I'm going to start this by saying that I have very little knowledge about electronics and ESD. That said, here goes:

I have recently taking up this hobby of modifying Super Nintendos, and now after a few of them broke because of my tampering I want to have more of a proper, and safe, workbench.

So this is what I've got:

enter image description here enter image description here

So as you can see, the bench has a wooden top that sits on a big metal frame, and the mat is connected to one of the feet. Not exactly ideal, but will it work?

Just so you know, I can't connect the mat to a grounded outlet because there isn't one in the room. I also can't drive a stake into the ground and run a cable up to the second floor of the house (where the bench is). And I can't use another room, so I have to make do with what I have.

enter image description here

Also included a picture of the water radiator because I've read that you could earth yourself through those, but then I've read that you have to make sure it's not painted with a non-conductive paint, or some such.

Anyway, sorry if this is a dumb post, but the whole ESD-protection world is very confusing to me as there are people that say you have to do things a certain way and some who would swear on their dead ancestors that all you need is to connect yourself to a radiator with a wrist strap, and have done so for the last three decades without any problems.

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    \$\begingroup\$ Nice lampshade, bro. \$\endgroup\$ – pipe Sep 26 '16 at 5:43

Don't get hung up about connecting things 'to ground', that is, that brown stuff outside the door.

What is important for you, your worktop, your tools, your components, is that they are all at the same voltage, before anything touches anything else.

That's all you have to achieve, it doesn't matter how you achieve it. People who say it must be done this way, or that way, are probably missing what we are trying to achieve. BUT, unless you get into a routine, and have a setup that allows you to do it effortlessly, it's real easy to screw up and get it wrong. Then, the best that can happen is you blow a component. Among the worst things that can happen are you half damage a component without realising it, which screws you up later (perhaps in front of customers), or you hurt yourself, which is why the safety resistors.

I see you are using a soldering iron. It is critical that your desk frame and conductive mat are connected to the soldering iron protective earth conductor for ESD safety, via a one megohm resistor for personal safety.

The safest most convenient common connection to use is the protective earth of your mains power supply. I have a three pin plug with only a series resistor'd ground lead coming out for the purpose. Everything else is wired to that. If you are not using any mains powered stuff, no soldering iron, no scope, no desk lamp, then any common connection will do, many people use the conductive benchtop, or its frame. You can use a radiator, but it doesn't add anything. Just establish one common connection, call it ground, and connect everything to that. Don't bus connections one from another, it's too easy to accidentally disconnect something you didn't intend, use a star connection of everything to your designated ground.

You could ground yourself before every time you touch something. But it's far easier to wear a wrist strap to ground. As this exposes you to an increased electric shock hazard, the wrist strap must be isolated from ground by a suitable resistor. One megohm is high enough for shock protection, and low enough for ESD protection.

Have a conductive work top, connected to ground. Metal is good, but hard on the eye, and you can't string circuit boards out across it. Conductive plastic is good, but expensive. Synthetic plastic furniture is a no no. Plain unwaxed unvarnished wood is often OK, it depends on the species and the moisture content how conductive it tends to be. Keep all your tools on the bench, and they will be at ground potential when you pick them up.

How do you take the component out of the bag? I have wept when I've seen even experienced engineers forget what the goal is, and juggle with a black plastic bag of components, trying to delay the point at which they touch them, while walking from component cupboard to their bench. They think they should do something, and have forgotten what to do in this circumstance. No. They should be achieving a goal. Everything at the same potential! Then figure out what to do to get that.

So sit down at your bench, put your wrist strap on. Touch the bag, or put it on the bench. Now you, bag and bench are at the same zero voltage. Now open the bag, take components out, and put them on the bench. All still at the same potential. There are other ways to do it, but what I've described is easy to follow, and worth getting into the habit of.

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    \$\begingroup\$ See, this is partially why I have such a problem with getting good understanding regarding ESD. The way I read your post, you're saying that I can just connect to the metal frame of my bench and everything is fine, while Ian Bland says that isn't enough and I should connect myself to the radiator. So whatever I connect to doesn't actually need to be earthed as long as I first discharge myself to it and then start working on my stuff? \$\endgroup\$ – Bossehasse Sep 26 '16 at 9:38
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    \$\begingroup\$ ... as long as your stuff is also at the same voltage as what you discharge to! Don't forget, just because someone else hasn't zapped any chips, or doesn't know they have zapped some chips, doesn't mean that their advice is good in your circumstances. The only thing you have to do is avoid sending a large current into a sensitive pin. You can do that by keeping everything the same voltage before they touch. And you can make that routine for yourself by using a common 'ground' point and connecting everything to that. If you use mains, protective earth is the safest point to choose. \$\endgroup\$ – Neil_UK Sep 26 '16 at 9:53
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    \$\begingroup\$ ... all your stuff, including soldering iron! Ian's suggested connection to the radiator will probably connect to the soldering iron if the house has a properly earthed heating system. But why use the roundabout route, when you should be getting into the habit of connecting everything to your mains ground? What happens if you work on your car with a soldering iron on the EMU or the radio? Everything at the same voltage, everything connected together, connect the car chassis to the extension lead ground, and your wrist strap. \$\endgroup\$ – Neil_UK Sep 26 '16 at 10:06
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    \$\begingroup\$ @Bossehasse The technical point is to create an "equipotential zone" so that your environs are all at the same voltage. In theory everything could be at 5 kilovolts relative to ground and be safe so long as everything is. Since in practice there is always earthed stuff around (the radiator, and at some impedance the floor, walls etc, and of course all the earthed equipment on your bench), the zone should be at 0V as defined by the electrical supply. The heating pipes certainly should be earthed, otherwise they are highly dangerous and need attention by an electrician. \$\endgroup\$ – Ian Bland Sep 26 '16 at 10:14
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    \$\begingroup\$ @IanBland If you're handing a bag of components over, it doesn't matter. If you are handing bare components over (you shouldn't be) then is the juggling I weep at. As you hold the component by a common lead, it's at your potential. Shake hands with your colleague to get him at the same potential as you (and the component), then give him the component. If you are holding it by the plastic, then it could be at any potential. Touch a robust common connection on it (tab, ground terminals, frame) to get it safely to your voltage, then handshake and give it. Everything at the same potential! \$\endgroup\$ – Neil_UK Sep 26 '16 at 10:30

The lead is currently just connected to the frame, which isn't earthed (grounded). The radiator on the other hand is grounded. Just scrape a bit of the paint off and ground the mat, strap, table, yourself, your cat etc to that metalwork.

