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Mahmood Elnasser
12/26/12 12:00
Read: 1811 times
Sacramento
USA


 
#189033 - RS485 supply voltage
I used the MAX483 chip with its Vcc connected to regulated 5V supply for my 7 clocks with a network of around 100 meters. It worked for a couple of years now. Customer expanded his firm and ordered another 7 clocks to be added to the network, 1 on the 5th floor one on the second floor and 5 on the 1st floor where the old 7 clocks are located. Looks like the trip to the 5th floor and back to 2nd floor and back to 1st floor took another 100 meters of length.
I noticed 2 of the 5 clocks at the end of line do not receive the data, I measured the amplitude of the RS422 signal and it was very low less than 0.5v. So I made RS422 repeater board for the last 5 clocks and supplied them with 5Vdc Vcc which solved the problem.
Thinking about the problem again (After it has been solved) I noticed that MAX48x chips are rated for 12Vdc supply. If I raised the Vcc of my master MAX483 chip to 12Vdc, probably I don't need the repeater board to extend the range and would have saved my self one day of work.
What Vcc supply voltage do you use for your RS485/422 applications?
Mahmood

List of 13 messages in thread
TopicAuthorDate
RS485 supply voltage      Mahmood Elnasser      12/26/12 12:00      
   Could the data rate be a problem?       Richard Erlacher      12/26/12 14:12      
   5V      Erik Malund      12/26/12 17:17      
   No!      Kai Klaas      12/27/12 06:24      
      Strange!      Mahmood Elnasser      12/27/12 10:56      
         stubs?      Erik Malund      12/27/12 11:38      
            Found it      Mahmood Elnasser      12/27/12 13:35      
               I made $$ on that one      Erik Malund      12/28/12 10:22      
   How to Protect ?      Satish S Munot      01/09/13 23:32      
      Use MAX3430      Oliver Sedlacek      01/10/13 01:49      
         Or the LT1785...      Kai Klaas      01/10/13 05:10      
      MAX485      Satish S Munot      01/10/13 07:43      
         low      Erik Malund      01/11/13 13:41      

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