Help picking mesa board redcaps/bldc component

Hi Andy,

Great to see you show up in this thread. The retrofit is a VMC with redcap motors and your BLDC component is key to the project. No doubt I will have some questions for you as things progress.

Mesa boards are fantastic and their ability to expand is almost limitless. Unfortunately, the selection of mesa boards is pretty overwhelming. I need a "Mesa for Dummies" book !! I have done a few retrofits with 5i25/7i77 combo's but that my entire experience with mesa boards. The 7i64 might well be a good solution from what I see.

The good news is that things are a bit easier than it first appeared. The redcap motors are only 2000 rpm models,(5S A06B-0314-B002#7000 ) used in a direct drive config to the ballscrews propelling the machine to 780 ipm spec'd rapids. So, for initial testing, at reduced speeds (50% ?) the strain on the servo thread isn't as bad as first thought. The plan is for me to bench test/run a single motor getting it running and positioning under BLDC as a first step.

The redcaps present the challenge part of the retrofit, after that is conquered its just a pretty routine mill retrofit.

Your input is greatly appreciated.

George

The 7I90 and 7I69 use 50 pin flat cables (AIO cables in our store) and are suitable for 5V I/O only
You can use a 7I42TA to get protected 5V I/O and screw terminals or a 7I37TA to get isolated 3-24V I/O
I do not suggest a 7I64 as its the slowest of our sserial devices and not good above about 2 KHz

You can also use the 7I69 or 7I90HD with 24 Module I/O module racks from Opto22 and Grayhill

Ok, lets assume I get 7i90hd and 3 pcs of 7i37TA. Is the 7i90hd hosted by the rs422 port on my 7i77?

Is there software out there to operate these boards under linuxcnc? I did some searching and found threads were a few were working on getting the 7i90hd working under linuxcnc. I wouldn't want to buy the boards and later find I have a unsupported combination for linuxcnc.

A rough outline the hal code to configure this 7i77/7i90/7i37 combination would be very helpful, so I can study this ahead.

Thanks,
George

gmouer wrote:

Ok, lets assume I get 7i90hd and 3 pcs of 7i37TA. Is the 7i90hd hosted by the rs422 port on my 7i77?

Yes

Is there software out there to operate these boards under linuxcnc? I did some searching and found threads were a few were working on getting the 7i90hd working under linuxcnc. I wouldn't want to buy the boards and later find I have a unsupported combination for linuxcnc.

A 7I90HD with the correct firmware (sserial remote) is a working sserial device, there are no unsupported sserial cards
This is because there is not any specific card knowledge of generic sserial devices in linuxcnc so
any sserial remote card will work even ones never seen by the driver writer.

A rough outline the hal code to configure this 7i77/7i90/7i37 combination would be very helpful, so I can study this ahead.

Thanks,
George

Heres a list of the 7I90HD pins when used as a sserial remote



Note that the hm2_hostcard part will be hm2_5i25 in your case and the sserial port number will be 2 instead of 1 (since the 7I77s expansion port is port 2)
(this is easily sorted by running halcmd show pin)

Thanks Pete ! that makes things clearer. The pin list gives me a idea of how the 7i90 I/O is connected in Hal (syntax wise).

I am not saying I am clear enough to write a hal file yet but clear enough for now.

Thanks much !

George

andypugh wrote:

PCW wrote:

gmouer wrote:

Is the 7i90hd hosted by the rs422 port on my 7i77?

Yes
A 7I90HD with the correct firmware (sserial remote) is a working sserial device, there are no unsupported sserial cards

I wasn't aware that this was possible, but I am wondering if it has any advantage over a direct-connected 7i90HD configured as a Hostmot2 host?

The possible Mesa card topologies just got even more complicated.

(Ponder.... 5i25 -> 7i77-> 7i90HD(remote) -> 3x7i44 -> 24x7i90HD -> 72x7i44 -> 576x7i90HD == 41,472 TTL lines

Sounds like a mighty fine setup, Pete awaits your credit card number. While he get the order packed up, you can write the HAL file in your spare time.

andypugh wrote:

PCW wrote:

Also if linuxcnc does the commutation you want the servo thread to
run at least 20 times as fast as the commutation waveform. This means
at least 5 KHz for a 8 pole Fanuc motor at 3000 RPM.

Is there a good argument for running bldc + hm2_read + hm2_write in a 5kHz thread, and the PID and other HAL stuff in a 1kHz thread?

I realize the question is intended for Pete but it prompted a question from me. I was not aware that more than one servo thread could be used, can you explain that a bit? All the HAL's I have seen (used) had a single base and servo thread.

Confused as usual
George