A computer with actual strobe-induced epilepsy. Looks like the singularity is closer than we thought.
A Xenon flash will cause the Raspberry Pi 2 to freeze
51–60 of 135 posts
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#52Oh 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…
Are you sure that's not induced current from the power spike required to operate the flash or the spark-gap inside the xenon tube? You've got the gear set up... would you mind terribly repeating the experiment but blocking the light with cardboard or something?
If I understand correctly the Speedlite is battery powered, so as such shouldn't cause any voltage spike on mains.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#53Earlier quoted context omitted.
Are you sure that's not induced current from the power spike required to operate the flash or the spark-gap inside the xenon tube? You've got the gear set up... would you mind terribly repeating the experiment but blocking the light with cardboard or something?
If I understand correctly the Speedlite is battery powered, so as such shouldn't cause any voltage spike on mains.
It's not a mains spike, but an EM discharge caused by the rapid voltage and current changes in the flash, that the parent comment is considering (IIUC).
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#54Oh 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…
Are you sure that's not induced current from the power spike required to operate the flash or the spark-gap inside the xenon tube? You've got the gear set up... would you mind terribly repeating the experiment but blocking the light with cardboard or something?
The most recent post [1] seems to indicate that covering one of the chips with blu-tac prevents the freeze
[1] http://www.raspberrypi.org/forums/viewtopic.php?f=28&t=99042...
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#55Earlier quoted context omitted.
If I understand correctly the Speedlite is battery powered, so as such shouldn't cause any voltage spike on mains.
It's not a mains spike, but an EM discharge caused by the rapid voltage and current changes in the flash, that the parent comment is considering (IIUC).
Yes thankyou. This is what I'm getting at. The momentary power flow in a xenon flash is very large. A great big capacitor charges up and then discharges very rapidly to create the bright flash of light. There is also a high voltage exciter coil that fires to kick the xenon tube into conduction at the beginning of the flash cycle. Both of these could be very disruptive to nearby digital electronics.
I thought the original poster would be in a very good spot to help us determine if the effect if photoelectric or the result of EM because he's got everything set up. All he has to do is repeat the experiment while blocking the light from hitting the Pi.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#56Oh 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…
I want to see this with a bare regulator. I might have some time Monday.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#57Earlier quoted context omitted.
It's not a mains spike, but an EM discharge caused by the rapid voltage and current changes in the flash, that the parent comment is considering (IIUC).
Yes thankyou. This is what I'm getting at. The momentary power flow in a xenon flash is very large. A great big capacitor charges up and then discharges very rapidly to create the bright flash of light. There is also a high voltage exciter coil that fires to kick the xenon tube into conduction at the beginning of the flash cycle. Both of these could be very disruptive to nearby digital electronics. I thought the orig…
I'll put it in a box and try in a little bit, sorry have to do a few things first. I'm 99% sure it's light dependent though, I had to aim the flash at the board and keep it somewhat close to get it to lock up (like 6" away or so).
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#58One of the standard tests to gain an EMC Compliance Certificate is a spark discharge test.
Any experienced engineer will have a Spark Generator (Car Ignition coil, spark gap and short Dipole) to test to see if his latest project misbehaves when confronted with Impulse Interference.
As an EMC Investigator I would always carry a spark generator to demonstrate to newby engineers why EMC Compliance is so important.
I've seen a spark from 50ft away crash or reset a microprocessor system. Just the static discharge from walking on carpet is often enough.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#59Oh 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…
My money is still on an electromagnetically coupled pulse onto either the 3.3V or ground rail.
I have seen that happen plenty of times, but I have never seen a light flash disrupt a power rail like that.
I'm not saying it couldn't happen, just playing the odds...
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#60A 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…
On the original thread, official Pi engineers have diagnosed this as light interference on a specific unshielded circuit. Just wanted you to know.