[Oldmanandhistoy]

Hi all
This is my first post on this site and before I go on I would like to say “thanks to every one on here for making this the excellent forum which it is”. Not sure if I can contribute anything at this time but hopefully will in the future (qualified wood machinist for 18 years, cnc building beginner and electronics dummy).
With the help of other posts and a Hobbycnc plan I have nearly completed building the mechanics of a MDF cnc router (no problem so far thanks to this forum).
Now it comes to the electronics of my project my head has began to spin. So much info out there, so many choices and many hours of reading really need some help please.
I made the big mistake of buying a so called part built Hobbycnc kit from ebay (which got me started in the first place). What I got was this.
Plans to built the router, 3 different lengths of trapezoidal 3mm pitch with anti backlash nuts, 2 lengths or 12mm shaft, 3 Shinano Kenshi unipolar 6 wire stepper motors (rated 5.1V, 1A, 4 phase at 5.1 OHMS per phase and holding torque 59.7 OZ-IN.MIN), 24V 10A psu, very old by the look of it Hobbycnc 3 axis board and 1 or 2 other bits and bobs.
I’ve scraped the board and am now looking for something to replace it. After a lot of reading this is what I’m thinking. Buying a Xylotex XS-3525/8S-3 3 axis bipolar drive board.

Will this board drive my steppers (if not will buy some bipolar steppers to replace them).Hoping to work with MDF and Ply?


Other than hardware (cables, switches and my PC) will I need any other boards or electronic components for this to work?

Thank you to anyone who helps in advance any help will be very much appreciated.
Really hope I put this in the right place ) .

[H500]

Since your motors are unipolar, you need to get a unipolar driver. 59 0z-in is a bit weak. Automation direct has 250 oz-in (or so) bipolar steppers for $40.

[Oldmanandhistoy]

Thanks for that H500. The reason I asked about the unipolar motors is because in the data sheet that comes with the board it mentions unipolar motor set up and was wondering how the steppers I have would work with that board. Would I be right in thinking I would loose power using a bipolar drive?
If the motors are no good for my router with xylotex driver board (think I made a mistake with torque and are 85OZ-IN not 59.7 by the way sorry) will I need anything else other than bipolar motors?
One other thing I’m in the UK so if anyone knows of good sources for new stepper motors over here would appreciate it.

[zoltan]

H500,

I have seen at certain moment some posts about a microstepping controller designed/built by you. Which is the development status of it? Have you finished it? Did it work? If the controller is working now, and as I remember it seemed to be a cheap solution and based on parts that I can find here in Romania, can you share with us the design and the source code?

[H500]

Oldmanandhistoy: Sorry, I make a mistake. A bipolar drive will have no problem driving unipolar motors if you wire them up properly. The torque will be same as a unipolar drive.

Your motors are a bit weak, but I think they will be useable if you don't need speed. You can always upgrade them later. I'm using ~130 in-oz motors on a dovetail type x-y table and I think it's underpowered.

Just remember that the xylotex is limited to about 2.5 amps, so if your motors need more, you won't be able to get full power out of them. I believe xylotex offer motors that are well sized for their drives.

[H500]

Zoltan, I done 2 microstepping controllers. One is based on the allegro 3977. Another is based on the national lmd18245.

The 3977 is the cheapest and simplest and don't need any programming. The 18245 is quite expensive, but is more not as easy to kill and handles more power.

If you're interested in the 3977, there's an open source design availble. If you prefer the 18245, take a look at PICSTEP or the board from EAS. Both are good open source drivers.

I was also experimenting with an AVR based controller. It's not microstepping, so I haven't been using it on my mill. It is theoretically not hard to change it to microstepping and I think someone else was looking into it. This board can handle much bigger motors than the others, so I might work on it again in the future.

The source code has been posted, but I can email it if you can't find it.

[zoltan]

Thank you for answer. I was referring to AVR, and i was thinking that it is a microstepping controller. Have you done a final design of it, or it is still on development. Could you make the development of source to microstepping? Iwould be interested in your design as I have a problem finding out the parts, but I found out four AVRs.

[Oldmanandhistoy]

Thanks again H500.
That clears up my thinking about loosing torque with a bipolar drive. I do believe my motors are probably too weak for what I have in mind but hoped they might run ok while I find some bipolar motors (still looking in UK for a supplier of new motors at a reasonable price).
The other question I have is do I need any thing else other than the driver board and what I mentioned above?

