Index homing Mesa 7i96s

More
07 Jan 2023 23:25 #261216 by routerman22
Hi, im wondering how to add index homing signals to the pncconf so i can do index homing. I cant seem to find the option to add the signal to the right io i put on the mesa 7i96s in pncconf.

I have 4 inputs. Index pulse x,y,y1,z axis. Can see the status. But dont seem to find the actual io option in needs to be to be recognized by pncconf as an index signal. What am i missing? 
if it needs to be a "full on" encoder in the 7i96s config... it only has 1 of those.

thank you,
routerman22

Please Log in or Create an account to join the conversation.

More
08 Jan 2023 00:14 #261219 by PCW
Replied by PCW on topic Index homing Mesa 7i96s
If you mean homing to index in a step/dir system without encoder feedback,
that requires special firmware. What is the source of the index signals?
Are they single ended of differential?
The following user(s) said Thank You: routerman22

Please Log in or Create an account to join the conversation.

More
08 Jan 2023 08:31 #261244 by routerman22
Replied by routerman22 on topic Index homing Mesa 7i96s
Single ended from my delta servo drives. They alo have encoder a/b output, but i dont see the direct benefit of connecting that.

Please Log in or Create an account to join the conversation.

More
08 Jan 2023 16:28 - 08 Jan 2023 16:31 #261274 by PCW
Replied by PCW on topic Index homing Mesa 7i96s
Are they isolated outputs?
Nonisolated single ended outputs from a servo drive are going to be pretty noisy...

Connection options are isolated I/O (stealing from the 7I96S's 11 isolated inputs)
or the expansion connector (but the expansion connector pins are not suitable for
direct connection to external signals with EMI issues like signals from servo drives)

Another possibility: if you are not using the 7I96S's encoder input, is to use it for 3 index inputs.

Yet another possibility is adding a daughtercard (7I85,7I85S,7I89,7I75 etc)
Last edit: 08 Jan 2023 16:31 by PCW.

Please Log in or Create an account to join the conversation.

More
08 Jan 2023 20:37 #261301 by routerman22
Replied by routerman22 on topic Index homing Mesa 7i96s
The ocz (index pulse) is not isolated (open collector). All others pretty much are. I use delta b3 and delta asda-m.

I still have room on the isolated io' on the 7i96s. Challenge i have now is how to let pncconf know it is index signal without adding 3 full encodes so to say (which i cant).

Please Log in or Create an account to join the conversation.

More
08 Jan 2023 20:51 #261303 by PCW
Replied by PCW on topic Index homing Mesa 7i96s
This is not something pncconf will be able to handle, and will required editing the hal file

Please Log in or Create an account to join the conversation.

More
08 Jan 2023 21:55 - 08 Jan 2023 21:57 #261306 by routerman22
Replied by routerman22 on topic Index homing Mesa 7i96s
But it is doable without needing custom fw on the mesa?
editing the hal file is not an issue for me. Other than figuring out what needs to be changed.
Last edit: 08 Jan 2023 21:57 by routerman22.

Please Log in or Create an account to join the conversation.

More
09 Jan 2023 01:09 - 09 Jan 2023 01:09 #261316 by PCW
Replied by PCW on topic Index homing Mesa 7i96s
It needs custom firmware or a specific component that simulates index behaviour
I think there is a thread where this was discussed, searching for stepgen index might find it

The disadvantage of using a component to simulate index behavior is that it
will typically miss index pulses shorter than 1 servo thread in length.

I don't mind making special firmware for this if you can live with the loss of 4 isolated inputs
Last edit: 09 Jan 2023 01:09 by PCW.
The following user(s) said Thank You: routerman22

Please Log in or Create an account to join the conversation.

More
09 Jan 2023 06:34 - 09 Jan 2023 08:01 #261335 by routerman22
Replied by routerman22 on topic Index homing Mesa 7i96s
I have a few friends that also need this. When doing index homing the velocity is very low so i dont think missing the pulse is an issue. That would be amazing!

Out of interest, what makes this method so slow? I assume that the "proper" encoder method responses faster?
Last edit: 09 Jan 2023 08:01 by routerman22.

Please Log in or Create an account to join the conversation.

More
09 Jan 2023 16:06 - 09 Jan 2023 16:17 #261361 by PCW
Replied by PCW on topic Index homing Mesa 7i96s
If you use the stepgen + index firmware, it works identically to homing to index
with an encoder and can detect short index pulses (sub microsecond)

If you use a special component to do this, it will be limited to detecting pulses
longer than 1 servo thread period.

Here is a link to a thread with a users hal component that implements stepgen homing to
index:

forum.linuxcnc.org/24-hal-components/463...der-m19-g33-1#246815
 
Last edit: 09 Jan 2023 16:17 by PCW. Reason: formatting
The following user(s) said Thank You: routerman22

Please Log in or Create an account to join the conversation.

Moderators: cmorley
Time to create page: 0.255 seconds
Powered by Kunena Forum