How do I use an antistatic wrist strap and mat

Question

I will be building my very own PC soon and I brought both the Rosewill RTK 002 Anti Static Wrist Strap and Rosewill RTK-ASM Anti-Static Mat. As far as I know both the anti static mat and the wrist strap should be connected to earth. The problem is that both of those don't include a plug to wall socket. I am thinking that there must be a cable that connects the alligator clip to a wall socket like the one below:

1. What is this cable called (so that I can buy it online)?

2. I need to stand on white part of mat and connect it to a wall socket and I will be grounded?

3. Will I be grounded if I just connect the alligator clip from wrist strap to the alligator clip from the wrist band?

While doing my research on the internet I have found that we can connect the wrist strap to the unpainted part of case but I feel that connecting to a wall socket would be more safe.

Answer 1

Actually, connecting to the case is probably better unless you also connect the case to earth ground. The easiest way to ground the case is to plug it in, but you don't want to do that until you're ready to power on.

What you're trying to prevent is Electrostatic Discharge (ESD), also known as a static spark, from you to the part(s) that you're working with. Nothing in that equation involves earth ground except that other things that you're likely to touch might be grounded.

So when you're working on stuff, you don't really need to be earth grounded any more than when you're not working on stuff. You just need to be connected to the stuff that you're working on.

An ESD mat will be conductive enough that you can just set the case on it, put the strap on, and be sufficiently connected to the case. Then handle all the other parts by whatever it is that will eventually touch the case anyway, and you'll be fine. No need for earth ground in most cases, though it usually doesn't hurt either.

As a side note, I've built several PC's on carpet without any grounding at all just by handling parts as described above and by casually touching the case a lot. Never had any problems. But I'm also naturally paranoid enough in general to remember to do that.

Answer 2

I live in the US so our 3-wire plugs are somewhat different from yours (essentially just a smaller version), but the same principle should apply.

You want to get one of your 3-wire plugs that you can open up and connect a wire to internally.

Your mat should have come with a ground wire that snaps onto the mat, like this:

If not, then you can buy them separately: "Anti Static Mat Grounding Cord with Mega Ohm Resistor". The link is for a US supplier, but you should be able to get them in the UK also.

Connect the open end of this ground wire to the ground plug inside your 3-wire plug (leaving the two power plugs unconnected).

The grounding cord may include a 1 MΩ resistor. Again in the US, only familiar with these, there is a coiled wire that connects the wrist strap to another snap on the floor mat. There will usually be an additional 1 MΩ resistance between the wrist strap and the mat.

In addition to the floor mats and wrist straps, we also put 2'x4' ant-static mats on our desktops nad lab benches. They also provide a nice surface to work on.

We use around a dozen of these mats and wrist straps throughout our office (every firmware or hardware developer has one). Why firmware? Because they are handling bare PCB's all the time.

Once a year, I go around and check that there is a connection from the mat to ground (either 0 or 1 MΩ), and from the wrist strap to ground (1 or 2 MΩ), fix any issues, and enter the results in a log in case we get audited by the UL.