Newbie questions - EAS Microstep

[dpdave73]

I'm considering converting my X2 mill to CNC, but I'm very new to all this.

Has anyone had experience with the EAS Microstep driver boards?
http://www.embeddedtronics.com/microstep.html

This driver is rated for 3amp at 55v, the stepper motor that I've been looking into (NEMA 23) are rated at 2amp at 4.5v. Is the Microstep board too much overkill?

I know you can over drive the voltage to decrease inductance. How much is too much overdriving in voltage?

This driver says it works with 4, 6, and 8 wire steper motors, but looking at the manual for it, it looks like you have to wire the motor to look like a 4 wire motor. Is this a problem?

It's a lot of questions, thanks in advance.
David

[itsme]

Hi there,

I don't have experience with the EAS drivers, but I can probably help a bit with some of the other stuff.

That board should be fine for those steppers. You should be able to limit the current to 2A and then overdrive the steppers all the way to 40 or 50 volts. My steppers are rated at 4.5 volts and I run them at 40V. This is limited by the driver that I use. There is a ballpark figure floating around for how much to overdrive your steppers, but I can't remember it and I'm not going to guess. Anyone?

I don't know the different wiring methods off-hand either, but it is no problem to wire 6 or 8 wire motors in a 4 wire configuration. Quite straightforward.

Regards
Warren

[LongRat]

They say to not exceed 25 times the rated motor voltage. I'm running my set-up at about 20 times rated I think.

[KDN Tool]

The EAS boards are based upon the LMD18245 drivers. I have used the EAS boards in many different systems I have built. They work great within thier "no-frills" structure. By no-frills I mean lack of idle-current reduction, no mid-band resonance dampening, and microstep level pre-programmed (not adjustable on the fly). I have been doing some limited testing with different capacitor sizes etc. to try and lessen the mid-band resonance. Nothing cast in stone yet to report though. You can run your proposed motors right up to the 55V limit. The higher the voltage, the better the high speed performance of the stepper. I typically use 48V for motor voltage. If you order the pre-programmed PIC from EAS, ask for the 10 microstep version.

Ken
KDN Tool

I sell kits with all the components on my site. I have also designed a 4 axis "motherboard" with quick connect pins / sockets for the EAS boards. It has a 26 pin header to mate with a DB-25 input, motor power supply rails, logic (5V) power supply rails, Molex 4 pin headers for motor outputs (with 12" leads), and a 10 pin header for pass-thru DB-25 inputs/outputs. It is not pictured on the site, but I can provide one. www (dot) kdntool (dot) com--look under the Electronics tab.

[dpdave73]

Thank you all for your suggestions, they deffinately help.

After posting this question, I found another driver that has more features; the 4 Axis HCNCPRO Driver Board. It looks like I'm going to go with that and three Stepper3's NEMA23 185 oz-in 6 wire 2A/phase motors for the x,y,z axis and one Stepper3's NEMA17 44 oz-in 6 wire 0.8 A/phase for the rotary table. The weird thing is Stepper3 does not seem to list the motor voltages. But based on the 25x rule, I think I will be fine at 24 to 36 volts.

If any of this sounds like I've got my head screwed on backwords. I would love to hear about it. Also I'm still not sure on what software to use, any suggestions there would be very helpful.

David

[Torchhead]

Also I'm still not sure on what software to use, any suggestions there would be very helpful. David

Look at MACH3. If you elect to go that direction we offer a compact interface product that can be anything from a single port buffered and isolated card to a full dual port (two parallel ports) model that has a 12 function pendant with rotary handwheel. All mounted in a case with shielded cable connections to all the componets. We have a small adapter card that plugs into the Step & Direction interface port and will directly connect to the HCNCPRO driver board. We also have remote relay cards and Combo paks with everything integrated.

Tom Caudle
www.CandCNC.com
Product support site at CandCNCSupport (Yahoo Groups)

[KDN Tool]

Four axes integrated into a single board is a great concept, however, what happens if, God forbid, one axis goes down? Out comes the entire board and you are looking at a manual mill again until it is repaired.
With four individual drivers, you can have a spare handy in-case of any misfortune. Also, you can get 260 oz 4 wire bipolar motors from Automation Direct for about $10 less each motor. That $30 would do well spent on bipolar chopper drivers as you will need all the rotational speed you can get if you plan to use the stock lead-screws in the X2.

