[App_rpt-users] Ras Pi 2 doesn't like xenon flashes???

[mike at midnighteng.com]

While not familiar with the Pi2,
I guess I have learned something.

Never would have dreamed of a photo-sensitive chip outside of a eprom.
Especially in the power supply area.
They must use a on-chip led/photo transistor as a flip/flop toggle of the
power. Opto-isolation. That would make sense. I have seen chips with just
that but have not used them. A good lesson on new analog things to
troubleshoot.

All these micro-controllers are susceptible to digital rfi/rfp noise.
Proper shielding your controller is still best practice regardless. Unless
you like surprises that make you scratch your head.

...mike/kb8jnm

>
> Hi Mike & Everyone,
>
> My initial questions (and alarm) were if the RPi2 might be excessively
> sensitive to external EMI---something like that can be really hard to deal
> with around high RF environments.
>
> But, after reading more threads, it appears this issue is truly light
> sensitivity in one of the switching PS chips (U16), due to how it's
> encapsulated (or lack thereof!) in plastic. Adding a small light shield
> apparently fixes this issue, based on what other testers say.
>
> I don't yet have a RPi2, so I can't test.
>
>
> 73, David KB4FXC
>
>
>
> On Sun, 8 Feb 2015 mike at midnighteng.com wrote:
>
>>
>> Not having tested it specifically, I would find it plausible for a xenon
>> flash in very close proximity to a micro-controller create a problem but
>> only in this way...
>>
>> RFI/EMP burst during flash, a pulse being picked-up on circuits. If not
>> RFI changing something directly in ram, EMP could just put a extra
>> binary
>> digit in a stream of data or a extra pulse in the clock line. The later
>> in
>> the clock line being most probable for a lock-up. Not from the flash of
>> light. The broad pulse comes from it's ballast. The wires attached to it
>> and the bulb act as a antenna.
>>
>> If it is a problem with a strobe light, I'll bet you could get a similar
>> action from a close proximity GSM cell phone during certain phone
>> actions.
>> And I would also bet you could find that the Pi would not be the only
>> type
>> of micro-controller than can be affected by this type of thing.
>>
>> Not to worry, Shield your Pi like you should be doing in any case and
>> provide sinks for RFI on all lines in and out of the shielded area. This
>> would be normal protection in a RF hostile environment. Radio 101 - It
>> should never be a real issue in a properly constructed repeater.
>>
>> ...mike/kb8jnm
>>
>> >
>> >
>> > Hi Everyone,
>> >
>> > I just saw this thread in another newsgroup. Basically, they're saying
>> the
>> > Pi2 will hang/crash if subjected to a close xenon camera flash
>> discharge!
>> >
>> > Weird! Can anyone confirm if this is true?  ...If they're sensitive to
>> a
>> > flash, they might be sensitive to RF as well. Perhaps an EMP issue?
>> >
>> > Here is a link to the thread:
>> > http://www.raspberrypi.org/forums/viewtopic.php?f=28&t=99042
>> >
>> > Again, I have NOT personally confirmed this report, but am sitting
>> here
>> > looking puzzled!
>> >
>> >
>> > 73, David KB4FXC
>> >
>> >
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