Newbie from the UK need a little assistance

Gr8funTargets wrote:

For reference, should anyone else have a similar issue the board known as ZP5A-INT has not got the +5v supply to the drivers.
I've attached an external supply, 1A for the short term while I'm building that will be replaced with a 3A for "proper" use.:

I have very similar drives.

Note that the fact that common is +5V means that the driver see a "step" command when the parallel port pin is low, and a "space" when it is high.
This is because the input is an opto-isolator and works on current flow rather than signal voltage.

+5 to +step and +5 from p-port to -step = no voltage difference, no current flow, logical 0.
+5 +5 to +step and 0 from p-port to -step = 5V voltage difference, current flow from +5, through the opto and into the p-port, logical 1.

It took me a while to get my head round this when I first started. But actually parallel ports are much better at sinking current than sourcing it. They can typically source 3mA and sink 15mA.

The parallel port almost certainly can't source enough current to drive all three "enable" inputs. It might be able to sink enough current, but you can also consider wiring them all in series, so the current flows from +5 into +enable, out of -enable, into +enable, out of -enable ... and then into the parallel port pin to earth/gnd.

When working with opto-isolated inputs it is helpful to think in terms of current flow as that it what lights the LEDs in the optocouplers.
This also applies to optical switches and led indicators.

Gr8funTargets wrote:

Are you saying there is a way to get this going with out the external power supply?

No, I was trying to explain why you need the 5V supply.
I was actually meaning to say that you might find you get better results with the step signals inverted in the config (0 for step) but got distracted by explaining why that was the case and never actually got round to mentioning it.