Basically you are trying to create a path to Earth, so you have to ensure that the strap is connected to something that is actually electrically earthed, and so far as I can see the table is not; it's a plastic foot on a wooden floor. If you want to find out what's earthed, a crude effective method is to build up a static charge on yourself (nylon clothing is good for this) then touching things until you get a little shock.

Having said that I've never ever destroyed anything with static electricity. Handling CMOS chips for instance I just touch my desk lamp (a bare metal part) before touching the chip, and half the time I forget to do that. But I have a notoriously low imepdance.

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  • \$\begingroup\$ Well, the whole frame is made of metal, even the foot. It's just a small plastic container around the very bottom of the foot so that it doesn't damage the floor. So my clip is connected to metal, not plastic. Although I guess that doesn't change much? \$\endgroup\$ – Bossehasse Sep 26 '16 at 9:44
  • \$\begingroup\$ That little plastic container is a nice little insulator :) \$\endgroup\$ – Ian Bland Sep 26 '16 at 10:15
  • looks good but have 1M on wrist strap and bench metal to earth
  • simple precautions are touch ground on boards before any other pin if not wearing strap
  • keep finger on case before touching anything inside PC case
  • beware that some devices may fail at -10V like LEDs without zener protection and one can walk on a carpet ground, raise one leg and create 200V just by changing the body Q from changing C... V=Q/C which you can't feel when discharging. ( Verified on ESD measurement tool in early 80's)
    • but it is the discharge like handing to someone that causes the damage, so we used to touch fingers before exchanging parts.
  • keep parts in antistat bags sealed until use as some like LEDs can absorb moisture and cause popcorn effect when soldered and shear micro" gold wire bond, not easily visible that it is sheared with naked eye. ( clear epoxy is generally less robust than black epoxy for moisture seal )
  • soldering iron can be modified with 1M + earth wire or touch ground before parts or use moist sponge with foil to ground wire underneath to clean tip.
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  • \$\begingroup\$ If you're earthing metalwork, you don't want a high impedance connection. The resistor in a wrist strap is to prevent current flow through the strap and yourself. The metal table, you want current to flow through to blow a mains fuse if live touches it. \$\endgroup\$ – Ian Bland Sep 26 '16 at 7:48
  • \$\begingroup\$ I used to have a cage in the back office in the early 80's to secure lots of expensive computers. there was nasty carpet and everytime we opened the cage the Motorola exercisor crashed . I resolved by ungrounding the cage but connected via 1Meg and carpet antistat spray. Electrical outlets are still proper ground but equipment with metal cases are a potential discharge point. LIVE wires was not a problem, just ESD with a nylon carpet and tons of equipment.. then I implemented an ESD protocol plant wide. moved out of that space. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Sep 26 '16 at 7:56
  • \$\begingroup\$ The theory behind 1Meg heel straps and wrist straps is called static dissipative to reduce the dI/dt and stray EMI impulse field voltages coupling to binned parts during assembly. Sometimes it was unexpected test techs with 10m cables and the SCSI drivers under test in tall cabinets were blown by the cable capacitance and tribolectric effect of dragging the cable on a concrete floor. Even though they wore heel straps, the PVC jacket cables were getting charged by dust and dragging them....and the conductive epoxy paint was not enough \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Sep 26 '16 at 8:03
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    \$\begingroup\$ Well, just being historically pedantic here but you were probably violating the IEE regs (at least, you would be if this was in Britain) since extraneous conductive parts are meant to be earthed. Live wires are not a problem until a fault condition occurs, at which point they're a big problem. My point is that we shouldn't be telling people to do earth lifts for functional reasons, even if those of us with expertise can do so with reasonable safety. I've got a mains lead with no ground connection for special use, but I know when it's practically safe to use and when it isn't. \$\endgroup\$ – Ian Bland Sep 26 '16 at 8:12
  • \$\begingroup\$ We didn't actually unearth the equipment, just the Faraday cage (aka security cage) and metal bench rails. the coarse fenced walls acted as antenna and induced soft faults in microcomputer boards with cables (aka antenna) \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Sep 26 '16 at 8:22
I have very little knowledge about electronics ... modifying Super Nintendos ... a few of them broke

It seems the real problem is that you're mucking with stuff you don't understand. Making sure your work area is ESD safe is a good idea, but is a distant third order concern to knowing what you're doing. No matter how ESD-safe you are, poking about with "little knowledge" is far more likely to break things than static discharge.

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    \$\begingroup\$ Well, it's not like I'm going in blind and hoping for the best. I do as much research as I can before I attempt anything. I follow instructions from other people with successful mods, so what I'm doing should work. So whatever the problem has been, I'm just trying to eliminate any potential issues that could have caused my attempts to fail. \$\endgroup\$ – Bossehasse Sep 26 '16 at 11:51
  • \$\begingroup\$ ...And Olin Lathrop wins today's crotchety answer award. \$\endgroup\$ – Ian Bland Sep 26 '16 at 12:54

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