This Tutorial is going to explain the basics of starting a ladder program in KW multiprog. This programming software is used to program Advantech PLC’s which are an up and coming alternative to Siemens and Allen Bradley PLC’s.
Once the software has been installed and opened, you should see a screen that looks something like this (Image 1.1).
Image 1.1 Multiprog On first Open
Click the “New Project” button in the top left of the window, this will open up a dialog box (Image 1.2) that lets you select which PLC you are using (The CPU May have come with a disk for a multiprog add-on for that specific type. If you do not see your PLC Listed, check the box for an installation CD).
For this tutorial, we are using an APAX 5520 – However, if you are using a different type of PLC, Do not despair, for the most part, the procedure will be the same. The I/O Card configuration will be different though.
Image 1.2 selecting a PLC type
Once you have selected a PLC type, your project has been created. Under “Logical POU’S” expand the “Main” tab, by clicking the plus sign, then double click the third Main in the list (as highlighted in Image 1.3) which should open up a blank white screen with a grid of dots. This screen is where all of the ladder logic is placed.
Image 1.3 Main ladder View
Take note that clicking anywhere on the screen will place a large + on the grid. This is used for placing things onto the page. Try placing a +, then click on the contact network button. (Image 1.4)
Image 1.4 Contact network button
On clicking the button, a contact network should be placed at your + (Image 1.5). This is made up of the basic building blocks of ladder logic. From left to right – Left power rail, wire, Contact, Wire, Coil, Wire, Right power rail.
Image 1.5 The Contact network in ladder view
One of the easier ways to think of ladder, is like an electrical circuit with logic built into it.
In ladder, power flows from left to right, leaving the left power rail, and ultimately ending up at the right power rail – These are important, as without them, the logic will not function properly.
Wires are used to join all of the components; they can be added by clicking the “Connect Objects” button. These do not affect anything except the direction of logic flow.
The contact – a -| |- symbol is like a switch, when the variable assigned is true, it allows the flow of power, when false, it blocks flow. Because contacts act like a switch, when they are allowing power, they are said to be closed, and when they are blocking, they are said to be open.
The coil – a -( )- symbol, is like the coil on a relay, when true, it will set the variable assigned to true, and when false, will set the variable assigned to false. (These allow you to turn the contacts on and off as appropriate, more on this later.)
Each of the components can be placed individually using their respective buttons – Now would be a good time to explore the interface and familiarize yourself with placing things into the ladder window. By clicking and dragging a box, you can move groups of components, note how multiprog will keep the wired connections by extending the wires for you.
Once you have gotten the hang of the interface, you can move on to Tutorial Two, where I will introduce you to the first of the more common ladder structures, and demonstrate how to assign variables to your contacts and coils.