Two G3s to one ML1400...

I'm looking to put 2 HMIs on an accumulation conveyor we're building. There is a mechanism at both the infeed and discharge end to load/unload product, so I'll have some (minimal) digital I/O at both ends. Almost 80' long, so I will also have local controls at each end. Besides the standard pushbuttons, etc., I want to include a G306K at both control stations, mainly just to display the status of the machine. Might want to be able to change a few parameters in the PLC from either station.

Customer wants a ML1400, but forbids me to use the Ethernet port for local communications. They want to use it to tie into their plant network ONLY. I'm left with the 2 serial ports on the MicroLogix. I planned on using DeviceNet for 3 PowerFlex drives (and maybe some remote I/O), so that ties up the mini-din (CH0) for a 1761-NET-DNI. That leaves me the 9-pin serial port (CH2) for my HMIs.

I'm wondering how I should connect the HMIs to the PLC. DF1? DH-485? If so, then who is the master? Looks like the G3s can only be masters, so I'm guessing that can't work? Maybe DH-485 from one G3 to the PLC, then G3 to G3 over RS-232? Will it work over the distance?

I've only ever used one HMI with one PLC, so this is confusing to me...

I'd actually prefer to just run one comm. cable between the two ends and have my drives, local I/O and HMIs talk over that cable. There's not much I/O on this machine. I'm only using DeviceNet because of the length. Two PowerFlex drives are at one end with some local I/O, and one drive at the far end, with some remote I/O. Maybe it would be easier to stick a ML1400 at each end and let them talk just to each other? Good chance I'll use separate power drops at each end, so maybe 2 totally independent control panels makes more sense?

Too many decisions!...

Looking forward to your thoughts and suggestions... :site:



-Eric

I am not sure that a ML1400 can do Device net, or remote I/O.

I think ML1500 can do Device Net

Compact Logix can do Device Net and Point I/O on at least Ethernet maybe other methods as well.

You could use one of your serial ports to drive a Net ENI for ethernet

Also a managed Ethernet switch could keep traffic from being a nuisance on the Network Ethernet system.

Per the manual it will support Device Net as a slave only.

Because DH-485 is a token passing protocol it will support multiple masters.

you could use a digi one iap. you can do pass thru from the 1400 serial port to the spare serial port on the digi and also do a serial to ethernet for the other panel.

also, I think the g3's can talk to each other... so you could do serial on one of the g3's and then have the other g3 talk to the g3 thru ethernet.

If it were my system, I would push very hard to switch to CompactLogix and to resolve the Ethernet issues with a router. You would get EtherNet/IP connectivity to the drives, the I/O, and the G3 HMIs.

If the customer requires the MicroLogix family, I would use the 1764-LRP version of the MicroLogix 1500. The 1769-SDN scanner will allow you to scan POINT or CompactBlock or even 1769 Compact I/O modules, as well as AC drives.

The 1761-NET-DNI will allow you to connect a DF1 Full Duplex device to the network (like the G3) and communicate with the MicroLogix controller via the 1769-SDN. That's a unique feature of the 1764-LRP and the 1769-SDN that no other MicroLogix controller has.

For Ethernet connectivity, you're going to end up with a bit of a bottleneck on the serial port of the MicroLogix 1500. I would us a Digi One IAP at 38400 baud.

For all of their excellent online editing and Ethernet connectivity, the MicroLogix 1100 and 1400 aren't meant to be remote I/O scanning devices, but the MicroLogix 1500 with DeviceNet is.

Thanks for the info and ideas so far. Keep 'em coming...

I'm leaning towards my dual PLC idea more and more. The infeed and discharge can be considered completely independent systems. The infeed is loading parts onto the conveyor. It doesn't care what the discharge is doing. It has its own high-level sensor, so as long as the conveyor is running and not full, it cycles. Almost identical situation at the discharge. When product is present, it unloads the conveyor. Similarly, it doesn't care what the infeed is doing.

The only common thing to both is the conveyor. The drive for it will be at the discharge, because that's the end with the motor. The infeed needs to know the conveyor is moving, but that could, in theory, be done by just monitoring the idler roller at the tail end (I may do this anyway just to confirm movement). Of course, the safety circuits are also common to both, but they will be hard-wired regardless.

Therefore, let's say that I build 2 independent control systems. Each one has a G304K plugged into the DB9 port. The Ethernet port is dedicated to programming and/or the customer's LAN. The drives cause a bit of an issue. I would prefer to have full communication with them, but since I only have 1 drive on the infeed, and 2 drives on the discharge, a ML1400 with plain ol' analog would suffice. In any case, this scenario would get me a fully functional machine.

Now, let's say I want to speed up the conveyor. The conveyor drive is in the discharge panel, but I'm standing at the infeed end, and don't feel like walking all the way down there to speed it up. It would be nice if I could simply adjust the speed at the HMI where I am standing. If I could just get this PLC to to talk to the other one...

So, I've got these spare mini-din ports. Is there any reason why I can't just network these 2 PLCs? Hmmmm, if I go Modbus, can't I also add the drives to this network? This entire system runs REALLY slow. I don't care how fast stuff updates.



-Eric

Eric,
If you go with a G306(non-Kadet) you can install an additional Ethernet Port, this uses it's own "nic" which may help make the customers IT "police" happy

http://www.redlion.net/Products/HumanMachineInterface/Accessories/G3ENET.html

Lots of options here. You can connect one G3 with the 485 or 232 to the PLC. Then network the two G3s together with Ethernet. This will make your development effort easy since the G3s can share data between each other over their own Ethernet trivially.

I might consider negotiating with the customer about the possibility of adding a router to deal with whatever issues that are causing them to forbid connecting to the 1400's Ethernet. With a router you could guarantee that your HMI's are on a totally separate network that cannot interfere with their plant network (your HMI network would have a totally unique range of IP addresses) and you could even set bandwidth limits to ensure their plant network always had highest priority for the PLC data. A router like the Mikrotik RB450G has gigabit Ethernet and a nice aluminum case for around $120.

I Have connected 2 ML1400 to 3 HMI's (yes it was a fun project).

The PLC's all connected to 1 G306 via RS232 (DF1). The HMI's connected thru Ethernet. I passed data back and forth between the HMIs using gateway blocks.

I found out later from Red Lion that once I created the Comms for each device I could just select which device my tag went to (same as if you had just one PLC and HMI).


Are you needing devicenet or some other Comms to run the drives?

What about using the G3with dual ethernet ports to do Ethernet routing. This way you can use Ethernet to the PLC and still get network connections while filtering out any **** from the I/O or drives. I know you said there don't want you to use the Ethernet but this could b an option. You could maybe use a managed switch to filter out broadcast packets as well.

Eric can use use Modbus? The 1400 can be a master the drives and HMI can be slaves. Or you could use the HMI (1) as a RTU master and everything else is a slave. Do HMI to HMI comms with Ethernet or serial. So HMI 2 could be the master on the HMI network and pass info to HMI 1 then HMI 1 can pass the commands to the PLC or drives. Not very clean but workable.

Just wanted to thank everyone for the replies!... :site:

Now the customer is looking to possibly reuse their existing controls, so I may be scrapping this approach altogether...



-Eric

Current plan is to add to their existing PLC5/40. We are skipping the HMIs on our system, and just sticking RIO at each end for a few sensors and valves. Someday they hope to upgrade to ControlLogix, but not at this stage.

Looks like we'll need to use PowerFlex 70s on the motors if we want communication to the 5/40 over RIO, but I'm not liking the price of those 20-COMM-R adapters!



-Eric

The way to go is to have one G3 connected to the PLC then have the other slaving off the main HMI.
I have used this several times and it's easy to set up. Lots of info on the redlion site about it or drop them an email and they'll point you in the right direction