Anelok: memory card eject direction

Werner Almesberger werner at
Sun May 18 11:27:45 EDT 2014

The first prototype of Anelok ejected the memory card towards the
upper long side of the device, towards the inside of the sidewall.
To remove the card, one had to open the case. This is intended as
a protection against accidental card ejection.

For the next version, I'm toying with the idea of ejecting the
card into the battery compartment.

Here is what this would look like:

- card fully inserted, battery present:

- card released by holder but not yet pulled out:

- most of the card pulled out:

  I put the card holder on a ~4 mm support so that the card could
  clear the bottom battery contact. That's why the pads of the
  holder look out of alignment.

- as above, but seen from an angle:


- presence of battery adds extra protection against accidental
  ejection, e.g., after a drop that opens the case,

- slows down potential "card snatchers",

- reduces area of case that needs to be opened regularly, thus

  - the rest of the case can be permanently closed, better
    protecting the main circuit, and

  - the battery compartment can get a small door, without the need
    to disassemble large portions of the device.


- more work to change the memory card,

- memory card extraction takes more time (if you're in a hurry),

- battery removal to change memory card increases wear on battery
  connector (*),

- prolonged battery removal may lead to loss of backup power and
  thus of timekeeping (it's okay to lose RAM content).

(*) it seems that it may not be as sturdy as I hoped it would be.
    More about this in the next mail.

Opinions ?

- Werner

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