Wednesday, July 27, 2011

PLC based on SC1x3-IEC and SC23-IEC

This application note provides a description how to make a programmable logic controller based on the programming system of CoDeSys and the IPC@CHIP®. Thus functionality, specifications and usage is explained. A programmable logic controller is a device designed for industrial processes automation. Characteristic examples for concerning a PLC are:
• room automation
• observation of process
• machinery control
• process of production
Usually PLCs contain of the microcontroller unit including memory, processor, and a variety of hardware interfaces. Outstanding of a PLC features can comprise:
• inputs and outputs standardization
• programming of platform independent
• temperature range of industrial
• management of power fail
• memory of non-volatile
• capability of real time
The standardization programming with the international standard of IEC 61131-3 for PLCs recommends portability of the programs between processor types and different platform.

Requirements :
To begin with this function the software and hardware required is described as below.
• Any development kits and evaluation kits of the IPC@CHIP®, such as DK61, DK55.. is sufficient to recognize this application.
• programming system of CoDeSys v2.3 for IPC@CHIP
• Release of CoDeSys@CHIP-SDK Edition 10.2007

Digital Inputs With Isolation of Galvanic:
PLCs are frequently utilized in a manufacturing atmosphere. To care for the PLC from equalizing current or transient voltages because of different mass potentials an isolation of galvanic can help decreasing those problems. There are some incorporated devices that offer a termination for the signal plus of digital the current limitation feature and overshoot protection. As an instance there is the CLT3-4BT6 from ST.

Digital Outputs Without Isolation of Galvanic:
If no isolation of galvanic required, it offers an easy method to switch PLC levels of 24 V. For security against inductive load a diode of freewheeling is use similar to GL34G from Vishay.

Real Time Clock:
In a real time clock of PLC is applied to provide the system with a time capacity which is autonomous from power supply. In case of a power loss in the system, the RTC continue the time information. This can be particularly helpful, if there is a power loss in the system which is date stamping the files. For instance, we get the device of Maxim DS1307, which can be related through the interface of I2C. The RTC is powered by the connected battery or capacitor in case the 5 V power supply drops below the 3.2 V level. Time can be improved throughout the RTC via I2C when the power is up again.

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