On Tuesday 18 August 2009, Peter C. Wallace wrote:
>On Tue, 18 Aug 2009, Steve Blackmore wrote:
>> Date: Tue, 18 Aug 2009 22:16:48 +0100
>> From: Steve Blackmore <st...@pilotltd.net>
>> To: Peter C. Wallace <p...@mesanet.com>,
>> EMC2-Users-List <emc-users@lists.sourceforge.net>
>> Subject: Re: [Emc-users] Realistic spindle encoder count for parallel
>> port?
>>
>> On Mon, 17 Aug 2009 16:54:54 -0700 (PDT), you wrote:
>>> If I get a free bit of time I'll cobble together a quadrature divider,
>>> basically:
>>>
>>> 1. Input digital filter
>>> 2. Quadrature decoder (quadrature to up/down)
>>> 3. Up down modulo N counter (for divide by N)
>>> 4. 2 bit up/down counter
>>> 5. 2 bit binary --> quadrature encoder
>>> 6. Optional index stretcher
>>>
>>> I even think we have some CPLD bds we never used that I can send over
>>> for shipping cost.
>>
>> That's very kind of you Peter, I'd appreciate that very much. From
>> experiments looks like the index stretcher is a must ;)
>>
>> I'm not happy with the Chinese 1024 pulse encoder, but I've also got an
>> unused Stegmann DG60L 500 pulse per rev encoder I'm going to test.
>> Looking at the docs that too only outputs a single quadrature count
>> index pulse, but it's much better quality and I'm hoping the signals out
>> from it are cleaner.
>>
>> Steve Blackmore
>> --
>
>I'll have some time at the end of the week and Ill put something together.
>
>I'll also try and make the long index synchronous with the divided
> Quadrature this will require the total encoder counts to be evenly
> divisable by the divide ratio. If I fail at that I'll just use a digital
> one-shot
>
I can see potential problems with that too. Related to direction of
rotation. Suggestion: latch it on its rising edge, which if the encoder is
properly timed should give one whole output count time to read it, then let
the trailing edge of the ports read strobe reset it so you only get it once
even at creep speeds.
Is that practical?
>Peter Wallace
>Mesa Electronics
>
>(\__/)
>(='.'=) This is Bunny. Copy and paste bunny into your
>(")_(") signature to help him gain world domination.
>
>
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