| 摘要 |
PURPOSE:To allow users to regulate the rotation speed of a fan depending upon their choice and place to be cleaned for efficient and effective cleaning work by providing a switch to allow users to chose optionally between automatic rotating speed control of the electric fan by means of dust detection and pre-set rotational speed control by means of a setting device. CONSTITUTION:A switch 24 is provided between a discriminating circuit 21, that drives an indicating lamp 23 when dust is detected, and a control device 25. A variable slide resistor 26, that is operated linking to a sliding knob on the setting device, is connected to the control device 25, and its output is connected to a gate of a bidirectional thyristor 27, so that the rotational speed of a fan 28 is changed. When a sensor detects dust, its signal is input to an amplifier 19 and then input to the discriminating circuit 21 after amplified, so that the indicating LED 23 is turned on. On the other hand, when the switch 24 is closed, the output from the discriminating circuit 21 is input to the control device 25 to shift the phase further in addition to the phase control value from the variable resistor 26 so that the rotational speed of the fan 28 is increased. When the switch 24 is opened, the rotational speed of the fan 28 is unchanged by the set point set by the variable resistor 26. |
