MESA 7i76e Modification - Encoders

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08 Jun 2020 10:58 #170621 by Tesremos
Okay, First post, I've been working on a Plasmac machine, XYZ+A.

I have a 7i76e, with a THCAD.

on my A axis i have a lot of un-avoidable (due to budget) play in the motor coupling to the gearbox input shaft.

I'm hoping to close the loop with an encoder on the output shaft of the gearbox,

the problem, even using the modified PL firmware for the 7i76e, it gives access to 3 single ended "A" encoders,


but, i need to one singe ended for the THCAD, and one quadrature encoder AB for the Axis, in theory i'd be using IDX for the THCAD, and A+B+ for the closed loop A axis.

i've looked into briefly into modifying or creating my own "bit" file for the mesa card, but that seemed a lot like a new degree i wasn't quite ready to sign up for.


is there a simpler way? can i use one of the GPIO pints as an encoder input? due to it being on the output shaft of the A axis, it wont be spinning more then 1-3rpm and with a 1000ppr encoder , that only brings a pulse rate of approx 60hz.


any input is appreciated. thank you for reading.

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08 Jun 2020 14:03 #170643 by PCW
Yes, at 60 hz, (an 1 KHz servo thread) you can use the software encoder,
a little confusing, but you could use the encoder channels 0 and 1 input-a pins:

net a_axis_enca hm2_7i76e.0.encoder.00.input-a encoder.0.phase-A
net a_axis_encb hm2_7i76e.0.encoder.01.input-a encoder.0.phase-B


To feed the software encoder component
These have the advantage over the associated GPIO pins
in that they already have some digital filtering.
The following user(s) said Thank You: Tesremos

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09 Jun 2020 09:48 #170794 by Tesremos
Thank you,

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09 Jun 2020 10:13 #170797 by bbsr_5a
it is always better to go for a SAFE fixed hardware
why not Timinbelt 4/1 it is 25USD and you are safe on that with steppers

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