Les67 (Customer) asked a question.
Can I connect multiple HMI to one PLC
I have RHMI-CM5 connected to a 22" touchscreen monitor through HDMI and USB. I would like to add a second monitor to the system. The PLC is P2-622 CPU Productivity system. Could I use a CM5 touchscreen with an ethernet connection to display the same information? Could I use another set of data tags that the PLC would use on the second touchscreen? Is there another way to do this.?
The goal is to have a display near the PLC panel enclosure and a remote display a distance away. Ideally, the remote display would allow for data changes, but it could just be viewing only?
You should be just fine with more than one HMI reading (and even writing) the same PLC tags with that hardware. Some PLCs may have limitations on the number of Ethernet connections they can support, but even the most restrictive PLCs will support at least two or three. I am not sure which type of Ethernet protocol connection your HMI(s) will be using, but I read that the P2-622 supports 16 Modbus TCP clients.
If multiple HMIs can write to the same tags, there may be concerns if there are scripted writes or other out of the normal things you are doing. In those cases you may need to consider splitting things up with unique tags per HMI. For most normal use cases, the HMI will only write to the PLC when there is an explicit action like pressing a button or entering a new value assigned to a numeric entry object. The rest of the time, it is just repeatedly reading what is required by the HMI application for the page being displayed along with all the tags configured for logging or alarms.
Also look at using a PC or mobile pad and the Remote HMI feature. It may accomplish what you are wanting to do without purchasing another HMI.
You can have lots of HMIs on a single PLC, but I would try and stagger their communication times a bit. So any HMIs used for less common things set up at like a 7ms poll rate. This keeps their traffic level much lower but still leaves them plenty respoinsive.
Nearly all of my machines have 2 HMIs on them, and many have 3-4. Sometimes the screens are copies of each other and control the same tags, just are located on opposite ends of the machine.