Correct ESD Desktop mat installation

[Spekkio]

I'm still curious to see what is inside my little cheap RCD thing I bought, I need to open it by force with my Dremel I think.

[helius]

three-winding transformer wired to a latching relay

[jlmoon]

I don't build PC's often. But I hear questions sometimes on how to connect your wriststrap when assembling PC components.

-"Just connect the wristrap to the PC chassis"

Is the only thing I've heard. Wouldn't that also be just a floating wireless wriststrap

Depends on what you're doing with the PC.  Installing PC cards , memory and other items.  Think about it this way, if your ground strap is tied to the pc chassis, is the PC ground via plugged into what ground level? what is the potential of the surface the memory strip, pc card?   Think of the potential difference between true ground (Earth) , you and what the cards or devices are sitting at.  This is where the damage can occur.  PE is only assumed unless you have run various test and such. 

[Spekkio]

three-winding transformer wired to a latching relay

I'll look into this.

I've been thinking that there must be something that I can do locally at my workbench to make it a safe workbench for electronics tinkering.

[Spekkio]

Depends on what you're doing with the PC.  Installing PC cards , memory and other items.  Think about it this way, if your ground strap is tied to the pc chassis, is the PC ground via plugged into what ground level? what is the potential of the surface the memory strip, pc card?   Think of the potential difference between true ground (Earth) , you and what the cards or devices are sitting at.  This is where the damage can occur.  PE is only assumed unless you have run various test and such.

Well, yeah. Hmm

I think I understand potential differences well enough, I have a bachelors degree in electronics engineering anyway. Altough that doesn't always mean anything, lol  Maybe I'm the worst electronics engineer ever.

Sometimes I feel so stupid that I can't get a good understanding of the most simple stuff.

...But, where was I.
Charges are invisible, so you never really know at what potential you are at if you have a wrist strap connected to a chassis that is not connected to anything else.
And if the floor you're standing at doesn't dissipate your static charge.

I have always had in mind, or had the understanding that a good connection to earth/ground (physical rod stuck into the earth) then you could safely say that my potential, or static charge has dissipated and is close to zero.

If you have your components and things you're working on at an ESD mat, an isolated upper surface that dissipates static charges to the conductive plane underneath and then through a 1MOhm resistor down to ground. And a wrist strap with an 1MOhm resistor would slowly dissipate your static charge down to ground if it was either positive or negative. Working with PC components on such a workbench would be much better, from my point of view.

But if there is no real connection to earth/ground (rod into earth) on your ESD mat and wrist band, like I have now with my isolated local ground point in my power strip, how can I be sure static charges are being dissipated? They're not, right?

Maybe it doesn't matter. If the ESD mat, my wrist band and my PC chassis (for example) all are connected to the same ground point. It doesn't matter if it has a 20kV charge on it. There is no way, I can touch something that would cause a discharge into some sensitive circuit because they all have the same charge.
Until I move away from of my workbench and touch something else that is not connected to my isolated workbench grounding.

But I would like to have the best set-up I possibly can, in this bad situation I'm currently in.

[jlmoon]

 [/quote]


Maybe it doesn't matter. If the ESD mat, my wrist band and my PC chassis (for example) all are connected to the same ground point. It doesn't matter if it has a 20kV charge on it. There is no way, I can touch something that would cause a discharge into some sensitive circuit because they all have the same charge.
Until I move away from of my workbench and touch something else that is not connected to my isolated workbench grounding.

But I would like to have the best set-up I possibly can, in this bad situation I'm currently in.
[/quote]


I agree but.... that 20kV charge will have the desire to neutralize one way or another.  Which means it could bleed through those parts you picked up off that ESD mat sitting at 20kV while you forgot to put that wrist strap on. 
Just as a matter of approaching  correctness, I would suggest to simply drive a copper clad 8 - 10' rod near as you can to that workbench and run a #6 wire to your common bench ground point.  Calling this your common PE ground node.  Be sure to use CAD welded lugs if you can and ensure the power ground system is common to this as well.  The best solution would be to find or install that ground rod at the base of power entrance and tie back to that point with that #6 copper wire if you can. 

