DirkS
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 1:05 pm

Fght wrote:does this means i better cancel my PI2 order and order an older model?
i'm not even sure what do you mean by taking a picture of the pi2.
It means using the flash of a camera from a short distance *could* cause a freeze.
I wouldn't be too worried about it, especially if the Pi is in a case.

supersat
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 1:16 pm

artag wrote:I think it's an On Semiconductor NCP6343
Unfortunately there doesn't seem to be a public datasheet for this part, but the overview confirms that it comes in a Chip Scale Package. I must admit that I didn't know what CSPs were before today, but they basically seem like bare dies in minimal packaging. Intel has a nice illustration on page 3 of this document, and it's known that CSPs are susceptible to light due to the photoelectric effect (which is more commonly exploited by photodiodes and image sensors).

If there isn't a non-CSP version of this part, then about the only way it can be fixed (short of changing it out for a completely different part) is to put a glob of epoxy over it. I'm not sure whether it's a big enough deal to go through the trouble of doing this, but the fact that you can get the power output to spike above 5v might be somewhat worrisome.

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STrRedWolf
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 1:25 pm

So for the laymen:
  • Don't photograph your Pi 2 with a Xenon flash (just turn it off and shine a regular light on it)
  • Put it in an opaque case, or cover the affected areas with electrical tape (don't use Scotch, masking, duct, or Duck-brand tape)
I really can't see how bluetac would be safe for operation of the Pi though.

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DougieLawson
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 1:29 pm

STrRedWolf wrote:I really can't see how bluetac would be safe for operation of the Pi though.
I've been using BluTack on my camera board for months. It's an insulator so perfect for holding PCBs in place. I also use it when soldering header pins into breakout boards.

If I wanted a permanent version of BluTack I'd use Sugru.

If I could find a light source that triggers my RPI2 I'd be testing whether a dob of my wife's nail varnish would fix it.
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Fght
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 1:57 pm

DirkS wrote:
Fght wrote:does this means i better cancel my PI2 order and order an older model?
i'm not even sure what do you mean by taking a picture of the pi2.
It means using the flash of a camera from a short distance *could* cause a freeze.
I wouldn't be too worried about it, especially if the Pi is in a case.
how does the pi2 can detect light? or maybe it's what's called electric field created by the light?
i'm a bit confused as you can see about how could it be possible


EJH
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 2:19 pm

If U16 is indeed ON Semiconductor NCP6343, then U16 is a wafer-level chip scale package (http://en.wikipedia.org/wiki/Chip-scale_package).

On a WLCSP, the circuit, that may be sensitive to strong light, is located on the side of the chip that faces the green pcb of the Pi2. So it might be sufficient to only shield light from the side of this chip, so that light cannot get in between the pcb and the bottom-side of U16.

If this theory is right, shielding could be done by deposing a (more or less) opaque glue around the sides of U16, the amount may be so small that it's hardly visible. You may test the theory by just putting a bit of blu-tac on the sides of U16.

simpex
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 2:31 pm

It should be also checked if Raspberry Pi 2 is sensitive to the light emitted by an energy saving lamp ( in a professional way like here: http://www.raspberrypi.org/forums/viewt ... 02#p688202 ):

Image
http://en.wikipedia.org/wiki/Fluorescent_lamp
Last edited by simpex on Sun Feb 08, 2015 3:30 pm, edited 2 times in total.

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FTrevorGowen
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 3:01 pm

simpex wrote: ...
Does Raspberry Pi 2 crashes, freeze or turns off in bright Sun? From what I have read till now a Xenon Flash or Laser Pointer induces glitches causing the board to malfunction. Normally the strong light of the Sun should do the same and possible generate a continuous voltage on that 3.3 V line, not just a short lived sinusoidal signal that quickly attenuates in time.
...
Many, many years ago, as a young post-graduate I assisted a colleague working with a pulsed-200kV coaxial Xenon flashlamp**. That device had a sub-nano second current rise-time (cf. the >1uS risetimes of typical, photographic flash-guns of the period) and I suspect that this may be "part of the problem". Such flashlamps, IIRC, also have a higher "colour temperature" than the sun (ie. are "bluer").
Trev.
** O.T. anecdote - one day, when I wasn't there, he tried connecting a 5kV rated capacitor between the "earth end" of the tube and a point ~0.5m away on the metal sheets forming the "ground plane" on the bench top. When he fired up the marx-bank that generated the 200kV pulse said capacitor "exploded into dust" ie. too much voltage developed across it as the pulse (edge) propagated.
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B+, P3B, B+, A+ and a B2) but Buster on the P4B's. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

simpex
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 3:07 pm

This is the spectrum of a Xenon Lamp:
Image
Source: http://zeiss-campus.magnet.fsu.edu/arti ... onarc.html
As you see, the spectrum has a lot of peaks in the infrared domain. They may cause the glitches to Raspberry Pi 2.
However, it should be mentioned that "xenon lamps produce broadband, almost continuous emission having a color temperature approximating sunlight in the visible wavelengths (often referred to as white light)", so it could be the visible light the one that causes the development board to malfunction and in this case the bright Sun should also have a negative effect over Raspberry Pi 2.

