[MrWild]

:boxing:

Is it possible to use this idea to use the logic of a PIC controller in this way <shematic> and thus use high power MOSFETs to drive higher than the 2.5~3a threshold?

http://www.cnconabudget.com/5804_2.gif

A friend is tossing me some surplus steppers with 2.5v 4.6a and 300 in. lb. of torque. I'd like to use the micro-stepping that has been coming out with these motors.

Thanks

[Corvus corax]

Kind of a basic schematic there. Is the 7414 supposed to be the PIC? Without the code, you'll have a tough time checking the diagram. Looks as if it supplies half stepping to the motor? You will want to make sure the steppers are the square frame type if you want to use microstepping. Aparently the magnetic circuit in the older round bodied steppers doesn't work as well with it.

[MrWild]

I guess I'll have to wait for them to fall into my hands to see if they are round or square bodied. (or I could just ask my friend... ) he round versus square argument is a new one for me. I didn't know there were motors that didn't fair as well as others for microstepping. Due to the amps drawn I've started leaning to the L297 driver at Phil's site. That one half steps and until I started reading about the speed and smoothness a micro stepping drive brings, I was happy with half steps.

Is a wave step sort of like a micro step in the magnetic profile as the step is made?

[fyffe555]

Mr Wild,

The shape of the motor has no effect on its ability to microstep. Square motors are typically hybrid types with better performance than the round. If you want to use a pic and Mosfets directly do a google on Linistepper. James Newton has some posts about it here on the Zone also.

[Corvus corax]

I heard that bit about round vs. square from one of the engineers at Geckodrive. I'm sure he was referring to the shape of the field coil laminations, and being a transformer designer, I could see where it might have an effect on local flux density on the poles. How this affects microstepping, I do not know, as steppers are fairly new to me. I concern myself mostly with the power end of things...

[pminmo]

Are they bipolar or unipolar? i.e. 4wire, 5wire, 6wire or 8wire...

[MrWild]

Unipolar

http://www.network54.com/Realm/tmp/1129669973.JPG

[pminmo]

The link doesn't work for me. At 4.6A you probably want to chop the mosfets for current limiting. Yes you can drive logic level mosfets from a PIC, such as IRLZ44.

[MrWild]

Thanks.

The link worked for me when I checked it, but that might have been due to havng been already seen by my computer.

The diagram shows a six wire unipolar from Superior electric. I've been self teaching myself electronics and have learned quite a bit but have also learned that I need to learn a lot more before I'll be able to design a PIC circuit with MOSFETs for switching. I'm pricing the parts for the L297 drivers now. I think I'd rather have just half steps and not have the drivers blow, than micro steps and always have the soldering iron out to replace stressed parts.

I really have my heart set on being able to mill aluminum and mild steel with a small and rigid home built machine. I've been building custom bikes as a hobby for most of my life and there are some things such as the worm on a internal throttle sleeve that CNC capability with a fourth axis will make possible. I know I won't get big machine capabilities, and that's fine. I have a Bridgeport and Southbend for my large machining needs, I just want to be able to do convoluted widgets without needing to do it all by hand like a gunsmith.

Today I finally made my first useable PCB. I'm in the electronics phase of building a stepper driven EDM. It was this EDM that got me involved with steppers initially, and it seems to have set the hook pretty deep. Interesting devices that let you play around quite a bit.