Beijer Electronics (formerly QSI Corporation)
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Power Specs
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Author:  jkpreglow [ Mon Mar 31, 2008 11:19 am ]
Post subject:  Power Specs

In regards to the Q-55 terminal, is there any protection circuitry if 24V is applied before ground with respect to the 485 serial pins?



We've had a customer experiencing loss of serial communication after plugging in the Q-55 terminal. We're using the DB-15 connector, and it looks like we're getting current flow through the 485 lines, causing our protection circuit to blow.

Author:  wjohnson [ Thu Apr 03, 2008 2:07 pm ]
Post subject: 

I have looked at the schematic for the G55 and there is no circuitry to protect the 485 interface if power is applied to the terminal before ground is connected. You said that your terminals have the DB15 connector. The power and ground pins in this connector are adjacent to each other so it would be difficult to have power or ground connect without the other also making contact.

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