Anelok: exploring the deep end

Werner Almesberger werner at
Tue May 19 22:16:46 UTC 2015

Ron K. Jeffries wrote:
> My sense is you are close to a decision that CR2032 will not support anelok
> operation for a long enough period of elapsed calendar time.

The main problem I found with CR2032 is that it can't support the peak
current Anelok needs, especially when using memory cards. So yes, my
plan is to eventually switch to AAA.

Here is the updated hardware evolution diagram:

I also changed the MCU from KL26 to KL26 + KL16, as discussed before

> Have you considered a case mod that would allow say 2xAAA batteries?

Actually, I just tried to see what it may look like. One AAA should
be plenty. Here is an early design study:

The device would be held as shown: the thick end with the battery
at the bottom, the thinner end up. USB and rfkill would be on the
right side, the antenna on the left side. The slider is also on the
right side, above the main PCB.

This hypothetical case would have a footprint of about 50 x 40 mm and
a height between 9 and 14 mm. So the volume would be roughly 23 ccm,
12% more than the current case with 67 x 34 x 9 mm = 20.5 ccm.

The main PCB in this design would be only about 45 x 24 = 1080 mm^2,
i.e., almost 20% smaller than the existing PCB with 42 x 31 = 1302 mm^2.
Such a small PCB probably means the end of in-my-kitchen DIY.

There are still numerous unresolved issues:

- what would the battery contacts look like and how would they connect
  to the PCB ?
- how is the battery accessed and would that still allow the memory
  card to eject into the battery compartment ?
- is there enough clearance for the antenna to perform properly ?
- is the area for the slider large enough ? (As shown, it's a bit
  smaller than in the current design.)
- will left-handed users find the device usable in this shape ?
- is there enough room for all the support structures and such ?
- how to actually make this case ?
and so on.

- Werner

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