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Grounding and electrostatic discharge protection of a problematic PC system

When winter comes or when someone watches The Verge PC build reaction video the topic of ESD protection and electrostatic discharge sees a surge in interest. People working with electronics or even more precautious PC builders do use various tools and safety measures to avoid damaging electronics via electrostatic discharges. Consumers of electronic devices don't care that much and often just rely that the device maker made the device to handle both electrostatic discharges as well as various electric faults that may occur.

In this article I'll go over basics of grounding, electrical bonding, electrostatic discharge and how that may apply to day to day use of your PC or other electronic devices.

Theory

After building my Threadripper PC and moving it from a test bench to a nice Fractal case I started to have system crashes somewhat caused by ESD wherever I touched something connected to the PC or not (and felt the zap). So I started researching the topic and also testing the power strip, power outlet, PC power supply and more. During this process I found few issues that could lead to those crashes. This article may serve as an action plan for troubleshooting or just checking your electrical wiring as well as ESD protection solutions.

Electrostatic discharge

As per wikipedia and electrostatic discharge (ESD) is the sudden flow of electricity between two electrically charged objects caused by contact, an electrical short, or dielectric breakdown. A buildup of static electricity can be caused by tribocharging or by electrostatic induction. The ESD occurs when differently-charged objects are brought close together or when the dielectric between them breaks down, often creating a visible spark.

For mere mortals electrostatic discharge is a spark and unpleasant zap when touching some objects. That's usually the effect of tribocharging where rubbing materials or walking on a rug causes charges to separate and we become charged with static electricity. When we touch an object that doesn't have the same charge potential - the charges will try to even out across us and the object we are touching causing electron movement - a flow of electric current. This may be a spark but often this charge movement won't be visible to us.

The discharge can happen when we touch objects of different potential like a metal pipe going to the Earth ground or objects that can hold electric charge and are insulated from the surroundings - aren't connected to anything. Even a plastic box can have an surface charge potential of like 20 000 volts (at an extremely low current) and may be hazardous to electronics.

ESD is dangerous to electronics, especially integrated circuits as it's a very high voltage and can cause physical damage to for example fine traces on the PCB or in a chip. Even when ESD won't damage a piece of electronics it can degrade some components make them fail quicker or perform worse. That's why nearly every PC component is stored in anti-electrostatic bags and has all the warnings on it. This video nicely explains all aspects of ESD:

Electrical bonding and ground

A correctly build PC should be quite resilient to ESD. The electric current will flow on the path of lowest resistance and that should be from the surface of our body to the metal case of the PC and then via power supply to the ground line of the power outlet. But is your power outlet grounded? Do you use correct cables (power strips, extension cords etc)?

There is a term called Electrical bonding which is also explained by wikipedia - electrical bonding is the practice of intentionally electrically connecting all exposed metallic items not designed to carry electricity in a room or building as protection from electric shock. If a failure of electrical insulation occurs, all bonded metal objects in the room will have substantially the same electrical potential, so that an occupant of the room cannot touch two objects with significantly different potentials. Even if the connection to a distant earth ground is lost, the occupant will be protected from dangerous potential differences.

grounded PC case

PC case should be grounded via the power supply

Electrical bonding and Earth ground are nicely explained on this video:

Electrical bonding aside of preventing electric shocks from faulty devices is also used to safely discharge any charges that can build up on connected objects - as Earth ground due to it's volume can hold immense charge is treated in general as neutral and can accept electrons from negatively charged objects or provide electrons to positively charged objects. If you want to know more about what is ground, watch this video:

Practice

Having problems with my PC I assumed I have ground as all the power plugs and power strips were 3-wire. But when I actually checked one power outlet to which my PC power strip was connected it turned out it was 2-wire with a plug shaped like common 3-wire plug. So my PC had no ground. Moreover actual 3-wire power outlets in my house actually had only two wires (it's a quite old building though). So I had to add ground line to the setup and check if that fixes the issues. Here how it can be done and checked:

Checking your electrical wiring

Depending where you live your power outlet may have different shape and size but what will be standard for most electrical wiring is 3 wires - hot (or phase), neutral and ground. In some cases you can have only two wires - hot and neutral. The electrical current will flow from hot to neutral. Ground if present will be used for the electrical bounding of connected devices.

A 3-wire EU power outlet

A 3-wire EU power outlet

If you want to be sure your electrical wiring has ground and is properly connected you can buy a socket tester. Those devices will show if wiring is correct and also which of the two main wires is hot and which is neutral.

