7i76 w/ GE AF-300 VFD - separate pins for FWD/REV?

Hi, I'm finally making progress on my Emco 120P lathe retrofit, having assembled the control boards and computer finally. I'm running 2.5.3 on 10.04 (a vanilla configuration, nothing oddball). PnCConf has generated a bare-bones profile that lets me jog the axis motors, telling me that the 5i25 and 7i76 are at least hooked up correctly.

I'm currently tackling the spindle control. I have a GE AF-300 E11 VFD (manual: dealerselectric.com/images/products/surplus/E11%20manual.pdf - connection diagram on page 23). It is a fairly flexible little unit, by the looks of it, but I'm uncertain how to fully connect it to the 7i76.

Spindle speed control is straightforward, and is hooked up and working when using the test axis feature in PnCConf, though I need to hit the START and STOP button on the VFD manually:

SPINDLE- to VFD 11 (common)
SPINDLE OUT to VFD 12 (pot input)
SPINDLE+ to VFD 13 (10V supply)

My problem is the enable and dir pins...

The VFD gives us:

CM - Digital input common
FWD - Forward command (24V sourcing)
REV - Reverse command (24V sourcing)
There is no explicit enable or start pin (that I could identify).

The operational mode is described in the manual as:
- Forward operation with FWD-CM connected and deceleration to stop when opened.
- Reverse operation with REV-CM connected and deceleration to stop when opened.
- No operation if both FWD-CM and REV-CM are connected.

How does this apply to the 7i76 pins (ENA-, ENA+, DIR-, DIR+)? Do I have to repurpose them as a FWD-, FWD+, REV-, REV+, and write something different in the HAL configuration (I have not yet dug into manual hal configurations, though clearly I will have to soon). Or am I just missing an obvious hookup option here?

Thanks-Sam

Unfortunately the 7I76 spindle interface only supports ENA/DIR type control inputs.
Many drives have this option but it appears that your drive does not.

It may be the the easiest way to control the VFD with minimum added hardware
would be to add a SPDT relay driven by the direction signal:

ENA- ---> GND
ENA+ ---> RELAY COM
RELAY NO ---> FWD
RELAY NC ---> REV

RELAY COIL+ ---> +24V
RELAY COIL- ---> DIR+
DIR- ---> GND

Thanks, that makes sense. Adding an additional relay is no big deal - I was getting afraid that I would have to make some more dramatic changes to the control scheme than that!

Appreciate the quick response too - so far, despite my inexperience with LinuxCNC I'm having a positive enough experience with the MESA cards that I'm already planning to retrofit my router as well (currently on Mach3, Smoothstepper and G540).

The other option is to use GPIO pins for fwd and reverse.
You can select the spindle control signals in pncconf

Chris M

Yes its hardwired into the enable/isolation logic

I had thought about using GPIO, but I was a bit nervous about straying off the path so early (I'm still just barely learning my way around). Fortunately my local electronics surplus store was having a sale when I dropped in - $10 for a canvas bag that you could fill with as much stuff as you could fit in it. Got some very nice 24VDC din-rail mount relays, 24VDC fans, a bunch of mounting hardware, and more, probably an easy $60 worth in my little bag.

Relay wired up in a few minutes as suggested, and I've now got spindle control as expected. I did have to manually jump into the HAL configuration and add the "absolute value" hack from another thread in order to get CCW working, but hey, it spins both ways, and the scaling seems accurate (I get logical speed increments as I click the + button).

Now I'm hung up on my encoder settings. It has pins for 100ppr, index, +5V and GND, which are connected to ENC A+, IDX+, +5 and GND. I can read on my manual scope the pulses, and I can see the counts in the HAL meter on the .count pin, but motion.spindle-speed-out shows an oddly low number. I think I just need to look at some good example configurations to see what I'm missing and better understand ENCODER_SCALE.

As a more general question, is there any benefit to me switching over to the master (~2.6) branch? It seems like there is a lot of active development going on with these cards and lathe GUIs. This isn't a production machine, and while I obviously want it to work, it's not like my business is relying on it.

Well, I suppose there isn't anything I NEED yet... Just the irrational desire to be on the cutting edge.

I'll keep plugging along with my HAL configuration. I noticed the warning that if you modify your .hal file then reenter PnCConf (to modify the configuration) it will overwrite your changes. Is there any way to put changes or additional HAL material in another file that won't get overwritten? Or once you step down the manual changes direction are you forever on your own? Should my strategy be to make a very full-featured PnCConf configuration with everything I can think of turned on (even stuff I haven't wired up yet) and then start down the manual path? Or does it make sense to just stay manual like a real LCNC master and leave PnCConf behind?