Advantages of Human Machine Interface (HMI)
- These allow control systems to be much more interactive than before.
- The basic purpose of an HMI is to allow easy graphical interface with a process.
These devices have been known by a number of names,
- touch screens
- Man Machine Interface (MMI)
- Human Machine Interface (HMI)
These allow an operator to use simple displays to determine machine condition and make simple settings.
The most common uses are,
- display machine faults
- display machine status
- allow the operator to start and stop cycles
- monitor part counts
These devices allow certain advantages such as,
- color coding allows for easy identification (eg. red for trouble)
- pictures/icons allow fast recognition
- use of pictures eases problems of illiteracy
- screen can be changed to allow different levels of information and access
The general implementation steps are,
- Layout screens on PC based software.
- Download the screens to the HMI unit.
- Connect the unit to a PLC.
- Read and write to the HMI using PLC memory locations to get input and update screens.
To control the HMI from a PLC the user inputs set bits in the PLC memory, and other bits in the PLC memory can be set to turn on/off items on the HMI screen.