Fanuc Serial Pulse Coders - Red cap servos, mesa 7i76e, how to?

Back from holidays, finally got to dig a little deeper with the oscilloscope. I managed to figure out the polarity of the connections and alas, I am now receiving the response from the encoder!

Some values are showing up on my HAL Show and now I need to figure out if everything is working correctly and whether or not I need to create a custom setup string.

After a slight turn (a few degrees) of the motor shaft in the reverse direction my HAL show reads:

 

Suggestions for next steps are encouraged.

What is the counts per turn value for the encoder?

I have not found any formal documentation on the encoders or any note in the machine’s schematics, so I don’t know.

You did say in a previous response that you thought my encoders are 1M units per revolution, in response to a post where I provided the model number.

Tomorrow I will do more testing - I will try to verify one complete rotation and see how the counts check out.

I'm under the impression that the encoders are 1 million counts per rev. I did a crude test where I rotated the pully associated with the motor one full turn as marked by a sharpie line on the face of the pulley. Seemed to deliver around 2 million raw counts, and the pulley appears like it could be 1:2 ratio. 



I also observed 4 cycles of the commutation output from the HAL Fanuc Encoder pin for one rotation (if I remember correctly!). 

These computer-side details can be adjusted as I setup the system. Now I need to figure out what extra hardware I need to talk to 4 of these at once, and also how to output either commutation to the Allen-Bradley Ultra-3000 drives or incremental encoder signals. I'm fully out of inputs and outputs on my 7i76e used on the machine so I will need to get some expansion hardware. 

Expansion needs: 
-4x serial ports (maybe just 3 if I can also use the one in the 7i76e, but Mesa seems to sell them in breakout boards of 4 or 6). 
-8 or more outputs to communicate encoder or commutation information to the Ultra3000 (still figuring out what the drives will need) 

Wondering what the most cost effective Mesa solution would be to add onto my system. 

Or maybe someone knows if there is there setup that does not require sending encoder or commutation information to the Ultra3000s. Can't seem to find whether or not these drives can be run 'open-loop' or/ with feedback only being taken care of on the LCNC side (doubtful?). 
 

Is it possible to run all these things together: 

Mesa 7i76 E  ---- 7I84 (Isolated remote field I/O card). Will use it to output quadrature signals to the Ultra3000s, it will generate this quadrature output from the Fanuc encoders [is this possible?], remaining I/O used elsewhere. 
                               
                         ---- 7I85 (4 Channel encoder 5 channel Serial RS-422 interface). Will hook up the 4 Fanuc redcaps to 4 of these RS-422 ports. And the encoder inputs are good to have around incase I want to add linear scales (2 axis) and maybe two MPG wheels. 

Sure would be great if this system worked because it happens to be two fairly inexpensive boards. Canadian dollar isn't so great right now 
I would be pleased to have those encoder inlets, too. 

Progress pic from a little while ago: 
 

Thanks for confirming this, I haven't used multiple Mesa boards at once before. What a great system.

I have received the additional Mesa boards and am putting some thought into the system and wiring.

I was thinking that I would use the encoder signals to generate commutation signals to output to the Ultra3000 drives. The drives have inputs for Commutation Channel S1, Commutation Channel S2, Commutation Channel S3. 

The question I have is: do I need to worry about torque ripple if I am providing the drives with only commutation pulses in this manner? If so, should I be outputting something else from LinuxCNC to the drives such as quadrature encoder pulses generated from the encoder signals? 

Trying to avoid getting this all wired up and then having to change it. 

My other option would be to output TTL incremental encoder pulses from LinuxCNC (is this conversion from absolute serial encoder data to TTL incremental possible?) out via the 7i84 into the Allen-Bradley Ultra3000s.. I'm starting to think that this is more of a failsafe path because its unclear if the drives will run motors on commutation signals alone. Here's a look at the manual pages regarding [standard] feedback into the Ultra3000s.  

 


Thoughts and speculations welcomed and encouraged.