PLC Hardware and Software Ladder Logic of Digital Input
The how to do the outside excitation of electrical to the PLC inside the ladder logic is symbolized as the next. To address it exactly, When we depress the switch of push-button related to module of the PLC input, let's think about what is occurred to the internal logic of PLC corresponding to the switch contact of push-button. The figure below as next is characterized before depressing the switch of push-button has a contact.
The current from power pole of P can not flow to the module of PLC input address X000 because of the opening of switch of pushbutton (NO: Normal Open state) in the circuit of the electrical. This is to declare, at the point of input addressed to the X000 input module, there exists not external excitation of the electrical, and we can state this "Electrically Dry State". Or else, in the inside of PLC, contact of Normal (Opened NO) of un-identified X000 (not agitated because of the opening switch of pushbutton) can not build the power flow proceed, so this contact of NO is OFF state electrically. But in the inside of PLC, Normal Closed (NC) contact of the anonymous X000 can advance power stream, so this call is ON state electrically.
Now by de-pressing the Push-Button Switch contact, there exists excitation of electrical at the X000 and we can state this Electrically Wet State. Normal the contact of Opened (NO) of recognized the X000 (energized because of pushbutton switch closing) can change to closed state and proceed the power flow, so this contact of NO is ON state electrically in the PLC Logic. But in the inside of PLC, contact of Normal (Closed NC) identified X000 can not changed to opened state and build power flow proceed, so this contact is OFF state electrically.
PLC Software Ladder Logic and Hardware of Digital Output
The how to do variation of internal ladder logic to the outside hardware PLC is characterize as next in the Digital Output Module case.
If Coil Instruction of Y010 in the internal Logic of PLC is Energized, the Relay 010 linked to addressed Digital Output Module Y010 is also Energized. Or else if Coil Instruction of Y011 in the internal Logic of PLC is De-energized, the Relay 011 linked to address Y011 of the Module Digital Output is also De-energized.