Stepper controller/motor questions and advice request

[Halfdone]

Hello,

First let me state that I am trying to make this project using most if not all used parts salvaged from decommissioned equipment and my cash budget is basically Zero.

That being said I have come into some stepper motor controllers and motors from some decommissioned equipment and need some advice on them. For over a year now I have been collecting various things in order to create a CNC router table similar to Joe's 4x4 table and am getting close to starting my build. I will most likely use Mach3 for PC control and am not yet sure if I will be using Lead screws for movement or some other mechanism (I would like to use Rack & Pinion but not sure if I can get them cheap, maybe I will make some) I also have some servo controllers and motors but they do not look to be very simple to integrate like these controllers so I will probably try to sell them to generate some funds.

Controllers and motors I have questions about are:

Positec (by Berger & Lahr) WDM3-004.1801 dual stepper motor controllers

Positec (by Berger & Lahr) VRDM 397/50 2NM 325VDC 3-phase Stepper motors

Positec (by Berger & Lahr) VRDM 3910/50 4NM 325VDC 3-phase Stepper motors

Here is a link to the PDF I found describing these controller and Motors.
http://www.germanytek.com//ziliao/bujinxuanxing.pdf


Some questions I have are:

1: The documentation which is linked above says these will run off of 110v or 220v. They were using 220V before and the 110V box isn't checked. While I have 220 in my garage 110v would be easier so do you think I just need to open these up and find a switch inside to get them to run off of 110V or are they maybe auto detecting. Would I damage something if I under power them for testing?

2: It looks like I could possibly run these straight from the parallel port using Mach3 for the control. The input control levels on the tag say 5V, and are opto-isolated. So based on the specs for the control inputs shouldn't I be able to bypass a controller breakout board?

3: Do these look like good solutions for this type of project? I'm not sure if they are overkill, under-rated or perfect. Since the controller doesn't support encoders I could add external encoders for more precision if needed. I may have do a simple breakout board for limit switches and relays.

4: Has anyone ever used a stepper motor or Servo motor for a spindle? It seems to me a Servo could be fast enough and controllable to use for a variety of machining applications, would a stepper be fast enough to replace a router. I would also like to eventually machine metals but will start with wood for now.


I don't want to waste time on these components if they are going to work for me. I really appreciate any comments or advice before I get started. And I may have more questions as I start testing these units this coming weekend.

Thanks,

Mark

[Halfdone]

After looking at the inputs on the controller I noticed that it has + step/direction pins as well as - step/direction pins. Now I am wondering if I can use one or the other set in Mach3. I know Mach 3 can use positive pulses or negative pulses for control but I am not sure if this controller needs both to function. Also what about the other inputs like Current control and microstep +-. Does Mach3 have anyway of controlling these? I think it would be great to be able to have the microstepping software controlled for rapids and such.

Any ideas????


Pin assignment

1 + Pulse
2 + Direction
3 + Gate|Enable
4 + Current control
5 + Micro-Step
6 - Micro-Step
7 Temp.Mot.
8 + Ready
9 - Pulse
10 - Direction
11 - Gate|Enable
12 - Current control
13 Rm Fault
14 Temp.Int.
15 Ready


Thanks,

Mark

[irving2008]

Mark,

Normally when an opto-isolated input has both + and - 'ends' available it means it can be wired for either active high or active low. For connection directly to a parallel port you need the active low configuration. For a powered, buffered breakout board usually either can be used.

To wire as active low, connect the - lines to the relevant parallel port output and the + to a positive power source of between 3 and 5v; a USB port or one of the spare disk power connectors is a common approach, or an external walwart with the -ve tied to the parallel port common lines.

The specification suggests that there is a 150ohm series resistor in the optoisolated input line so with a 5v supply this will give a input current of 25mA which is a little high for a typical parallel port on a modern 'one chip' PC and more applicable to a PLC system. If you want to use the USB or disk supply connector I would add a 150ohm resistor in series with each line to bring the current down to 12mA. Alternatively use a 3v supply (i.e an adjustable walwart).

