Ricoh FT7770 Service Manual page 97

- Operation -
To operate the development motor, the control circuit energizes drive coils
U, V, and W by turning on drive transistors 1 to 6. (See figure A.) The
coils are energized in sequence two at a time.
erated by the coils cause the rotor, which is made of four permanent mag-
nets, to turn.
Figure A shows the drive transistors that energize the coils and the
quence of drive transistor activation. The rotor turns 60° each time
drive coils are shifted, so a complete cycle is six steps.
Three Hall effect IC detectors feed back rotation velocity data to the con-
trol circuit. Based on this data, the control circuit increases or decreases
the drive pulse rate to maintain a constant motor speed.
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April, '89
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