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I'm a beginner in electronics, and in my free time I love making stuff with my Arduino.

As I was handling a few Bluetooth modules with my hands, I thought about static electricity discharging on the chips. I'm not very familiar with this, so I have a few questions about the topic, and I hope you could help me out to get some stuff straight in my head.

  1. Is static electricity really so dangerous?
  2. Can I really destroy something simple like an Arduino module if I touch it?
  3. Assuming that I need a discharge in order to pass the electricity, how is this happening?
  4. Anything more I should know?
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    \$\begingroup\$ I wish I could show you the retraining notes on this... I have to have ESD "requal" every 2years and my refresher is tomorrow... Its burnt in but we still need a tick in a box. Yes it is bad, yes it can damage and the worst kind is partial damage so that it appears to work but significantly shortened its lifetime \$\endgroup\$ – JonRB Mar 1 '15 at 20:46
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    \$\begingroup\$ you can get a lot of volts per metre across a micron... \$\endgroup\$ – Brian Drummond Mar 1 '15 at 20:48
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    \$\begingroup\$ @BrianDrummond very true, especially if someone rubs you up the wrong way and charges you for the privilege. \$\endgroup\$ – JIm Dearden Mar 1 '15 at 21:11
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    \$\begingroup\$ "Is static electricity really so dangerous?" - Have you ever been struck by lightning...? \$\endgroup\$ – Majenko Mar 1 '15 at 21:45
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    \$\begingroup\$ Ref question 3 - IME humidity makes a huge difference too. So if you're wondering how you got away with doing all that careless handling, that could well be the reason. \$\endgroup\$ – peterG Mar 2 '15 at 0:16
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Is static electricity really so dangerous?

Yes.

The conductive paths inside an IC are really small, so it doesn't take much energy through them to vaporize them.¹

There are millions of such paths inside the ICs of an Arduino, and it only takes damage to one of them to break the device. It is possible that you could get lucky and break some feature that you aren't using, but this is not a good gamble to take.

Can I really destroy something simple like an Arduino module if I touch it?

What makes you think an Arduino is "simple?" Microcontrollers are among the most complex and delicate objects humans make. Fabergé eggs are simple and durable by comparison.

How does this happen?

It happens the same way you get a discharge when touching a doorknob. Whenever the path through the device is a better path for the electricity than leaking away through your shoes and the air, it will take that path.

Generally, the device is a good path because it is plugged into a power source, which means there's a ground path, which is a low-impedance path to a much lower voltage potential.

Some of an Arduino's input pins will be protected against static discharge, but probably not all. Even those that are protected can be killed with enough hits. Protection doesn't make a pin invulnerable, it just allows it to withstand a certain amount of ESD energy. Like any armor, hit it enough times with enough energy, and you can break through.

This is not to say that unplugging the device is a good solution to the problem, however. For one thing, it defeats much of the protection built into the device, because some of it works by shunting the dangerous energies to ground. When you unplug the device, you remove that path, so now the electricity is forced to take a different path through the device, one without this protection. An unplugged device still has other conductive paths that lead to a lower voltage potential. Consider that humans and shoes are poor conductors, yet we manage to get static buildups, and can be electrocuted.

Anything more I should know?

Go to a good electronics tool shop and look at all the antistatic products available. They're made for a good reason. Buy some. Use them. :)


Footnotes:

  1. The sort of static discharges you feel when touching a doorknob range between 5 kV and 15 kV depending on several factors;² the peak current can be 1 A. The static electricity is equalized in about a microsecond and doesn't pass through your heart, so it is merely annoying to a human but potentially fatal to a semiconductor gate.

    The human body can also charge to less than 5 kV before discharging. There is a range where there is still enough energy in the discharge to damage a sensitive IC, but where the energy is too low for your nerves to sense it.

  2. Dry air allows the human body to store more charge because it leaks away slower than in moist air, so that the energy in a static discharge generally gets higher in winter. Your shoe type also affects the amount of energy you can deliver in a static discharge, as does the carpet. Then you have effects like how moist your skin is, whether your fingers are callused, etc.

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    \$\begingroup\$ +1 for "Fabergé eggs are simple and durable by comparison" - great phrase! \$\endgroup\$ – pjc50 Mar 1 '15 at 21:41
  • \$\begingroup\$ You know those Hollywood movies scenes where electrical goods fail, with arcs and sparks? Reality is much more boring: think of a light that simply fails to turn on. A static discharge can be big enough to destroy circuits inside a chip, yet be too small to see or even feel. \$\endgroup\$ – Alan Campbell Mar 2 '15 at 13:13
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ESD is based on the fact objects can hold a static charge, e.g. when electrons are scraped off them by friction; contact with another object creates a destructive transfer of charge if not properly controlled. If rearranging your pullover can set a car's tank on fire, you can be sure ESDs can be dangerous to the incredibly tiny traces in any integrated circuit. A chip under ESD has pretty much the same survival rate as anyone standing under a tree in the middle of a field during a thunderstorm.

It's all down to prevention and protection. First, protection. Most widely spread boards like Arduino have ESD protection (they would have very small success otherwise seeing how people can easily generate discharges), and generally very few reports are made of boards rendered non-functional by ESD. However discrete components such as transistors exclude those, therefore if you build a circuit around those you and you alone have to make sure the circuits are protected of such discharges.

Generally those are based on diodes that clamp the input voltage/drain the energy away from the input:

enter image description here

I have a yearly certification training on ESD in my company (prerequisite to have access to labs), and they've shown us one of those old training films in which the instructor was using an ESD detector (a 'scope with an RF antenna basically) in experiments. You would be surprised at how easy it is to generate 10000V: shuffling your feet, sliding a piece of plastic on paper... Even sliding those chips out of their tubes (if not one of those ESD safe ones) will. And when it happens, the high voltage can puncture the semiconductors' isolation and reduce drastically its input resistance (from 10's of Megohms to 100k in the video), if not causing a short. It doesn't sound like it's much, but make a short where there is supposed to be none and chances are your circuit will not work.

Usually this is prevented via the use of proper grounding: using dissipative mats (neither conductive nor isolator) as a work surface and wrist straps tied to them via an integrated 1Mohm resistor for controlled, harmless discharges (and no charge buildup) of both your body and the unit under test. Air ionisers also exist to cancel out charges of non-conductors such as paper or tape. The floor itself is usually of a dissipative material, tied to the Earth network. enter image description here

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