Ok, so now all we have left is the lamp..how do we access the data of the relay?
Block Properties
The lamp and the contact are related though a logical (wired) connection. In EPLAN we can make use of these direct and indirect relationships by creating a custom data property known as a Block Property. I will avoid trying to define what a block property is, I will leave that to EPLAN, but I will state that they are a powerful tool available to communicate information in EPLAN to devices that share some type of logical relationship.
In the case of the contact and the lamp they are logically related via the connection point X2 on the lamp and the N.O. contact. EPLAN is aware of this relationship via the connection (wire) and you can use this relationship to access information about the relay contact via this connection. In essence EPLAN will look out from the connection (H23:x2) to the next device and you can tell EPLAN to make information about that device available at the lamp.
Block Properties at the Part Reference level
Block Properties can be created at two different levels, at the symbol or object reference level or at the project level. I like to first create them at the symbol level to make sure that they work and then copy them to the project level. At the symbol level we have access to specific data values that makes the creation process much easier.
This means that we can create a block property locally for this instance of the lamp symbol and any copies that we make of it, but if we insert a new lamp symbol using symbol insertion, that data format will not transfer because the definition was created in the schematic for a particular instance of the symbol. To make the block property available to ALL symbols in the project we need to define the block property at the Project Level AND then assign it at the schematic level as a display property.
Are you starting to think about local and global variables? Good, because that is essentially exactly what we are talking about.
Block Property Format
We will begin by defining the relationship between the objects and the data, this is known as a block property format.
We will open the device properties of the lamp.
On the first properties tab (Signal Lamp) we will look at the properties in the grid at the bottom of the dialog. Let’s start by looking for existing Block Property formats and find an available slot.
I will be creating a new Block Property: Format at position #10, you may already have some in your project so if #10 is already in use just select another position and make note of it.