Re: [CAD_CAM_EDM_DRO] Re: Encoder on spindle question

On 7/28/2011 1:24 AM, KalleP wrote:

>
>
>
> Hi Ron,
>
> Hope the breakout board was the culprit.
>
> If you need an accurate phase you will need to use a 1:1 encoder and
> locked speed as mentioned by Dave for threading.
>
> If the index (or A/B) pulses are a bit narrow you can square them up
> with a divide by 2 circuit (clocked D-type flip flop or the low bit
> on a binary counter) This will make the reading of the pulse
> reliable in software. The parallel port only has one interrupt
> typically implemented on the ACK pin and in the past I have seen
> this implemented as edge and level sensitive and on either edge on
> various boards so I would not rely on that feature too much without
> testing.
>
> Jitter is most likely to be due to low sampling rate.
>
> Unless you have an unlikely analogue A/B output encoder (used by
> specific controllers for interpolation between the steps for special
> applications) then it should have clean digital signals and
> debouncing should not make any difference.
>
> A DMM may also read false frequency on the index signal because of
> the low duty cycle and squaring up this signal should give
> consistent results there too.
>
> Kalle
> --
> Kalle Pihlajasaari
> Johannesburg, South Africa
>

Thanks for the input. I ordered a new breakout board, but it hasn't
arrived, yet.

The Fluke meter reads the encoder rock steady.

I wired up an SB5B and tried that, but it is still jittery. I suspect
either the flakey break out or noise. I am going to try a different 5V
supply and add decoupling caps to see if it makes a difference.

--


Ron Thompson
On the Beautiful Florida Space Coast, right beside the Kennedy Space Center, USA

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