[Spekkio]

I don't know if this has anything to do with my ESD setup

But I just tore one of these RCDs apart just to see what is inside, and it seems to be a very interesting device to analyze

http://spekkio.blogspot.se/2015/08/tearing-apart-residual-current-device.html

I was expecting some connections to the ground pins, but there is none? Or there is something hidden inside that plastic between live and neutral that I cannot see.

The thing didn't work in my kitchen. The relay was open.

But when I put it in my non grounded outlet I could hear the relays clicking inside atleast.

[rs20]

I don't know if this has anything to do with my ESD setup

But I just tore one of these RCDs apart just to see what is inside, and it seems to be a very interesting device to analyze

http://spekkio.blogspot.se/2015/08/tearing-apart-residual-current-device.html

I was expecting some connections to the ground pins, but there is none? Or there is something hidden inside that plastic between live and neutral that I cannot see.

The RCD circuitry doesn't need the ground pins, it measures an imbalance between the live and neutral. After all, fault current may go through the earth wire or through a human being, it's a fault either way. The imbalance is tested for by passing both live and neutral through a current transformer; under normal operation, they will cancel out perfectly. See this link, number 6 is the current transformer, and you can see the thick live and neutral wires passing through it.

[McBryce]

If you have central heating in your house you just need to take the Earth from the nearest radiator to your workbench. It will have to be earthed.

McBryce.

[Spekkio]

If you have central heating in your house you just need to take the Earth from the nearest radiator to your workbench. It will have to be earthed.

McBryce.

That was what I was thinking of doing in the first place. I suppose, if I do that, it should not be a direct connection from my power strip ground pins to the radiator?
I need to put some large resistor in-between? Like 1MOhm, maybe even 10MOhm?

But there there has been comments here making it sound like it is a bad idea. Like, I should first make sure the radiator is connected to mains earth...but there is no mains earth/ground wiring in this house... except in the kitchen. And I need to get the thumb out and ask my landlord how things are set up in this old house... Where is mains earth wiring really located here in this house. I don't want to drag a cable out to my kitchen sink.

Maybe I could check if the kitchen sink is connected to my radiator pipes? I just need a long cable.

Some say, a large mass of copper (or other good conductor material) would do just fine as a decent ground point.
It sounds like an easy and good solution, if it really works as intended. Not only in theory I mean, but actually works very well in reality.
It's not the first time I hear about that. I think my understanding of this comes from my basic knowledge in physics that I might have read it in a physics book or got taught in school.

Wiring something out of the window down to ground from the second floor where I live just feels awkward.
I don't want to build a nice lightning rod connected into my expensive equipment.

I can measure from my floating ground in my power strip to the radiator a 113VAC, what that does that mean really?

Reminds me alot of when I got floating Vcc pins on circuit boards, and I measure 1.65V on them with reference to ground (or what is supposed to be ground).
When they're supposed to be 3.3V, but the connection is broken somewhere, it is an open circuit. 

I don't have a very good understanding of what that means, why it gets that way. Why half the voltage?

Also, a little bit outside of the ESD question, but. For safety of not getting electrocuted, can I actually have good use of an RCD unit in my wall outlets for my  workbench equipment, or will it only cause problems?

I installed power strips with surge protection (Also not really ESD related), but then read in the manual that they're useless in ungrounded wall outlets.
But are they useless if I have an RCD before it?

I wish I just had more time and motivation to work on these things and thoughts and stupid ideas I got a little bit more.
Maybe I could have gotten things in good order already now.

But I've got so much to do surrounding my bad health situation also. And having problems both physically and mentally.
which you can read about here if you want.
https://www.eevblog.com/forum/chat/hello-from-a-sad-and-sick-engineer/

Anyway, I've gotten some really good information from everyone here! I thank you so much! 
I really like the EEVBLOG forum.

