Minimum timing between encoder pulse edges for acorn?

[DannyB]

The ACORN can take an extremely high encoder frequency. However, there may be filtering added in the future to reduce the frequency to 1 - 5MHz. To maintain future compatibility, it would be best to consider the maximum frequency 1MHz.
The best bet is to follow tblough's advice. Frequencies should be kept as low as possible for best noise immunity and lowest emission. The multiple choices are probably made available so that slower slew rate drivers can be used where higher frequency is not required.

It could also be a 100khz input with really fast pulses and a lot of idle time.

(that's why they define it in edge separation time for something like this - the spindle may not be moving at max velocity, but the pulse separation will still be the same whether it's going 1rpm or 10000rpm)

This is incorrect. Quadrature frequency or edge separation is a function of encoder speed. If your A or B channel is not 50% duty cycle at fixed speed, the encoder is bad.
Here is a quick overview of quadrature encoder signals:
https://www.dynapar.com/technology/enco ... e_encoder/

Thanks.
I'm not sure what you think is incorrect - that page, and what you just said, is what i just said (or thought i said).

The pulse length does not depend on the current RPM of your spindle, only on the encoder speed, you just get more or less pulses in the same time interval as the thing moves faster or slower.

https://3l4sbp4ao2771ln0f54chhvm-wpengi ... terval.gif

In any case, doesn't matter (just trying to become less ignorant!), it looks like i should go with the 1us versions

[ScotY]

Sorry, Danny, hate to butt in on your thread. I am just very interested in finding these different type of encoders and hope I can, at some point, figure out how to incorporate one.

[DannyB]

Oh no, it's perfectly fine.

It took me a while to find some of these types and how to incorporate them, so i get it!
I actually got turned onto this brand by a spindle manufacturer (cncdepot) who uses them on their spindles.

It may be worth starting a thread about encoder types to use on spindles, etc, so that people realize there are more than just shaft based rotary encoders out there.

[eng199]

The ACORN can take an extremely high encoder frequency. However, there may be filtering added in the future to reduce the frequency to 1 - 5MHz. To maintain future compatibility, it would be best to consider the maximum frequency 1MHz.
The best bet is to follow tblough's advice. Frequencies should be kept as low as possible for best noise immunity and lowest emission. The multiple choices are probably made available so that slower slew rate drivers can be used where higher frequency is not required.

It could also be a 100khz input with really fast pulses and a lot of idle time.

(that's why they define it in edge separation time for something like this - the spindle may not be moving at max velocity, but the pulse separation will still be the same whether it's going 1rpm or 10000rpm)

This is incorrect. Quadrature frequency or edge separation is a function of encoder speed. If your A or B channel is not 50% duty cycle at fixed speed, the encoder is bad.
Here is a quick overview of quadrature encoder signals:
https://www.dynapar.com/technology/enco ... e_encoder/

Thanks.
I'm not sure what you think is incorrect - that page, and what you just said, is what i just said (or thought i said).

The pulse length does not depend on the current RPM of your spindle, only on the encoder speed, you just get more or less pulses in the same time interval as the thing moves faster or slower.

https://3l4sbp4ao2771ln0f54chhvm-wpengi ... terval.gif

In any case, doesn't matter (just trying to become less ignorant!), it looks like i should go with the 1us versions

"pulse separation will still be the same whether it's going 1rpm or 10000rpm" is incorrect.
The image you linked is not a quadrature encoder waveform, and is not like the one in the article:
https://www.dynapar.com/hs-fs/hubfs/upl ... rature.jpg
The quadrature format does not have fixed width pulses as you claim.

"The pulse length does not depend on the current RPM of your spindle, only on the encoder speed" - For ACORN, the only encoder input is for the spindle and the encoder must be a 1:1 ratio to the spindle. In the context of the ACORN forum, encoder RPM is spindle RPM.

[DannyB]

Interesting, good to know, thanks for taking the time! (really do appreciate it)

FWIW, that picture is not from the article, yes, but it does claim to be a picture of a single channel of a quadrature encoder stream.
It was in fact, taken from a manufacturer's quadrature encoder documentation that says "Quadrature pulse widths are of fixed time duration, whereas the width of a square wave ON state is a function of speed". Now i just know not to buy their encoders

I did later look at the TI quadrature encoder chip docs (since i usually find their docs informative), and they do spell out pretty clearly that they are not fixed width.
¯\_(ツ)_/¯
Live and learn.