Stepper Motor


	Stepper Motor

The stepper motor was removed from an old full-height IBM 5.25 inch floppy disk-drive (Tandon TM100). The motor was used to move and position the read-write heads. It contains 4 coils that opeate at 12Volts dc. The motor is operated by energizing coils in sequence. There are three sequences of coil excitaion.

Single-Coil

Excitation

Two-Coil

Excitaion

Half-Step

Excitaion

Resolution of 3.6 degrees per step (100 steps per revolution), smooth, consumes little power but low torque.

Same resolution, more torque but less smooth and consumes more power.

Double resolution (1.8 degrees per step).

The stepper motor controller is able to operate the motor in any of the three modes by programming the output pins to go high and low in the proper sequence. The rotation is reversed by reversing the sequence of excitaion rather than reversing polarity.

The transistors are NPN-Type switching transistors. Radio Shack Cat. No. 276-1617
All resistors are 1/2W, 5% tolerance.
Four of circuits are needed, one for each coil.
A coil and the LED are turned on when the Basic Stamp user ouput pin goes high.
A coil and the LED are turned off when the Basic Stamp user output pin goes low.

Fault tOlerant Real-Time Systems

FORTS Car

forts@cs.pitt.edu
Disk drive, stepper motor pictures and excitaion animations are by Ian Harries <ih@doc.ic.ac.uk>