That comments thread contains a head-smacking quantity of ignorance. "Is it the light or the EM pulse?" What?
A Xenon flash will cause the Raspberry Pi 2 to freeze
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Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#12Explanation: Camera's have capacitors that charge up in order for the flash to happen. They are usually quite powerful. Now during the discharge (aka flash) what you have is very high energy electrons flowing across the wire creating aa magnetic field, coupled with the electric field of the electron you get a mild EMP. And if it is light sensitivity then it should be tested with a bright continuous light
The entire purpose of a camera flash is to create a directed electromagnetic pulse.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#13A xenon tube is a spark gap.
If there's anything in this world noisier than a spark gap, I don't know what it is.
I think the first radio transmitters were spark gaps.
The energy flies thru the air, and is coupled onto the power line.
The power supply doesn't cope well with the oscillations, and hiccups.
I see the notes about U16 being photosensitive, but if it is a black epoxy like most IC's, I'm not buying that light gets into it.
It's possible that blue tack shields the EMP a bit.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#14Shortcut to a video of this phenomenon: http://youtu.be/wyptwlzRqaI?t=1m29s
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#15Why would a switched-mode-power-supply chip be photosensitive?
All chips are photosensitive and a xenon flash produces light from UV through to IR, so my guess would be that the plastic used for the casing on that chip is not entirely opaque to something at the top or bottom end of the visible spectrum, which is why most bright lights don't trigger it. At a bet, I'd say the top end, as otherwise radiant heaters would also probably kill them. Would be fun to play around with some filters and a flashgun and narrow down the frequency.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#16Why would a switched-mode-power-supply chip be photosensitive?
All semiconductor materials are photovoltaic to some extent.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#17That comments thread contains a head-smacking quantity of ignorance. "Is it the light or the EM pulse?" What?
He's asking if it's RF interference or just the light.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#18Explanation: Camera's have capacitors that charge up in order for the flash to happen. They are usually quite powerful. Now during the discharge (aka flash) what you have is very high energy electrons flowing across the wire creating aa magnetic field, coupled with the electric field of the electron you get a mild EMP. And if it is light sensitivity then it should be tested with a bright continuous light
The entire purpose of a camera flash is to create a directed electromagnetic pulse.
The entire purpose? Not really. I think it has something to do with a mess of directed photons.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#19Why would a switched-mode-power-supply chip be photosensitive?
All silicon is photosensitive to some extent. The power supply will be one of the few chips which is primarily "analog"; in particular it will have a bandgap voltage reference. That's exactly the sort of thing to be badly affected by a charge pulse from the flash. Glitching the power supply will then destabilise the digital logic it's powering.
The real question is how the light manages to get through the epoxy casing.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#20Good find OP! I wonder how many electronic devices would have similar problems if we took out the covers?
All of the badly-designed ones and none of the well-designed ones :) Often you'll see audio equipment with LED-biased voltage amps where the LEDs have some opaque glop slathered on them so they don't make popping sounds under bright lights, and to a lesser extent so multiple channels inside the same box are optically coupled, which is a concern. LEDs are photovoltaic like any other semiconductor but for obvious reasons they are not sold in opaque packages.
You could probably find devices that are disturbed by loud sounds and physical shock, because ceramic capacitors are microphonic.