I just need to sort all of this information out, because all of it feels a little bit tangled up in my head right now 

And also, I am not certain at all about my radiators here, they're connected down in the basement to some heating device and pump I assume.
They're old, some pipes are rusty. Some radiators leak out water. The system needs to get a refill with water every winter. The radiators was bone-dry one winter.

What I know about my radiators in this house is they are heated by water, and are earth heated (geothermal energy),or jordvärme in swedish.
I translated that here http://sv.bab.la/lexikon/svensk-engelsk/jordv%C3%A4rme

Maybe it would be a  good idea to have an ESD mat also on the floor, but they were so expensive. I can't afford one at the moment.
Now I only got this plastic mat from IKEA so that my chair won't wear out the nice wooden floor underneath.
I'm afraid this plastic mat might actually build up some charges when I'm moving around on it :|

[Spekkio]

I don't know if this has anything to do with my ESD setup

But I just tore one of these RCDs apart just to see what is inside, and it seems to be a very interesting device to analyze

http://spekkio.blogspot.se/2015/08/tearing-apart-residual-current-device.html

I was expecting some connections to the ground pins, but there is none? Or there is something hidden inside that plastic between live and neutral that I cannot see.

The RCD circuitry doesn't need the ground pins, it measures an imbalance between the live and neutral. After all, fault current may go through the earth wire or through a human being, it's a fault either way. The imbalance is tested for by passing both live and neutral through a current transformer; under normal operation, they will cancel out perfectly. See this link, number 6 is the current transformer, and you can see the thick live and neutral wires passing through it.

I might start another thread on this later, because I find this RCD to be very interesting.

It would be fun to experiment with, though I have respect for mains voltage.

Maybe it is possible to simulate with smaller voltages, for example take a sine wave from an function generator.
I would need two signals, one that would simulate the live, and the other the neutral. they would need to be shifted in phase 90 degrees (or is it 180 degrees?).

Would I be able to do something practical with that, or is it just too weak?

[Spekkio]

I've talked to the landlord. The radiators are NOT connected to mains earth he said. But the tubes are definetly going down into ground. Ground heated water, there are loops of tubes going all around the farm field outside. And connected to some pump device in the basement. Some white box that looks like a fridge. Dont know what it really does. But I assume it is for the water.

I'll still check if there is a connection from the sink to the radiator anyway.

And there is no RCD in this house he said.

(Feeling very tired and unmotivated today.)

But he thought that it was no danger in using the radiators as ground. I might buy one of those large crocodile clips you use for your car batteries to get a good contact on the radiator. I might need to grind a little bit on the surface to get a good contact on the copper.

Just an idea of a safety system:
 What if I get an RCD for my outlet. I found one a little bit more expensive with 4 outlets that felt like quality, but really made for outdoor use. Connect ground to the radiator from my RCD ground connection. And connect my surge protected power strips to this RCD. All equipment would all have the same common ground connected to the radiator system, and my ESD mat too ofcourse, not forgetting the 1MOhm resistors.

I can feel safe in many situations? Not only from zapping my IC's.
But also protected from unwanted voltage spikes.
And also feel safe from any chassis getting live.. right?

Or am I getting everything wrong here, or am I just being crazy?

Skickat från min GT-I9305N via Tapatalk

[McBryce]

You can buy a proper piping Earth connection in any decent hardware store for pennies. They look like this: http://smg.photobucket.com/user/lewy8/media/P4130383.jpg.html

This will give you a much better connection than the crocodile clip.

McBryce.

[Spekkio]

You can buy a proper piping Earth connection in any decent hardware store for pennies. They look like this: http://smg.photobucket.com/user/lewy8/media/P4130383.jpg.html

This will give you a much better connection than the crocodile clip.

McBryce.

Ok, that looks good.

But the pipes are painted white, I need to remove that first. It's not really my house, I rent it as an apartment.
But the part that is not painted, the valve.
I thought I could get a large crocodile clip with a very tight grip and sharp teeth to put on there. And it is also easier to find in stores around here.

