[CNC Bill]

Hi, I am trying to figure out how best to connect my Parker E-AC and VS31 stepper motors to Mach3? They have Step+ Step- and Dir+ Dir- connections.
The installation directions show 243 ohm res and 2 diodes, and this would make the connection to the parallel port or breakout board. Am I correct on this?

As these drives are optically isolated, what would be a good choice for a Breakout Board? No Vfd at this time, but maybe later.

Thank You, Bill

Parker pdf: http://www.parkermotion.com/manuals/...Inst_Rev_A.pdf Page 22

[CNC Bill]

After looking up more info, i'm thinking that Step- and Dir- equals ground. I hope i'm right, lol.:withstupi

[Torchhead]

You could elect to drive them on several ways: Tie both - inputs to PC Ground (com) and drive the Opto's with positive pulses (MACH Active low on STEP outputs set to POS (red X)). Option 2 is to tie both + to +5 source and drive the individual - for each one using a negaive pulse.

It's hard to tell, but I don't think you need to add the external components they show in the pinout (243 ohm resistor and protection diode). Those are parts (including the HCLP2631 opto) that are inside the drive, and based on the specs, all you need is logic level signals. It's common for the engineer to show you what the input looks like so you can know what type of signals are needed. I would take that as "here is what our inputs look like".

If you use the 243 ohm value (as the inside value) you will see that with a 5V logic signal you will get about 14ma of diode current. Conversely you will need that much current out of your Step & Dir signals and most parallel ports won't source that reliably. With a good BOB you get the buffering to drive opto input drivers.

The other signals (Fault and Reset) are optional. Neither is required to make the drive work.


Your choice of a BOB solution should include the handling of inputs (isolated) and the option for VFD (spindle Speed) control without a lot of rework on your part.

TOm Caudle
www.CandCNC.com

[CNC Bill]

Thanks for your responce Torchead.

After posting, I re-read the directions and noticed that you are correct, in that those are internal connections.

So what you are explaining is: Single-ended vs Differential Inputs, correct? As I understand it, Differential gets rid of elec noise. Is there a preformance difference? And do the two squigly arrow electrical symbols mean Optically isolated?

I did get it to work by grounding Step- and Dir- using pin 19 and 20. Or could I ground to a single ground pin when I mount my drives?

I am trying to be a little more cautious as I have already burn't up a HobbyCNC board, lol.

Again,Thank You for your time.
Bill Thurston

[Torchhead]

True differential would mean that there is no common ground (balanced line). It's done that way (choice of inputs) so you can just pick how you want to source or sink the opto currrent. Since the PC side has a logic ground and the step & dir signals come from there, the common ground is the PC side. You can elect to run the power (DC motor) side on a different ground system (and keep the local ground noise off the logic side) by using the opto isolators on the drives. Opto's do two things. they break galvanic conduction (no common ground) and they require a lot more current to push through a signal, making them more noise immune that raw TTL inputs. You can trigger a logic input with as little as 3.0V and less than 1ma of current. You can get that from a local ground loop connection or high current wires too close in parallel with logic inputs.

If you ground everything together then you can count on noise issues.

We use a "floating common" return (aka ground) on our inputs using a separate power supply to drive the opto inputs. It's to isolate the input signals from the nasty ground from the PWM high current to the motors (and on the motor neg side). Since a lot of our stuff goes into plasma applications the noise issue grows exponentially. through in HF start plasma and it adds another quantum jump!

TOM caudle
www.CandCNC.com
Totally Modular CNC Electronics