Eisermann, Phil [Ridg/CO] wrote:
>
> Well, I did a little HALT testing on a board with a PIC in it. HALT = Highly
> Accelerated Life Test. One of the tests was a 6-axis random vibration test.
> The rms value of the G-force on the board was 20g-25g when the transformer
> failed. The PIC and crystal survived around 35g before strange things
> started happening. The PIC was a 16C711, the crystal a 4MHz through hole. I
> have performed a similar test on an ADuC812 with a 11.0592MHz SMD crystal,
> and again strange things started happening around 35g. So, it is unlikely to
> be the crystal, either.
>
> But, have you considered ESD? when you shake the board by hand, you will be
> electrically charging yourself. The voltage will be high enough that the
> potential can jump an air gap. I'm going to guess that you're seeing an
> ESD-related event. Try protecting the inputs by inserting a series resistor,
> decoupling capacitor, and a zener diode. Also make liberal use of decoupling
> capacitors throughout the board.


Great point, esd or even hand capacitance and the
PIC osc. Also, when finding dry joints in appliances
they are usually VERY movement sensitive. Using
veroboard can often give bad joints, I scrub mine
with abrasive before soldering. It's usually non-tinned
and gets corroded easily.
-Roman

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