11.3.3.5. Simple Divert Example

This example shows how to use a PLC to control a simple divert mechanism to divert a Carton from a ZPA zone and capture its tracking. This example also illustrates how to use the set downstream arrival function with the PLC to keep the discharging ERSC from generating a jam condition when the Carton is moved from the ZPA zone to the divert lane. The PLC will be connected to Module B.

*This example assumes that the tracking data arriving from each new Carton arrival at Module B Upstream Zone contains a value that will indicate to the PLC that a Carton does or does not need to divert. However, it is not required that the PLC use Carton tracking data be used to determine when to divert a Carton. The PLC can use whatever criteria it needs to make a divert decision.

Prepare Module B Upstream Zone:

1. Set bit 0 in Accumulation Control for Local Upstream Zone register to instruct this zone to accumulate any Carton that arrives.
2. Monitor Arrival Count Local Upstream Zone and Departure Count Local Upstream Zone registers. On the leading edge when these two values become not equal, the PLC knows there is a new arrival. Note that as long as a Carton is physically occupying the upstream zone, these two values will not be equal.
3. Upon a successful arrival of a Carton in the upstream zone, then tracking data in Current Upstream Zone Tracking Word 1 and Current Upstream Zone Tracking Word 2 will be valid for the newly arrived Carton

If the PLC determines that the newly arrived carton needs to divert:

1. Set bit 8 of Accumulation Control for Local Upstream Zone register. This will keep Module A from releasing a Carton to Module B while the divert operation is in progress.
2. PLC will then initiate it’s divert mechanism.
3. When carton reaches PE-1, the PLC will then set bit 9 of the Accumulation Control for Local Upstream Zone register. This will tell Module B that the carton “successfully arrived at its downstream position”.
4. Once carton has cleared PE-1, then the PLC should clear bit 9 of the Accumulation Control for Local Upstream Zone register.
5. PLC then can clear bit 8 of the Accumulation Control for Local Upstream Zone register to instruct Module A that it is OK to allow the next carton to enter Module B’s upstream zone.

If the PLC determines that the newly arrived carton does not need to divert:

The PLC can simply modify Carton’s tracking data if desired and release the Carton as described in Basic Accumulate and Release section

*Do not release the Carton by clearing bit 0 of Accumulation Control for Local Upstream Zone in your PLC program. Follow the procedure in the “Basic Accumulate and Release” example