I posted this on another thread, but it has merrit here about Pixie drives:
I have been getting more into the controls now that the machine is running well. The Pixie cards can all be wired together so that when one faults, they all fault. I decided to wire them this way for safety. For instance if the Z axis faulted when it was supposed to retract, the X or Y axis could crash the tool. The Pixies can also be wired so that when you reset one, they all reset. I did that as well. I mounted a lighted switch on the control panel so that when a drive faulted, the switch would light up. Pressing the switch would reset the drives. I needed some way of having the Pixie light up the switch. I found the solution at
http://www.cncbuildingblocks.com They have a 8 relay board that will take a TTL signal and control a relay. In addition to the Pixie being able to fault each other, any of the fault signals can also supply a TTL signal at the same time. The relay board arrived yesterday and I wired it up like the manual said and it worked the first time. My lighted switch had a 120V light so that is why I needed the relay.
After playing around with it, I found that I had another problem. If the servo drives are enabled and the Pixie’s are faulted, the motors will creep. I thought about it over night and when I woke up this morning I had the answer. If the Pixie TTL output could drive a second relay, I could use that to tie into my EPO circuit which disables the servo drives. It also has the added benefit of shutting down the VFD that is driving the spindle.
After work tonight I wired in another relay to the Pixie fault output and tied that relay through the EPO wiring. It all worked. Now if a Pixie faults, it shuts down the spindle, servo drives and lights up the switch.
Vince