Learn about things you need to know before using the GS4 Variable Frequency Drive's built-in PLC to control the drive in this live tutorial Video/Demo from AutomationDirect.com.
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In part 1 we did a quick little example to show how easy it is to control the Drive from the Built-in PLC. In this video we’ll dive a little deeper and show you how to get the most out of your GS4 Drive. When you use the frequency command in your ladder code, that tells the drive that you want the PLC to control the frequency and that it should ignore whatever you told it to do in parameters 4.00 and 4.01, as long as the PLC is enabled. If you disable the PLC then the drive goes back to being controlled by Parameters 4.00 and 4.01. Likewise, if you use ANY of these special function registers to control the drive – even just one of them – the PLC owns run, stop, forward, and reverse of the drive as long as the PLC is enabled. If the PLC is disabled, then Parameters 3.00 and 3.01 regain control of the drive until the PLC is enabled again. If you have ANY question about whether the PLC or the drive owns the frequency or the controls, Parameter 9.34 shows you what the drive thinks the PLC is controlling the Frequency or the run stop controls. This screen tells us the PLC is controlling both the Frequency and the Run/Stop Controls. Remember, these will only be lit up if the PLC is enabled! We said earlier that these registers control the acceleration and deceleration and that they had two implied decimal places. That’s only for the default case. You can actually change that using parameter 1.15 from hundredths of seconds to tenths of seconds. We only used these special function registers to control the drive in this example. There are a few others you can use: Enabling M1042 issues a quick stop – that tells the drive to stop immediately. Of course your actual stop time depends on load inertia and whatever braking resistors you might be using. So you could have one of the inputs drive this Special Function Register and use that as a super easy way to stop the drive via ladder code – BUT don’t think of it as an E-Stop – use the drive’s STO function if you need a true E-Stop. STO is built in, requires no coding on your part and is completely independent of the PLC. It will stop the drive regardless of how the PLC is configured. Enabling register M1044 Pauses whatever the drive is doing and uses the current deceleration parameters to ramp the speed of the motor down. When you disable M1044 the drive ramps back up to speed and continues on its way. Once you tell the drive to ramp up to speed, it takes time to get there. How does the PLC know when the drive has reached the requested speed? Or if the drive is even running and which direction is it running? There are a bunch of special function contacts that indicate all of that. There is a Run status contact, Forward reverse status contact, an at frequency contact and even a contact that is active for the first scan only which is great for initializing things. And look at this: These contacts – there’s a normally open and a normally closed version – tell OTHER controllers if this internal PLC is running or not. Help topic 104 lists all of those contacts and their associated relays. The special function registers are in help topic GSL 105. Again take a few minutes to review those – there are lots of cool things you can do with these special function relays and registers that will make or ladder logic programming so much easier. How did I know all the stuff we covered in this video? Well, truth is, I didn’t. I literally just read you the help topic on the Frequency command and bits and pieces of a few others. There is no user manual for GSLOGIC because the Help topic has everything you need to know, it’s searchable and it’s really comprehensive and easy to read with lots of examples. So, go there first when you have any questions about programming the PLC. Click here to learn more about the GS4 drives. Click here to learn 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.