Forward Step / Backward Step - Vexta Question

You actually have:
Which is a bit odd, but ought to work (the second "setp" for each parameter should over-write the first).

Out of interest, how does your base-period (in the INI) compare to the step length you are seeing there?

If I am reading things right that is a 22uS step, which is probably the shortest step that can be made with your base period.

I think the question is why the rise-time is so slow. Do your drives have an option to use sinking inputs? Most parports have rather more drive capacity sinking current than sourcing it.

Good catch! I didn't even notice the extras : |

Yes, the rise is may be out of driver spec. I thought my board had schmitt triggers on it. I'd guess not on outputs. The supplied parallel cable is only 3 feet long. The scope reading was made directly to the terminals. That rise time in itself could be trouble.

About the driver inputs....
So these were custom drivers made by Vexta. I've been playing with them for a year or so, for various things. I've tested several drivers and motors. I've not been able to get them to sleep, but they otherwise run very reliably. All the motors, drivers, and axis work fine, driven from an Arduino, one at a time, during the construction of my machine.

I've been driving them from an Arduino. (which has really nice square wave edges, up until the point when the processor just can't switch the ports any faster. Without a terminating resistor, there's a little ringing, but the edges look otherwise nice.)
I had been been really running them non-inverted and varying the high side of the pulse length, thereby inverting them.

I've been doing some experimentation in LinuxCNC.

I just got done doing a test, inverting the parallel port signals and shortening the times, but it still doesn't work.
Looking at the scope, the high is inverted as I changed it to be, but pulse was only 1.45v high inverted.

I am going to clean up those duplicates and do one more test. Then I need a break.
Thanks for all the help.

I have heard good things about the Vexta 5-phase steppers and drives.

Some of those interface boards for the parallel port need a power supply. Some (apparently) need two. I assume that it has those?

If the drives have opto-isolated inputs, and you can get to both sides, then I would suggest a 5V supply pulled-down through the opto by the parport driving the drive directly. (bypass the interface board).

It seems like the problem here might be the parallel port or the interface board. (I think that we have concluded that LinuxCNC is making steps? The step length can only be integer multiples of the base period. (Actually, there is a way to get shorter steps, but it doesn't gain you much really).

I have the parallel port powered by the USB of the computer.

I think that the steps are small enough.

The machine is made from discarded wafer fabrication equipment : )

The aluminum plate the monitor arm is on, as well as the x-axis horizontal plate are 20mm thick. The ballscrews and rails are THK; the things that some companies throw in the scrap heap : O

Most of the gantry plates were cut out with an electric sabre saw. I had to grind them, and file the inside corners square. The long rails have the linear rails underneath to keep dust and chips out of them. I've drilled over 100 holes, and tapped more than 50 to put this thing together.

The envelope will be about 900mm x 1100mm x 120mm.

Aside from the interfacing, I have to pick out a spindle motor, get a longer monitor cable, get something for a table....

I got it working!!!

: )

It was a voltage problem with the Optocoupler board. I can't exactly double-post, so:
forum.linuxcnc.org/27-driver-boards/3443...lator-board?start=10

Thank you in no particular order: Andypugh, Tommylight, Grotius, Ozzyrob, Todd Zuercher, PCW, and Rodw, others, and for LinuxCNC.

I lowered the Y- acceleration really low to around 100 so the whole cart wouldn't roll when the y-axis moves, for now, and the thing runs smooth as silk. It was really cool to finally move two axis at once, three even!

I have to make a block setup to put under the cart so it won't roll.

I still have a myriad of adjustments to make.

Thanks again.

I guess I have to learn how to run this thing.