Earlier quoted context omitted.
https://www.youtube.com/watch?v=4huRNCrwfNw
Is your cursor nyan cat?
How do you do that? I want a nyan cat cursor!
A Xenon flash will cause the Raspberry Pi 2 to freeze
71–80 of 135 posts
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#72There's nothing mysterious about this. Semiconductor gates are light-sensitive. There's usually carbon black in the plastic of plastic-packaged ICs to prevent interference from light. The opacity isn't perfect, though. For that you need ceramic or metal-encased ICs. Still, this is a rare enough problem that IC data sheets don't specify a maximum tolerated illumination level.
Try some laser pointers, especially towards the blue end of the spectrum where the photons have more energy. You may be able to trigger this effect by pointing at a specific IC.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#73Why 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 casin…
there is no epoxy, smps controller is a flip chip bare die bga
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#74There's nothing mysterious about this. Semiconductor gates are light-sensitive. There's usually carbon black in the plastic of plastic-packaged ICs to prevent interference from light. The opacity isn't perfect, though. For that you need ceramic or metal-encased ICs. Still, this is a rare enough problem that IC data sheets don't specify a maximum tolerated illumination level. Try some laser pointers, especially toward…
red laser makes it crash too
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#75A 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 lig…
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 interferes with reception. With FM, not so much.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#76Earlier quoted context omitted.
Is your cursor nyan cat?
How do you do that? I want a nyan cat cursor!
It appears to be Nyanology[1] on Terminology[2]
[1] https://github.com/anisse/nyanology [2] https://www.enlightenment.org/p.php?p=about/terminology&l=en
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#77There's nothing mysterious about this. Semiconductor gates are light-sensitive. There's usually carbon black in the plastic of plastic-packaged ICs to prevent interference from light. The opacity isn't perfect, though. For that you need ceramic or metal-encased ICs. Still, this is a rare enough problem that IC data sheets don't specify a maximum tolerated illumination level. Try some laser pointers, especially toward…
red laser makes it crash too
OK, that part is a reject. It will probably crash in bright sunlight, too.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#78I just ordered two of these, and they will arrive on Tuesday. Makes me sad because I'm imagining a Raspberry Pi 2.1 release in the near future now...
Bugs like these are the reason I never order version 1 of anything new.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#79Why 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 casin…
Not exactly the same thing, but here's a really cool hack where it's possible to use a photosensitive dram chip as a digital camera.
https://www.cs.uaf.edu/2007/fall/cs441/support/dram_sensor_1...
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#80Oh neat, I just reproed it with a Pi 2 and a Canon Speedlight flash. I'll put my scope on the power lines and see what's happening when you flash the board. Sounds like from the thread one of the power ICs is photo sensitive. edit: Wow yeah, here's a look at the 3.3V power line when you flash the board, it drops almost down to 0V and then wildly fluctuates for about 100 nanoseconds: http://imgur.com/hG86pRy edit 2: A…
The historical importance of the photoelectric effect is to demonstrate the relevance of the work function Ω. It works like this:
V ~ E_0 - Ω
where hf is the energy per photon and Ω is the work function of the target. If Ω > E_0, no voltage is produced. This provided the basis for Einstein's demonstration that energy is proportional to frequency (E_0 = hf), and won him the Nobel prize.
What does this have to do with xenon? Xenon lamps produce not only visible light, but also ultraviolet light, in fact, xenon lamps extend further into the UV than natural sunlight:
http://en.wikipedia.org/wiki/Xenon_arc_lamp#mediaviewer/File...
LEDs by contrast produce almost no UV light:
http://en.wikipedia.org/wiki/Light-emitting_diode#mediaviewe...
With this data we can determine that the work function of silicon (in the Raspberry Pi 2) is somewhere in the range of hc/(400 nm) http://journals.aps.org/pr/abstract/10.1103/PhysRev.127.150
http://www.sciencedirect.com/science/article/pii/00223697599...
we see that the work function of silicon is around 4.7-4.9 eV, which agrees well with our observations.
draws a little box