Re: Switch encoder problems

Mike wrote:

On Thu, 30 Mar 2006 08:47:55 -0800, Tim Wescott <tim@xxxxxxxxxxxxxxxx>
wrote:


Spehro Pefhany wrote:

On Wed, 29 Mar 2006 20:05:51 -0800, the renowned Tim Wescott
<tim@xxxxxxxxxxxxxxxx> wrote:



Mike wrote:


On Wed, 29 Mar 2006 17:01:57 -0800, Tim Wescott <tim@xxxxxxxxxxxxxxxx>
wrote:

<snip>

Without knowing what the encoder _does_ when it stops between detents I can't say. Where you will have problems is if the encoder sits there vacillating between two values -- should that happen, and should you be using the simple and obvious rule for loading your synthesizer, your tuning will be jumping up and down continuously.


and that all probably depends on exactly where it stops.

Yup. I'd check to see if it's just the one encoder in the batch that does it, or if the other's do to.

OTOH, you can probably learn pretty quickly to make sure the thing drops into a detent before you let go -- after a while it'll become automatic, and you'll be surprised when your significant other can't operate your radio.


The ones we use have one output guaranteed at the detent (A guaranteed
'off'), but the other (B) can be in either state (or can go back and
forth). Ignoring that, there are (ideally) four edges per detent.


Best regards, Spehro Pefhany

That's interesting. The one that I used has one transition per detent -- i.e. each 'click' is 00, 01, 11, etc.


This particular encoder at rest on the detent has both switches open.
When the shaft is rotated to the next detent both switches will close
then open again. That would be a leading and trailing edge for each
switch, so I suppose that would be four edges per detent.

I hooked up a digital scope to the 2 switches and there isn't all that
much bouncing of the edges. It's hard for me to explain, but what is
happening is that when the shaft stops the detent doesn't hold it good
and tight and it's very easy to get a partial rotation out of the
detent position then rocks back to rest. resulting in another switch
transfer. That is when it doesn't go far enough to just stay between
detents with the switches closed. I need to treat them as if they have
no detent and can be in any position at rest.

If that is the case then use the algorithm that I suggested but divide and round the result. I.e. take the state, add two (to avoid the transition on 0 0), then ignore the bottom two bits. This should give you something that will only switch when you're right between detents.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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Relevant Pages

  • Re: Switch encoder problems
    ... Where you will have problems is if the encoder sits there vacillating between two values -- should that happen, and should you be using the simple and obvious rule for loading your synthesizer, your tuning will be jumping up and down continuously. ... OTOH, you can probably learn pretty quickly to make sure the thing drops into a detent before you let go -- after a while it'll become automatic, and you'll be surprised when your significant other can't operate your radio. ... Wescott Design Services ...
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