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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
#92Earlier quoted context omitted.
A xenon tube is not a spark gap, in terms of the early radio receiver 'spark gaps' which were a primitive tuned circuit used to then feed an antenna (it wasn't the spark itself that was used for the transmission). Sparks produce a broadband radio signal, that decays strongly with increasing frequency. Very little is present in the Megahertz region, which is why lightening doesn't interfere with FM radio that much. Ra…
I think the reason lightning doesn't perturb FM transmissions much is that lightning, being a source of additional energy in the receiver's passband, is an amplitude modulation interference source, whereas FM transmits its information by Frequency Modulation, which is nominally insensitive to AM EMI sources. Any amateur radio operator in the Midwest or Florida using AM on 144MHz will tell you that lightning for sure…
I have heard the spectrum of lightning EMI described as "from DC to daylight".
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#93Earlier quoted context omitted.
Alright I put the Pi 2 in a cardboard box and held the flash at the same spot (but the box obscures the light). It keeps running just fine and doesn't have the nasty spike. Definitely is something light related.
Thanks! Well done. Photoelectric it is. Now I wonder what color its most susceptible to...
Since the effect seems to be caused by a silicon component that isn't properly shielded from light, anything with a photon energy higher than the bandgap should do. The bandgap of silicon is 1.1eV, which means the effect should start in near-infrared.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#94This reminds me of an old Finnish engineering legend from the early days of Nokia. The guys had just built an important prototype of some network equipment (early GSM base stations IIRC), which was going to be demonstrated for the press. All tests and previous demos had gone fine.
But as soon as the demo for the press started, the machine crashed. The management was upset. Later, the reason was found to be some old EPROM chips that are erased using UV light, and the photographers' cameras had strong flashes that went through the tapes covering the "window" on the chip. This caused the program memory to be corrupted when a photograph was taken.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#95Earlier quoted context omitted.
Thanks! Well done. Photoelectric it is. Now I wonder what color its most susceptible to...
Since the effect seems to be caused by a silicon component that isn't properly shielded from light, anything with a photon energy higher than the bandgap should do. The bandgap of silicon is 1.1eV, which means the effect should start in near-infrared.
What about glass, then that should work, right?
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#96Earlier quoted context omitted.
Since the effect seems to be caused by a silicon component that isn't properly shielded from light, anything with a photon energy higher than the bandgap should do. The bandgap of silicon is 1.1eV, which means the effect should start in near-infrared.
What about glass, then that should work, right?
Not sure I understand you correctly.
The problem should happen with near-infrared, visible, and UV-light. Glass is transparent in the visible range, and depending on type, also in IR / UV, so glass won't work as a shield.
The easiest, reliable way to shield would be wrapping in aluminum foil (also helps against RF-interference).
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#97The problem IMO that the chip in question doesn't have a plastic cover,
look how shiny it is in this video:
https://www.youtube.com/watch?v=c7p2OcQ7G58
A laser (no EMP!) shone on that chip will also crash the Pi.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#98The new wave of single board computers really exposed me to the amount of failure that can happen at the electrical level. Growing up with large ATX boxes I'd never expect so many things to go wrong.
btw: anyone tried to light-freeze other devices (banana, orange, cubie, etc) ?
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#99Reminds me of old EPROMs. You can buy special "light sensitive" transistors, but they're really just ordinary transistors with a window in the case, since ordinary transistors are light-sensitive. You can even use an ordinary 1N4148 diode as a solar cell, it just doesn't generate much power. The fix is simple: apparently, you just have to cover U16, which controls the power supply.
LEDs can also be used for narrow band detection. It's called the Mims effect since Forrest Mims was the first to publish about it.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#100This reminds me of an old Finnish engineering legend from the early days of Nokia. The guys had just built an important prototype of some network equipment (early GSM base stations IIRC), which was going to be demonstrated for the press. All tests and previous demos had gone fine. But as soon as the demo for the press started, the machine crashed. The management was upset. Later, the reason was found to be some old E…
Interesting that the Finnish version of this story is about Nokia, GSM base stations and EPROM memory. The version from 1990 from The Devouring Fungus which I quoted in a separate comment is about the IBM 701 and CRT memory.