| 摘要 |
<p>The large display has rows and columns of character displays, each consisting of a drum driven by a stepping motor. The motor makes one step when its stator current is reversed and then restored to its original direction. The stator winding (1,2) has a centre-tap (7) connected to the positive supply terminal. The ends of the winding are connected via switching transistors (8,9) to the negative terminal. The transistors are driven, each via an AND-gate (10,11) by a bistable circuit (12) so that when one is ON the other is OFF. The bistable can only be driven when row and column selection voltages coincide in an AND-gate (19). The bistable and transistor AND-gates (10,11) are then driven for the required number of steps by a pulse train, which is fed to all the displays in the row. The advantages of the circuit are that the supply cannot be short circuited, even if both windings become energised together, and that transients can be suppressed simply by diodes (3) across the windings.</p> |
