Programming the built-in SoftPLC in the WEG CFW300 Variable Frequency Drive is easy once you see how. This short video gets you up and running quickly by showing the basic workflow without getting bogged down in PLC programming details. This is the best VFD, with a super low cost, but with high end features like Dynamic Braking, Fire Mode, PID, 65,000A SCCR, Zero Stack foot print, Multi-Speed, etc and is even cULus listed!
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I have a switch connected to digital input 1 on the drive. We’ll program the SoftPLC to take that input and send it to digital relay output 1 through the normally open contact which will turn on the light that is built into this switch. That will give us a super simple ladder program, so we can see how to setup and program the SoftPLC without getting bogged down with PLC ladder logic details. Before doing anything though, let’s do a factory reset on the drive so we are all starting from the same place. Let’s bring up the WEG Programming Software, which I will refer to as “WPS.” Create a new configuration, name the first resource – our Soft PLC Demo Drive in this example and hit next. I’m connected to the drive using this RS485 Com module and this USB to 485 converter which to my PC looks like a serial port, so I choose this guy. I see in my PC’s device manager that the drive is on serial port 13, so I make sure that is here. The rest of these are the drive’s default values and since we just did a Factory Reset, I know these are what I need, so I hit test to make sure WPS can see the drive. It does, so we hit NEXT. Since we are connected WPS already knows which drive we are connected to, so we just hit next again. This is so we can import ladder code from the WLP software – we don’t need to do that - so we can skip it and hit finish. Great – here is our configuration and here is our Soft PLC drive resource. As usual we can see all of our parameters and diagnostics. This is where we enter PLC ladder code. Double click on the Main Ladder code and we are ready to go. Make sure you are not connected – you can’t edit ladder code while connected to the drive because that cold open you up to unsafe and dangerous situations. Just reach over into the tool box and drag a normally open contact onto the rung. Double click on the name and search for a digital input and select DI1. Now I go over to my coils and drag an output coil on to the rung. Double click the name, search for a digital output and select output one. That’s it for the Ladder Code. We’ll take a closer look at all the functions available to you and a lot more in the next video. One of the cool things about the WEG drive is the Digital Inputs aren’t limited. In some drives if you use a Digital Input in the SoftPLC, then you CAN’T use it in the drive. And vice versa. So, the good news is the WEG drives don’t limit you like that. The bad news is, you need to be extra careful because the drive may be using a digital input that you are also using in the SoftPLC. Let’s look at our Digital Input and see if we have any conflicts. If we go to our parameters and search for DI1 – and we connect to the drive - we see Parameter 263 tells us that DI1 is currently assigned by default as the Run/Stop for the drive. Again, there is nothing wrong with that IF you intended for DI1 to be both the manual switch input AND a Run/Stop for the drive. In fact, that’s a pretty common thing to do. But, since we haven’t even entered our Motor parameters yet, let’s limit DI1 to just the SoftPLC right now and change parameter 263 to NOT USED by the drive. Remember- this happens automatically because we are connected to the drive. Now because DI1 was defaulted to control Run/Stop something was probably expecting to use it. Let’s search the parameter list for Run/Stop. Look at that, the Remote run stop was planning to use DI1 as the run stop control. We don’t have to change this – it’s not going to work anyway since we turned it off in Parameter 263, but it’s nice to go ahead and change it anyway so in the future when others look at your setup there won’t be any confusion. Let’s change the remote run/stop to be controlled by the HMI just to get it out of the way. What about the Digital OUTPUT 1? We want to use it to turn the indicator on, does the drive have any default plans for it? Search on DO1. Yep, Parameter 275 says the drive is planning to use this to indicate a no-fault condition. This one we DO have to change. We can’t have two different functions trying to control a single output – The drive will let you do it, but we would never know which one is controlling it. So, let’s tell the Drive that for our demo only the SoftPLC will be controlling this output. Great, we entered our ladder code and we made sure the Digital I/O we are using doesn’t conflict with the drive. To build - or compile - the ladder code we just hit the Build Resource button. And we see down here we have no hits, no runs, no errors. Perfect. Now we just use this button to download the ladder code to the drive. Do we want the ladder program to run automatically when the drive is powered up and when we are done transferring the ladder code? Sure. If I reach over and flip the switch, the Soft PLC sees the switch toggle and then sends it back out to control the light bulb. Exactly what we expect. How do you know that I didn’t just connect the switch directly to the indicator? Well, f we re-connect to the drive and go to parameter 901 and set it to a zero to stop the SoftPLC, give it a second to take … looks good … and now try to flip the switch – nothing happens because the SoftPLC is no longer passing the input switch signal to the digital output. Let’s change parameter 901 back to a one to get the SoftPLC running again and sure enough, everything is back working again. And look at this. Since we are connected, if I go back to the ladder program, I can also see that here. When I toggle the switch both the contact and the coil light up. I know that seems silly in this simple example, but when you start getting into real PLC programming applications it’s an absolute life saver to be able to see exactly what is going on inside the ladder code as it runs. And how cool is it that you can change drive parameters AND do your ladder programming AND do your diagnostics all in one application? It’s so handy to be able to bounce back and forth between all of these without having to bring up separate applications. And if we had multiple drives or even multiple systems, it’s just as easy to bounce back and forth between all of them and quickly configure, program or do diagnostics on any of them. This WEG programming software is really well thought out … and the more you use it the more you are going to appreciate that. And remember - it’s a free download at Automationdirect.com. That ought to be more than enough to get you up and running with the Soft PLC. Click here to learn more about the WEG CFW300 Variable Frequency Drive. 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