Browse Prior Art Database

# Stepping Motor Drive Circuit

IP.com Disclosure Number: IPCOM000075877D
Original Publication Date: 1971-Dec-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 34K

IBM

## Related People

Fitzpatrick, DB: AUTHOR

## Abstract

In Figs. 1 and 2 coils A B, C, and D represent the four coils of a stepping motor. In the static state, coil A or B and coil C or D must be energized. Assuming coils A and C energized, if A was de-energized and B energized the motor would take a step in a particular direction. A state shift between C and D would cause a step in the opposite direction.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 54% of the total text.

Page 1 of 3

Stepping Motor Drive Circuit

In Figs. 1 and 2 coils A B, C, and D represent the four coils of a stepping motor. In the static state, coil A or B and coil C or D must be energized. Assuming coils A and C energized, if A was de-energized and B energized the motor would take a step in a particular direction. A state shift between C and D would cause a step in the opposite direction.

The stepping rate depends upon how quickly the current can be turned off and on in the stepping motor coils. To effect the quick current transitions, a resistor is put in series with the stepping motor coils (Fig. 1). This has the effect of putting the source potential on the coil until current builds up at which time the voltage is dropped across the series resistor. This method is effective, but often results in an intolerable heat production in the series resistor.

Fig. 2 shows a circuit which will improve stepping characteristics without the high-heat production.

Assume motor coils A and C are energized. Current i(o) is flowing through both coils in series. Assume that the resistances of coils A, B, C, and D are all equal and the transistor collector-to-emitter voltage drops are negligible. The voltage at point (a) is E - i(o)R(1) and the voltage at (b) will be (E - i(o)R(1))/2.

Let transistor Qc be turned off and Qd be turned on to effect a step. The current in coil C will induce a voltage, which will back bias the zener diode Z2 causing it to go into the zener region providing a path for decay current.

The current through R and coil A will also be interrupted, since transistor Qc is no longer...