Stepper Drivers

Posted in Electronics, Making - August 29, 2011 - 0 Comment

I have three head-positioning assemblies from CD-ROM drives. In the drive, they would move the optical components around to read the various parts of the disk. Removed from the drive, I’m planning to use them to make very small CNC machines. The head positioning assemblies use bipolar stepper motors, which turn a threaded rod, which draws the optics along.

Normally, I use the electronics from floppy drives to control stepper motors. The floppy drive interface has step and direction pins that directly control the motor used to position the head of the floppy disk drive.

Unfortunately, all of the floppy drive motors I have around used unipolar stepper motors. This makes driving them slightly easier, as power is supplied to the motor on one wire, and all the other windings are driven with current sink drivers. As a result, each winding is either on or off, but the current always flows through it in the same direction when it is powered.

All the stepper motors I have are bipolar stepper motors. Instead of current sink drivers, they are driven by a driver that can reverse the direction of the current flow through the motor windings. I can think of ways to drive a unipolar motor from a bipolar driver, but I’m not seeing any good way to drive a bipolar motor from a unipolar driver.

I may end up just building my own drivers, and running them with an Arduino or other microcontroller. I have all the parts, and it’s certainly cheaper than buying a bunch of drivers.