Don_Dubé

March 15th, 2005, 07:25 PM

Hello everyone!

We are trying to convert an existing proprietary system to a ControlLogix PLC. This is a sortation system which consist of a 580' conveyor running at about 160'/min and 75+ diverts. The current system uses a low resolution incremental encoder (360 Counts) and a "Carrier" Sensor which detect each carrier evenly space at 12"

The timing is very inconsistent. For example we set the scanner to be ON for 6" and they only stay on for 1-2". Since we are using a 16 bit encoder (FlexLogix 1794-ID2) We were forced to reset the encoder at every carrier. Because (580' X 360 count) is greater then an Integer value or the ID2 limit. So we decided to try to use a DINT for the conveyor count timing. We take the carrier count and multiply it by 1000 and add it to the actual encoder value which represents the distance between each carrier. For example 96100 would correspond to carrier 96 and encoder count 100. We are using a LIM instruction to trigger the scanner for 6" or 180 counts. Therefore the Low limit is 96100 and the high limit is 96280. Anyway it is just not working the way we want it to be. Our PLC scan time is about ~5ms and we are using ControNet with an update time of 5ms between the ControlLogix PLC and the FlexIO

I haven't really used encoders before and I was wondering if there would be a better way of doing this. I was thinking of getting the 1756-HSC and let the encoder counts for the length of the entire conveyor?

Any help would be greatly appreciated.

Thanks

We are trying to convert an existing proprietary system to a ControlLogix PLC. This is a sortation system which consist of a 580' conveyor running at about 160'/min and 75+ diverts. The current system uses a low resolution incremental encoder (360 Counts) and a "Carrier" Sensor which detect each carrier evenly space at 12"

The timing is very inconsistent. For example we set the scanner to be ON for 6" and they only stay on for 1-2". Since we are using a 16 bit encoder (FlexLogix 1794-ID2) We were forced to reset the encoder at every carrier. Because (580' X 360 count) is greater then an Integer value or the ID2 limit. So we decided to try to use a DINT for the conveyor count timing. We take the carrier count and multiply it by 1000 and add it to the actual encoder value which represents the distance between each carrier. For example 96100 would correspond to carrier 96 and encoder count 100. We are using a LIM instruction to trigger the scanner for 6" or 180 counts. Therefore the Low limit is 96100 and the high limit is 96280. Anyway it is just not working the way we want it to be. Our PLC scan time is about ~5ms and we are using ControNet with an update time of 5ms between the ControlLogix PLC and the FlexIO

I haven't really used encoders before and I was wondering if there would be a better way of doing this. I was thinking of getting the 1756-HSC and let the encoder counts for the length of the entire conveyor?

Any help would be greatly appreciated.

Thanks