On Saturday 03 February 2018 00:26:33 jeremy youngs wrote:

> Gene, just expanded to dual par ports, and am eliminating optos from
> my stepper drives with a direct via db25 Bob . My drive is +-10 and I
> do have a Chinese opto'd bob that has a pwm , but it is not
> bi-directional . And I don't really want to put a flip flop relay in
> the output , so I'm still rather trying to solve this puzzle.

I solved that problem 4x now. My first mill, a tiny HF, has a PMDX-106 
interface, the deluxe version with hand controls that can be used if 
LCNC is not running. But of course it can't move without LCNC running. 
But its nice to be able to flip a switch and take over from LCNC if I 
have to. That one is still doing siftware stepping, so it not very fast. 
OTOH it is fast enough to stall the spindle motor even in low gear if I 
have a 1/4" tool in it and take too deep a cut. The PMDX takes logic 
signals for direction, but I used that to control a 10 amp rated 
ice-cube relay.

On the small lathe we call TLM, I built a honking big PSU for a 1 horse 
treadmill motor, and have a Pico PWM-Servo amp in the middle, which has 
a logic level reverse, so thats 3 outputs, enable, pwm, and fwd/rev.  
Works well except for the need to profile the direction change else its 
so sudden it strips the teeth of the lower timeing belt gear since 
theres a 5" chuck to reverse.

I have essentially the same setup for the 1hp spindle motor on the G0704, 
1hp OEM motor, honking big PSU that can bang that 90 volt motor with a 
125 volt surge, except its rotating mass isn't near as high, so even 
with the profiled direction change, it can switch from 1000 fwd to 1000 
in reverse in about 400 milliseconds. If I listen carefully, I can here 
the servo amp go into current limiting at around 16 amps into that 9 amp 

On the sheldon, with 30 to 40 lb chucks to reverse, that profile is 
obviously limited too, by a limit3 and the vfd. That spindle is turning 
much slower when rigid tapping, primarily because theres so much mass to 
reverse, so between the profile of the reversal, and my delaying of that 
reversal to take advantage of the vfd's braking,its still around 4 turns 
of overshoot. On TLM, I time the reverse by watching the encoder for a 
very nearly stopped before I send the actual direction change.

Even then the drive belts yelp now and then on the sheldon. The vfd on it 
is the cheap one, and can only be fully optimized for turn around at one 
speed. Which is many times faster than the default setting.

> I just 
> tried the mesa site

out in CA.
Big Johns site at
in southern MO.

> for that spinx 1 card and it appears the site is 
> down, or my internet here in East bfe Ozarks could be causing issues
> as we are one of only 5 houses on this road out here. I will likely go
> to an fpga board when I get ready to do servos. I am also going to get
> some of those omron encoders as I would like to Ridgid tap with this
> machine eventually
> . I  am nearing completion of a bunch of retrofit upgrades since I
> cabbaged this old knee mill to CNC 5 years ago . It's been a bit of a
> road after some surgeries, a new wife and baby the last year or two
> but I'm finally seeing this thing near fully functional and I want to
> put a fourth axis and lathe spindle on this machine as well. I'm
> trying to get it all together with what I have on hand to get it all
> under cnc control.
> I have been paying attention to your ramblings

ramblings, Chuckle, you "get it" exactly.

> on the old Sheldon and 
> the pi retrofit and find it quite interesting. And have considered
> making a go of the pi on my next machine. But I'm trying to get this
> one to make a few $

I'd not do the pi again, but we need to find a coder who can turn the 
pi's spi driver (rpspi.ko) into one (rpspi.ko) for a rock64, $44 with 4 
gigs of memory, absolutely smokes to pi for real speed.

The pi has an architecture problem that can result in very poor keyboard 
or mouse control.  Throws away input events.

> I also found a couple threads on the forum about rs485 but I haven't
> concluded if that was pwm or serial data and the night is almost long
> so I will dig deeper after the sun comes up.

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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