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gromit

SLC500 Flex I/O

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I ran out of room on a SLC500 chassis but need another 9 analog outputs. What is the best option? I used Flex I/O on a PLC5 before but recall the setup was combersome. Any suggestions?

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Which SLC processor do you have?

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It is an SLC5/05 ---1747-L552 PLC.

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FLEX is generally going to be a compromise between ease-of-use and long-term availability. If it were my system, I would probably use a 1747-SDN DeviceNet scanner and then use CompactBlock LDX or POINT instead. But then I use DeviceNet a lot and don't mind the extra steps of configuration. If you can invest the time in configuration and programming, the simplest thing will be a 1747-SN scanner in the main SLC chassis, then a 1794-ASB and a few Analog modules. You'll write Block Transfer logic in the SLC controller. Once you get it going, maintenance or replacement will be only "set the DIP switches and connect three wires". I don't usually recommend controller-to-controller messaging as an "I/O" method, but you could wire up a MicroLogix 1100 controller with expansion Analog modules and just have that send values over the Ethernet network to the SLC-5/05. I would only do this if the analog data is not time or process critical.

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Thanks Ken. I don't have any extra slots for the 1747-SN scanner and I don't have RSNetworx either. I think I like the MicroLogix1000 idea but don't have much money in the budget, so I'll have to check on pricing.

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Do you just have the one chassis? If so, you can add up to 2 additional chassis in the SLC system, with special cables daisy-chaining them. I don't know the part numbers for the cables, but I've seen this done with SLC 5/04s. You may run into the limit on the number of IO points the CPU can address before you run out of slots.

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The cable is 1746-C9 (36") or 1746-C16 (50"). See page 108 of 1747-UM011_, SLC 500 Modular Hardware Style User Manual. Your expansion chassis will need its own power supply.

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Thanks Joe. I didn't mention we have a small footprint so adding another chassis would be very tight.

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Still interested in maybe using MicroLogix with analog output module. Which part numbers or model would best connect to the SLC5/05 for this application?

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Joe, I walked it down and it looks like there may be room for a 1746-A4 chassis to be connected with the 1746-C9 cable. Thanks for the recommendation. I've already put in a call to the local distributor to provide a quote. The only question that I could think of is what logic changes need to be made for the existing program to recognize the new 4-slot chassis???

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The extended chassis will need to be added to the I/O configuration along with any modules that it houses. Then you will need to add logic to make use of the new data, if required. With analog modules, this usually entails some scaling of raw numbers into engineering units. With some of the modules, you can configure them in the i/o config. under advanced configuration to get engineering units right from the card.

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I've also seen ladder logic used to write the configuration data to output words in the data table. This was generally done just on first scan.

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