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Wolfbrother
12-28-2009, 01:26 PM
Hi all,

A bit over my head on this whole stepper motor thing. I ran the Nuts and Volts article on the standard stepper from Parallax. I used the PDB for the Basic Stamp and then I used a propeller demo board with the L293D. So that all worked.

Now the issue I run into. I have a linear actuator with a Keling Motors KL23h276-30-8B ( http://www.kelinginc.net/KL23H276-30-8B.pdf·) motor.

I'm doing an art project where the actuator moves back and forth with reasonable accuracy, it doesn't have to have the precision of the CNC's this thing is normally used for. It will run continuously for up to 7 or 8 hours a day. My questions are, what's the best way to hook this up electrically, Unipolar, Bipolar (Series) or Bipolar (Parallel) for this kind of operation? Then based on that response, this motor seems to draw anywhere from 2.1A to 4.2A, that pretty much ends the L293D's chance of running it. Anyone have a good suggestion for a driver or do I have to make a discrete H-bridge?· I'm pretty open to any suggestions that an make this part easier. I also have the propeller robot control board I am using to control this, but one of the dedicated motor outputs is being used to drive a wheel.

Thanks in advance.

photomankc
12-28-2009, 03:28 PM
Look at the L298N.· It's a dual H-Bridge that I believe can handle 2A per bridge.· You can gang the two on each chip for 4A per if needed.· It's not an easy package to breadboard though.· It should however be compatible with the·Nuts and·Volts type interface.

There are some other high-current ICs out there too but·some will have step/direction type inputs not the sequenced type of the L293/L298.

StefanL38
12-28-2009, 06:15 PM
Hi Wolfbrother,

I googled around and found this brochure from infinion (http://www.infineon.com/dgdl/AP+MotorDrives+Brochure.pdf?folderId=db3a304312bae 05f0112bd749c09001e&fileId=db3a30431936bc4b01193e1a730e53b0&location=Search.AP_MotorDrives_Brochure.pdf)

I don't have any experience with these devices but seems to be for professional use

best regards

Stefan

Wolfbrother
12-29-2009, 12:04 AM
Thanks,

I ordered some L298s and also the 297 for interfacing to the 298. I'll look for a lighter motor than the one I have since it's still taking quite a bit of current. Can anyone with the motor experiences tell me what method of hooking up the motor is best for my application?

photomankc
12-29-2009, 01:03 AM
There is no universal answer for that. It all depends on what it's moving, how fast it needs to move to get it there, and what you have to drive it with. Steppers lose torque as RPM is increased. They also have a band of RPM where they drop torque significantly below the curve due to resonance. I would recommend using half-step as a minimum to help with the later issue. Other than that most people go overboard on the motor torque because it will drop off severely at speed and you can't have it losing steps since it's open loop. It has to be powerful enough to move the load 100% at all speeds you plan to use.

-Bipolar series is usually the best torque at low speed but falls off faster at high speed.

-Bipolar parallel generally has a flatter curve and can do higher RPMs with decent torque.

-Unipolar is not really much use with the chips you are using. You'd have to wire it up as a bipolar anyway. In general it has a similar but slightly lower torque curve to Bipolar parallel. It enjoys the advantage of possibly being easier to find drive ICs for.

Since the L297 moves you to a step/direction interface you might look at some other chips like:
SLA7062 and family for Unipolar .
LMD18245 for Bipolar.

There are of course others as well. Good luck! I'm working on a driver for the SLA7062 right now but my application is for CNC control.

ManAtWork
12-30-2009, 02:32 AM
Hi Wolfbrother,

my favorite chip for driving small steppers is the TA8435. It cost only a few $ and can deliver up to 2A at 40V with 1/8 microstepping. It needs very little external components. With·2A and a 36V supply·and bipolar series connection you get almost full torque up to 330rpm. If you need more power you should consider buying a complete driver from keling.

Cheers
·