I have a 10 slot rack with a 1747-asb module, 4 32 point input modules and 4 32 point output modules. Now it appears that I might need more than IO than that. Is there anyway I can add more IO to a single 1747-asb?

An -ASB module can have a maximum of 32 logical groups assigned, that means 32 Input words and 32 Output Words... (4 logical racks)

See attached image, reference is User Manual.

Hope this helps....

- fuzzy logic


[attachmentid=6928]

How do I set up the dip switches and RSLogix to do 5 output cards and 4 input cards? I know how to do 4 of each(with 1 slot addressing), and 2 of each(with 1/2 slot addressing).

I guess I don't know how to tell RSLogix to do more than that. While doing a full rack RSLogix only shows an address range of 20-27.

I have a 10 slot rack and I want to use all of the slots available.

You can't with the ASB. With a PLC-5 in the rack, the local rack gets numbered as rack 0 and rack 1. If you went with a full 17 slot rack and 32 bit IO cards, you can actually end up with 3 "local racks" (0, 1, 2, and 3) with every 4 slots being a separate rack.

There's nothing to do in RS-Logix 5 for this. The PLC will automatically recognize everything in the local rack. You can document it using the IO map stuff, but that's just documentation. The IO configuration stuff is totally voluntary and on many PLC programs I've found that it was never set up or never maintained. Only the channel configuration (the scan lists) are actually required. This is very different from Logix 500 and Logix 5000. In those PLC's, the IO configuration is REQUIRED and must match the actual IO or the processor will not work right.

Maybe I should have been more clear on this, I don't know. All of my IO is on slc500 racks. There is no local IO to the PLC-5/60.

Either way, it looks like I am out of luck.

Oh, OK. Yes, you are correct about not being able to expand it. At the time (80's), the SLC was intended to be a cut down version of a PLC 5. If you wanted PLC 5 power, you buy PLC 5.

However, that just means you have to go a DIFFERENT direction in terms of remote IO. Here are two suggestions that will be roughly the same cost as putting IO into your existing chassis. In fact, it may even be less expensive (and quite often is)! AB is purposely pricing 1746, 1747, 1785, and 1771 stuff such that you won't buy it anymore for cost reasons in new projects or even on old ones. I'm going to walk you down through the same thing that was presented to me by an AB salesman that used to be the "inside sales" guy for Chrysler. One of the maintenance/engineering managers at the company I work at is a former Chrysler guy so I also have enough insider information from the other side of the table to verify that what he was telling me was true.

First, consider 1791R (CompactBlock) IO, aka "butter sticks". This is effectively the replacement for the old 1791 standard block IO (which I highly suggest you don't use if you don't have to because it is now very expensive and hard to get). The reason that I suggest you don't go with it is if you go with a new processor any time in the near future, you will be stuck with your old Remote IO and the same problem you have now. Chrysler went with it a few years back and now they are wishing they didn't because they have to rip it all out and start over whenever they want to upgrade to newer communication and/or PLC's. The future of IO for a situation like yours is probably eventually going to be Ethernet. AB was slow to get on the Ethernet bandwagon but now they are full steam ahead. You could go Ethernet too except that you'd have to upgrade from your existing processor fleet to ControlLogix or CompactLogix. This is a very expensive move the first time around, but you gain massive flexibility. And the reality is that AB is just starting to come out with what will represent this IO series. If you want to see what they are cooking up, look at ArmorBlock. It uses the same connector system as most types of sensors (M12) and doesn't need a cabinet at all. It is not (and will never be) available in Remote IO.

Second, consider 1794 "Flex IO". This stuff is sort of like SLC IO. You put your choice of network adapter on the front (RIO (ASB), Ethernet, or DeviceNet). Then you simply attach terminal blocks (up to 8) with or without one or two extension cords (to make it fit in the enclosure) and plug in your IO. You can get nearly any kind of IO you want with this stuff and your choices are not nearly as limited as 1771/1746 stuff. For instance, the 1794-OB16D is a 16 bit output card with "diagnostics". The card doesn't need fuses. It has electronic fusing which means if you short out an output, it just shuts down the output until the impedance drops back down to normal. It also checks for a few milliamps of power on the output and signals this as an error, too (open wire). Effectively your most common failures (shorted wires and broken wires) are automatically troubleshooted by the on board diagnostics in the card. They also have true isolated analog IO at a reasonable price, something you don't get with 1746 IO. And you can do RIUP (removal and insertion under power) with no chance of damaging something.

