Thank You, Andy and Charles!

2012/11/14 Peter C. Wallace <[email protected]>:
>
> if these are indeed 1000 CPR (250 line) thats correct, but if they are 1000
> line encoders (4000 counts per rev) max count frequency would be 200 KHz
>

I do not get this one. The way I understand this is: each line on
encoder is one count for the counter in each line - A or B. And only
after both lines has been counted, together then they provide a chance
to decode it to get 4x resolution of each separate line. Or am I wrong
on this one?

Anyway, I will have 5i23 card in that machine, so encoder counter will
have max rate of 33 MHz. Even with a default digital filter and 15
times slower actual counting rate, it is 2 MHz. Even 200 kHz is only
10% of that, so filter constant could be increased at least two times.

I do no know, what exactly is there on motors - I am still in process
of setting up the control cabinet and assembling the mechanics, so
wiring has not been started, so I cannot attach motor, turn it by hand
and observe, how much pulses are reported. Those are MotionKing
brushless DC servos (size 60 metric flange, almost Nema 23 size), it
is indicated everywhere that there are 1000 counts per revolution. I
would not be surprised if those actually were 1000 PPR (250 CPR)
encoders - I already have had similar surprises from chinese
suppliers...
I just hope that 250 CPR would not be too small number to tune PID
loop - motors are attached to 16:1 planetary reducers, so the actual
resolution should be fine.


> All hostmot2 encoder counters have digital filters on all inputs (A,B,Z). The
> pass frequency of these filters can be set from MHz down to Hz Unfortunately
> there is not a convenient HAL parameter to set the filter time so it must be
> done using the raw-write facility.

Where can I find out, how does the raw-write facility work?

-- 
Viesturs

If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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