Return to “Why is the PI2 camera-shy ?”

by PiGraham
Mon Feb 09, 2015 10:25 am
Forum: Troubleshooting
Topic: Why is the PI2 camera-shy ?
Replies: 162
Views: 292364

Re: Why is the PI2 camera-shy ?

OringinalGeek wrote:It's been a long time since my field theory classes, but I believe the problem isn't photons. Most digital designers forget about EMI problems. We use "standard" Solutions to solve EMI. One poster talked about his experience with Xenon flashes & how they're triggered. This is the real culprit I suspect. The fast rise time that triggers a multi spectrum signal ( think Fourier Transform). The Raspberry Pi 2 shown is a bare board so it's probably quite susceptible to EMI. Shielding it from light won't help (as the bluetac experiment failure showed). Notice also too that there seems be some distance sensitivity as well. The interference path isn't via conduction through power cord or rails, it's through radiation, not magic photons. I suspect if you used some kind of (grounded) shielding it would make the problem go away. Longer term, the right capacitance on the right signal lines might be the solution.
The bluetac experiment showed the opposite, that blocking the light cured the problem. Of course the bluetac has to be on the right chip.
by OringinalGeek
Mon Feb 09, 2015 6:57 am
Forum: Troubleshooting
Topic: Why is the PI2 camera-shy ?
Replies: 162
Views: 292364

Re: Why is the PI2 camera-shy ?

It's been a long time since my field theory classes, but I believe the problem isn't photons. Most digital designers forget about EMI problems. We use "standard" Solutions to solve EMI. One poster talked about his experience with Xenon flashes & how they're triggered. This is the real culprit I suspect. The fast rise time that triggers a multi spectrum signal ( think Fourier Transform). The Raspberry Pi 2 shown is a bare board so it's probably quite susceptible to EMI. Shielding it from light won't help (as the bluetac experiment failure showed). Notice also too that there seems be some distance sensitivity as well. The interference path isn't via conduction through power cord or rails, it's through radiation, not magic photons. I suspect if you used some kind of (grounded) shielding it would make the problem go away. Longer term, the right capacitance on the right signal lines might be the solution.
by DougieLawson
Sun Feb 08, 2015 1:29 pm
Forum: Troubleshooting
Topic: Why is the PI2 camera-shy ?
Replies: 162
Views: 292364

Re: Why is the PI2 camera-shy ?

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.
by STrRedWolf
Sun Feb 08, 2015 1:25 pm
Forum: Troubleshooting
Topic: Why is the PI2 camera-shy ?
Replies: 162
Views: 292364

Re: Why is the PI2 camera-shy ?

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.
by mikerr
Sat Feb 07, 2015 9:14 pm
Forum: Troubleshooting
Topic: Why is the PI2 camera-shy ?
Replies: 162
Views: 292364

Re: Why is the PI2 camera-shy ?

Yes, bit of bluetac on that chip and it survives the flash:
Image

Looking at the board under strong light, both U8 and U16 are much more reflective than other chips,
but as you say covering U16 fixes the issue.

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