Then in the future if you put in a different processor and/or different IO and you want to walk away from Remote IO, your upgrade consists of pulling the new IO cable and replacing the network interface card with a different one. This by the way is currently the IO of choice in my shop (18 PLC-5's, one SLC, and 1 CLX).

Your third option is one you probably didn't ever notice because they file it in a different catalog altogether. If you have Ethernet capability on your processors and speed is not a tremendous issue (or on the contrary, speed is very important), consider AB's entire line of super smart IO (as opposed to their semi-smart IO). I'm referring to Micrologix. A Micrologix 1100 will set you back about $500 US, about the same price as a 1746 chassis IO card (or less). It comes with 10 inputs, 6 outputs, 1 serial port, 1 Ethernet port, and two kind of wimpy (10 bit 0-10V DC only) analog inputs. It can expand with up to 4 IO cards and the IO cards are between about $150US and $300US each. It has a very small LCD display that is somewhat programmable as well. Oh, and it comes fully capable of running 95% of the SLC ladder logic language. It's basically a "brick" SLC with an IO card price. The IO configuration even for digital IO is kind of strange looking because you have to use MSG blocks even for digital IO, but it works flawlessly without any hassle. The only warning I have is to make absolutely sure that you download the latest firmware and flash the processor whenever you get one. They still have a lot of old crap drifting around but it's all upgradeable.

I have placed these in several places where I have literally used them as "smart IO". I have one of them that doesn't even have a program! It just sits there acting as an output card for a real PLC. I only have one of them in the entire plant that actually gets used as a "real" PLC. The others (about 4 or 5) are nothing but IO to me.

Granted, this approach lacks certain things. MSG blocks are ugly, no matter how you look at it. And it has an odd sort of speed problem. Also, it assumes that you've already run Ethernet all over your plant and you are familiar and comfortable with it. The IO CAN be very fast (as fast as remote IO). But it is still TCP and still subject to occasional problems with Ethernet, so it's OK for command/process oriented things. But I wouldn't trust it for direct machine control (if you are using it as remote IO). That being said, I do have two of them in my plant that are literally just an extension of the IO on a PLC-5 including handling operator push buttons and nobody really notices the slight of hand going on. Since you do have a local PLC though, you can still do machine control if you treat it as a "master/slave" situation, such as having the Micrologix run some sort of carriage mechanism with a few actuators and the master PLC simply sending high level commands (carriage start, carriage stop).

I have not bought a Micrologix 1400 yet but it looks very intriguing. I had a recent project which I was going to go in a different direction due to the amount of IO and the limits of a Micrologix 1100 but the 1400 has much more on board capacity.

Well, unless I've completely misunderstood your request, I can't see problems in your needs...

Attached is an example on how I think you may proceed; assuming you start from rack 2 group 0 for your ASB, you need to configure it as 1/2 slot addressing, that means 2 Input and 2 output words every slot.

So you need to use 18 logical groups (words) to cover all your modules (5 input 32pt./4 output 32 pt.)
Then in RSLogix 5 you have to configure the use of two FULL RACK and a 1/4 RACK to addressing you modules (no matter if the logical rack are ALL attached to a single ASB !)

Again, have a look to ASB manual using the link in my previous post....

[attachmentid=6931]

Hope this helps...

- fuzzy logic

Excellent! That is exactly what I needed. I think i understand AB RIO setup much better now. Now if I understand RIO setup correctly. I can use the other 3/4 of the 3rd logical rack(n+2) at the beginning of another physical rack.

Yes.. you can use the remaining image... just be aware of the rule shown in the picture below...

[attachmentid=6939]

If you use a new ASB with addressing mode 1/2 slot, the starting group should be 4 (assuming you want use the remaining image of the rack n+2) so you have only 1/2 logical rack available.
(you can't use all 3/4 rack remaining, because with 1/2 slot addressing mode you can't use starting group 2)

- fuzzy logic

I figured that out after I posted last. And I got it to work! now that I know my addresses, I can actually do the programming.

Thanks again for the help!