7i76 spindle control

Hi all,
I have 7i76 and want to control my vfd for the spindle. It seems a bit of a odd unit because it has different contacts for fwd and reverse along with a analog input voltage for speed. Its a altivar18 vfd if that matters.

I have it wired with DIR+ connected to the control contact +ve feed (L0+), and DIR- to the fwd input on the vfd (Li1), and analog voltage control set up. That is working in forwards with speed control/fwd direction from Linuxcnc gui.
It needs either fwd (Li1) OR reverse(Li2) selected to move, if both are activated the vfd wont start, so if I wire DIR up to the reverse contact (Li2) and Ena to Li1, because Enable & Dir is triggered it doesnt spin. I could ignore enable, and use DIR to switch into forward, but then how to select reverse using the 7i76.

So my problem is how to wire/switch direction from fwd to reverse with this vfd, any suggestions?

To head off the why bother with reverse at all, I need reverse because I've kept the mechanical low speed gearbox in my machine's spindle, and in low the spindle rotates the opposite sense even though the vfd is spinning it "forwards". Previously with a parport and spindle control board + linuxcnc I had it set up with a gearbox component that knew from the rpm and a mechanical gear selector contact which way was needed to rotate the vfd to make the spindle spin the right way regardless of speed commanded.

I'll add the altivar instructions diagram to make it clearer hopefully.
Switch wiring


vfd pin functions

The way I read the docs, fwd and reverse need to be connected to seperate 7i76 outputs per this heading
linuxcnc.org/docs/2.8/html/examples/spin...l#_spindle_direction
So then those outputs should trigger separate relays that connect LO+ with Li1 (forward) and Li2 (reverse)
Be sure to add a flyback diode around the relay coil with the diode band pointing toward the 7i76 output
That way direction will be controlled by M3 and M4

centreline wrote: I have it wired with DIR+ connected to the control contact +ve feed (L0+), and DIR- to the fwd input on the vfd (Li1), and analog voltage control set up. That is working in forwards with speed control/fwd direction from Linuxcnc gui.
It needs either fwd (Li1) OR reverse(Li2) selected to move, if both are activated the vfd wont start, so if I wire DIR up to the reverse contact (Li2) and Ena to Li1, because Enable & Dir is triggered it doesnt spin. I could ignore enable, and use DIR to switch into forward, but then how to select reverse using the 7i76.

Why would you do that? Where did you get that wiring idea?
7i76 has a connector for wiring VFD's to it, so read the manual.
I am skipping the wiring for now to give you time to read that and find where the VFD should be wired.

tommylight, I have read the manual, Its how I got the spindle to rotate and speed control to work. But most the threads I can find use a enable wire on the vfd to start, and a dir input wire to swap direction. This vfd doesn't behave like that.
I have the connections from tb4 to the vfd as follows
TB4 VFD
1 Spindle- ---> Com
2 Spindle out --> A/1
3 Spindle +v --> +10
4 NC
5 Ena

---

> ? (as per text, I have no enable and cant use it for reverse)
6 Ena +

---

>? (as per text, I have no enable and cant use it for reverse)
7 Spindle Dir ---> Li1
8 Spindle Dir+ --> LO+

RodW, last time I had a spindle control board and I used a relay on it to swap dir between the fwd and reverse inputs to select direction in that way, Someone suggested there would be a way to do this without a external relay using the native 7i76 connections so that's what I'm trying to figure out.

centreline wrote:
RodW, last time I had a spindle control board and I used a relay on it to swap dir between the fwd and reverse inputs to select direction in that way, Someone suggested there would be a way to do this without a external relay using the native 7i76 connections so that's what I'm trying to figure out.

Oops I got it a bit wrong. I've never used a spindle. The direction signals are on TB4 spindle interface.

Look at the circuit diagram. It shows the fwd and rev have a switch between the input and +24v on the VFD.
The 7i76 outputs are not switches.
I think you need relays!