| 摘要 |
PROBLEM TO BE SOLVED: To provide a dry contact input circuit without using a photocoupler or a CD-DC converter. SOLUTION: The dry contact input circuit has a CPU 2 for determining whether a dry contact signal input to a signal input part 1 is "opened" or "closed", and an interface circuit 3 for notifying the CPU 2 of the input dry contact signal as an H/L signal. The interface circuit 3 is provided with a capacitor in the signal input part 1, including an output transistor Tr4 for outputting the H/L signal corresponding to the opened/closed state of the dry contact signal to an input port Pi of the CPU 2, a start transistor Tr1 for charging capacitors C1 and C2 and starting the output transistor Tr4, and a discharge transistor Tr2 for discharging charge potentials of the capacitors C1 and C2, and the CPU 2 determines the opened/closed state of the dry contact signal by checking a state of a signal H/L input to the input port Pi at predetermined timing. COPYRIGHT: (C)2011,JPO&INPIT
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