LC switch output roughly divided into three types, relay output, transistor output type and triac output type. AC to DC relay outputs are transistor common with 5VDC and 24VDC output, SCR is relatively rare, and only special output models only. Considering the selection of the output module type.
2014年8月18日星期一
PLC's IO module input sampling stage works
PLC works: When the PLC into operation, their work is generally divided into three stages, namely the input sample, a user program execution and output refresh three stages. Completion of the three phases is called a scan cycle. During the entire operation, PLC's CPU to a scanning speed of repeating the above three phases.
(A) input sampling stage: input sampling stage, PLC scan mode sequentially reads all input status and data stored within them plc
analog io module image area corresponding the unit. After the end of the plc input
module sample, into the user program execution and output refresh period. In both stages, and even if the input data changes state, status, and data g-input-output-module/">IO module
plc of the image area of the corresponding cell is not changed. Therefore, if the input is a pulse signal, the width of the pulse signal must be greater than one scanning cycle, in order to ensure that in any case, the input can be read.
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