3 Ladder Logic Controllers

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Date: 2012-05-31

3 Ladder Logic based Embedded Programmable Controllers

3 Ladder Logic ControllersLadder Logic is a widely used programming language based on circuit diagrams of relay logic hardware. It can be used to develop software for programmable logic controllers (PLC’s). The programs resemble ladders with two vertical rails on each side with horizontal rungs between them. Each rung of a ladder typically has a coil on the far right. There are different types of coils that represent whether a rung is closed or open. There are also different types of contacts for coils that represent whether a contact may be open or closed depending on the input. Function blocks are often available to help with implementing arithmetic operations or complex functions.

Touch Screen PLCs programmable in Ladder Logic or C Language are flexible solutions since different languages are better for implementing different applications and touch screens help users to interface with the controller. Users can navigate through different screens with the touch of a button and can check the status of different operations quickly and easily. The screen can be programmed to flash green when the operations are normal and red when there is an error. Touch screen PLC's like TPD-430 have a 4.3" touch screen display and come with free HMIWorks WYSIWYG development software which allows you to drag and drop buttons and objects onto screens and then apply ladder logic as needed. Easy to use software, demo programs and training videos help speed up development time. Touch screen PLC's like TPD-430 can be mounted in electrical outlets or in wall mountable boxes. They have RS-485 and USB ports for uploading programs from a PC. Modbus RTU devices can be interfaced with through the controller through the RS-485 port. TPD-430 can be used with I-7000 data acquisition modules or any Modbus RTU based devices.

ISaGRAF is an IEC-61131 based programming develop environment that can be used to program controllers in languages like Ladder Logic, Instruction List and Structured Text. Embedded controllers like uPAC-7186EG are programmable with ISaGRAF development software. uPAC-7186EG has an Ethernet port, one RS-485 port and one RS-232 port for program downloading and interfacing with other devices. uPAC-7186EG has an 80 Mhz processor, 512 KB flash memory, a real time clock and supports Modbus RTU and Modbus TCP protocols. Since it has a real time clock, it can be programmed to implement scheduled operations. It can be mounted on a din rail for easy installation in a control panel.

More rugged touch screen PLC's like VPD-130 have a 3.5" Touch Screen display and a rubber keypad. It is din rail mountable for easy installation in control panels. It has an RS-232/485 port and a USB port. It can be used with Modbus RTU devices or I-7000 data acquisition modules. VPD-130 has a real time clock so it can be used for scheduling operations like turning lighting on or off or opening or closing drapes at a certain time. It can be programmed with free HMIWorks development software and comes with demo programs.

Ladder Logic programmable controllers are easy to use and often come with software development kits which will help speed up the development process. They can be used for applications like building automation systems, automated carwashes, gas detection systems, cold storage or monitoring systems.

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ICP DAS USA is a provider of Industrial Data Communication, Automation Control and Test and Measurement products. We specialize in PLC hardware, Ethernet controllers, distributed I/O modules, Industrial Ethernet Switches and protocol converters. We provide programming services, training classes and free technical support.

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