Ideal grounding point for ESD

[king.oslo]

Hello there,

I have previously grounded myself to ground in the mains. However, recently I have been becoming worried that I could be shocked if an item in my home is faulty. Therefore I have thought about the possibility of grounding myself to an independent rod outside my house. However, I wanted to write and ask if this is safe, or if there is an alternative way to ground oneself that is more ideal.

Thank you for your time.

Kind regards,
Marius

 

[BrownOut]

A cold water pipe makes a good ground, assuming youre plumbing is metal and not plastic.

 

[Reloadron]

Hello there,

I have previously grounded myself to ground in the mains. However, recently I have been becoming worried that I could be shocked if an item in my home is faulty. Therefore I have thought about the possibility of grounding myself to an independent rod outside my house. However, I wanted to write and ask if this is safe, or if there is an alternative way to ground oneself that is more ideal.

Thank you for your time.

Kind regards,
Marius

You do not want to ground yourself to mains ground or direct earth ground. Actually mains neutral and mains ground should be tied at the power point of entry. It all ties to earth ground.

When working and using for example an ESD wrist strap ground the strap is a woven conductive material and the strap cord should incorporate a 1MΩ minimum resistor to ground. You are grounded through a 1MΩ or greater resistance.

Directly tying yourself to ground without a high resistance is dangerous. So exactly how are you tying yourself to ground? I hope with an approved wrist strap and cord containing a high resistance.

Ron

 

[Sceadwian]

The thing about that BrownOut is that the cold water pipe is often already used at the electrical panel as a ground so the power company doesn't have to add any grounding rods at the house, one of said faults could be the cold water pipe breaking and causing an electrical short from live to ground via the now floating copper pipe system in the house.

Grounding rods are pretty simple, they're steel rods coated with copper, between 4 and 10 foot long. You pound them into the ground (rocks can be tricky so your local geology is important) You can use multiple shorter rods if you have extremely rocky ground, installing them is pretty easy with a hammer and some patience or with a post hammer which can be nothing more than a plugged steel pipe with some weight on the plugged end raised and lowered to drive the rod in.

A seperate ground rod for basic ESD is a bit overkill though, it's more commonly used for grounding lightning rods or antenna lightning protection.

 

[BrownOut]

A broken water pipe cannot cause a short from live to ground. If there were the case, and it was a common occuranace, there would be alot of fried people. Using a cold water pipe for grounding is a very common practice, and nobody ever gets hurt by it.

Actually, using the electrical system's ground is safe too, as long as you have a proper electrical system and you're using a proper ESD wrist strap. If you live in a 3rd world country, then I wouldn't try it.

 

[king.oslo]

Oh, of course. I forgot about the 1Mohm resistance. I will try and ground myself to a water pipe. Sounds pretty simple.

Thanks.

Kind regards,
Marius

 

[crutschow]

You should be working with the circuits on an ESD mat and then all you really need to do is connect your ground-strap to the mat. If you always connect the ground-strap to yourself before touching the circuits you will be safe, since you will be at equilibrium with the ESD mat and any circuits on the mat. Having the mat or yourself absolutely at earth ground potential is not really a necessity.

 

[king.oslo]

That's interesting. Can I buy this item: https://www.elfa.se/elfa3~eu_en/elfa/init.do?item=80-081-79&toc=18875 and ground myself to it with a 1Mohm resistance wristband, and all will be well?

Is that correct?

Kind regards,
Marius

 

[Sceadwian]

If you have the mat you wouldn't need a wrist band you'd just place your hands on an unused portion of the mat, keep in mind the mat itself still needs a connection to ground. A wrist band would still use the resistor, but it would be tied to the common ground the mat shared, not to the mat itself.

 

[Reloadron]

The mat you linked to would likely be fine. Most of the ESD work mats I have worked with are like the attached image. They have snap connections. The point where the mat connects to ground uses a snap connector with a few banana jack connections for the wrist strap. This wire is a straight shot to earth ground. There is no resistor in the mat connection to ground.

