Jim Knee
Member
Hi;
We do a lot of work using PLC's as RTU's. In a typical system we have a master PLC connected to an HMI compter. The master also communicates to a number of remote PLC's. Each of the remotes controls a sub system.
Each of the remotes will have a number of operating setpoints which are adjustable thru a touch screen connected directly to the remote PLC.
We also allow the operator to adjust these setpoints thru the master HMI.
When we use an ethernet backbone to link the whole system together it is easy to allow any HMI device in the system to adjust any system setpoint. Usually however we use one or more serial connections between the master and the remotes. This involves mapping the data to be exchanged with the remotes in send and recieve sets. It is in this case when it gets more difficult to adjust setpoints from more than one location.
We have been using a method of using increment and deincrement buttons as outputs from the master HMI and treating the setpoint as an analog input into the HMI.
Does anyone have a better (cleaner) approach??
Jim
We do a lot of work using PLC's as RTU's. In a typical system we have a master PLC connected to an HMI compter. The master also communicates to a number of remote PLC's. Each of the remotes controls a sub system.
Each of the remotes will have a number of operating setpoints which are adjustable thru a touch screen connected directly to the remote PLC.
We also allow the operator to adjust these setpoints thru the master HMI.
When we use an ethernet backbone to link the whole system together it is easy to allow any HMI device in the system to adjust any system setpoint. Usually however we use one or more serial connections between the master and the remotes. This involves mapping the data to be exchanged with the remotes in send and recieve sets. It is in this case when it gets more difficult to adjust setpoints from more than one location.
We have been using a method of using increment and deincrement buttons as outputs from the master HMI and treating the setpoint as an analog input into the HMI.
Does anyone have a better (cleaner) approach??
Jim