On Monday 12 February 2018 00:12:21 jeremy youngs wrote:

> It's a brown boveri 2.5 kw servo motor with a 10 v /krpm tachometer.

That will function to tell you how fast its spinning alright, but there 
is no spindle position feedback available from such a device, so its not 
usable to cut threads where synchronous motion is needed.

The omron with its ABZ style pulses, can tell linuxcnc exactly where in 
its rotation it is, updating the info in my case as often as 350,000 
times a second or nearly 15000 times a spindle turn in low gear.

Thats way overkill but sure precise. Had I known the gear ratio between 
between the motor and spindle was as high as it was, I would have bought 
a 250 or 256 line/turn encoder, it would have been plenty. 1000 line was 
overkill, but the .hal file & a couple mux4's, and sum2's took care of 
that rather precisely. In my case I still use the Z (index) from my old 
setup that used opto-interrupters, and the AB quadrature signals come 
from the omron, passing thru a pair of rs485 gismo's, dollar each from 
fleabay to make good TTL level signals then that submitted to the opto 
stripped inputs of the bob. Such a lashup works well with a 5i25 
interface, and would likely work just as well with a 7i90HD if you 
needed the plethora of gpio (72 minus whatever the firmware loaded uses) 
the 7i90 has. I've added lots of "gingerbread" stuff on the bigger 
lathe, and still have around 22 uncommitted i/o's I could use to run a 
coffeepot, the lights, lube pumps, coolant/mist pumps, yadda yadda. I 
already have all the motor power controlled by the  motion enable button 
on linuxcnc, so its all off for the night with a poke at the f2 key. 
Having i/o to throw away? Priceless.

Where the 5i25 is protected from high voltages by the bob, the 7i90 is 
not, its basically its own bob, so figure on using a 7i42TA on each 50 
pin i/o the 7i90 has 3 of for protection against i/o noise that exceeds 
the 7i90's 3.3 volt ratings. The 7i42TA also gives you nice screw 
terminals to hook everything up to. I stacked mine above the 7i90 and 
already had a bunch of old scsi-ii cables that I cut down and 
reassembled for the 2 to 4" 50 pin cables that took.

> I'm running a selema 1224 servo amplifier , at 100 dc . I still have
> some room for more voltage but my transformer cabbaging skills aren't
> as solid as my ability to find drives and motors.

Old but solid state PA amplifiers in the kilowatt of audio range make 
good sources of such critters. And an old ex(now long retired like  me) 
employee has a nose for power toroids that I've taken advantage of on a 
couple occasions. My psu for TLM's spindle is the remains of a Phase 
Linear 750 watter, and I've 4 of a 350 watt toroid stacked in series and 
paralleled for the G0704's 90 volt 1 hp. So I'm banging it with around 
125 DC. Pico Systems PWM-Servo drivers are serving as the controllers 
for both. Just tell Jon you need the spindle motor version as he makes 2 
slightly different versions of it.

> I may well try one 
> of these for an index pulse, thanks for the heads up about low speed
> instability and the positive feedback on the omron. I need to figure
> out how to mount one of them in this contortionist box called mill
> head. Time to turn in , good night

A pix might get some suggestions.

Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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