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Per Westermark
02/10/12 02:29
Read: 505 times

#185815 - Current loop?
Responding to: Mahmood Elnasser's previous message
Consider a low-bandwidth current loop instead, with optical isolation. Then you don't need to think about any potential differences between the two sites, and the driver side will adjust the power to take into account the length of the cable, i.e. the cable resistance.

Using a scheme with differential voltages requires you to have large enough voltages that the other side will still have distinct potential differences, so whatever solution you do, normal transceiver chips will often have too low transmit voltage. And a custom transmit stage with higher voltages would produce too high voltages if you connect without that long cable.

List of 12 messages in thread
long range RS-485      Mahmood Elnasser      02/10/12 01:51      
   Current loop?      Per Westermark      02/10/12 02:29      
   Repeaters?      Daniel Contarino      02/10/12 06:10      
   can you use repeaters?      Erik Malund      02/10/12 07:58      
      No      Mahmood Elnasser      02/10/12 14:10      
   Profibus people...      Kai Klaas      02/10/12 08:03      
      details      Mahmood Elnasser      02/10/12 14:24      
         just a note      Erik Malund      02/10/12 17:04      
         Phone lines...      Kai Klaas      02/10/12 17:06      
            phone lines      Mahmood Elnasser      02/10/12 23:06      
               Data collision      Kai Klaas      02/11/12 05:35      
   It just works at slow speeds      Oliver Sedlacek      02/14/12 05:03      

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