It should be also verified whether the board is sensitive just to short duration bright lights or it behaves strangely also under continuous strong illumination.

silly_sad
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 3:17 pm

Dear topic starter, i love your question, and i know the exact answer.
ALL p-n junctions are photo sensitive to some degree.
And not all of them are optically shielded in practice.
Most likely your particular problem originates from a glass cased diode -- many low-current diodes have glass casings (it is actually a mainstream casing of them).
I bet on a zener somewhere in the on-board power regulator. (light should cause a breakdown, therefore dramatically drop the voltage over the zener, that causes voltage regulator to drop its output by a significant factor.

It was a shame, however, on the side of topic followers to build up 3 pages of nonsense.

simpex
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 3:35 pm

silly_sad wrote:I bet on a zener somewhere in the on-board power regulator. (light should cause a breakdown, therefore dramatically drop the voltage over the zener, that causes voltage regulator to drop its output by a significant factor.
It was a shame, however, on the side of topic followers to build up 3 pages of nonsense.
And then how do you explain this:
"Another ... measurement, with the board totally unplugged and powered down you get a big spike on the 3.3V line from the flash:"
See post: http://www.raspberrypi.org/forums/viewt ... 02#p688202

DrakoTrogdor
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 3:53 pm

Would using a Sharpie marker on the component work? How about an Etching pen?

jdb
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 5:07 pm

After a bit of mod cleanup...

Please keep this thread on-topic.

Posts that are unconstructive or off-topic will be deleted, or split off into separate threads.
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jdb
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 5:14 pm

simpex wrote:
silly_sad wrote:I bet on a zener somewhere in the on-board power regulator. (light should cause a breakdown, therefore dramatically drop the voltage over the zener, that causes voltage regulator to drop its output by a significant factor.
It was a shame, however, on the side of topic followers to build up 3 pages of nonsense.
And then how do you explain this:
"Another ... measurement, with the board totally unplugged and powered down you get a big spike on the 3.3V line from the flash:"
See post: http://www.raspberrypi.org/forums/viewt ... 02#p688202
The flash lamp will also produce a very large electric field spike with principal frequencies in the RF range. This will couple into scope leads/ground loops and produce a voltage bounce even when the Pi is switched off. The only way to measure this properly is to use a differential probe on the PSU line.

Sunlight (or at least the paltry excuse we have in the UK in wintertime) doesn't seem to affect operation of the board.
Rockets are loud.
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 5:19 pm

Fght wrote:
how does the pi2 can detect light? or maybe it's what's called electric field created by the light?
i'm a bit confused as you can see about how could it be possible
https://en.wikipedia.org/wiki/Photoelectric_effect

Silicon that doesn't have a IR/visible opacity layer will be affected by incident photons that have enough energy to dislodge electrons from the semiconductor lattice. For III-V doped silicon, this is about 1.1eV - so infra-red photons can manage it.

WLCSP packages are basically chunks of silicon with BGA balls on the bottom - so-called "wafer level" packages. These packages are popular in mobile applications as weight- and space-saving has a high priority.
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PeterO
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 5:26 pm

silly_sad wrote:Dear topic starter,
That'll be me then
i love your question, and i know the exact answer.
And then you go to show you havn't bothered to read the rest of the thread where the problem has clearly been identified and discussed at length.
Please read all previous replies in a thread before making another post in a thread on these forums.

PeterO
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poing
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 5:37 pm

PeterO wrote:Discoverer of the PI2 XENON DEATH FLASH !
I'd opt for 'XFOD' (Xenon Flash Of Death) as in 'BSOD' (Blue Screen Of Death) with Windows.

That said, I use my Pies in a photo studio filled with professional (xenon) strobes. I have no Pi2 so I cannot test anything, but I do know a bit about 'flashing'. What seems relevant to the question at hand is that it needs a serious amount of flash light to equal the illumination provided by the sun. Therefore it surprises me that 'a flash from a point and shoot' would trigger the problem while regular sunlight would not, despite the time of year and 'England'.

