The downy woodpecker is virtually identical in plumage pattern to the larger hairy woodpecker, but it can be distinguished from the hairy by the presence of black spots on its white tail feathers and the length of its bill.
A programmable logic controller, PLC, or programmable controller is a digital computer used for automation of typically industrial electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures.PLCs are used in many machines, in many industries.LC applications are typically highly customized systems, so the cost of a packaged PLC is low compared to the cost of a specific custom-built controller design. On the other hand, in the case of mass-produced goods, customized control systems are economical.
INPUTS AND OUTPUTS. Inputs to, and outputs from, a PLC are necessary to monitor and control a process. Both inputs and outputs can be categorized into two basic types: logical or continuous.Consider the example of a light bulb. If it can only be turned on or off, it is logical control.e can also use relay outputs to switch the outputs. The example shown in Figure 2.5 An Example of a 24Vdc Output Card (Sinking) and Figure 2.6 An Example of a 24Vdc Output Card With a Voltage Input (Sourcing) is repeated yet again in Figure 2.7 An Example of a Relay Output Card for relay output.