How to control PLC from the Internet or Webserver (IoT)?
So in this article we will learn about PLC control from internet using webserver concept with Internet of Things. Now a days every technology is integrated with IOT due to flexibility and remote monitoring and access anytime anywhere i.e. future of Internet of Things (IoT)
First we will learn about webserver and then will see procedure.
What is Web server?
The Web server lets you monitor and administer the CPU through authorized users by means of a network. Evaluations, diagnostics, and modifications are thus possible over long distances. Monitoring and evaluation is possible without STEP 7; all you need is a web browser. Make sure that you take appropriate measures (e.g., limiting network access, using firewalls) to protect the CPU from being compromised. The Web server is deactivated in the delivery state of the CPU. This means that you must load a project in which the Web server is activated to enable access using the Web browser.
Security functions in webserver
The Web server provides the following security functions:
● Access via the secure transmission protocol “HTTPS” using the CA-signed Web server certificate
● User authorizations you can configure by means of user list
● Activation for specific interfaces
You need a web browser to access the HTML pages of the CPU. The following web browsers have been tested for communication with the CPU. Other web browsers may also work, especially newer versions. However, if problems occur with web browsers not mentioned here that cannot be rectified, use one of the following tested web browsers:
Internet Explorer (Version 11)
● Microsoft Edge (Windows 10)
● Mozilla Firefox (Version 42 to 47)
● Google Chrome (version 46, 47)
● Mobile Safari and Chrome for iOS (iOS 9)
● Android Browser and Android Chrome (Jelly Bean 4.3, KitKat 4.4, Lollipop 5.0 … 5.1.x, Marshmallow 6.0 operating system)
Procedure for Activation of webserver in PLC.
As per our standard procedure we will first select Siemens S7 300 PLC and configure in TIA portal software. Activate Web server In the default setting of a configured CPU, the Web server is disabled. Proceed as follows to enable the Web server:
1. Open the “Devices & Networks” view with a double-click in the STEP 7 project tree.
2. Select the required CPU in the device view, network view or topology view.
3. Navigate to the “Web server” area in the Inspector window properties, “General” tab.
4. Select the “Activate web server on this module” check box. The following note is output:
|Webserver Activation from Properties|
In TIA, you can manage the user list in the “Web server > User management” area.
The user list provides the following options:
● Create users
● Specify access permissions
● Assign passwords
|User Management in Webserver|
Users only have access to the options that are permanently linked to the access rights. You can assign different user rights depending on the used CPU and firmware. If you are not logged in, you automatically access the Web server as the user “Everybody”. It does not matter in this case whether you have configured additional users.
In the “User pages” area you can download your own web pages to the CPU and make your own web applications available via the web browser.
|Integrate User Defined Webpage in Webserver|
Now create new data block and assign its name as per given name In user defined webpage in HTML, also create variable In data block same as you created in webpage. In our case we have assigned data block name as “webdata” and one bool variables “motor” for controlling PLC tag.
|Create Web data and variable in data block|
Now we will configure “WWW” block in main OB to call webserver from the PLC. Note always data block number of WWW block is always 333.
Also take any memory bit and assign tag name same as per web data variable name, so here we have given tag name ”Motor” as symbolic address.
After making logic and programming download PLC hardware and programing block.
Establish a connection to the Web server by entering the IP address of the interface of the configured PLC CPU which is connected to the client in the address bar of the web browser, for example, http://192.168.7.5 . Remember PLC must be connected with Internet via wifi module or any LAN connection with same subnet of router.
Now open any web browser which is in siemens standard list and enter IP address of PLC CPU, so you will get siemens web portal. The figure below shows the first page (Intro) called by the Web server.
|Web portal intro page|
Now enter User id and password as per given in user management list. Once you login , you will now access all required data of the PLC CPU like identification, diagnostic buffer, module info, communication, tag status and customer pages.
|Remote access page after login in web server|
We will open customer pages as we can open User defined webpage from this option, so here for the demo we have only created Motor ON and OFF button and one IO field to enter speed of motor. So after opening this portal we will get view as per below image.
|User Defined web page for controlling|
From this web page you can control motor ON OFF and speed of motor by clicking button and entering speed data.
Check Video Demonstation: