I've seen recent articles on the Raspberry Pi 2 being affected by a light source (http://www.raspberrypi.org/forums/viewtopic.php?f=28&t=99042) . Apparently the cause is in the power regulation circuit of the Pi.

Does the Pi B+ have the same problem, or is the circuit sufficiently different that it does not have the affected component?

  • First I've heard of this. I have not seen it mentioned on the raspberrypi.org forums. Have you a source?
    – joan
    Feb 8, 2015 at 22:52
  • @joan: raspberrypi.org/forums/viewtopic.php?f=28&t=99042 . I will add it to the question
    – John Smith
    Feb 8, 2015 at 22:54
  • 3
    I didn't read that thread as I thought it was a joke (because of the title). I have just skimmed through. My PI 2 locked up when I took a flash photo. A B+ was unaffected.
    – joan
    Feb 8, 2015 at 23:05
  • Wow. Guess that got skipped in QC. I've noticed a B and a B+ that would often reset an I2C device the moment something was unplugged on the same (household) circuit.
    – goldilocks
    Feb 8, 2015 at 23:10
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    All semiconductors are light sensitive. (I discovered this the hard way - more than 50 years ago when I scraped the paint off my 1st transistor - in those days transistors were in little glass tubes). The encapsulation keeps light away, but surface mount components are not designed to be exposed to the environment.
    – Milliways
    Feb 8, 2015 at 23:59

2 Answers 2


According to the Raspberry Pi Foundation, the problem lies with component U16 in the power supply. This is not a component used on previous models.

The explanation is given here.

This also explains that the problem is a photoelectric effect caused by specific long light wavelengths, particularly Xenon camera flash guns. So other light sources have no effect.


I wouldn't consider this authoritative but the following article suggests it is "light" sensitive and not EMF as I had originally thought. Previous models are not affected.


  • 1
    but why are previous models not affected? Component types? Circuit changes?
    – John Smith
    Feb 10, 2015 at 23:25

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