Static electricity, a point to ponder

So with todays processor controlled lights, would anyone figure static electricty could be an issue?

My place is very "staticky" <---is that a word?) this time a year, and it has caused issues with other electronics, so I could easily imagine a problem with my flashlights. Peeling my lazy butt off the couch at night results in some pretty good shocks.

What's everyone elses thoughts?

If I have a light that is at all sensitive to an exterior static charge of less than spot welding intensities, then I don't want the light. -I'd expect those to be fine as well so long as the body didn't heat up beyond the limits of the epoxies and battery chemistries inside.
My lights should be able to withstand momentary shorts across their metal bodies without any problems.

eh4 said:

If I have a light that is at all sensitive to an exterior static charge of less than spot welding intensities, then I don't want the light. -I'd expect those to be fine as well so long as the body didn't heat up beyond the limits of the epoxies and battery chemistries inside.
My lights should be able to withstand momentary shorts across their metal bodies without any problems.

Click to expand...

Edit: I suggest you read Cataract's post below. He knows more about this than I do. Ignore what I wrote.

It's not so simple. All ElectroStatic Discharges happens because of extremely high voltages. The visible spark is one mechanism of damage, where extremely high voltage equalizes. This is low-current, high-voltage, thankfully. At my workplace if the electrostatic suppression devices (Confusingly also called ESD) go out, then I can draw centimeter-long sparks continuously. It's not fun.

Extremely high voltage electricity doesn't act like low-voltage DC. Just the capacitance of an object can cause significant current flow as its voltage equalizes. This is one of the mechanisms of damage to small devices. If I touch a charged object at work and experience an unpleasant 1cm spark, the flashlight in my pocket is also charged to high potential. More importantly, every wire and component in the flashlight is charged. This happens by electrons moving quickly, which easily damages semiconductors. Clever (expensive) design can mitigate these effects.

tl;dr, all electronics are sensitive to ESD, especially once you reach the 30 kV range. Charging the diodes and wires in the silicon chip cause damage directly and indirectly by induced fields. It's exciting stuff, and there's no easy way to build a "static-immune" light. Maybe a spherical light inside a spherical conductive shell?

Ok, maybe I haven't been thinking about this the right way, but wouldn't your light's electronics be basically grounded to the head of the light? At those high voltages I imagine that very tiny flaws in anodizing would let the current pass, or maybe the anodizing will pass the high voltage itself.

Take yourself, messing with a light in a nearly 0% humidity environment and arcing like crazy. Say you're messing with an aluminum bodied flashlight and a Malkoff dropin. Wouldn't you have to manage to get your finger way down to the positive end of the battery tube without touching the sidewalls in order to shock the electronics?

I think you are misunderstanding, but maybe I am. Who knows? HV is weird.

"Grounded to" is the same as "connected to." In this case, that's the downfall of the electronics. My limited understanding is that the high voltage rushing in to equalize potential (with the aluminum body, circuits, and LEDs) induces interesting effects that damage the electronics. The tiny wires in a control chip are subjected to high currents and voltages (Which often exceed the breakdown voltages of insulators, gaps between bond wires, and such) that damage the chip irreversibly.

Because circuits have tiny wires that are close together, the wires conduct across their insulation. There may also be induced magnetic fields creating further stray current. Anyway, putting a few kilovolts anywhere on a flashlight will get the whole flashlight equalized to some new voltage. When the flashlight in my pocket equalizes with a few hundred pounds of fabric at 30 kV, it can be damaged. So far, mine has survived - Probably since I am never touching it directly when I get shocked. I think this helps protect it from a near-instant rush of current.

Electrostatic charges are generally distributed evenly. Only the surface where (and immediately around) the spark can be seen are submitted to current, which is an extremely small current, but very high voltage as already mentioned.

To damage electronics, the discharge itself would have to be directly on or very very near the part you want to protect. Your flashlight is surrounded by a conductive tube which also acts as protection against electrostatic discharge for your components by absorbing the bulk of the charge.

On top of that, if your body is charged, your flashlight would only share a very very small amount of that charge if at all, since your clothes are what create the charge - your body only transmits and holds part of it like a capacitor.

Finally, ESD's mostly happens when touching something that is grounded (not exclusively, but 99.99999% of the time unless you are talking about power transmission line electrostatic strength) and your flashlight is not grounded unless you leave it on a conductive surface. When a person carrying an electrostatic charge touches a conductive (that is electrostatically conductive) object, the charge is shared proportionately. Since most objects are a lot smaller than we are, very little charge is being transfered and this is mostly a sparkless event. When touching a ground, you share the charge with the whole earth, therefore you will have very little charge left after experiencing a visible spark (a miniature lightning bolt, actually.)

I repair and have built plenty of boards for a few companies and I never ever heard of a failure due to a spark on the production line or during repair. The important part in this case is that the boards and components are NOT grounded while working on them and most of us only wear a ground bracelet just for show when clients come by. I definitely would not worry about ESD killing your flashlight unless you are a line worker - in which case you would have been trained to avoid such problems.

Great info Cataract, thanks!