A Hidden Threat To Handhelds

Logic Bomb writes: "An article from the San Francisco Chronicle focuses on a lawsuit against Palm, but talks about a larger issue: static and handheld computers. Basically, as computing equipment becomes smaller and more likely to be carried around, major damage from static becomes a serious threat. As the blurb at the end of the article says, it takes 3500 volts for a human to feel a shock, but only 200 to potentially scramble a microchip." We already mentioned the lawsuit, but this has more information about the supposed risks to your motherboard.

Comments

Re:It's a class B computing device... no big deal

[choco]

You are confusing ESD (electrostatic discharge) with EMC (electromagnetic compatibility). They are very seperate issues.

is a serious problem. It IS possible to design interfaces which offer useful resistance. But it is suprisingly hard to design and build in practice and it causes problems throughout the electronics industry. To build a Port (USB, serial, whatever) which can resist electrostic discharges requires that you use most of the following :

Protective devices which can dissipate the energy. The risetime from Static discharges is very fast and overwhelms all but the best protective devices.

Drivers/receivers which are hardened against static (the major semi manufacturers who do such chips do now make some - but they tend to cost more

Careful mechanical design to further reduce the problem - arrange that the "grounds" always touch first - preferably through a few hundred thousand ohms of resistance.

Optical isolation (although many people fail to understand the limitations of this technique - the stray capacitance between the isolated section and everything else is almost always high enough to allow static damage to happen.

More importantly manufacturers need to test their designs properly using realistic test models. Much equipment - including from the big name manufacturers pays little or no attention to this issue. Presumably for cost reasons - although if the right measures are "designed in" from the start the premium is going to be pretty small. It's interesting to compare the serial interface from a top branded PC with a functionally-identical interface from some serious telecomms kit.

I'm an engineer - not a lawyer. But I do know that I'd hate to have to do the finger pointing in the "Palm v motherboards" issue. If forced to comment I'd say that both sides should share the responsibility.

Re:ESD isn't a joke - but everyone thinks it is

[baptiste]

if you connect your strap to a case and DONT plug it in, that is fine. the strap is there to allow you and the case to be at the same potential. As long as this is the case, you will NOT zap anything.

Wrong - when you pick up that motherboard sitting on teh table and zap it (cause you may not be at the same potential) you still hate it. Ground a strap to GROUND is important. Why? Because it disappates the charge from your body. Storing boards in ESD bags? They disappate any stored charge on teh board when you picj it up. Grounding your PC case - again, disappates any charge in the case.

So yes, if you strap yourself to an ungrounded case, you won't zap the case cause you are at the same potential, but you can still zap external compnents you pick up. Yes its rare and something is betetr than nothing - I agree. But for proper protection every thing MUST be grounded. But at the bare minimum, always touch the metal of the case before messing with a PC - that helps but you STILL can zap something in a dry environment.