VSD-A + emc2 + pluto-servo

[Esa Hippolin]

Hello!

First, a BIG thanks for Tero for creating amazing cost-quality ratio!

It's been slow and sometimes even slower with this project, but now there seems to be some light at the end of the tunnel. I've been working to get pluto_p to work with VSD-A drives (bought these way too early, I would like to use the E-series... .

I now have one axis communicating well from the PC to the drives. My problem was for a long time, that I tried to make the pluto_p as a part of the servo drive box, but the card doesn't want to communicate unless it's directly connected to the PC.

The solution was to make a small BOB directly to the pluto_p. The ribbon cable from the BOB to the D25 cable also relieves the weight of the cable from the pluto_p. Now it lays on the table nicely. I also made a couple of modifications to the pluto_p itself, but they might not be necessary.

The other PCB is an optoisolator card with some logic for e-stop, limit switches and VSD error signals.

The design is based on the VSD-A Breakout board rev 2, so not all that much done from the scratch.

Intended features:
- 3 axis and spindle PWM control
- enable signal to drives
- enable signal to spindle
- one limit signal for all maximums
- e-stop signal
- drive error signal stops the machine
- Z signal is not used from the encoders

I still have a lot to do. PID have not been fine tuned to any axis. The .hal and .ini files are not final yet. I also haven't soldered the opto board completely and I have only tested one axis the limit switch signal. For the one axis, quadrature signals, PWM, and drive enable signal works well, so I'm assuming they should work for all axis.

This project should be quite easy to convert for the E series. Basically changing the cables connecting to the opto board should do the trick.

Please note that I used a male D25-PCB connector in the opto board because I already had made the front panel to have a gender changer attached to it. If you want to use a female connector, make changes to the design accordingly.

[Xerxes]

Thank you for sharing your experiences and files, Esa! I hope these are useful for many people and also you get your new machine flying chips soon :-)

BTW, is there EMC experts who could tell whether RS232/422/485 can be controlled in real time manner from EMC? I'm interested of that because it seems that it would be possible to implement multidrop RS485 on VSD-E with tiny add-on card and firmware modification.

[evo4wrx]

As long as you use a real time kernel and then compile on top of that you could communicate RT just fine.

Telco industry use real time linux kernels all the time with sound DSP equipment for timing control of voice over carrier networks.

[Esa Hippolin]

Hello!

I now have managed to get all axis working with decent accuracy (I might fine tune them more later on). I'm using 20mm pitch ballscrews for X and Y axis and at full speed (3000rpm) the movement is too scary to use... . So, as a learning experience I found out that 12000mm/min is quite enough for a small desktop hobby-scale machine. Maybe in the future I'll change the screws to 4mm pitch for better precision and torque.

About the electronics:
I had to change the pluto interface so that the VSD-fault signal uses a dedicated input. When it was ANDed with the e-stop the machine-on would not reset the VSD-drives' fault state and the whole thing had to be rebooted (not including the computer). So I made the needed changes to the PCB and schematics, but hacked the changes to the existing boards for the convenience. I'm assuming that the new version works ok .

I'll post the edited files when I have the EMC2 configuration working properly.

At this point I have tested all axis which seem to move rather nicely. Also the spindle signals work as they should (spindle-enable and PWM (which still needs fine tuning)). However, I'm experiencing heavy interference from the other drives and thus I cannot use more than one drive at a time, which sucks... . Also my table on which the machine rests is too shaggy and has to be reinforced .

Anyway, there is now light at the end of the tunnel and I'm getting exited of actually finishing this project after way too much time.

I'm quite pleased with the pluto-p board for it's low cost and good performance. I used only about the minimum IO signals for the machine and there's plenty of them left for other signals if needed.

I'm currently working on the axis pyvcp interface to have a spindle speed monitor and speed control. If you have experience with that one I wouldn't mind getting some help with it .

[Esa Hippolin]

Hi!

I'm now rather satisfied with the machine.

I managed to get the UI almost like I planned. I set pyVCP panel for spindle speed monitoring and controlling. Please see the attached .png. The topmost monitors the spindle speed in rpm through lowpass. The G-Code/pyVCP radiobutton selects (via MUX) the source for the spindle speed. When G-Code is selected the S command controls the speed (motion.spindle-speed-out), otherwise spindle speed is controlled by the pyvcp scale element with 500rpm intervals. The UI also displays the set (gcode S) spindle speed so that you know what to expect if you accidentally select that.

Since there doesn't seem to be any reasonable way of putting the pyvcp scale element value to spindle speed and to have the option for controlling the spindle speed from g-code, I set up three buttons. ON and OFF send M3 and M5 respectively. S5000 send exactly that. If there's no spindle speed defined the M3 won't start the spindle so I made an extra button to click if I just want to turn the spindle on without controlling it directly from the g-code.

In the zip there are Eagle files for pluto BOB, VSD-A quadrature signals, and the opto board. As I mentioned in my previous message, I didn't actually made these revisions, I simply hacked the functionality to the previous boards and they seem to work ok. If you make then, please tell me if they also work properly .

The quadrature board should work so that changing the 4-pin connector to the other pins would change the motor direction in emc2. Didn't test that one either. The difference in the two rows is that other gives A, other -A. B is the same for both. This should change the motor direction according to some page I found.

So it seems that the software is set up and the pluto communicates correctly to each axis and the spindle. My next step is to change the motor cables into shielded ones and also change the internal wiring for better EMI protection.

Over and out.

[Xerxes]

Really nice to read about all the details!

I hope you could some day show us a video :-) No hurry though.