UNIT-T UT07B-EU socket tester

UNIT-T UT07B-EU socket tester connected to a grounded power strip

Power outlet with missing ground wire

3-wire power outlet with missing ground wire may be misleading

Possible results

Possible results

Some older electrical wiring may be missing the ground wire and may be less secure to use. Some people try to hack the solution and use the neutral wire also as a ground but it's not guaranteed that neutral and hot wires will remain the same when some work will be done on the AC power grid (and AC connectors don't have fixed polarity like in DC current circuits). If such thing happens you PC case instead of being grounded will be hot and could shock you. Metal pipes and similar structures going into the ground or having their own proper Earth grounding are often mentioned as a source of Earth ground but that is very specific to given installation. It's not that easy to check if given pipe is a proper source of Earth ground - and not only does it has to be ground it also have to work with conjunction with the AC power line to trip the circuit breaker if a fault occurs on one of connected devices.

Metal pipes can be sometimes a source of Earth ground

Metal pipes can be sometimes a source of Earth ground

Grounding your devices and workspace

Winter with cold and dry air is an ideal conditions for static charge to build up. As it was winter I could zap myself and a keyboard (which caused it to unplug for a moment and plug again in the system), or display mounting pier (metal) or when touching the PC case. Pretty much it's easy to get static electricity in such conditions and zap other things.

Shops with electronics components will offer various earth bonding points which are convenient connectors that can be connected to some source of Earth ground (like ground wire of a power outlet) to which then we can connect other things - ESD wrist strap, ESD mats and alike. Many of such devices are listed on farnell but should be available in many other shops.

Earth Bonding Point in a shape of a power plug

Earth Bonding Point in a shape of a power plug

Earth Bonding Point connected to a power strip

Earth Bonding Point connected to a power strip

esd wrist strap, esd mats cables can be connected to earth bonding point

ESD wrist strap, mat cables can be connected to earth bonding point

The earth bonding point is not just a plastic power plug using ground wire. It also has a one megaohm resistor inside. The resistor will limit the fault current to less than 0.3 mA at 240 V supply. If overstressed the resistor will open the circuit. In short - it prevents high current from flowing through us if we touch something under hot wire.

Earth Bonding Point has a built in resistor to limit current that could flow through the user

Earth Bonding Point has a built in resistor to limit current that could flow through the user

ESD wrist strap is not something we use daily. It's recommended for use when working with electronic compoments - like building a PC, but not for day to day use, like playing on a PC. But there are other options:

Display connected to earth bonding point via metal VESA mount

Display connected to earth bonding point via metal VESA mount

Alphacool ESD mat as desk mat for all peripherals

Alphacool ESD mat as desk mat for all peripherals

The display uses 2 wire power supply so it doesn't use that ground line. The effect was that I could get a ESD when getting close to the metal pier on which it was mounted. Also the back of the display did electrostatically attract dust. After adding an ESD wire from the VESA mount to the bonding point the display doesn't seems to attract dust any more and discharges are rather gone. Do note that the resistors in the ESD wire and bonding point limit the current and the ESD may still occur but in a less spectacular form.

The Alphacool Eisplateau antistatic mat or GamersNexus ModMat are high quality mats with nice cloth surface. Those are quite good mats to use as a normal desk mat. Average ESD mat in electronics shops will be rather more rubbery, less pretty and less nice in touch to use them daily. This mat was also connected to the bonding point. Instead of shocking the keyboard I can safely move the charges either by explicitly touching the connector or by just being in contact with the mat in general.

Also a hint - those mats (either normal or ESD) with rubbery back and cloth top do wash nicely in a washing machine. When der8auer washes his graphics cards in a dishwasher we can wash our pretty mat in a washing machine. And in the case of Alphacool electrostatic mat... it's packaged in a plastic bag (something like a polypropylene bag). When you are taking that mat out or even when are you placing it on the desk - you will generate a solid charge ;)

ESD plugs on the mat are only for ESD, not for wiring to Earth ground

ESD plugs on the mat are only for ESD, not for wiring to Earth ground

The end of the story

So I have ground in my power strip. I added ESD connector to the display metal VESA mount to limit dust attraction and occasional ESD sparks. I also placed an electrostatic mat on my desk to avoid shocking the keyboard connected to the PC, which by now does not crash from random ESD discharges wherever in the room... but it's not solved yet. Plugging something to the case (USB, headphones) can crash it - although not when I'm holding the case with the other hand. Sometimes I get an ESD to the chair metal structure from my legs - that also can sometimes still crash it. I will have to move the system out of existing case to check if it's the components or the case fault... but at least I have much improved ESD/grounding in my office room.

How does your setup looks like? Do you use any ESD protection elements or had problems with PC grounding or electrostatic interfering with your electronics?

RkBlog

Hardware benchmarks and reviews, 11 March 2019, Piotr Maliński

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