Thursday, June 30, 2011

Ladder Logic of TEP PLC

Ports of Expansion and Slave
The TEP PLC is prepared with 4 expansion ports to let future modules of input and output to be connected. Possible modules comprise analogue to digital converters, temperature sensors, motor controllers, and so on. Future software of pending updates, an added PLC can also be linked as a slave device, doubling the inputs and outputs number.

Software and Ladder Logic
Fundamental software is integrated with the TEP PLC permitting simple creation of Ladder Logic programs and gives a one-step way of programming via USB. The software is free of charge and if there is updates can be downloaded from the product page website. The software main screen consists of a Tool Box where the variety of the symbols of Ladder Logic can be found; an area of Log which gives information about the connection of PLC and error feedback; an area of design where the Program of Ladder Logic is written; and a menu bar providing access to PLC programming operations, File operations and, unlimited undo/redo.

Ladder Logic
If you transfer a current throughout the coil, from point A to B, the normally open contact will be connecting C to D. even though almost all the symbols used in a Ladder Logic program don’t symbolize real relays, it is useful to recognize their source, and in some logic can be consideration of as parts of virtual relays.

The symbol of LOAD or normally open contact symbol can be used to represent an input, and the OUT symbol or the symbol of relay coil can be applied to adjust the state of an output in a program of Ladder Logic. The fundamental output of a PLC is typically a simple relay, with the normally open contact showing to the outer world. To close the contact of coil have to be energized, therefore the symbol of OUT or symbol of coil is used to adjust the output state from within a program. The PLC input is typically not a relay, but an optically of switch coupled or opto-isolator. An opto-isolator is created by an LED and a transistor of photosensitive.

When current transfers to the LED, light stands out on the photo-transistor and it switches on. This display is very alike to current transferring throughout the relay coil, causing the normally open contact to close. Therefore it is the LOAD symbol that reads the input state or its photo-transistor.


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