EEVblog #299 – Retro Phone Camera Teardown

Teardown Tuesday.
A look at the systems engineering inside one of the worlds first mobile phone flash camera attachment, the Siemens S55.

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  1. Skanhex seems to be a Taiwanese contract designer/manufacturer for cameras and media players:

  2. The chip on the bottom is the memory.

    The one with the copper tape is the flash chip. The copper tape on it is because the xenon tube is immediately above it so it’s either to protect the chip against high voltages jumping to ground via the firmware (or corrupting the firmware) and/or shielding.

    The “inductor” that Dave ripped off is not an inductor, but a transformer used to kick off the flash (I believe it’s called the gate or trigger electrode). In a xenon flash, the two end terminals are charged to high voltage, but to kick off the reaction requires ionizing the xenon atoms so the tube can conduct. To do this, a small capacitor holds a high voltage that’s then passed through the transformer to transform it to even higher voltage to ionize the atoms. It’s capacitively coupled to the tube via a band on the outside. Once ionized, the xenon conducts, where the big capacitor discharges to give the brilliant light. But the gate/trigger electrode needs a higher voltage still (for a brief time) to kickstart it. That little transformer there is all that’s needed. It just needs a brief enough pulse to ionize a few Xenon atoms to get them to conduct.

    You can see the red wire from the cap to the xenon tube, there’s also another one from the tube to ground, and the white is the trigger (that Dave ripped off).

    • Jep, as Worf explained, the ignition pulse for the flash tube is coupled through the glass of the flash. Because the capacitance formed by the outer metalisation on the tube, the glass and the inside of the tube is very low you need a pretty high voltage (typ. 4 to 20kV) with a reasonably sharp rise to actually couple it trough to the inside.
      For sure you don’t want to see this HV spike in your memory chip.
      (If it manges to “jump” trough 1mm of glass and get the gas ionized… what would it do with 1.5mm of plasic and some millions of memory cells as “second electrode” 🙂

  3. Thanks for the Teardown, Dave! I actually owned a S55 with the camera attachment and took it apart too… It was nearly useless, the resolution was only 640×480, the memory in the phone below one megabyte, and when you used the flash, the battery of the phone got drained after 5 pictures. Well, it was one of the first “camera-phones”.
    The camera version you have there is for the M55, hence the angled design, the one for the S55 is more rounded.

  4. Hi Dave!
    Not really relevant to this particular blog but I just had to say that since you’ve been working at full time you’ve done an amazing job (not that you weren’t before). The volume of quality content you’ve put out lately is AWESOME!
    I work at a CM here in Canada and LOVE your blog. Helps keep me interested in my day to day work. I hope you never go away.

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