New on Anelok TV: capacitive sensing
Werner Almesberger
werner at almesberger.net
Tue Apr 29 17:47:23 EDT 2014
To evaluate the possiblity of using a capacitive slider instead of
the mechanical wheel in Anelok, I made a very simple slider and
gave it a try.
Here are some first impressions:
http://downloads.qi-hardware.com/people/werner/anelok/tmp/anelok-cap1.ogg
http://downloads.qi-hardware.com/people/werner/anelok/tmp/anelok-cap1.webm
Design files and the demo application are here:
https://gitorious.org/anelok/ybox/source/touch/
The sensor code is here:
https://gitorious.org/anelok/ybox/source/fw/touch.c
I used the Y-Box for this since the right pins happen to be
conveniently accessible.
The result doesn't look too bad. While the sensor wouldn't be usable
in this form, I'm pleased with the range of values I'm obtaining
(see below) and the overall quality of the signal.
Counts Event
------- --------------------------
< 10500 No finger
10620 Normal touch on the right
10860 Normal touch on the left
> 11050 Strong press on the left
I could probably tune this to even better sensitivity.
The environment also contributes a bit to the measurement. E.g., I
had to raise all the thresholds by about 50 counts when moving the
sensor from table to monitor.
- Werner
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