Conundrum1859
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 5:54 pm

Noticed that some calculators notably the Aurora el cheapo ones have this "feature".

I've seen this chip design used on a lot of phones so it would be interesting to see how many of these are similarly affected.

artag
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 6:23 pm

I'm surprised that a 1mW laser pointer can upset it, but not a bright LED lamp.

technos
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 6:28 pm

supersat wrote:
artag wrote:I think it's an On Semiconductor NCP6343
Unfortunately there doesn't seem to be a public datasheet for this part, but the overview confirms that it comes in a Chip Scale Package.
If you look carefully at On Semiconducto's datasheet on the case http://www.onsemi.com/pub_link/Collateral/567GB.PDF, it indicates that the part (U16) is going to be inscribed with date/lot codes - which the light sensitive parts do not have. I *really* have a hard time seeing how On Semiconductor would sell such a light sensitive part. While you can go through the various possibilities of how such a part can end up on the board, it tends to point to one of two things imho. A bad part made without it's 'case', or a counterfeit part possibly bought on price through a bad supply chain.

Tracking this down certainly would be educational.

desertengineer
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 6:36 pm

OK, so one ting I've learned working in the EMI/EMC world - nothing is ever the obvious.

Xenon flash bulbs and electronics are VERY noisy for both radiated electric and magnetic fields. A DC-DC converter charges a rather large electrolytic capacitor to a large voltage (usually like 200-300 volts DC). Most simple models use a current-driven chopper circuit feeding a step-up transformer that is rectified and applied to the capacitor. An SCR is used to trigger the discharge though the bulb. The entire charge (or most of it) is dumped through the xenon gas within a millisecond or so. It is essentially a nice EMP generator. Wherever you have current pulses, there will be a magnetic field radiating from the loop. I predict you were taking close-up pictures, right?

The most plausible explanation is that the processor is being 'upset' by EM pulse coupled onto something in the board. The board contains lots of little antennas that, given the right conditions, will couple a pulse into the wrong place. Components on the board are usually totally sealed, so light will have little or no effect. Diodes, MAYBE, but these guys are usually tested for this in the design phase. You would need A LOT of light.

To me, the litmus test for this would be to try a MIL-STD-461 RS105 (or EIC 61000-4-4) test on your configuration. Knowing there exists susceptabilty, you would start low and increase the intensity until something happens (Called 'threshold').

Were these boards tested for fast transient?

jdb
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 6:38 pm

desertengineer wrote:OK, so one ting I've learned working in the EMI/EMC world - nothing is ever the obvious.

Xenon flash bulbs and electronics are VERY noisy for both radiated electric and magnetic fields. A DC-DC converter charges a rather large electrolytic capacitor to a large voltage (usually like 200-300 volts DC). Most simple models use a current-driven chopper circuit feeding a step-up transformer that is rectified and applied to the capacitor. An SCR is used to trigger the discharge though the bulb. The entire charge (or most of it) is dumped through the xenon gas within a millisecond or so. It is essentially a nice EMP generator. Wherever you have current pulses, there will be a magnetic field radiating from the loop. I predict you were taking close-up pictures, right?

The most plausible explanation is that the processor is being 'upset' by EM pulse coupled onto something in the board. The board contains lots of little antennas that, given the right conditions, will couple a pulse into the wrong place. Components on the board are usually totally sealed, so light will have little or no effect. Diodes, MAYBE, but these guys are usually tested for this in the design phase. You would need A LOT of light.

To me, the litmus test for this would be to try a MIL-STD-461 RS105 (or EIC 61000-4-4) test on your configuration. Knowing there exists susceptabilty, you would start low and increase the intensity until something happens (Called 'threshold').

Were these boards tested for fast transient?
Correct regarding the EMI effects, but I suggest you read the thread. The precise cause has been identified.
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PeterO
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 6:42 pm

desertengineer wrote: The most plausible explanation is that the processor is being 'upset' by EM pulse coupled onto something in the board.
Please, read the previous posts on this thread. Laser light also causes the fault, and there's no EMP from a laser ! Optical shielding will prevent the problem.

PeterO
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Re: Why is the PI2 camera-shy ?

Sun Feb 08, 2015 6:43 pm

technos wrote: If you look carefully at On Semiconducto's datasheet on the case http://www.onsemi.com/pub_link/Collateral/567GB.PDF, it indicates that the part (U16) is going to be inscribed with date/lot codes - which the light sensitive parts do not have.
Don't they ? Mine has the legends

6343
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