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# Direction and Speed Detection Circuit

IP.com Disclosure Number: IPCOM000077720D
Original Publication Date: 1972-Sep-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 43K

IBM

## Related People

Crisp, JM: AUTHOR

## Abstract

The direction and speed of motor 1, Fig. 1, is measured by two-phase tachometer 2 and the logic network of Fig. 2.

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Direction and Speed Detection Circuit

The direction and speed of motor 1, Fig. 1, is measured by two-phase tachometer 2 and the logic network of Fig. 2.

The tachometer provides two 90 degree phase-shifed output signals, phase A and phase B, on conductors 3 and 4. When the motor rotates clockwise (CW), the signal phase relationship is as shown in the left-hand portion of Fig. 3. When the motor rotates counterclockwise (CCW), the phase relationship is as shown in the right-hand portion of Fig. 3. For CW rotation, the signal state sequence is AB, AB, AB, AB. For CCW rotation, the state sequence is AB, AB, AB, AB.

Exclusive OR's 5 and 6 provide an output pulse on conductor 7 each time that phase A signal makes a transition. Exclusive OR's 8 and 9 provide an output pulse on conductor 10 each time that phase B signal makes a transition. Exclusive OR 11 provides an output on conductor 12 whenever the present state of the two signals is AB, or AB. Exclusive OR 13 provides an output on conductor 14 whenever the present state of the two signals is AB or AB.

AND 15 sets latch 16 whenever signal A makes a transition into the

or the AB state. AND 17 sets this latch whenever signal B makes a transition into the AB or the AB state. As shown in Fig. 3, all of these conditions indicate CW motor rotation. So long as the motor continues to rotate CW, latch 16 remains set, providing a continuous CW direction output on conductor 18. During CW rotation, each transition of phase A sign...