| 摘要 |
<p>Motor torque (1) is only transmissible unidirectionally through a coupling unit (3) to e.g, the shutter drive roller (2), which has a Hall-effect or other speed and direction sensor (4) inputting to the microprocessor (5). The processed signal is compared with appropriate (rise or lower) preset threshold value; if the speed falls below this, the motor supply (6) is interrupted. To prevent spurious interruptions, e.g,while the motor is running up to speed, a delay unit (9) is provided. The free-wheel feature prevents motor overloading or stalling if an obstacle is encountered by the descending shutter, or it sticks. Detecting this, the controller will disconnect the motor supply, so averting the undesirable effects of continued free-wheeling.</p> |