Have you looked at DeskCNC for software? It incorporates a slave controller card to produce the motor drive pulse trains. This allows it to not rely on the host PC for timing functions and hence is not subject to funky Windows timing issues. There is even a book "Easy CNC" written entirely about learning DeskCNC.

My $.02

Ken

[ger21]

Originally Posted by KDN Tool Have you looked at DeskCNC for software? It incorporates a slave controller card to produce the motor drive pulse trains. This allows it to not rely on the host PC for timing functions and hence is not subject to funky Windows timing issues.

Due to the nature of how Mach3 works, there really are no "funky Windows timing issues". Mach3 basically completely takes over Windows when running.

The next generation DeskCNC step generator, btw, will be supported by Mach3.

[Ron111]

DPDAVE73,

The board that you have decided on, the Hobbie cnc pro board, is a unipolar driver board, so just realize that the in/oz is reduced.

Ron

[dpdave73]

Oh... That puts me back at zero.

So, I guess I'm back on the hunt for a bipolar driver board with idle current reduction abilities. I don't mind building it from a kit or plans (I would rather spend the money from expensive prebuilt controllers on other things).

I would like to use the stock lead screws because I don't want to give up the manual ability.

Mach3 looks very fancy. I'm hoping to run this on an IBM Thinkpad with Windows 98. So I don't think it will run, but I'll look closer.

Looking at DeskCNC, it looks pretty good. I'll have read it over though, at first glance it only mentioned x and y axis.

Still searching and thanks for the help.
David

[Ron111]

dpdave,

Don't feel that way, Dave. I use the older version of the HobbyCNC board, and it works well. The new board has a couple of enhancements, but when using the board you will have to take in consideration that the stepper motor will not perform at it's rated bipolar torque rating, instead it will perform to it's unipolar torque rating. For example I needed 200 in/oz for my x axis on my 9X20 lathe, so I used a Nema 23 keling 282 in/oz stepper motor (the 282 in/oz was the biploar rating) which gave me a 200 in/oz torque rating in the unipolar configuration. Now the 282in/oz motors were $39. FYI on my Z axis(long axis on a lathe, I used a Nema 23 motor that was rated for 425 in/oz bipolar $54 (300 in/oz unipolar torque rating). I acheived 60 + imp rapids on the z axis.

In other words, Dave, I like the Hobbycnc board and highly recommend using it, when possible, like in your project. I just wanted to make sure that you bought stepper motors with the correct unipolar torque specification for your project.

I cought your thread before I trotted off the work and did not have time to give a complete post as to what may help you most in making your decision.

Also, you will want to take into consideration that you will need more torque using stock acme screws vs. ball screws because of the efficiency of (90% ballscrews compaired to 40 to 50%). For example, with the acme screw on my z axis(9X20 Lathe) I have rapids to about 20 to 25ipm, and with the ball screw/ ballnut I had 60+ ipm rapids.

Please rest assured that the hobbycnc board, when mated correctly with the correct size stepper motors will do a good job and I hope this is a more thorough answer. Do us all a favor, detail your conversion on the forum and share the knowledge of doing this project where many can benefit!!!!!!!!

The more pic's you post, the more help the guys around here will help.

Hope this helps,

Ron

[dpdave73]

OK, I think I'm starting to get this. If I'm going to go with a bipolar motor, I should use a bipolar controler. This sounds very simplistic now that I write it, but I now realize that bipolar motors can only have 4 wires.

Looking at the specs in general, I'm seeing that unipolar motors are producing more torque for the amps. For instance a 185 oz-in 6 wire 1Amp produces the same torque as a 185 oz-in 4 wire 2Amp.

So, is it better to us bipolar or unipolar (I know is far to general of a question)?
I know if I stick with the stock lead screws, I going to want more speed and torque.

Thanks
David

I'll post pics of some of the modifications I've made to my mill shortly.