You'll need up to 180 - 200mA from the walwart for three drivers so size accordingly.

Hope this helps.

[Halfdone]

Thanks Irving2008,

So based on the attached image I should be able to use the negative step and direction pulses, set in Mach3, connected directly to the appropriate driver input and then use a common enable output pin connected to the "Gate|Enable" input of all controllers that I use right? How about the enable, should I use the negative pulse for that as well, I see Mach3 has this option? Then you are saying that I should tie the positive step and direction inputs to an external 5V through a resistor to limit the current that feeds back to the input of the parallel port. The PC 5V line for drives power seems the most convenient. I could even use an extra PC power supply setup just for this with the proper resistance in series.

That sounds simple enough. How about the "micro-step" and "current control" lines? Can these be ignored on the inputs of the controller? It looks like some of these settings can be set via the switches on the controller though I don't know what settings to use yet (I guess I will have to experiment). I don't have detailed documentation on these controllers, just the .pdf that I linked above.

I do not yet have the skills for all of the electronics, though I am learning. These controllers should save a lot of effort, I was going to be making my own driver and controller boards. Now I can skip all that and just make a few connections hopefully.

Thanks for the advice!!! this info is really what I need.

Mark

[irving2008]

Mark,

If you go the resistor route you need one in each line, not one common one. Alternatively you could drop the 5v to 3.6v using two IN4001 diodes in series in the common line.

All signals driven from the parallel port need to be active low.. the port doesnt have the drive capacity to drive them high, this will apply to 'gate/enable', 'microstep' and 'current control'. Not having used Mach3 I can't tell you what it can or can't drive. I'd imagine 'gate' turns the driver on/off, 'microstep' switches between full and some predefined microstep size set by switches and 'current control' is used to lower the coil current when stationary. It may be you can leave these disconnected, or just ground them if they need to be 'on'.

You cannot drive all three 'gate' lines from one parallel port output, they need too much current. If you want to drive them you will either need a separate pin for each (assuming Mach 3 can handle this) or an external buffer (2 or 3 components - let me know if you need more info on this).


regards,
Irving...

[Halfdone]

Irving,

Thanks again your your quick responses. I only suggested connecting all the enable pins to one output after reading the Mach3 manual and the following statement within the output signals section:

"You will probably only want to use one Enable output (as all the axis drives can be connected to it). Indeed if you are using the charge pump/pulse monitor feature then you may enable your axis drives from its output."

I can just as well have one per axis anyway. Worst case scenario is I have to use 2 parallel ports if I run out of outputs. Mach3 can handle 2 P-ports.

I could use 3.6V to drive the positive side, I have a lot of old walwarts and may have one in the 3.6 volt range. I just need to make sure I have enough available current for each of the 3 or 4 axis that I plan on using. and of coarse follow your example of tying its negative to the common on the parallel port.

Now after reading your post I am thinking I can use one of the extra outputs in Mach3 (6 enables and 6 outputs available) to enable a different microstep mode for precision work or rapids. Also I could do the same for setting a smaller current when an axis is stationary for a time, like Z while making 2D only cuts. I assume that larger currents are used for running the motor and/or starting movement of the motor, then if its not moving needs only small current to keep stationary. I would just have to edit my G-code to enable the special modes of of the controller.

I am flying home tomorrow and can't wait to test out some of this on the controller. I have been delaying my build do to lack of a way to control it. Now I might be able to get the control up and running relatively quickly, providing my testing is successful.

Mark

[Halfdone]

Well I got everything hooked up, I think, and it doesn't seem to want the work. The stepper goes solid as soon as I power up the driver and it goes into ready mode. But while the stepper looks like its ready for action I can't seem to get it to move through the parallel port using Mach3.

I have attached the + of a 3v 300mw walwart to the +step, dir, and gate pins of the driver to pull them up and the - to one of the parallel com lines. I have wired the parallel pins 2,3,4 as my step, dir, enable to the appropriate "-" pins on the driver/controller and configured Mach3 to use these pins in "LowActive" mode for all of the pins.

