| 摘要 |
PURPOSE:To accurately set the opening of a damper, by controlling a damper motor by a resistance circuit varied according to a load provided between buses and a voltage outputted from a potentiometer according to the opening of the damper, in a controlling circuit for the damper for regulating the quantity of combustion air supplied in a hot water supply device or the like. CONSTITUTION:A control signal from a control signal generating circuit 12 is varied with a load, whereby a sliding contact of a variable resistor part 20 is moved, and a voltage at an output point 22 is varied in a range between a maximum and a minimum. The voltage VB at the output point 22 appears at an output end of a voltage follower circuit 23, and a voltage VC at an intermediate contact 24 is inputted to a positive-side input terminal 261 of an operational amplifier 26 of an amplifying circuit 25. On the other hand, a voltage VP according to the opening of a damper is inputted from a potentiometer 16 to a negative-side input terminal 262 of the operational amplifier 26, and a voltage VG according to the voltages VP, VC is outputted from a terminal 263 to a damper motor-driving circuit 27. Thus, the opening of the damper can be accurately set. |
