Patent GB-960079-A (GB)
Title: Improvements in or relating to electrical circuits for selecting and controlling stepping motors
Inventor: CALDAROLA LEONARDO
IPC: H02P8/40
Filed: 1962-01-26
Abstract: 960,079. Electric selective signalling. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Jan. 17, 1963 [Jan. 26, 1962], No. 3006/62. Heading G4H. A control circuit for operating any one of a number of stepping motors comprises a drive circuit adapted to apply D. C. to pole pairs of a selected motor, means for selecting one of the motors, means for stopping the drive circuit on a given phase and switching means actuated after stopping to earth this phase. The stepping motors Fig. 1 each consist of a toothed rotor and six toothed poles connected in opposite pairs A, B and C. They are energized sequentially in pairs AB, BC, CA, to rotate the rotor through one step. One of the motors is selected by a selector switch S1, Fig. 2, the bank S1-2 of which operates one of the relays Y1-Y3 corresponding contact Y1-1 to Y1-3 &c. connecting the selected motor to three lines a, b, c. The A phases are earthed at the completion of the setting by relays X1-X3 selected by another bank S1-1 of the same switch S1. The extent of rotation to be given to the selected motor is set by rotation of a knot 21 Fig. 4 which controls switch S2. Bank S2-2, Fig. 2 selects one of the input leads of the counter, pulses being passed from line a to the selected input so that the counter gives an output after the selected number of steps to stop the motor by energizing relay ST opening contacts St-2 to actuate a stop interlock circuit and de-energize relay N. The drive pulses are derived from a disc 11, Fig. 4 having peripheral openings which are sensed by a photocell. The disc is driven through a magnetic clutch CL-1 by a synchronous motor when the forward or reverse button is pressed. The shaft 16 of disc 11 also carries cams operating switches SWO-SW4 and blades 17 Fig. 5, one switch and one blade for each selected amount of drive. The bank S2-1 of switch S2 selects the appropriate switch so that if the counter fails to stop the motor this switch actuates the stop interlock circuit by opening in the same way as contacts ST-2. Pulses from the photocell step a three stage transistor ring adapted to energize the outputs 1, 2, 3 in pairs sequentially. The stop contacts N-1 control this ring, there being no out put when the contacts are opened by de-energization of relay N. The outputs from the ring are amplified and applied to direction controlling contacts F-1, F-2, R-1, R-2, controlled by the forward or reverse relays F, R each having a corresponding push button. These contacts reverse the order of energization of the pairs of inputs a, b, c to the power amplifiers, and the order of energization of the corresponding drive lines a, b, c. As an extra safety measure the shaft 16 is brought to rest shortly after delivering the required number of pulses by abutment between one of the blades 17 and a stop blade 18 on the control shaft 19. If the setting of knob 21 is to be changed it must first be pressed axially inwards and this operates a switch SWS which causes the stop circuit to operate and to deenergize the clutch CL1, Fig. 4 allowing the shaft 16 to return to its initial position under the influence of spring 25. Resetting takes place in the same way on normal operation of the stop circuit. Operation of the switch S1 to select a different motor also operates the stop circuit and effects resetting of the shaft 16.