Controlling stepper-motors

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(see also Unipolar stepper motor)

When disassembling a malfunctioning CD or floppy drive, we can surgeon-out some very nice parts, screws, springs, cogwheels, and... motors. There are different functions that are serviced by the motors:

  • rotating the CD or floppy in the drive
  • ejecting the CD drawer
  • moving the read/write head

The following motors have been obtained:

  • PL15S020 datasheet
  • MSAPO20501 0403b5 DC5V S C (datasheet?)
  • 11F6NA 1552 MA1 (datasheet?)
  • BML5E8DRD (datasheet?)
  • MDN3BT3DRA (datasheet?)
  • F4MJR04 (datasheet?)


Image:stepper.jpg

The first three seem to be bipolar stepper motors, and thus we should be able to control them with one HB2 H-bridge module from digilent and the Cerebot board. They take 5V DC power. We will now experiment with these motors to see, if they could be used to propel a robot. Read more about how the stepper motors work in Wikipedia

Circuit connections

Image:stepper_cerebot_hb2.gif

Software

  • Simple test program that drives a stepper motor using HB2 module and Cerebot board: stepper.zip

Conclusions

The stepper motors we obtained from 3 1/2" floppy that were originally driving the floppy-drive heads could be controlled with Cerebot and HB2 module using the above program. The motors however, could not reach speed much higher than ca. 150 rotations/minute, and the lead screw cannot be applied to rotational force easily as it requires additional support (it is fixed in a specific position using plastic parts inside of the floppy drive). The strength of the torque is hardly sufficient to make the robot propel itself, but definitely not to carry and propel a robot. Thus these motors are not sufficient. Their bipolar driving is an additional complication, which makes them more difficult (even though also more fun) to use. It was recommended to us to use the motors from 5 1/4" floppy drives instead, which are not bipolar, and stronger. The motors driving the disk itself are permanently soldered to the PCB and thus they are also not very suitable for driving robot. We are now chasing for more motors that we could use as a propelling force for our robots.

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