistance removes this added danger. With it, you're more or less as safe from electrocution as if the wrist strap weren't there at all. – ksadowski Jun 24 '20 at 19:03
  • Oh, and the metal legs of the table don't change the situation, since they're not (presumably!) grounded or connected to anything. – ksadowski Jun 24 '20 at 19:04
  • @ThePointer Note that there are plugs for ESD grounding (i.e. for ESD mats, wrist straps, etc) that consist of only the ground prong that plug into the wall. – DKNguyen Jun 24 '20 at 19:04
  • Hmm, the laptop on the table would be connected to the mains through the charger, though. Does that change anything? – The Pointer Jun 24 '20 at 19:05
  • @DKNguyen This https://www.mektronics.com.au/clipsal-grounding-plug.html is what I plan to use. I will attach the ESD bench mount to this, and then plug it into the mains. – The Pointer Jun 24 '20 at 19:16
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    @ThePointer That's sort of the thing I was talking about. I am kind of surprised though that they bothered using conductive materials for the hot and neutral prongs when they shouldn't be going anywhere. The one I have just has plastic tabs for the hot and neutral. – DKNguyen Jun 24 '20 at 19:20
  • @DKNguyen In your assessment, does everything here with the tables and ESD precautions seem fine from a safety perspective? (I want to be doubly sure that I'm not going to kill myself (or my electronics!) somehow.) – The Pointer Jun 24 '20 at 19:21
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    @ThePointer Safety for you is pretty difficult to mess up as long as you are using properly made ESD equipment that includes resistors and everything and don't connect something to the hot or neutral. Rolling around in a chair is probably not so good for the electronics. Static takes time to drain. That's how we get rid of charge and not have it to damage while doing so: we drain it slowly so currents are low. And if your chair is regular fabric or plastic that's a no no. – DKNguyen Jun 24 '20 at 19:23
  • @DKNguyen I'll be rolling around on wooden floors -- no carpet. Although, the chair seat is made of fabric (not fuzzy, but fabric). – The Pointer Jun 24 '20 at 19:24
  • @DKNguyen Ok, thanks for the clarification. – The Pointer Jun 24 '20 at 19:28
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I could recommend if you have the budget to invest in a swivel laptop arm that you can mount you laptop above your work and move it where you want it.

You were asking about safety and this could prevent rolling back and forth with eliminates that hazard of tipping over or banging into something or possibly while falling over grabbing stuff and bringing it down.

Ben Madison
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