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Author Topic: are stepper drivers required?  (Read 1227 times)
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I'm working on building a spherebot ( http://www.thingiverse.com/thing:7656 ), but I have a question:

Are stepper drivers required? I know that the arduino CAN control the steppers directly, but "can" is a lot different from "should". I know that they increase the current, but that much torque may not be necessary for something that rotates a spherical object and moves the pen holder five inches along the X axis.

If they're not required, would I need to add something else like resistors to the circuit?
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Depends what current the stepper takes - if its more than 30mA you definitely need a driver, even if its less the backEMF and other motor effects could cause higher voltages/currents to flow and risk damaging an Arduino pin.  Basically a logic signal is not rugged enough for electromagnetic components.

I don't think you'll find 5V 20mA stepper motors!

With a unipolar motor you have the simple option of using a transistor or darlington array as driver.
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It looks like one of my steppers (SLC-42D003) is 24V / .69A / 11ohm. The other stepper is SLC-42D005, but I couldn't find any information about it other than that it's 3.1ohm. Both steppers are 1.8deg, if that has any importance to my question. These steppers came out of old HP scanners.

The steppers have 4 wires each. Do you think that they're unipolar or bipolar? I'm still very new to this stuff, but I'd really like to build something cool and cheap!
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A 4 wire stepper is a bipolar motor. I would suggest an Easydriver from Sparkfun. It's inexpensive, easy to use and you can use the onboard regulator to power the Arduino board. The Pololu drivers on the Spherebot webpage look good also but I haven't tried them.
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24V, 0.7A and 11ohm?  Is there a datasheet?
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Thanks for the EasyDriver tip... I'll look into getting two of those since they're just a little more than the price of one Pololu!

I don't have any kind of datasheets because they were salvaged parts and the internet hasn't helped. I can only find useless Russian and Chinese pages that list a TON of part numbers but no information at all.
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