Re: gEDA-user: sparkfun 4 layer boards

["Mark Rages" <markrages@xxxxxxxxx>]

On Sat, Aug 23, 2008 at 1:48 PM, John Griessen <john@xxxxxxxxxxxxxx> wrote:
> Eric Brombaugh wrote:
>> Dave McGuire wrote:
>
>>>    I'd be shocked and amazed if they could detect thermal IR.
>>
>> Agree - there's a big difference between the short-wave IR that's used
>> by common IR remote controls (which is easily seen on most any webcam)
>> and the long-wave IR used in thermal imaging.
>
> Ohh...  we can control the situation to get near enough IR.  We're looking for shorts
> anyway, not normal operating temps of + 1 degree...   Seeing just the really hot spots
> -- meaning  120 deg F is plenty good, and the amount of near IR in that temperature surface is
> enough to see with a CCD I bet.  Thermally emitted IR is a continuous curve or frequencies for a given temperature.
> Low temps just emit less near IR, but always some.
>
> So, I still bet CCD cameras could be very useful even without long IR sensitivity for
> a short detector, including shorted outputs and shorted traces.
>
> One way to test shorted traces without just burning through them would be to power with a current source
> to generate heat, then look with hacked CCD camera.
>

Don't discount just burning through the short.  In my experience,
random PCB shorts are usually caused by a tiny whisker of copper.
Vaporize it and the board will work fine.  No heroic troubleshooting
devices required.

Regards,
Mark
markrages@gmail
-- 
Mark Rages, Engineer
Midwest Telecine LLC
markrages@xxxxxxxxxxxxxxxxxxx


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