What I did not see in the 1mm thick mat you linked to was a connection point. Like I mentioned, generally a snap connection. While ESD mats can vary quite a bit depending on the work-scope I don't see it as a big deal for home use.

Ron

 

[crutschow]

That's interesting. Can I buy this item: https://www.elfa.se/elfa3~eu_en/elfa/init.do?item=80-081-79&toc=18875 and ground myself to it with a 1Mohm resistance wristband, and all will be well?

Is that correct?

Well, others disagree with me but I believe that should be fine. Since that mat normally has a relatively high resistance so you don't need the 1 meg resistor but it won't hurt. The objective is to keep you and the circuits you are working on at the same potential, which connecting the wrist strap to the mat will do. It's nice to also keep the mat at earth ground potential but that's not a necessity as long as you and the mat are at the same potential. There's nothing magical about "earth ground".

 

[BrownOut]

The may is mostly for placing the parts on when you're not handling them. If you intent to pick up the parts and do something with them, you should be wearing a ground strap. The may is useless once you lift a part off of it. You wrist strap and the ground to the mat are usually at the same point. There should be a bananna connector that snaps to the mat with receptors for both the wrist strap and the ground wire.

 

[Sceadwian]

If you intent to pick up the parts and do something with them, you should be wearing a ground strap.

Not if your other hand is on the mat. If you have so high of an ESD problem that you have to look beyond this there is something fundamentally wrong with the environment.

 

[BrownOut]

One generally uses two hands when working with electronics.

 

[Sceadwian]

Yep, one on the mat, one handling the chip =) You can rely on a strap, but as safe as one hand in your pocket is for high voltage, so is one hand on the nearest ground for components. Humans are really very good high voltage capacitors up to near 10kv. Better safe then sorry.

 

[BrownOut]

Use a ground strap and a mat. You'll never get anything built tyring to use just one hand. Your concern is ESD, not human capacitance.

 

[Reloadron]

Use a ground strap and a mat. You'll never get anything built tyring to use just one hand. Your concern is ESD, not human capacitance.

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Do what he said. You and your electronics will live long and prosper.

Ron

 

[ericgibbs]

Use a ground strap and a mat. You'll never get anything built tyring to use just one hand. Your concern is ESD, not human capacitance.

I agree with 'D' about using a wrist strap , but ensure that its NOT a direct connection to Ground, the 1meg series resistor is a MUST.

 

[king.oslo]

The mat you linked to would likely be fine. Most of the ESD work mats I have worked with are like the attached image. They have snap connections. The point where the mat connects to ground uses a snap connector with a few banana jack connections for the wrist strap. This wire is a straight shot to earth ground. There is no resistor in the mat connection to ground.

What I did not see in the 1mm thick mat you linked to was a connection point. Like I mentioned, generally a snap connection. While ESD mats can vary quite a bit depending on the work-scope I don't see it as a big deal for home use.

Ron

How can it be safe to ground the mat without a resistor?M

 

[Reloadron]

How can it be safe to ground the mat without a resistor?M

If you look back to your mat specifications you will see: Surface resistance 100 kΩ. So while the work mat is conductive it isn't like a straight piece of wire or placing your work on a conductive metal surface. That number is also based on a point to point distance and a specific weight or force on the mat covering a defined area. So the mat has plenty of resistance. There are volumes of text and specifications written on this stuff but real quick:

ESD Mat is made of high density closed cell expanded Polyvinyl Chloride material. These ESD mats are resistant to degradation by inorganic acids, detergent solutions, alcohols, mineral oils. Surface resistivity is is 10^9 – 10^10. Service temperature of -20oF to 160oF. Meets ASTM D412, D624, D2240 and ESD S4.1-1997 standards.

There you have it and why the mat does not require an external resistor.

Ron