Version 1.0, August 31, 2001, Copyright, Hugh Jack 1993-2001

32.1 INTRODUCTION

 

· 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,

  1. - touch screens
  2. - displays
  3. - Man Machine Interface (MMI)
  4. - 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,

  1. - display machine faults
  2. - display machine status
  3. - allow the operator to start and stop cycles
  4. - monitor part counts

 

· These devices allow certain advantages such as,

  1. - color coding allows for easy identification (eg. red for trouble)
  2. - pictures/icons allow fast recognition
  3. - use of pictures eases problems of illeteracy
  4. - screen can be changed to allow different levels of information and access

 

· The general implementation steps are,

  1. 1. Layout screens on PC based software.
  2. 2. Download the screens to the HMI unit.
  3. 3. Connect the unit to a PLC.
  4. 4. 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.