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glass scale reading sample rate problem
#1
Hi !

               I built this project (quadrature version). I use Ditron 11F scales and 0.001mm resolution.
When I move the reading head the everything is ok, but when I move a little bit quicker the MSP can't follow
the moving.  What is the max speed what this controller can follow ?

Thanks!
Andrew
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#2
Anybody use it with 0.001mm glass scale ?
It isn't work correctly.
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#3
I've done quadrature decoding logic in the past and implemented it in hardware in order to maintain accuracy. I don't know how Yuriy implemented it, but maintaining a resolution of 0.001mm means that you have to detect 1000 edge transitions per millimeter of movement. If his implementation is interrupt-driven, I don't think it would take very rapid movement to overwhelm it. The example that I found at TI claims that it can respond to encoder position changes up to 200khz on an MSP430 running at 16Mhz. So a tiny little program that does nothing else would fail if you were moving faster than 200mm per second.

I think that handling high-resolution quadrature requires external logic and counters if you're moving very fast at all. Are you testing it with the scales mounted on your machine? If not, mounting them will slow things down considerably.
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#4
(10-19-2017, 05:41 PM)Briney Eye Wrote: I've done quadrature decoding logic in the past and implemented it in hardware in order to maintain accuracy.  I don't know how Yuriy implemented it, but maintaining a resolution of 0.001mm means that you have to detect 1000 edge transitions per millimeter of movement.  If his implementation is interrupt-driven, I don't think it would take very rapid movement to overwhelm it.  The example that I found at TI claims that it can respond to encoder position changes up to 200khz on an MSP430 running at 16Mhz.  So a tiny little program that does nothing else would fail if you were moving faster than 200mm per second.

I think that handling high-resolution quadrature requires external logic and counters if you're moving very fast at all.  Are you testing it with the scales mounted on your machine?  If not, mounting them will slow things down considerably.

Hi,
Thank You for your answer!
As I see the MSP can't follow the 30-50mm/sec. 
I tested the linear scale in my desk. I think I need a bigger microcontroller or a quadrature encoder chip.
https://www.roboticshardwarestore.com/pr...d-version/
I will read this chip with a PIC and write it for a seven segment display.
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#5
(10-20-2017, 05:06 PM)bundyland Wrote: Hi,
Thank You for your answer!
As I see the MSP can't follow the 30-50mm/sec. 
I tested the linear scale in my desk. I think I need a bigger microcontroller or a quadrature encoder chip.
https://www.roboticshardwarestore.com/pr...d-version/
I will read this chip with a PIC and write it for a seven segment display.

Hand cranking furiously, I would be hard-pressed to achieve more than 10mm/sec on my mill, so it still might work.  Power feed's another matter.
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#6
(10-20-2017, 05:31 PM)Briney Eye Wrote:
(10-20-2017, 05:06 PM)bundyland Wrote: Hi,
Thank You for your answer!
As I see the MSP can't follow the 30-50mm/sec. 
I tested the linear scale in my desk. I think I need a bigger microcontroller or a quadrature encoder chip.
https://www.roboticshardwarestore.com/pr...d-version/
I will read this chip with a PIC and write it for a seven segment display.

Hand cranking furiously, I would be hard-pressed to achieve more than 10mm/sec on my mill, so it still might work.  Power feed's another matter.
Maybe You are right! First I will try it on machine and if it will fail I will choose the external counter/encoder version.
I would like to use on a manual lathe (EU400)
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