Mesa 5i25 & 7i76 to GE Af-300 VFD?

I'm updating my Boss 5 and have run into trouble getting the 7i76 and the AF-300 interfaced. The speed control via the potentiometer replacement on the 7i76 was straight forward. Getting the enable and direction from the 7i76 to the AF-300 is unclear. I did find a reference to using a SPDT relay and have procured one. If I have properly wire it in has me at a standstill. I think I have but could use a sanity check. Here's the link and excerpt.

forum.linuxcnc.org/39-pncconf/27291-7i76...ate-pins-for-fwd-rev

The pertinent passage from the above link is:
=============================================
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

REPLY
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
=============================================

Do I read this as the ENA+ 24v from field power being the source that is passed to the VFD via the relay's NC and NC contacts?

I just want to be sure I have it right and don't smoke anything when it gets it's first power.

-Mike

I have a feeling that, in your scheme, ENA- should go to CM not GND.

You need two relays, [strike]one relay for forward action and the second relay for reverse.[/strike] one relay for 'enable' second for direction See attached revised diagram to help you wire this part of you project./

Benb wrote: You need two relays, one relay for forward action and the second relay for reverse. See attached diagram to help you wire this part of you project.

I think that his scheme with one relay will work.

His plan seems to be to use the 7i76 "enable" to turn on forward or reverse, and uses the relay to select which terminals the "enable" output is connected to.

However, it is probably worth testing to see what the drive does if both FWD and REV connections are made at the same time. If this results in reverse running, then no relay will be needed.

OK, I've made progress. All the axes move. The TB4 analog output seems to be working M3 S2000 gives me 10.13V and M3 S1000 gives me 5.04V. I still can't get the spindle to turn on.

I have it wired as mentioned above.

Here are the the voltages I'm seeing:
State
Pin Off M3 M4
+A1 28.42 28.17 28.11 Coil Pos
-A2 28.09 27.84 27.81 Coil Neg
11 0.011 0.013 27.44 Relay COM
12 0.014 0.016 27.43 Relay NC
14 0.014 0.016 27.42 Relay NO

Interestingly, the VFD responds with a frequency displayed on it's front panel only with the M4 command. Close, but no cigar.

Any ideas on where to go from here?

-Mike

Before you connect _anything_ to the 7I76 you should verify
that you can control the spindle drive with hard wired inputs or
mechanical switches.