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Aaron Bloom | Support Engineer
By now it’s no secret that Red Lion’s FlexEdge series has a wide range of features that can introduce cutting edge technology to almost any control system. In this tech tip, we’ll focus on the GPS functionality, not only a great feature for mobile equipment to report location or trigger events based on location but can be used to ensure an accurate time without worrying about built in batteries or the dreaded clock drift that’s an issue with most real time clocks.
The GPS functionality is part of the cellular modem sled available for the FlexEdge and comes in a few variations based on region. All the cellular modems should function in the same way however, this tech tip was written with the Australian variant (DAS00CL9C1SAZ000) in mind. Before beginning, it’s important to note the cellular sled needs a valid SIM and connection to the cellular network for the GPS functionality.
Getting started in the Device Configuration section of Crimson 3.2, you need to add the sled into the Crimson database either at the database creation or by changing the Hardware Configuration as per below.
Don’t forget to Commit the hardware changes!
Now, you should have a Modem available under System Configuration > Network > Interfaces.
Under that Modem we need to Enable the Modem. Standard Interface will be suitable for most applications.
GPS should default to Enabled.
Now that the GPS configuration is setup, we need to decide how we want to use the GPS information with two options, Time and Location.
Using external sources for the time on the FlexEdge are set under System Configuration > Services > Time Sync.
The Time Zone tab controls which time zone the FlexEdge is in, which is required to display the local time. Setting Zone Selection to Automatic is preferred as it will look at the Cellular Modem, Location and Public IP address respectively to figure out the correct time zone thus, if a method fails the next one can be used. For the Installation Type, Fixed will check the time zone less regularly whereas Mobile will regularly check for changes as the time zone can change as the device moves.
The GPS tab enables/disables the GPS time sync, defines a source if multiple modems are used and defines the frequency to update the time in which a lower time will result in less drift between checks.
The location functionality is useful in two ways. Firstly, it can be used programmatically to inform the decision making of your process and alarming. Secondly, it can be used as part of a larger deployment management solution.
Location functionality is enabled under System Configuration > Services > Location. The source can be set to Fixed which is useful for Time sync based on location or locating a unit on a large site without having a cellular modem sled installed. However, setting this to a modem is when the true magic happens. Note: Reporting Threshold is a feature for Six View Manager users.
To get the location information into the Crimson environment, use the GetLocationProperty function, which can return the longitude, latitude, altitude and also the fix and sequence state of the GPS, so you can know how confident to be in the location data presented. Below is the Reference for this function from the Crimson 3.2 Reference Manual.
Here is an example of using this as a Tag source.
Add this all together with an active GPS antenna on a cloudy day and we can get a fix without issue.
For those paying close attention you will have noticed two things:
1. These are the coordinates for Control Logic’s head office on Brisbane.
2. The accuracy is about 110m for latitude and roughly 1km for longitude, which is very important when considering how you will use GPS for your application.
For more information contact Control Logic’s Technical Support Team and we can assist you in tailoring the FlexEdge to your application.