Now that I think about it I don't have any grounding from the common pins of the parallel port or the PC to the driver/controller. Could this be my problem? Should I connect all of the common pins (18-25) together and to the shield of the cable? I think the shield of the Driver/controller is ground (Housing-Screen) on its side as it has no dedicated ground pins.

Unfortunately I do not have an O-scope available to test with right now. I might have to try and borrow one to test if the parallel pins are actually doing anything, unless someone knows how to test them without it.

Thanks again for any advice.

Regards,

Mark

[Halfdone]

I got it!!!!

I was trying everything tonight trying to get this thing going and was starting to get very fustrated. I found my computer scope and was checking signals and seeing that I did indeed have an output on the parallel port when I was jogging in Mach3 but the motors wouldn't spin at all.

Then in desperation I went back to the basics and tried to use the positives instead of the negative pins. Just playing with the gate/enable I found that when I connected the +gate/enable to the proper output from the parallel port and the -gate/enable to common from the parallel port I was suddenly able to turn on and off the enable on the driver/controller!! So working on the premise that this was the way to go I re-wired everything to use the +pins and the -pins I put to ground. Now I can control the motors perfectly!! So now I am not using an external power supply to pull up the +pins but only using the parallel pins directly connected to the driver/controller. This seems to be working fine and after playing with it for over an hour it still works fine. Hopefully I am not overdriving the parallel port. I might go buy a PCI parallel port and use just in case so I don't fry the on board one. I also noticed that if I switch to active low on the output the motor just spins backwards from active high output. I thought this could lead to bad motor performance but it doesn't seem to make a difference in the sound of the motor at all. I ran two motors side by side with the differant settings and they sounded identical.

So now I spent the rest of the evening playing with steps and different settings in Mach3 to see its effect on the motors. I still need to figure out how to tune them but I seem to have fairly smooth steps when I speed them up a bit. At slower speeds I seem to get some extra vibrations while turning. It seems like some weird harmonics or something because it drives fine then hits a magic speed and vibrates going through that speed, then smooths out again when its faster.

I have no idea what the steps or the step angle is set too, but with some research and experimentation I hope to figure these out then tune the motors for the best performance.

Thanks for your help Irving, however in the end I didn't use your advice on the connections. I guess sometimes it helps to just start carefully experimenting.

Regards,

Mark

[irving2008]

Hey Mark,

Thats OK. I am surprised both that it didnt work active low but more that it did work active high! I suspect that it works because the parallel port is able to drive enough current to light the LED in the opto up even tho its output is probably being pulled down to 2v or so... How long it will keep doing it for is another guess.


Anyway, good that its working and you can play

So now I spent the rest of the evening playing with steps and different settings in Mach3 to see its effect on the motors. I still need to figure out how to tune them but I seem to have fairly smooth steps when I speed them up a bit. At slower speeds I seem to get some extra vibrations while turning. It seems like some weird harmonics or something because it drives fine then hits a magic speed and vibrates going through that speed, then smooths out again when its faster.

Thats called mid-band resonance. If you think of the motor as a spring... as it steps from one pole to the next inertia causes a little overshoot and then it comes back to the pole and undershoots a little until it comes to rest. But what if the dynamics and electrical signals combine to cause the overshoot to get large enough to flip to the next pole and then back again.. then the motor can't decide which pole it wants to be on and may bounce from one to another....

have a look at this stepper motor tutorial , section 2 deals with resonance

[Halfdone]

I suppose I will look into why it wasnt working on the negative side of the inputs. I will also try to detirmine what kind of loads I am putting on the parallel port. I will install another port and may find that it doesnt work at all, so I need to make sure I have solutions in place.

Thanks for the link, I have been reading a lot of material on Steppers and the resonance issues. There is a lot of info to absorb and I am just starting out in my learning. Now that I have something working I can test things on I should be able to learn exponentially more about them.

I hope to soon start a build log for my project, now that I have a drive solution in hand.

Thanks,

Mark