There are many vendors and sources of PLCs: Automation Direct, FactoryMation, B&B Electronics, and yes, even eBay, among others. I will use the Click PLC available from Automation Direct as an example ...

AutomationDirect has released the new CLICK PLC programming software version 3.30, which allows any CLICK PLUS CPU to be configured as a 3-axis PTO/PWM motion controller. 100kHz high-speed inputs and ...

PID loop control capability (up to 8 loops simultaneously) has been added to the CLICK® Series of stackable, Ethernet-capable micro brick PLCs. AutomationDirect adds PID control functionality to CLICK ...