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Here is a copy of the status report I just sent my boss, for you that are interested.
After spending the last two months researching the possibility of developing a web based interface to our Allen Bradley plc's, I am convinced that it is very doable. This is a summary of what I want to accomplish, how it can be done and progress to date.
Goal:
Develop a browser based HMI for Allen Bradley plc's that is completely standards based and does not require any special software or plugins on the client computer. The first incarnation will be read only to provide
diagnostic and troubleshooting information. This will provide proof of concept. The next stage will be to add interactive capability to provide
full operator interface capability. Full implementation would use a dedicated in plant network for operator interface access and provide read only access to the general network. This approach will allow us to use inexpensive internet appliance type devices for operator interface terminals in locations with a controlled environment such as the ROC and
lil' ROC. In the field, we could use the Allen Bradley ( or similar ) NEMA rated flat panel touchscreens such as Ken had in his office for a while.
Implementation:
I am using an older pc that the IT department said was not adequate for use on the network as a desktop computer. It is running RedHat Linux 6.0 which includes most of the web server and programming software needed. Any other software I need is freely available for download off the internet. All the software that I am using is free ( Ken oughta appreciate
that ). After first review of the HTML and XML standards, it did not look like it was going to be possible to meet the goal of not requiring java or some kind of plugin on the client computer, as the existing standards did not provide any way of developing dynamic graphics or any way of providing dynamic data links to drive dynamic graphics. After further research I
found two new standards being developed that eliminate the need for java or browser plugins.
1. SVG - scalable vector graphics.
This is the new standard for 2-D graphics for the web. The
specification has been released for approval and should soon be a
public standard. There is already several implementations for
developing SVG graphics, such as Adobe Illustrator, CorelDraw and
several other free and shareware programs. The SVG standard provides
much more capability then any of the existing DCS or HMI graphics
packages, although at this time it will require hand coding the
dynamic effects as there are no tools available yet that offer the
easy fill in the blanks configuration that traditional packages offer.
The dynamic effects can be programmed with java, javascript, vbscript
or any of the other scripting languages available. I plan on using
javascript, since every browser supports it.
2. XML-RPC - XML based Remote Procedure Call
This is a method for embedding a remote procedure call into a web page
to allow requesting data or services from the server. It requires a
XML-RPC server on the server machine to respond to these requests, but
does not require anything special on the client. The SOAP (Simple
Object Access Protocol) standard being proposed by Microsoft and
backed by IBM and others is an XML-RPC.
Progress:
PC setup with necessary software
Defined initial graphic screens
Demonstrated ability to access and manipulate data tables in plc5 over
ethernet using Allen Bradley ethernet library for Linux from Ron Gage.
(Way to go Ron)
Obtained program for drawing SVG graphics. Have a simple logic type
diagram complete.
In Progress:
Use javascript to make graphic dynamic.
Download and setup XML-RPC server.
Use XML-RPC to access data to drive dynamic graphic.
Write interface between XML-RPC server and plc to obtain data. I
believe that this is the only thing that will requre any C programming
and should be fairly minor. ( Good thing too, since my C programming
skills are fairly minor )
_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
After spending the last two months researching the possibility of developing a web based interface to our Allen Bradley plc's, I am convinced that it is very doable. This is a summary of what I want to accomplish, how it can be done and progress to date.
Goal:
Develop a browser based HMI for Allen Bradley plc's that is completely standards based and does not require any special software or plugins on the client computer. The first incarnation will be read only to provide
diagnostic and troubleshooting information. This will provide proof of concept. The next stage will be to add interactive capability to provide
full operator interface capability. Full implementation would use a dedicated in plant network for operator interface access and provide read only access to the general network. This approach will allow us to use inexpensive internet appliance type devices for operator interface terminals in locations with a controlled environment such as the ROC and
lil' ROC. In the field, we could use the Allen Bradley ( or similar ) NEMA rated flat panel touchscreens such as Ken had in his office for a while.
Implementation:
I am using an older pc that the IT department said was not adequate for use on the network as a desktop computer. It is running RedHat Linux 6.0 which includes most of the web server and programming software needed. Any other software I need is freely available for download off the internet. All the software that I am using is free ( Ken oughta appreciate
that ). After first review of the HTML and XML standards, it did not look like it was going to be possible to meet the goal of not requiring java or some kind of plugin on the client computer, as the existing standards did not provide any way of developing dynamic graphics or any way of providing dynamic data links to drive dynamic graphics. After further research I
found two new standards being developed that eliminate the need for java or browser plugins.
1. SVG - scalable vector graphics.
This is the new standard for 2-D graphics for the web. The
specification has been released for approval and should soon be a
public standard. There is already several implementations for
developing SVG graphics, such as Adobe Illustrator, CorelDraw and
several other free and shareware programs. The SVG standard provides
much more capability then any of the existing DCS or HMI graphics
packages, although at this time it will require hand coding the
dynamic effects as there are no tools available yet that offer the
easy fill in the blanks configuration that traditional packages offer.
The dynamic effects can be programmed with java, javascript, vbscript
or any of the other scripting languages available. I plan on using
javascript, since every browser supports it.
2. XML-RPC - XML based Remote Procedure Call
This is a method for embedding a remote procedure call into a web page
to allow requesting data or services from the server. It requires a
XML-RPC server on the server machine to respond to these requests, but
does not require anything special on the client. The SOAP (Simple
Object Access Protocol) standard being proposed by Microsoft and
backed by IBM and others is an XML-RPC.
Progress:
PC setup with necessary software
Defined initial graphic screens
Demonstrated ability to access and manipulate data tables in plc5 over
ethernet using Allen Bradley ethernet library for Linux from Ron Gage.
(Way to go Ron)
Obtained program for drawing SVG graphics. Have a simple logic type
diagram complete.
In Progress:
Use javascript to make graphic dynamic.
Download and setup XML-RPC server.
Use XML-RPC to access data to drive dynamic graphic.
Write interface between XML-RPC server and plc to obtain data. I
believe that this is the only thing that will requre any C programming
and should be fairly minor. ( Good thing too, since my C programming
skills are fairly minor )
_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc