Bipoler Stepper Control

crgwbr

I just looked in the exchange; seems that no one has released an object for bipoler steper motor contol.· I can handle the h-bridge driver aspect; but does anyone have experiance with the software?· I guess I just don't really know where to begin.

Thanks,
Craig

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NerdMaster
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Life

T Chap

More info is needed to determine what you need. An Hbidge(*2) just drives the fets. How the Hbridge is sequenced is another matter. Current limiting is a separate issue too. The size motors you want to drive also dictate the hardware requirements.

Are you building your own boards? There are various mosfet drivers that would allow a simple Step and Dir pulse. The IRF2184 is a good one that I think is available in Dip. The ultimate bipolar driver IC is called the Allegro A3986, that is Step and Dir input, configurable step rate(1, 1/2, 1/4, 1/16) and current limiting.

Without a driver like the above, you will have to sequence the output lines yourself, but why bother with all that. Creating Step and Dir pulses is relatively simple, and you don't really need an object. Just loop the Step output at the rate to get the speed you want. You would need to ramp up the start of the move as a stepper cannot start at full speed. Here is the just the idea:

1. New position received(or number of steps to move)
2. Ramp up the motor from near stall to the max speed you want to travel at, ramp up some limited amount just to get to Speed, say 10% of the total travel to reach Speed
3. Travel 80% of the total move at Speed
4. Decel down to near stall the lst 10%

Provide more details on what you are doing, maybe I have some code examples I can post. All my code will be based on Step and Dir outputs, not 4 pin sequences.

Are precise moves needed as in CNC, or is this just moving a robot loosley from point a to b?
How many motors? What size? What voltage power available to the stepper drives?


3986 link (only TSSOP fine pitch(.5mm) available)
www.allegromicro.com/sf/3986/index.asp

Post Edited (originator) : 3/12/2007 10:11:05 PM GMT

Kaio

Hi Craig,

here's a thread where you can find a code example from big_mark.

crgwbr

Thanks Guys, I'll probable end up using 2184.

Oh, These steppers are being use in a CNC router for pc boards.

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NerdMaster
For
Life

T Chap

There is a guy offering a "stamp" version of the A3986 in a 28 DIP package, it would be much simpler to use in your case, since you are still lacking current limiting features on the 2184. The DIP 3986 would be plug and play from Step and Dir. PM me and I'll send you his info if you are interested. You need high voltages to run a CNC to avoid missed steps, this means current limiting is required, and very simple on the 3986, it is more involved using the 2184 since you have to design the chopper circuit externally on that IC. With the 3986 you get much ore flexibility, with only a few parts extremally of the DIP 8 mosfets, a few resistos and caps.

Post Edited (originator) : 3/12/2007 10:51:01 PM GMT