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Daryl

Isagraf Workbench - FBD Help

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Folks, I am using Isagraf Workbench to program an Omniflex PLC. I don't have much experience in programming using Workbench and am looking for some assistance. In RSLogix ladder logic, i can disable an output by using an "Always Off" instruction. I'm not sure if the "Always Off" instruction is unique to RSLogix, or even to ladder logic, but I need something similar for a Function Block Diagram using Isagraf Workbench. I have three on/off inputs going into an instruction that looks for =1 (obviously looking for an On signal) which sends an ouput to begin a sequence. I wish to disable these inputs from activating the output sequence. Therefore an "Always Off" instruction at the output side of the compare instruction would be ideal, but I don't know how to do this with FBDs or with Isagraf Workbench. Can anyone assist?

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To start, I always use a FALSE bit in a ControlLogix (not an AFI!). Possibly multiple false bits even, with a unique description for each indicating why it's there (I usually chastise people I see using AFIs!). To ensure that the bit is always false, I use an OTU latch that is always on. Back to IsaGraf, my experience with IsaGraf is version 3.55 for SCADAPack, but it should be similar. You can use a false bit, just like I mentioned. Create a power rail on the left an attach it to an inverted coil with your FALSE bit. Then use a contact with your FALSE bit before the actual output. This should accomplish what you're looking for. If you need any extra help, take a picture of what you're trying to work on to make it extra clear. Best of luck! Edited by MrAutomation

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