8i20 with 7i77/7i74 combo

You can do it, but the motor needs to shake / move to find an index first.

andypugh wrote:

You can do it, but the motor needs to shake / move to find an index first.

I have not confirmed this, but i believe that is exactly what those Yaskawa drives do when i turn on the machine power, otherwise how would it know that regenerative braking is not functioning? Just to be clear, drives have a regenerative braking resistor AND a braking resistor, so two separate resistors. As the electronic and the main power switch are behind the machine, i could not see that actually happening, but now i have a reason to check that. Will report back.
If that is the case, how would one go about implementing that for 8i20 ?

tommylight wrote:

how would it know that regenerative braking is not functioning?
...
If that is the case, how would one go about implementing that for 8i20 ?

You probably can't. The 8i20 is quite a dumb drive, and LinuxCNC is too far down the chain from the motors to do anything clever like infer braking resistor state from the back-emf.

You will get an overvolt cut out, if the braking resistor fails, though.

Andy, i meant the original drives probably do that ,will go check later today if they actually move when powering on the machine.
Jon, the encoders are wired to the drives and from there to 7i77 encoder inputs, at 7i77 they are normal A B and index pulses, for sure. To check the output from encoders i will have to dissmantle a 50 pin connector and provide 5V. Might as well check that also when i get there.
Regards and thank you,
Tom

Jon, you are correct, thank you for explaining that.
I did check today and i can not notice the motors moving on power on, as 1 or 2 counts on a 5000 PPR encoder translates to no visible movement. Oh cra..
The second drive is failing quickly as i got twice that A03 error inside of 5 minutes.
Oh cra..
Bevins, i did notice on half a schematic i got for those drives that encoders have A, B, and C outputs, not A, B and indez or Z as normal incremental encoders do, so that magic happens in the drives, as Jon explained it. It looks like i will have to change the encoders, i do have 6 of the 2500 PPR variety, but i would rather change the motors also, less mechanical work, me thinks! Also less fidling vith electronics, a bit of research is in order........tomorrow !
The spindle drive turned on today and worked for some 30 seconds and stopped again. Old stuff......
Question : regarding hal sensors, does it have to be only one, or 3 for each winding one? What about placement? They must be at a certain place inside the motor? Will read about that too while i am at it.
Any tips on a decent motor/drive combo for 1KW?
Working with 7i77 is a must as i prefer having the loop closed in Linuxcnc.
Also any tips on a VFD for over 7.5 KW ?
Thank you all.