| 摘要 |
<p>A time delay unit is easily connected to the supply of an electric motor. The motor is then required to drive the wipers of a car winds screen and position the blades at a set position of rest. The timer (10) is connected to a motor (1). The timer (10) is also connected to a d. c. supply by a switch (15). The circuit to the motor (1) also has a change-over switch (4) and a cam-driven switch 7). The timer (10) has a relay (16) with a moving contact (17). In one of its positions, the moving contact (17) closes the circuit to the motor and the motor is stopped. In its other position, the moving contact (17) connects an amplifier with transistors (T1, T2) to the motor (1). The amplifier has a resistor (21) adjustable time constant. The timer can set the frequency of operation of the motor and wipers without affecting the speed of operation.</p> |
