Detecting the direction of a conveyor belt
The detected running direction of the belt is indicated by a RIGHT arrow or a LEFT arrow. If additional conveyed material is approaching PEB1 from the right or PEB2 from the left, the displayed arrow is initially switched off until, after both photoelectric barriers are passed, the running direction can be detected again and the corresponding arrow displayed. For the solution of the task, 2 edge memory bits are needed that detect the signal change from "0" to "1" at the two photoelectric barriers.
Implementation
The following table shows the definition of the tags used:
|
Name |
Declaration |
Data type |
Description |
|---|---|---|---|
|
PEB1 |
Input |
BOOL |
Photoelectric barrier 1 |
|
PEB2 |
Input |
BOOL |
Photoelectric barrier 2 |
|
RIGHT |
Output |
BOOL |
Display during movement to right |
|
LEFT |
Output |
BOOL |
Display during movement to left |
|
CM1 |
Input |
BOOL |
Edge bit memory 1 |
|
CM2 |
Input |
BOOL |
Edge bit memory 2 |
The following networks show the FBD programming for solving this task:
Network 1:
If the signal state changes from "0" to "1" (positive edge) at photoelectric barrier "PEB1" and, at the same time, the signal state at "PEB2" is "0", the object on the belt is moving to the left.
Network 2:
If the signal changes from "0" to "1" (positive edge) at photoelectric barrier "PEB2" and, at the same time, the signal state at "PEB1" is "0", the object on the belt is moving to the right.
See also
Basic information on FBD
Settings for FBD
Working with networks
Inserting FBD elements
Editing FBD elements
Inserting operands in FBD instructions
Branches in FBD
Logic paths in FBD
Example of controlling a conveyor belt
Example of detecting the fill level of a storage area
Example of calculating an equation
Example of controlling room temperature