1756-IF8 - PLC Programming & Automation

PLC Hardware Components and the Software That Uses Them

Timing chart showing a field input rising, the input image bit following at the next input scan, the coil in logic changing during the program scan, and the physical output finally switching after the output scan, about one scan behind the field

What is in a PLC rack and how the software sees it: power supply budget, CPU memory, I/O cards, tasks and routines, and tags against S7 addresses.

PLC I/O Modules: Sinking, Sourcing, Keying, Scaling

by PLC

Timing chart of a 24V DC input: the field sensor edge, the module input filter delay, and the controller tag updating at the next RPI

How to pick discrete and analog I/O, get sinking and sourcing right, set RPI and electronic keying, wire a 4-20 mA loop and scale the raw counts.

PLC Water Treatment: Levels, Lead/Lag Pumps and Dosing

by PLC

Timing chart of lead and lag pump alternation: the lead call starts pump 1, the lag call brings in pump 2 at high level, and on the next cycle pump 2 takes the lead

Wet well level control, pump alternation that shares the wear, chlorine dosing with long dead time, and remote sites over cellular Modbus that go quiet.