Example of detecting the fill level of a storage area

Detecting the fill level of a storage area

The following figure shows a system with two conveyor belts and a temporary storage area between them. Conveyor belt 1 delivers packages to the storage area. A photoelectric barrier at the end of conveyor belt 1 near the storage area detects how many packages are delivered to the storage area. Conveyor belt 2 transports packages from the temporary storage area to a loading dock where they are loaded onto trucks. A photoelectric barrier at the storage area exit detects how many packages leave the storage area to be transported to the loading dock. Five display lamps indicate the capacity of the temporary storage area.

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
RESET	Input	BOOL	Reset counter
LOAD	Input	BOOL	Adjust the current counter value to the value of the PV parameter.
MAX STORAGE AREA FILL AMOUNT	Input	INT	Maximum possible number of packages in the storage area
PACKAGECOUNT	Output	INT	Number of packages in the storage area (current count value)
STOCK_PACKAGES	Output	BOOL	Is set when the current count value is greater than or equal to the value of the "MAX STORAGE AREA FILL AMOUNT" tag.
STOR_EMPTY	Output	BOOL	Display lamp: Storage area empty
STOR_NOT_EMPTY	Output	BOOL	Display lamp: Storage area not empty
STOR_50%_FULL	Output	BOOL	Display lamp: Storage area 50 % full
STOR_90%_FULL	Output	BOOL	Display lamp: Storage area 90 % full
STOR_FULL	Output	BOOL	Display lamp: Storage area full
VOLUME_50	Input	INT	Comparison value: 50 packages
VOLUME_90	Input	INT	Comparison value: 90 packages
VOLUME_100	Input	INT	Comparison value: 100 packages

The following networks show the FBD programming for activating the lamps:

Network 1:

When a package is delivered to the storage area, the signal state at "PEB1" switches from "0" to "1" (positive signal edge). On a positive signal edge at "PEB1", the "Up" counter is enabled, and the current count value of "PACKAGECOUNT" is increased by one.

When a package is delivered from the storage area to the loading dock, the signal state at "PEB2" switches from "0" to "1" (positive signal edge). On a positive signal edge at "PEB2", the "Down" counter is enabled, and the current count value of "PACKAGECOUNT" is decreased by one.

If there are no packages in the storage area ("PACKAGECOUNT" = "0"), the "STOR_EMPTY" tag is set to signal state "1", and the "Storage area empty" lamp is switched on.

The current count value can be reset to "0" if the "RESET" tag is set to signal state "1".

If the "LOAD" tag is set to signal state "1", the current count value is set to the value of the "MAX STORAGE AREA FILL AMOUNT" tag. As long as the current count value is greater than or equal to the value of the "MAX STORAGE AREA FILL AMOUNT" tag, the "STOCK_PACKAGES" tag supplies the signal state "1".

Network 2:

As long as there are packages in the storage area, the "STOR_NOT_EMPTY" tag is set to signal state "1", and the "Storage area not empty" lamp is switched on.

Network 3:

If the number of packages in the storage area is greater than or equal to 50, the "Storage area 50 % full" lamp switches on.

Network 4:

If the number of packages in the storage area is greater than or equal to 90, the "Storage area 90% full" lamp switches on.

Network 5:

If the number of packages in the storage area reaches 100, the lamp for the "Storage area full" message switches on.

Example of detecting the fill level of a storage area - STEP 7

Creating FBD programs