(Trying not to mention hijacking ) )

[H500]

Zoltan: The circuit was experimental, so I wouldn't recommend anyone build it unless they are able to do some design modifications. A microstepping version will need a slightly different circuit.

[H500]

Oldmanandhistoy: I think you might also need an opto-isolated breakout board to connect your PC's parallel port to the driver. I did not use one on my design. I just cut one end off a printer cable and connected direct to my driver. This needs to be done with care since wiring mistakes could fry the PC.

[mdreitzusa]

Oldmanandhistoy,
if your motors only need 1 amp why not use a ucn5804 based driver.
nelnick has them for 4.79 ea. you will need one per axis.but they give you the wiring diagram,and it is very easy to put together. i have one on my machine and it work just fine.it has 1 or 2 phase and 1/2 step built in.you can check it to see if it meets your needs at http://www.nelnick.com/nelniech.html
hope this helps

[Oldmanandhistoy]

Oldmanandhistoy: I think you might also need an opto-isolated breakout board to connect your PC's parallel port to the driver. I did not use one on my design. I just cut one end off a printer cable and connected direct to my driver. This needs to be done with care since wiring mistakes could fry the PC.

Have looked at opto-isolation and seen it mentioned many times on this site. Would it be a mistake for me not to use one? Do off the shelf printers have these or are they just for people like me (likely to make a mistake with wiring)?
Is there a case for opto-isolation to protect the PC once every thing is wired up correctly and up and running?
One other thing I guess as you didn’t mention them I don’t need current limiting resisters with this drive?
Just so you know H500 I very much appreciate your time and input ) .


Mdreitzusa
Thanks for your reply )
The reason I’m looking at the Xylotex board is I plane to upgrade the stepper motors in the future to bipolar. As far as I can work out bipolar are superior to unipolar, please correct me if I am wrong.

[H500]

Optoisolation is like insurance. You probably don't need it, but you'll be glad you have it if something goes wrong.

Printers don't use them, but they're not hard to make. Just use one of the circuits in the open source forum.

You do not need current limiting resistors with the xylotex board. It is done electronically. As a matter of fact, you should avoid any board that require them. They're antiques.

Bipolar motors potentially give you 40% more torque for a given motor size, by allowing you to apply more current without overheating. But remember that the xylotex is limited to about 2.5 amps max.

If you buy the xylotex, remember to NEVER disconnect the motors when power is applied. This will likely kill the driver.

[Oldmanandhistoy]

Thanks H500 for all the help and info you’re a star. :cheers:

[mdreitzusa]

if you are planning on using bigger motors then the 5804 won't work.it is limited to only 1.5 amps and the limiting resistors do cause the responce to be a bit slow.but for a starter project it is cheep and if you get that little oops(puf of smoke)your not out much.for faster responce and to run larger motors then the xylotex controller would be a better choice for you.i have read some good reports about it.wish you the best of luck in your indevers.

[Oldmanandhistoy]

Thanks very much mdreitzusa much appreciated.

[drk]

It is amazing how much you can understand about steppers and their drives by making a drive yourself. Starting from the simplest ones to those based on 5804 or my preference of L297+L298 Ic package from ST, there are free circuit designs all over the place and the Ics are very good, they can handle 2A/Phase, and whats more, if you put two L298s in Parallels you have a chopper dive rated for 40V, 3.5A/Phase,
and most people will agree thats a pretty neat rating for a drive that can be built within $40. It should run upto 450ozin motors of the correct kind.

If you dont wanna learn much, just buy geckos if budget is not an issue.

[Oldmanandhistoy]

Hi drk
Thanks for your input.
At this time building a driver board is beyond my capabilities. So looking to start with the simplest set up I can find and use it as a learning tool. Think I should leave the electronics to the more capable out there. To be honest it’s going to be a major task for me to set up the Xylotex. Am sure to be back here many times for info.
Building the mechanical part of the router has been very enjoyable (working to within 0.05mm at times) and is my thing.
In my ideal world I would have built two and exchanged one for the electronics (if only).
Any way I’ve just tonight ordered a Xylotex 3 axis driver. Should be with me in a couple of days, just enough time for me to finish the router. Then the fun will really start.