Tutorial advanced 3:
Web Server Chrono controller!
Content of the tutorial:
Dear User, in the former tutorials we have learnt how to handle switches and sensors through a Web Server interface. In those examples both the update of the read value of a sensor and the setting of a switch/relay are triggered by a user action, through the web page interface available in your Control Panel.
In this new tutorial you will see how to give an automatic behaviour to some devices. In other words, once programmed, those devices will be activated or deactivated on a time based event, without a direct user interaction. This functionality is useful for instance when we want switch on or off a light, or the heating system, or whatever you like every day at a specific time.
A Chrono controller is a software service you can add to your control system. It's purpose is to give some time based behaviours to the system itself.
If we look at the picture, we can see that the chrono object is 'linked to' the device (usually a relay switch) that needs to be controlled. In this way any digital devices can be controlled on time base. However, through the manual sub-object attached to, you can also give manual commands to the same objects.
Refer to Chrono controller section in Devise Home User Manual to get more information about how to set a Chrono controller.
Configuration is the way to program a Chrono. When you access from the control panel to the web page of your project (see previous tutorials for more details), the configuration button appears on the main page. Through this button you can access to a page where all the configuration parameters are presented. In this page there are input fields, check-boxes and son on.
The main difference between the configuration page and the main page is that all the value set in the configuration page are not volatile: they are kept unchanged even if you switch off your system and switch it on again. So if you program a time for your Chrono, it will survive after any power on or restart.
Once more, please, refer to Chrono Controller section in Devise Home User Manual to get more information about how to program a Chrono controller.
Real Time Clock (RTC) is a hardware device that provides the system of a real time clock. The advantage of this device is that it is powered by its own lithium battery, so it will count the time even when the system is not powered at all. When a hardware clock is set in the project, the configuration page will present the input fields to adjust the time and the date.
If ther isn't any clock devices in the project, the system can still work fine, using a software real time clock generator. In this case it is automatically synchronized to the web and there is no need to manually adjust time and date.
But how can I choose between hardware or software real time clock?
It mainly depends of your internet connection:
- if it is guaranteed for a long life time, use software RTC without problems. In fact the software RTC is not so accurate as the hardware one. However it is continuously resynchronized to the web clock source.
- if you need your system working fine even without internet connection, hardware RTC is the better choiche.
Refer to RTC section in Devise Home User Manual to get more information about how to set a RTC.