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Old January 15th, 2014, 11:33 PM   #1
David.Reed.Schmidt
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RedLion HMI, an AB Drive, and a couple of pumps.

I have a coworker who wants to take on a project to control a variable speed belt and four water pumps with a small HMI instead of wiring switches on a panel.

Incorporating an HMI like this will be a first for him. I have reassured him the first project is always the most intimidating and online forums like this are helpful.

Can you please share some ideas on how to do this? The final state is that the operator will input the speed of the belt into the HMI in in/min, the HMI will apply a scaler to change it to the corresponding Hz for the drive, the pumps just need basic I/O from the HMI. He will be using an AB powerflex 5HP drive and would like to use a Red Lion HMI because he has had good experiences using them in the past.

Some of his concerns are the ability to program the HMI with the software, and establishing the correct communication with the drive. As long as the HMI has I/O outputs I'm not concerned about the pumps. He has not ordered the drive yet.

From my end I'm concerned about the future connectivity of the HMI such as via the Ethernet with a driver for our SCADA system, of which we use Ignition by Inductive Automation. Ignition has Modbus TCP driver for devices.

Thanks.
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Old January 16th, 2014, 01:17 PM   #2
Ken Roach
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There are two elephants in the room: Timeout and I/O Modules.

You can run an Allen-Bradley AC drive over a network as long as you keep sending it periodic command data. If it doesn't get a command packet for a period of time (often measured in tens of milliseconds) it considers itself to not be under the control of the network device, and will fault.

This is the way of the world with any sort of networked I/O device; you can't just send a command that says "start, and keep running until I tell you otherwise". That's why PLCs have firmware that keeps the cyclic data flowing back and forth constantly.

Most HMI devices don't have an easy way to keep sending output data periodically. Most HMI devices also don't support real I/O.

Red Lion is an exception to both.

Red Lion has background programs that can be configured to perform actions, including writing to PLC and network devices, on a periodic basis.

Red Lion also has the new Graphite series of terminals that have actual I/O modules that plug into the back.

Unfortunately, the datasheet is where my experience with those features. There are some other much more experienced Red Lion users on this Forum.

I think that the first step for your co-worker's project is to get a real list of the field I/O. If there will be sensors (flow, presence, temperature, fault) then you're probably going to want to use the Graphite HMI.

If you want to use a more conventional Red Lion product like the G306, you'll need to test messaging over a network to the drives.

The last item on your list is the least worrisome; Red Lion devices can run as very ordinary Modbus/TCP peers, and talk to Ignition's built-in OPC-UA driver all day.
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Old January 17th, 2014, 10:30 PM   #3
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Ken you are becoming a Red Lion guy. After all those years of PV+.
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Old January 18th, 2014, 12:34 PM   #4
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You could constantly send data to the drive via ethernet or rs485 using the force() command applied either on tick or in a loop with a wait() after it.

I must emphasize that whatever you do you need to have a hardwired emergency stop at minimum. Communications can be funky at times and I have seen things not stop when commanded to.

Also, using a powerflex 4m or 4 would be inappropriate in that they do not have a hardware disable. Meaning that these drives use software to process stop commands. A PF40, at minimum, would be needed for this application. If this is an application below 25hp I would strongly look at the PF 525 because it has safe torque off built in and ethernet. The PF 525 would probably be the most appropriate and safest of the drives I mentioned.

The worst part about this is going to be getting the communications going the first time. Until you do it a few times it feels like you are stumbling around in the dark.
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