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The Basics: Stepper Motors

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Will_D:
Delighted with the chat on the original basics thread. Just whats needed!

So as not to dilute that, this is a sub-thread about stepper motors!

So Santy came early ["Typical Male Problem" says Mrs Claus]

I got these from:

http://www.ebay.ie/itm/3-Axis-CNC-Kit-425oz-in-Nema-23-Stepper-Motor-Driver-CNC-Mill-Router-Lathe-/121787136378?hash=item1c5b14397a

Sorry I missed the bit about using low torque steppers.

So the motors I understand, 2 coils, 4 wires. But what about the stepper driver controllers?

These are M542T units and have 8 dip switches!

Sw1..3 are current limiters [1.5, 2.0, 2.4, 2.8 Amps] This limits the max current to a coil (understood I think)

Sw 4 is the Mode Table [Full or half mode] (not underswtood!!)

Sw 5..8 are for the step angle (understood i.e a pulse will move the rotor by this amount) BUT what should I select (and assume I must tell the cnc controller)

Will_D:
Now the controller I ordered is another story!

I still fancied the one that started this whole thought process for me:

The 4 axis cnc 1508 (available on banggood but no longer on e-pbay!!)

Anyways ordered this one, got a confirmed the delivery from the seller (Mmmm?) then my ebay summary showed that th e seller was 'de-listed' but if I had paid then no worries! Huh!! So I now have to wait for the China slow boat to arrive, if it does great!, If not I have to order another [like the DDCSV!]

Alarm!!

Take away Indian just arrived so will check and edit this later!

Joules:
That was Custer's fatal mistake too.

Not a bad set of parts Will, you are still in the low power stepper region (NEMA23)

identify your coils (Black, Green and Red, Blue)  Your driver is labelled A- A+  B- B+  they are your stepper pairs  i.e Black to A- Green to A+ etc  swap over one pair AA or BB to reverse motor direction, but don't connect AB BA  the music is awful.    :lol:

Full current, half current usually refers to the holding power when a stepper is powered but at rest between moves.  If you can get away with half current the motors will run alot cooler, but if any axis can be  back driven, you would need full current at rest.  It kind of contradicts the bit they say about auto current control at idle, especially if you don't use the enable line.

If you are just making the motors spin add some tape flags to watch the shafts spinning and start out at 2 microsteps 400steps/rev and try the different options.  In the real world you don't really want to be going beyond 8-16 microsteps, the torque falls off a cliff as you increase the microsteps, so unless you are wildly over spec'd  wouldn't recommend it.

When you get a controller we can advise as it will depend what they ask for.

 

Will_D:
Many thanks Joules for the info. Again that's exactly whats needed for the "Basics"

I reckoned that 3 Nm should be enough for my Sieg SX2P (at least for X and Y)

Z may be another matter though

Received PM from the seller that he had shipped and gave me a tracking number that seems to work!

PS: Take away Indian was gorgeous!

Will_D:
So my controller arrived (rhis the one with th emicro-Sd card (the SMC4-4-16A16B))

Hooked power to controller and the controller works as expected.

Connected up one stepper (X-axis) and nowt! didlly squat! No motion.

Connections are:

PUL +ve, DIR +ve
The negatives go to the controller.

Hmm time to read and think and get the meter out.

Eventually found the parameter thats sets the "Step Low Active" bit. Default is 1 so it aint goint to pull down the Pulse line. Set it to zero and now it works as expecetd.

Lesson learned!!

Now its a question of setting the params so that 1 mm of travel in real like equals 1 mm og travel in the controller.

Due to the weird correspondance with E-pray about the seller etc and the fact that it didn't work, and also following Joules' thread of fitting the MPG pendant to the DDCSV1 controller - guess whats on order??

I obviously have a severe case of  :proj:

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