Wiring diagram (including opto-coupling) for Xylotex

[Richster]

I thought I'd post this schematic of how my electronics is wired up, proving it IS possible without a breakout board I'm no electronics expert, but this is one of the few circuits I have built which actually works properly!

I have a fairly typical homemade 3-axis machine, with the following features:

• opto-coupling of all inputs/outputs
• X home/-limit & +limit
• Y home/-limit & +limit
• Z home/-limit only
• relay control of mains router
• e-stop coupled to router relay and signal to Mach 3
• enable/disable switches on all axes
• enable/manual switch on router

I haven't illustrated the servos, but these are wired direct to the board as intended. Although the connections are indicated for a xylotex board, this is only in terms of the enable/disable switches and everything else should be fairly generic. For the 12V supply, you could use a dedicated PSU, or as I did, use a voltage regulator to reduce the 24V from the Xylotex PSU for the stepper motors. Another option could be to use a 24V relay instead of 12V, adjusting all components appropriately, so it could be connected direct to the Xylotex PSU. Based on this - the 0v connection to the enable/disable switches on this diagram is shared with the same PSU which powers the steppers, therefore is equivalent to the 0v on the Xylotex controller.

schematic:


control panel:


The router control switch is actually of center-off type, so has three positions (PC control/off/on) Couldn't find a symbol for this in the library, but you get the idea...

Please pay particular attention to PSU and PC connections. I really hope everything is in order here - if you end up cooking something, I didn't mean it Obviously you're dealing both with the delicacies of your parallel port, and mains voltages, so care is needed with both.

I hope you guys find this useful it's info I struggled to find when starting out

[Al_The_Man]

Incidentally, is the PSU 12v referenced to ground?
Al.

[Richster]

Not sure on that one Al - what are the implications, and how would I check? Forgive my rudimentary understanding of things here! I remember you mentioning that when I was having fun with my shielded cable, but this design seemed to get around that. I have my de-bounce set to zero now in Mach 3, and have never had a 'bad trip', as it were

[Al_The_Man]

The reason I asked is that if you have a desk/tower PC the PC P.S. is most likely grounded through chassis screws through the MB.
If your 12v PSU is truly isolated then you may not notice anything untoward.
Laptops are of course, usually isolated.
Although I have never used Mach or any parallel port system, I have used PC based systems, and I subscribe to the other method of, as Siemens calls it, uni-potential bonding, which is bonding all power supplies and everything metallic on the machine to a common ground reference.
I have seen problems posted here of so called 'debounce' of limit switches and have never seen a real description of what is actually happening?
I believe it is a caused by the attempt of complete isolation, where in fact the isolation is not actually in effect, if I were to use Mach I would use my present method of common ground, which has served me well.
With the power off, you could do a resistance test to ground of the PSU common just to confirm.
Al.

[Richster]

Just checked between COM and GND power connections on the PSU with an ohm-meter. Didn't get anything here.