1/8 step in bipolar

[TigerPilot]

Reading through this site and other places I always see the mention of 1/2, 1/4, 1/8 steps and so on for unipolar motors but never for bipolar. Why is that. Is it not necessary because they run smother or is it because it is difficult to do, electronic wise?

[Garfield2]

http://www.fromorbit.com/projects/picstep/

This is bipolar. Most microstepping controllers are bipolar.

Cheers,
Alan.

[TigerPilot]

http://www.fromorbit.com/projects/picstep/

This is bipolar. Most microstepping controllers are bipolar.

Cheers,
Alan.

Alan

I've emailed you, I think it's you :-), not realizing that it was you who put the link up.

As I’ve emailed you I couldn’t find how to micro step it. Is it done though the PIC? Can you post it here instead of emailing me? Also, who made the boards for you?

Yoram

[Garfield2]

Alan

I've emailed you, I think it's you :-), not realizing that it was you who put the link up.

As I’ve emailed you I couldn’t find how to micro step it. Is it done though the PIC? Can you post it here instead of emailing me? Also, who made the boards for you?

Yoram

I think you're misunderstanding what micro-stepping is. You don't "micro-step" it, it does it itself depending on what mode you have it set to. So for each pulse on the step line it can move either 1 full, 1/2, 1/4 or 1/8th of the mechanical step of your motor.

The PIC is simply setting the current limit DAC's to the appropriate values for the given mode and step position. Read the datasheet for the LMD18245 if you need a better description of how they micro-step.

I made most of the boards myself with toner-resist and etchant, but I did have some professionally made by CustomPCB.com

Cheers,
Alan.

[TigerPilot]

I think you're misunderstanding what micro-stepping is. You don't "micro-step" it, it does it itself depending on what mode you have it set to. So for each pulse on the step line it can move either 1 full, 1/2, 1/4 or 1/8th of the mechanical step of your motor.


Cheers,
Alan.

That was my question, how do you set the mode. I've asked since I saw the HobbyCNC board and they use jumper to control it. I know that your board is an other design so I think that it is a legit question. From your answer I gather that it is done by controlling the PIC. True?

BTW, great board. It is so simple. I don't know why the comercial ones are so complicated. I guess that way they can charge an arm and a leg :frown:

Thanks for the good work, Alan

Yoram

[MrBean]

The jumpers on the breakout board (interface), set the step mode. There are no jumpers on the actual driver board.

Hope that helps.

Regards Terry.....

[H500]

Reading through this site and other places I always see the mention of 1/2, 1/4, 1/8 steps and so on for unipolar motors but never for bipolar. Why is that. Is it not necessary because they run smother or is it because it is difficult to do, electronic wise?

Actually, bipolar drives are just as common.

[TigerPilot]

Actually, bipolar drives are just as common.

You are right, but mostly I see here the xylotex and the hobbycnc boards mentiond. Besides, the commecial bipolar boards tend to be much more expensive. Look at Alan Garfield's site (he posted the url in a post above) and it is really simple and inexpensive bipolar driver. I'm waiting for a quote from a PCB maker and then I'll probebly order the boards and build his system.

Yoram

[ger21]

Xylotex has both bipolar and unipolar boards. You can also get bare boards for bipolar drives from http://www.embeddedtronics.com

[H500]

One thing to note is that the hobbycnc and xylotex boards can control several motors. Also, before you select a controller, make sure it is compatible with your motors.

[TigerPilot]

The jumpers on the breakout board (interface), set the step mode. There are no jumpers on the actual driver board.

Hope that helps.

Regards Terry.....

Terry, I saw on your web page that you have that setup. Tell me please, how do I program the PIC? I know that there is a hex and a asm script. How do I get them to the PIC?

Yoram

[TigerPilot]

Xylotex has both bipolar and unipolar boards. You can also get bare boards for bipolar drives from http://www.embeddedtronics.com

Thanks for the headsup, Gerry. I guess I've missed it in all my googleing, :-)
Their board is simmilar to Alan's. I saw also on that site that they have a dual axis board for US$20 including the programable chip. That might be interesting. I'll check other sites to compare prices. :-)