JPS6423046A - Protective device for ventilating fan electronic circuit - Google Patents

Abstract

PURPOSE:To prevent an electronic circuit from being loaded owing to environmental changes by feeding the output signal from level comparator which compares and detects the level of a sensor which detects the degradation of environmental conditions in the area where a ventilating fan is installed as well as the control signal from a control circuit, and driving the fan with the output signal from the level comparator given the priority. CONSTITUTION:In the case of a sensor 1 which shows a reduction in resistance as the environmental deteriorates, the point C of the output of a voltage comparator 11 is at 'H' level, and, if the voltage at the point (a) drops below the point (b) owing to the environmental deterioration, the point (c) of the output of the voltage comparator 11 becomes 'L' level. The output signal from the level comparator 2 is given priority over the control signal from the control circuit in a fan drive section 3, and a ventilating fan 4 is driven on the signal from the level comparator 2. As the ventilating fan 4 is driven, electronic circuits formed in the level comparator 2, fan driving section 3 and control circuit 5 are cooled and dried, and are not risked in an adverse environment.