[sdiy] Selecting a rotary encoder, transistions per detent?

Spiros Makris spirosmakris92 at gmail.com
Fri Feb 7 14:00:39 CET 2020

I am putting together a teensy application that uses rotary encoders. I
picked up two different ones from my local shops, but they seem to have a
different output waveform scheme.
One is an EC11e15204a3 alps (according to the guy selling it) and on each
detent, the outputs switch between high and low. So, 00->11->00 and each
transition from 00 to 11 and vice versa happens when you hit a detent.
The other is a bourns by the looks of it, and works differently: When
resting, it defaults to 00. When turned, it briefly becomes 1, then returns
to 00.
(obviously, the turn direction is detected during the transitions).
The second type detects two increments instead of one, as a result.
Where in the datasheet is this specified? Both are sold as "2 channel
quadrature outputs" but the detection code is slightly different (unless
I'm missing something?). Is there code that can work with both? I am using
polling and shift registers and don't need any significant accuracy- the
delay so far feels great.
Is there a cheaper alternative to the 5pin arrangement of the EC11? It
seems that those without switches only have 3 pins- they will be going on a
prefboard and the extra support would be welcome (I'm not compelled to
drill 64 holes for the side supports :P ).

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