PLC Quick Start on the GS4 Variable Frequency Drive (VFD) - Part 1 of 2 from AutomationDirect

Every GS4 Variable Frequency Drive has a built in PLC that's perfect for those times when you need just a little extra logic. For example, suppose you have an irrigation system and you just want to run the pump a couple times each day. All you need to do that is a timer and a little bit of logic. The PLC that’s built into the GS4 drive is perfect for that. Or, suppose you have a conveyor that you need to stop automatically so you can swap out containers? All you need for that is a couple inputs and a little bit of logic. Again, the built in PLC is perfect for these kinds of applications. Since you no longer need an external controller, power supply, wiring or enclosure, you get your system up and running quicker, have lower maintenance costs, save on control system foot print, save on reduced spares inventory, and will have an all-around less expensive and more reliable system. BUT, because you have both a PLC and a Drive in the same box, you need to be very aware of a couple things. While the drive comes with a PLC built in, it comes from the factory with the PLC disabled. And for all practical purposes, it’s not there until you enable it. That means you can’t even talk to it or set it up until you enable it. How do you enable it? Easy – just go to the keypad, hit the MENU key, scroll down to PLC and select either RUN or STOP. Either of those “enables” the PLC part of the drive. Once the PLC is not disabled you now have something new to keep in mind. The GS4 Drive has built in analog and digital I/O and more I/O available via expansion modules. When the PLC is enabled you now have two different devices trying to access the same I/O. Which one gets control of the I/O? The answer is: The PLC AWLAYS wins IF the PLC is not disabled AND the PLC uses the I/O in its ladder code. So, for example, if the PLC has Ouput3 in the ladder code – then the drive’s corresponding digital output won’t function – even if you set it up in the drive to do something. If you disable the PLC, then the drive will regain control of that digital output, until you re-enable the PLC again. Keep an eye on the various mask parameters – they will show you graphically which I/O are owned by the PLC. For example, here is the digital output mask and we see that that output three we used in the ladder code is shown as being owned by the PLC. And finally, when trying to remotely communicate with the two devices, remember that the Drive and the PLC have different addresses which you can change. So be careful not to set them to the same address. They come from the factory as address 1 and 2. Why do they have different addresses? Because they both use the SAME RS485 serial port for communications! There are two modular jacks, but they are connected in parallel so you can Daisey chain drives. Of course, you can only have one master device connected and since GSoft2 and GSLogic are both masters – that means you can only have one running at any time. That is, you can only program the PLC OR Configure the drive – you can’t do both at the same time because they will try to talk over each other and mess up everybody’s communications. OK, That’s enough background stuff. Join us in Part II of this Quick Start we’ll do a live demo to show you how to get up and running quickly. Click here to learn more about the GS4 Drive. Click here to learn more about AutomationDirect’s free support options and click here to subscribe to AutomationDirect’s YouTube channel so you will be notified when we publish new videos.