[apis]

According to regulation if any contact in a room is to be earthed, all of them has to be, and only a certified electrician is allowed to do the installation.

In theory you should be able to ground to the radiator, but mixing grounded and ungrounded equipment is a bad idea so you need to make sure any ungrounded and grounded equipment is sufficiently far away apart that you can't touch them at the same time. (And if you do it, measure to make sure there isn't any excessive current going to the radiator etc, old buildings can have really wonky electrical wiring.)

You should only have a resistor between yourself and ground and the esd mat and ground (it's for your own protection, i.e. to prevent large currents from passing through your body to earth if you touch something at high voltage potential). The rest of the equipment should have a very low resistance connection to ground or it won't work (the current must be large enough for the fuse to blow in case of a fault).

As rs20 says though, I don't think it's necessary to ground everything properly. What's important from a ESD perspective is that your equipment, the esd-mat, the components and yourself are all at the same relative zero volt potential. So if you are all hooked up to the same ground wire, even if that is not connected to the buildings earth connection/radiator, you would still prevent any esd discharges damaging your components. So, a wire and resistor from your mat/wriststrap to the same ground connector as your test equipment should be enough and you don't have to jury rig something illegal.

[Spekkio]

According to regulation if any contact in a room is to be earthed, all of them has to be, and only a certified electrician is allowed to do the installation.

In theory you should be able to ground to the radiator, but mixing grounded and ungrounded equipment is a bad idea so you need to make sure any ungrounded and grounded equipment is sufficiently far away apart that you can't touch them at the same time. (And if you do it, measure to make sure there isn't any excessive current going to the radiator etc, old buildings can have really wonky electrical wiring.)

You should only have a resistor between yourself and ground and the esd mat and ground (it's for your own protection, i.e. to prevent large currents from passing through your body to earth if you touch something at high voltage potential). The rest of the equipment should have a very low resistance connection to ground or it won't work (the current must be large enough for the fuse to blow in case of a fault).

As rs20 says though, I don't think it's necessary to ground everything properly. What's important from a ESD perspective is that your equipment, the esd-mat, the components and yourself are all at the same relative zero volt potential. So if you are all hooked up to the same ground wire, even if that is not connected to the buildings earth connection/radiator, you would still prevent any esd discharges damaging your components. So, a wire and resistor from your mat/wriststrap to the same ground connector as your test equipment should be enough and you don't have to jury rig something illegal.

Thank you, that feels good to hear

[Spekkio]

I just noticed. I had my hand on my computer chassis. And then I touched the radiator. Getting small electrical discharges. Doesn't kill me. But they are strong enough to notice very clearly.

As we already know. The ground connection on my powerstrip and and everything is floating. Theres no ground pin in my wall outlet.

What does this say about my radiator. It the radiator properly grounded?

I have built a small device with three bc547:ns in like a darlington pair except three. A diode that lights up when all transistors are open.

It  lights up when I hold it close to wires. It also lights when I touch the base on the last transistor ofcourse. I've isolated it so I don't touch it.

But it lights up when I hold it close to my radiator. I thought if everything was peoperly grounded It would really detect any static charges around the radiators.

I am confused.

I found another strange phenomena with this simple device I will write a new thread about.

Skickat från min GT-I9305N via Tapatalk

[DimitriP]

1) First suggestion, speak to an electrician as I have no idea of the wiring codes in Sweden.

2) Wiring your anti-static mat to a radiator will probably be OK as your central heating system will use copper piping. Please check that your incoming water pipe is connected to mains earth.

3) Running a workbench off mains sockets that are not grounded is a very bad idea as the chassis of anything you are working on may become live, please see (1) about speaking to an electrician.

^^^^
What he said

On a good note:

Or is my ESD mat just not even necessary in my home lab on this quiet large wooden desktop that I have?

Considering you are surrounded by wood, esd mat or not you are better off than in  carpeted /metal/ plastic environments out there.

And before you forget .... 3,1,2