Re: "Arrows" pads?

On Wed, 03 Dec 2008 08:53:01 -0800, D from BC
<myrealaddress@xxxxxxxxx> wrote:

On Wed, 03 Dec 2008 10:49:46 -0500, legg <legg@xxxxxxxxxxxxxxx> wrote:

<snip>

I dunno how someone figured out a typical spike energy level so the
PCB gap doesn't get fried to the point of uselessness.

If the arc occurs, the energy released locally is minimized. The test
waveforms for these surges has a characteristic amplitude, waveshape,
duration and characteristic source impedance. The arc occurs across
terminals of the circuit that normally do not experience high stress,
ie across the coil ( a DC ~short circuit for creepage and cleerance
purposes ).

Only testing will demonstrate effectiveness and durability - hence
reference to assembly spec sheets. It does no harm, so even failed
attempts at design (if it was a serious design effort and not just a
whim) may have been left in place, by default.

Sounds like what some might call that a 'cheap shot' or 'a better than
nothing' philosophy. But that's ok.

Very often, opportunities for 'probing the limits' of a design
iteration are only available to the tightly-scheduled new product
developer in this way. If it works ('free' samples for testing!), it's
a new value-added feature that can be advertized and re-used; if it
doesn't, there's no skin lost and no budget blown - just a gradual
accumulation of savvy for the next attempt (if the developer lasts
that long).

RL
.

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