7i76 spindle control

I'm probably wrong about no Enable on the vfd on reflection, If removing the +24 -> LO+ jumper on the vfd itself disables the drive, I'll test, and if so I can enable the motion with the 7i76's ena outputs, and have a external relay driven by 7i76 DIR output to switch between forward and reverse with a single output.

centreline wrote: 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+

That is how it should be. Above you had Dir + and Dir- so that was wrong in many levels.
On your last post you are on the right track as that could work.

centreline wrote: .... and have a external relay driven by 7i76 DIR output to switch between forward and reverse with a single output.

I don't think you can use a single relay. M3 turns on the dir+ direction. M4 turns on the dir- direction. These two signals are managed by linuxcnc and will never be enabled at the same time. eg an M4 will cancel any active M3 and vice versa.

But they will not cancel "enable", so his method should still work by making the default forward and when the relay is triggered to go in reverse, so the relay would be active only on M4.

@rodw I'm not sure that is the case, as last time I used the mycnc board for spindle control, and I checked it now &it has two relays, one for enable and one for direction on it and four wires off to the parport, gnd, step, enable and dir.
I pulled my old hal file and in the gearchange component it reverses by changing the dir pin state and these are the only lines relating to rotation direction. ;-

net spindle-cw <= stepgen.4.dir => parport.1.pin-17-out
net spindle-cw => parport.1.pin-17-out

I could be wrong though, I thought last time that my drivers enable pin was held high in use and that turned out to be wrong. If I add the relay I'll just be back to how I had it before minus the enable relay and board to supply analog voltages and I can port the old config to new pin names.

Typically when a 7I76 is used with drives that have only FWD/REV inputs
(and cannot be reprogrammed for DIR/ENA), you can use a single SPDT relay
to steer the enable signal to FWD or REV depending on the state of DIR

So:

+24V --> RELAY_COIL+
RELAY_COIL- --> DIR+
DIR- --> GND

ENA+ --> RELAY_COM
ENA- --> GND

RELAY_NC --> FOR
RELAY_NO --> REV

This assumes the VFD inputs are active low.
The relay needs a flyback diode.