| 摘要 |
PURPOSE:To attain simple constitution by setting a duty ratio or a frequency of a pulse signal fed to a CR time constant circuit and using a digital signal inputted from the 2nd digital input port so as to detect the physical change in an object to be detected. CONSTITUTION:The duty ratio t1 of a pulse signal outputted at first from an output port D0 is set to t1=t2/2 by a microcomputer 11, the 1st input port D1 is read, and when t3>t4, the pulse signal where the duty ratio is changed to decrease the t1 is set and when t3>t4, the pulse signal where the duty ratio is changed to increase the t1 is set. Then the relation of t3=t4 is attained finally. Then the value of the 2nd digital input port D2 is read for temperature detection in this state for a control such as heater control. Since a CR time constant circuit 15 and a transistor 16 only are used in place of a conventional voltage comparator circuit, the constitution is simplified.
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