Hello,
I am working on a conveyor application that transports pallets of steel sheet rolls. In this application there are a number of conveyor stations following each other. Each has a through-beam photocell for pallet detection. Blocking a photocell starts the conveyors on that station and the next, unless the next station is occupied. A negative flank on a photocell means that the station is unoccupied.
The problem is that between the wooden pallet and the steel sheet roll, is a transparent plastic protection sheet that extends outside the pallet. When the package approaches a photocell, the plastic sometimes blocks the photocell and sometimes not, and sometimes something in between which leads to a flickering signal. When the signal goes high and then low, the station is considered unuccupied. To prevent something bad to happen, I have implemented on delay timers on each photocell signal in the PLC.
Now to the question:
Is this the best way to prevent flickering signals? Are there any disadvantages in doing this? Say I got a hundred photocells... I'm thinking mainly of timing errors and such in the PLC.
I am working on a conveyor application that transports pallets of steel sheet rolls. In this application there are a number of conveyor stations following each other. Each has a through-beam photocell for pallet detection. Blocking a photocell starts the conveyors on that station and the next, unless the next station is occupied. A negative flank on a photocell means that the station is unoccupied.
The problem is that between the wooden pallet and the steel sheet roll, is a transparent plastic protection sheet that extends outside the pallet. When the package approaches a photocell, the plastic sometimes blocks the photocell and sometimes not, and sometimes something in between which leads to a flickering signal. When the signal goes high and then low, the station is considered unuccupied. To prevent something bad to happen, I have implemented on delay timers on each photocell signal in the PLC.
Now to the question:
Is this the best way to prevent flickering signals? Are there any disadvantages in doing this? Say I got a hundred photocells... I'm thinking mainly of timing errors and such in the PLC.
