blaablaaguy
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Grounding static electricity.

Sun Feb 21, 2016 10:23 pm

Normally I ground myself on a radiator pipe before handling my pi, so as not to static shock it, but someone mention touching the outer casing of the pi's usb connector because its connected to the pi's ground. If I touch the usb connector or a ground pin will it do for static electricity?
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GTR2Fan
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Re: Grounding static electricity.

Sun Feb 21, 2016 10:29 pm

If you're still holding the unpainted radiator pipe while you touch the Pi's USB housing, yes.
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Heater
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Re: Grounding static electricity.

Mon Feb 22, 2016 4:43 am

What we want to do here is discharge your body to ground. That is the actual ground of Mother Earth.

Those wall warts we generally use to power the Pi do not have any connection between 0v and ground. They are isolated. The "ground" on the Pi, like the USB housing, is not connected to real ground.

So, when your highly charged finger touches the USB housing your static charge will be trying to find it's way to ground, perhaps through the circuitry of the chips on the Pi and out through GPIO pins or whatever. Poof you have blown it!

Better to grab that water pipe first.
Memory in C++ is a leaky abstraction .

Mithrandir
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Re: Grounding static electricity.

Mon Feb 22, 2016 8:12 am

A 5v PSU suppling a Pi will not have an earth pin, so you can never discharge static via this. Pick up an anti static wrist strap if you are worried, these are a 1 meg resistor in line with the ground pin of an electrical earth, it will discharge your static but not give you a good path to earth if a proper electric shock comes when working on mains powered equipment.

pksato
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Re: Grounding static electricity.

Mon Feb 22, 2016 11:35 am

blaablaaguy wrote:Normally I ground myself on a radiator pipe before handling my pi, so as not to static shock it, but someone mention touching the outer casing of the pi's usb connector because its connected to the pi's ground. If I touch the usb connector or a ground pin will it do for static electricity?
Hi,
You work room have a tendency to accumulate static electricity?
Some conditions favorable to static electricity.
Dry environment;
Carpet on floor;
Wool or synthetic clothes;

Most circuity have protection to static electricity discharge, what is safe to handle on low or none static electricity favorable conditions. But, if you see or hear spark on you fingers when closer to big metal object or ground, need to use ESD protection things.
To work area (desk), use a anti-static mat.
To you body, a anti-static wrist straps.
Both need to be connected to real ground. The ground pin on socket wall (if correct installed).
Avoid fake anti-static wrist straps and mats.

https://en.wikipedia.org/wiki/Antistatic_wrist_strap
http://www.amazon.com/StarTech-com-24x2 ... B00009XT3H

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GTR2Fan
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Re: Grounding static electricity.

Mon Feb 22, 2016 12:22 pm

pksato wrote:Most circuity have protection to static electricity discharge, what is safe to handle on low or none static electricity favorable conditions.
This isn't so much of a worry once the individual devices are in-circuit, as the internal impedance of supply regulators and decoupling lends considerable extra protection against floating voltages even when powered down, but it has reminded me of a situation at a company where I worked for many years where the importance of antistatic precautions with unmounted static-sensitive devices was proven beyond any doubt.

I'll not mention the company by name as I wouldn't want to sully their reputation for competency, but they sold tens of thousands of products to the general public every year for several decades, and the vast majority of products returned under warranty had suffered failures of CMOS 4000-series logic ICs.

The ICs were delivered in the manufacturer's standard antistatic tubes, but were handled entirely manually during the individual handling and assembly phases with no thought given to antistatic protection on the basis that the internal antistatic protection in the devices was being relied upon to keep them safe prior to insertion.

During the first 12 years that I worked there, the vast majority of warranty returns for repair (well over 70% IIRC) were down to failed 4000-series logic ICs. This was obviously costing the company a considerable sum as the products were generally quite heavy, and the cost of not just the repair but also postage and packaging on the inward and outward journeys had to be covered by the warranty.

An alternative manufacturer of 4000-series ICs was chosen for as many of the devices as possible as the boss had decided that it was highly unlikely that anything we were doing to the devices could be responsible for the failures, yet the failures continued at approximately the same rate. The alternative manufacturer was also more expensive, so this was yet more money wasted, and the slim profits the company was making were now being dented quite badly by warranty repair costs.

A few of us test engineers were fairly convinced that we already knew what the problem was, so we eventually convinced the boss to install antistatic wristbands and antistatic mats at ALL handling and assembly stations. A careful record was kept in the product serial number record books of which batches of products were shipped before and after these changes and, to cut a long story short, the problem was nailed. Failure of static-sensitive devices had dropped to nearly zero, and remained that low from that day forth.

The moral of this story is that, just because a static-sensitive device is still functioning normally initially, that's no guarantee that it hasn't already been terminally damaged and doomed to a fate of early failure. Never underestimate the effect that your actions today can have on the outcome of tomorrow. :)
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blaablaaguy
Posts: 623
Joined: Sun Sep 27, 2015 3:26 pm

Re: Grounding static electricity.

Mon Feb 22, 2016 3:13 pm

pksato wrote:
blaablaaguy wrote:Normally I ground myself on a radiator pipe before handling my pi, so as not to static shock it, but someone mention touching the outer casing of the pi's usb connector because its connected to the pi's ground. If I touch the usb connector or a ground pin will it do for static electricity?
Hi,
You work room have a tendency to accumulate static electricity?
Some conditions favorable to static electricity.
Dry environment;
Carpet on floor;
Wool or synthetic clothes;

Most circuity have protection to static electricity discharge, what is safe to handle on low or none static electricity favorable conditions. But, if you see or hear spark on you fingers when closer to big metal object or ground, need to use ESD protection things.
To work area (desk), use a anti-static mat.
To you body, a anti-static wrist straps.
Both need to be connected to real ground. The ground pin on socket wall (if correct installed).
Avoid fake anti-static wrist straps and mats.

https://en.wikipedia.org/wiki/Antistatic_wrist_strap
http://www.amazon.com/StarTech-com-24x2 ... B00009XT3H
Ive got carpet but no big zaps or anything :)
I dont realy need any static protection or anything, just wanted to know if i could ground myself on the pi- more convenient than a radiator anyway.

Thanks for the answers tho
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rurwin
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Re: Grounding static electricity.

Mon Feb 22, 2016 4:08 pm

The advice you got was correct so far as it goes. By handling the Pi by the USB housing you are passing any static into the ground of the Pi, where it is likely to do as little harm as possible. However, it doesn't ground you. You still need the radiator for that.

So touch a ground point before picking up your Pi, and when you pick it up do so by the connector housings. If at all possible don't carry it around without it being in a conductive bag. But if you do, ground yourself again before you put it down. Otherwise you could charge yourself up while walking and then ground yourself through the Pi.

All of these procedures are best practise, and in the real world we forget from time to time. It's nothing to get paranoid about. Chips in circuit boards are much more resiliant than chips before they are installed and a single mistake is unlikely to kill your Pi. But it might, you won't notice anything happen (no sparks necessary), and it will probably continue to work for a few weeks before it fails so you'll never know what did it.

I built myself a static discharge device once out of a piece of conductive rubber and a neon bulb that plugged into the Earth pin of a mains plug (don't do it unless you know enough to be safe). I could light the bulb simply by gently tapping my foot on the carpet, and that takes at least 100V.

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