ggc
Member
In the last 2 weeks I have managed to blow up 2 *Red lion G308 screens during commissioning of a modification to an existing machine. The problem appears to be a potential difference across the ports of the laptop, I'll lay out the scenario here and see if anyone has any further suggestions before we blow up another one.
Destruction 1: Existing G308 with opto-isolated serial ports.
New ethernet cable was run from the G308 to a network switch, then onto a VIPA 313 PLC. Cable was run in close proximity to resistance welding SCRs (thyristors). Panasonic toughbook was connected via USB to the G308, via a serial port and PM2 cable to an Allen Bradley Micrologix 1500, and via cat 5 cable to the network switch. The laptop was also connected to mains power, which is not fed from the same supply as the machine. All items inside the cabinet are tied back to the same earth, and are all supplied from the same 24V DC supply. On energisation of the resistance welding SCRS, the 24 V supply was dragged down until it eventually tripped, the G308 now has a black screen, no comms and the smell of failure, and all USB ports on the laptop are fried. Conclusion was that the SCRS had induced a potential difference across the new ethernet cable, which eventually resulted in significant current being pulled down the USB programming cable. Ethernet cable was rerouted outside of the cabinet and a new G308 screen installed. Earths were checked, no potential difference between any of the items in the cabinet was noted.
Destruction 2:
Machine had been happily running for a few hours after recommissioning. IBM laptop plugged into mains power, USB port 1 connected to red lion using quality USB cable, cat 5 cable connected to ethernet switch. Operator requested program change in the AB Micro 1500, PM2 cable was connected to a USB-serial converter, on plugging the USB cable into the laptop, a small spark was noticed. A few seconds later, the stench of failure was noted coming from the red lion. USB cable has extensive burn marks on the ground pin, and the USB port on the laptop is fried. Earths were checked again, everything in place.
Can anyone suggest what has happened and why?
Destruction 1: Existing G308 with opto-isolated serial ports.
New ethernet cable was run from the G308 to a network switch, then onto a VIPA 313 PLC. Cable was run in close proximity to resistance welding SCRs (thyristors). Panasonic toughbook was connected via USB to the G308, via a serial port and PM2 cable to an Allen Bradley Micrologix 1500, and via cat 5 cable to the network switch. The laptop was also connected to mains power, which is not fed from the same supply as the machine. All items inside the cabinet are tied back to the same earth, and are all supplied from the same 24V DC supply. On energisation of the resistance welding SCRS, the 24 V supply was dragged down until it eventually tripped, the G308 now has a black screen, no comms and the smell of failure, and all USB ports on the laptop are fried. Conclusion was that the SCRS had induced a potential difference across the new ethernet cable, which eventually resulted in significant current being pulled down the USB programming cable. Ethernet cable was rerouted outside of the cabinet and a new G308 screen installed. Earths were checked, no potential difference between any of the items in the cabinet was noted.
Destruction 2:
Machine had been happily running for a few hours after recommissioning. IBM laptop plugged into mains power, USB port 1 connected to red lion using quality USB cable, cat 5 cable connected to ethernet switch. Operator requested program change in the AB Micro 1500, PM2 cable was connected to a USB-serial converter, on plugging the USB cable into the laptop, a small spark was noticed. A few seconds later, the stench of failure was noted coming from the red lion. USB cable has extensive burn marks on the ground pin, and the USB port on the laptop is fried. Earths were checked again, everything in place.
Can anyone suggest what has happened and why?