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Anelok: power-only fixture (1/3)

Werner Almesberger werner at almesberger.net
Mon Apr 10 03:16:03 UTC 2017


I'm having fun with fixtures these days. This one is a variant of the
programming fixture I've shown last week:

http://downloads.qi-hardware.com/people/werner/anelok/tmp/mk3-quick/quick-pwr-top.jpg
http://downloads.qi-hardware.com/people/werner/anelok/tmp/mk3-quick/quick-pwr-bottom.jpg

It only has pins for battery and USB power. By omitting all the
other contacts, most of the "floor" of the fixture can be left
open, giving access to the circuit there:

http://downloads.qi-hardware.com/people/werner/anelok/tmp/mk3-quick/quick-pwr-loaded.jpg

I used this to measure the performance of the boost converter. The
power supply circuit has changed considerably since the CR2032 days,
in part because we now have to operate with a much lower battery
voltage (and thus higher current), and also to avoid power drops
when handing over between USB and battery [1].

The results of the first round of testing will be in my next post.

The above picture also shows a new addition to the fixture: so far it
consisted of the frame that holds the PCB and that contains the holes
for the pogo pins, and a stand that goes below it, providing
clearance from the table and holding the connector.

There is now a third element: a clamp that snaps onto the frame and
presses down on the circuit:

http://downloads.qi-hardware.com/people/werner/anelok/tmp/mk3-quick/quick-clamp.jpg

It's admittedly not the prettiest piece of engineering but it does
the job so far. And if it breaks, it's easy to print a new one :-)

The design of the power-only fixture is here:
https://gitlab.com/anelok/mexp/blob/master/quick/quick-pwr.slvs

It also has its own design for the base, which adjusts size and
placement of the opening for the connector:
https://gitlab.com/anelok/mexp/blob/master/quick/quick-pwr-base.slvs

And this is the design for the clamp:
https://gitlab.com/anelok/mexp/blob/master/quick/quick-clamp.slvs

- Werner

[1] Section "The USB plug - a hidden killer" in
    http://lists.en.qi-hardware.com/pipermail/discussion/2015-April/010843.html



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