First thing
first
HMI = Human
Machine Interface
MMI = Man
Machine Interface
SCADA =
Supervisory Control & Data Acquisition
HMI (or MMI) is
a device which depicts the process in user understandable form, kind of
pictorial form. You see, user does not know what is happening inside a PLC, all
the programming etc is written in some special languages like Ladder, Step etc,
all the values are in binary or hexadecimal…so values inside PLC will be of no
use to user directly. For example thermocouple will sense the temperature and
give certain voltage values to PLC, an engineer would know how to convert this
value as true temperature, but for user this value has no meaning, this is
where the HMI/MMI comes into picture. We take information from the PLC (how ?
Connect a cable between HMI and PLC) and program it in such a way that PLC
information is dynamically animated on the HMI/MMI screen. Nowadays HMI/MMIs
are available in touch panel mode and the entire process can be shown
pictorially and dynamically with the help of animation. HMI not only shows the
PLC parameters in user understandable mode, it can also change the values, for
example if process parameters like timer value etc is to be changed as per
process requirement, then the operator can change the same through HMI screen.
[But the key part
is how to program the HMI ?]
Nowadays HMIs
are generic, that means an HMI can be connected with any brand PLC, for example
Delta HMI can be connected to Delta PLC, Siemens PLC, Schneider PLC etc. It is
possible that cable which connects the HMI with PLC will be different depending
on the PLC used.
So before you
start your project with HMI, you should ensure as follows.
1.
Make of PLC and HMI specification sheet which should
confirm that HMI can be connected to this make of PLC.
2.
Cable required to connect the PLC and HMI.
3.
PLC program written for the application. In most of the
cases you will be writing the program for both PLC and HMI, so this should not
be a problem.
4. HMI Power Connection details, like what power it
requires to switch on, mostly it will be 24 VDC, but in some cases it can be
230 VAC also.
5.
HMI programming software copy.
6.
A cable which would connect HMI with PC/Laptop for
programming.
Once you have all this
information, install the HMI software on the PC/Laptop. Create a new project
and assign some name to this project, somewhere in the project you will be
asked to select the PLC to be connected, this is where you should select the
PLC used. Once this is done you are ready to program further.
[So, how will the HMI get information from PLC ?]
PLC has all the information in certain addresses, like the status of switches (Limit Switch, Proximity Switch, telling you about the position of some mechanical part) in the form of digital inputs, the status of temperature and Pressure (as taken from Thermocouple, RTD or Pressure Transmitter) in the form Analog Inputs. So first identify the Digital Inputs/Outputs, Analog Inputs/Outputs and other PLC variables, which you need to map on the HMI. Once you have identify these addresses, then they will be called as 'tags' for HMI. So HMI programming software will have tag configuration. Open that assign the tags with user understandable names. Once you have completed the tags configuration, now the entire PLC information will be available with HMI on connecting the same with PLC.
[Now how to do the Screen Design ?]
This is the last step. In the HMI software, there must be some menu to make/edit the screens. You can design as many screens as you want, and link them too. [You have to read the software manual for that, which will be very easy as you are grasping the concept.]. In the screen editor there will be many ready made library for process designs, like tank photo, motor photo etc, use them to design your screen. This screen will be a static screen as no dynamic point is assigned. So the next step is to assign the dynamic/animation aspect by associating the required tag as configured earlier.
Dynmaic Screen or Animated Screen will contain..
1. Change of color based on tag value.
2. Assigning some set point through tag.
3. Filling or emptying a tank or vessel based on tag value.
4. Hide or unhide based on tag value.
5. Giving some kind of motion.
6. Jumping from one screen to another.
Once you have understood the concept of assigning a tag with any screen object, it is simple and fun !!
[If you want live training with hands on experience, please send a mail to indway1000@gmail.com and we will fix the same for you. On completion of extensive training, a certificate shall be issued to you.]
[So, how will the HMI get information from PLC ?]
PLC has all the information in certain addresses, like the status of switches (Limit Switch, Proximity Switch, telling you about the position of some mechanical part) in the form of digital inputs, the status of temperature and Pressure (as taken from Thermocouple, RTD or Pressure Transmitter) in the form Analog Inputs. So first identify the Digital Inputs/Outputs, Analog Inputs/Outputs and other PLC variables, which you need to map on the HMI. Once you have identify these addresses, then they will be called as 'tags' for HMI. So HMI programming software will have tag configuration. Open that assign the tags with user understandable names. Once you have completed the tags configuration, now the entire PLC information will be available with HMI on connecting the same with PLC.
[Now how to do the Screen Design ?]
This is the last step. In the HMI software, there must be some menu to make/edit the screens. You can design as many screens as you want, and link them too. [You have to read the software manual for that, which will be very easy as you are grasping the concept.]. In the screen editor there will be many ready made library for process designs, like tank photo, motor photo etc, use them to design your screen. This screen will be a static screen as no dynamic point is assigned. So the next step is to assign the dynamic/animation aspect by associating the required tag as configured earlier.
Dynmaic Screen or Animated Screen will contain..
1. Change of color based on tag value.
2. Assigning some set point through tag.
3. Filling or emptying a tank or vessel based on tag value.
4. Hide or unhide based on tag value.
5. Giving some kind of motion.
6. Jumping from one screen to another.
Once you have understood the concept of assigning a tag with any screen object, it is simple and fun !!
[If you want live training with hands on experience, please send a mail to indway1000@gmail.com and we will fix the same for you. On completion of extensive training, a certificate shall be issued to you.]
