Runout of communications ports on v570

[active]

Hi

Hope someone can help on one of my jobs I've ran out of communications ports on the V570 using com 1 for modem (sms), com 2 for modbus and com 3 has an ethernet port for modem my problem is that due to the type of pumps that my customer bought I need three pumps on one modbus and another pump on seperate modbus only one lot of pumps will be running at one time, cant run them on one due to the three pumps using cascade control mode, third pump slave model so unable to run pumps as individuals. Trying to find a cost effective solution, does anyone know of a device that will allow me to use one master com port to plug into plc and switch between two slave ports going to the two groups of pumps or any other ideas would be appreciated.

Thanks

[Bill Smith]

I really can't figure out what the issue is but anyway i'll give it a shot -

Modbus has a Unit Identifier, so not sure why you can't have all the pumps on one Modbus RS485 link. Just address the devices you want to, don't address the devices you don't want. Except for broadcast, messages destined for another device are to be ignored.

The ethernet port supports multiple connections - 4 ports if I recall. It's very unusual to hook a modem (these are usually serial) to an ethernet port so not sure what your doing, but whatever it is I would assume you still have three other ethernet ports available. With these other ethernet ports available (not physical ports - TCP or UDP ports) you can put in a an ethernet/serial converter. There are many of these on the market - search google for 'serial to ethernet'. I like Digi (One IAP) or Schneider Electric (ETG100), but have used many of these from B&B Electronics too. Your ModbusTCP request will go to this device, be converted to serial, sent to your serial device, and the response will get returned in the reverse manner transparently.

[Simon]

There are port sharing devices available, but they rely on appending a code to each packet to tell the device what serial port to send it out on. This isn't useful for Modbus, unless you want to manually code the modbus packets with the protocol send blocks.

As per Bill's post above, I am a little unsure why you need electrically separate networks, rather than separating the pumps using their modbus IDs. Maybe if the unused pumps are powered down do they kill the RS485 comms?

Next option, maybe a DPDT relay controlled via one of the PLC outputs?

[Damian]

Hi

Hope someone can help on one of my jobs I've ran out of communications ports on the V570 using com 1 for modem (sms), com 2 for modbus and com 3 has an ethernet port for modem my problem is that due to the type of pumps that my customer bought I need three pumps on one modbus and another pump on seperate modbus only one lot of pumps will be running at one time, cant run them on one due to the three pumps using cascade control mode, third pump slave model so unable to run pumps as individuals. Trying to find a cost effective solution, does anyone know of a device that will allow me to use one master com port to plug into plc and switch between two slave ports going to the two groups of pumps or any other ideas would be appreciated.

Thanks

Can you please explain what is meant by "cascade control mode"?

On Comm 2. Are all devices RS485? Or is one device only RS422?

Also an option to consider, getting a CAN to serial converter since it does not sound like you are using your CAN port.

[active]

Thanks for replies

Basic problem is that 3 pumps work as a group (one master pump controlling a dumb slave and a spare master) pumping to one place the fourth needs to pump to another, according to the pump expert if I connect all pumps on one modbus the pumps will be a group of four even if I give seperate modbus Id's. Think the only way around is to replace the dumb slave as a master as well then will have all masters and can put on one modbus system and control as seperate pumps through the ladder logic.

Life would be so much easier if customers ask for input during design phase.

Oh yeah Damian these pumps can work on a cascade mode if one master pump cant keep up that pump will automatically start up the slave pump without any outside input control needed ,also using canbus to communicate with a V130 300 meters away so only have one com port avaiable for controlling these pumps.

[Damian]

Thanks for replies

Basic problem is that 3 pumps work as a group (one master pump controlling a dumb slave and a spare master) pumping to one place the fourth needs to pump to another, according to the pump expert if I connect all pumps on one modbus the pumps will be a group of four even if I give seperate modbus Id's. Think the only way around is to replace the dumb slave as a master as well then will have all masters and can put on one modbus system and control as seperate pumps through the ladder logic.

Life would be so much easier if customers ask for input during design phase.

Oh yeah Damian these pumps can work on a cascade mode if one master pump cant keep up that pump will automatically start up the slave pump without any outside input control needed ,also using canbus to communicate with a V130 300 meters away so only have one com port avaiable for controlling these pumps.

I'm still confused. Why can't you setup all the pumps to be modbus slaves to the V570? Does the "master" pump necessarily have to be the Modbus master??

Also, if you have a V130 in your system talking CAN with the V570, doesn't that have the additional comm ports your looking for?

What's really in control here? The Unitronics or the Pumps?

[active]

Damian

The V570 is in control of the master pump in requards to start/stop running pressure ect but the master pump controls the slave pump and spare master, as for using the spare ports on the V130 its 300 meters away running 3 seperate pumps I could use it then it means V570 down to V130 Canbus then back to the building where the V570 is on modbus to control pumps, the plcs control cabinets are on different supplies. Think its just easier to convince the customer to change slave pump to another master then set all pumps to run seperate of one another and do all the controlling through the V570 ladder logic in reguards of which pumps to run.

[Bill Smith]

This pump control configuration seems odd. Do you have a manufacturer / part numbers for this pump control hardware?