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Old March 9th, 2007, 07:08 PM   #1
johnyu
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RS485 / RS422 Connection Bridge

Hi, I have a RS485 sensor need to be connected to a RS232 port on a Micrologix PLC, communication will be one direction only, i.e. from Sensor to PLC.

I also have a RS422 / RS232 adapter, does anyone know how can I connect the RS485 sensor to the RS422 converter?

I heard you can bridge the connections on the RS422 converter to allow it to handle unidirectional RS485, I'm not sure how to bridge or connection the devices, can anyone help?

Connection on RS422 as follows
DATA IN +
DATA IN -
DATA OUT -
DATA OUT +

Connection On RS485 sensor
RS485 A
RS485 B
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Old March 9th, 2007, 07:47 PM   #2
rdrast
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Perhaps something like this?
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Old March 9th, 2007, 07:50 PM   #3
Singapore_Mats
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I normally use only 2-wire for RS422 since my signals only go in one direction (gyrocompass navigation data etc.)

If your sensor also just send data in one direction, the you should be able to connect to data in+ and data in-.

BUT. Measure first, RS422 and RS485 may or may not use the same voltage.
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Old March 9th, 2007, 07:52 PM   #4
rdrast
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422 and 485 are nearly identical, the difference being that 422 is a defined 4-wire interface, and 485 is a two-wire interface, with each tranceiver on the network being able to tri-state itself when not actively communicating.

Quote:
Originally Posted by Singapore_Mats
I normally use only 2-wire for RS422 since my signals only go in one direction (gyrocompass navigation data etc.)

If your sensor also just send data in one direction, the you should be able to connect to data in+ and data in-.

BUT. Measure first, RS422 and RS485 may or may not use the same voltage.
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Old March 12th, 2007, 07:44 AM   #5
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Thanks everyone, I connected from 485 to 422 directly and it worked fine.
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