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[on:]

I have been reading and looking through post/videos online with excitement. I am going to make a motorized slide cam. I must apologize ahead of time as I have limited electronics knowledge. I just received this list
Arduino uno
EasyDriver 4.4
Stepper motor (vexta pk266-02a) http://www.interinar.com/public_docs/PK266-02A.pdf
PowerSupply for EasyDriver (old laptop PS) 18.5v 3.5A

The question? I failed to realize EasyDriver has a max amp of .75 and my motor requires 2.8a minimum. Im trying to think this through, The power supply is connected to the easydriver which is then supplys power to the stepper motor. With a max Amp of .75 will the motor try to get its 2.8a minimum frying the motor and Easydriver? Trying to find out if I either need a more powerful driver or a smaller stepper motor. Thank you for the help, Im just trying not to fry everything I just received.

[Reply #1 on:]

You likely will destroy the EasyDriver and power supply it there is no current limiting.
Do you really need that large of a stepping motor?

[Reply #2 on:]

There is also a "Big Easydriver": http://schmalzhaus.com/BigEasyDriver/index.html

You MIGHT be able to run your motor at low current if that supplies enough torque for you application. See the Data Sheet:
http://www.sparkfun.com/datasheets/Robotics/A3967.pdf

It says: "The H-bridge
current at each step is set by the value of an external current sense resistor (RS), a reference voltage (VREF), and the DAC’s output voltage controlled by the output of the translator."

More links here: http://goo.gl/bvgzk

There's a tutorial here:  http://xavierstechno.blogspot.com/2012/02/easy-driver-with-arduino.html


DISCLAIMER: Mentioned stuff from my own shop...

[Reply #3 on:]

Ill try to explain without having to go into too much detail. dual linear bearings will run across metal tubing. Alum plate attached to the bearings will have a coupling nut attached to the bottom. Threaded Rod will run down the center and as the motor turns the threaded rod it will move the motor forward or reverse. I know I didnt need as much torque as that motor produced but I wanted to be sure I had enough as the project will be 7 feet long. Sadly in doing so I failed to realized the EasyDriver had a max of .75a and the motor was 2.8a
I have 2 options.... smaller motor, or the new driver which nobody has confirmed I will be safe and not blow the motor. Im thinking cut my losses and just get a smaller motor.

Do you think this motor will be enough, without strain to easy spin the 3/8 ATR?
http://www.robotshop.com/456v-bipolar-stepper-motor.html
 

[Reply #4 on:]

Some suggestions:
See JPG below.
Since the motor is attached to a threaded rod, you achieve huge power advantages.
This image shows an 20 ohm stepper, in this configuration it easily pushes/pulls 3 pounds (2KG).

http://www.ebay.ca/itm/Nippon-Pulse-Stepper-Motor-6V-PF35T-Uni-Bipolar-/280652253394?pt=LH_DefaultDomain_0&hash=item41582d88d2     AND

http://www.loctite.com/index2.php?cc=ca

[Reply #5 on:]

You really need to use numbers here.

Build the mechanical leadscrew driven system, with all bearings in place, and a representative camera weight load.

Decide if the camera slide system will sometimes be non-horizontal and by what angle.  Set up that configuration.

Move the slide with the leadscrew. Attach a disk or short arm to the leadscrew and use a small spring or electronic scale to measure the force needed to move the slide.  Convert that to torque ( Distance * force) like inch-ounces or cm-kg etc.

Compare that to the rated torque of the motor you propose to use.  Try to find a complete motor data sheet that will show torque at reduced currents.

Finally decide what motor to use, and if a larger motor can run successfully at lower current and lower torque.

Once your system is all assembled, run tests which slowly move through the speed ranges you may use, to check for resonance effects that might cause step errors. Check that repeated moves come back to exactly the same position/step.

OK, That's my take.. others may have experience to add...

[Reply #6 on:]

Thanks for the advice. I'm going to wait and get the frame built so I can see what im dealing with... Ill try to see how easy it is to turn the rod with my hand.