HMI with a little bit of I/O?

A customer is deadset on using a slc500 processor. One of the HMIs is in a remote location. They do not want to use the HMI as an input device, so a HMI's touchscreen and buttons are useless to me. They are two discrete inputs at this location that I need to look at. I do not want to use a remote i/o rack for this application due to space limitations and cost. Nor do I want to run dedicated wires to these two inputs. An HMI that has a tiny bit of I/O would be handy. I'm open to using either an AB or Red Lion HMI for this application. The communication between the plc and HMI would be ethernet. Could one of the unused communication ports be used to communicate with an i/o device, have that value written to a tag, and the tag read by the plc? For example MODBUS I/O DEVICE ----> HMI ----> PLC. any reliable ideas out there?

This looks like a possibility:

http://www.opto22.com/lp/io4ab_slc_micrologix.aspx

I think you'll find that Snap stuff to be pretty expensive for just a couple of input points. Any EtherNet/IP node would be.

The easiest thing, by far, would be to put in a MicroLogix 1100 controller and be done.

Your idea of having a serial port on the HMI poll a little I/O module is good, too. I would grab something like this:

http://www.dghcorp.com/d1700m/diomodules.htm

http://www.proconel.com/Industrial-Data-Acquisition-Products/PROMUX-%E2%80%93-I-O-Modules/PM16DI---16-Digital-Input-Module.aspx


http://www.acromag.com/catalog/365/Ethernet_Network_I_O/Modbus-RTU_I_OModules/Digital_I_O/904MB___905MB___906MB

On a Red Lion it's trivial to do a "port to port" mapping of I/O. On an A-B PanelView Plus, I think you'd have to use one of the Global Macros.

If you want really cheap, then use a Red Lion HMI, and hang a 'Click' PLC on the Modbus port. $99 for the non-analog ones with Modbus. Very compact as well.

http://www.automationdirect.com/adc...Series_PLCs_(Stackable_Micro_Brick)/PLC_Units

As Ken mentioned, the port-to-port mapping is sooo easy on the Red Lions. You will not need any program running in the Click (aside from one END instruction, so it will go to RUN)

I needed a few digital I/O on a standalone Red Lion HMI a while back, and the Click was the cheapest I/O over Modbus that I found. Worked great!...



-Eric

I just added a Red Lion to a click worked great. From the time I walked in the door 30 minutes and I had tags on a screen reading and writing. That time included making a cable. I did have my cabling tools with me.
I will probably use these on a few mire jobs for what there is they work great.

Schneiders magelis xbt also have io that you can clip on the back of the hmi and program from hmi software. Cant for the love of me remember the xbt range

Thanks for all of the ideas. The CLICK is definitely the least expensive route, but I'm not too fond of proposing its use on this project for this customer (I am going to buy one to experiment with). I am going to go the ML1100 and Red Lion G310 route since the main plc is a slc500. The customer has rslogix 500 and they are comfortable with it.

My next question is: Do I put the ML1100 on the ethernet network and use a MSG instruction to poll it or should I let the ML1100 communicate directly to the G310 and let the G310 relay that info to the plc?

If it were me, I would MSG from controller-to-controller. This gives you better ability to reduce bandwidth (by only sending data on a change of state) and to handle watchdog logic.

I seconds Ken's motion to use MSG between devices.

I have a guy right now that is having problems with a Bridge connection between 2 plc ans a G3. I think we have it nailed down to one of the PLC is JUNK (YASKAWA). It looks like they are having buffer issues when handling the IP stack. If the network gets noisy the PLC comms will lock up.

Thanks. I'll have the ML1100 do a MSG write to the slc (maybe once a second) or immediately if there is a change of state.

I believe what you are looking for is something like these...

Unitronics - http://www.unitronics.com/Content.aspx?page=All_In_One

Maple Systems now has a product that incorporates I/O:

http://www.maple-systems.com/products/graphic-hmc/index.htm

Hope this helps.