| 摘要 |
PURPOSE:To enable to decrease the discharge quantity of a fan gradually and to stop operation of the fan after passing of a predetermined time, by providing a comparison circuit which makes a comparison between values stored in memory circuits and the count value of a counter and lowers the operational speed of a fan motor when the above two values become equal to each other. CONSTITUTION:In memory circuits 27, 28, 33, smaller values are stored at a prescribed ratio to the count value of an up-down counter 24. When the count value of the counter 24 becomes equal to a value stored in the third memory circuit 33, a high-level signal is produced from a first comparison circuit 34 and applied to one input terminal of an AND circuit 17, whereby a triac 3 is turned ON and operation of the fan is switched from ''strong draft'' mode to ''weak draft'' mode. Subsequently, if a triac 4 is turned ON, the operation of the fan is switched to ''gentle draft'' mode. Finally, when the timer is counted up, triacs 2-4 are all turns OFF, so operation of the fan is stopped. |
