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Kai Klaas
02/15/06 08:40
Read: 477 times

#110069 - Exactly!
Responding to: Mahmood Elnasser's previous message
Mahmood said:
Could it be because they coat the contacts with special material to stop corroding the contacts during sparking. and this could affect low current for it increases the contact resistance?

Take a relay with Cadmiumoxid for instance. This material is so bad, that contacts are not glittering at all. It looks like oxidized conatcts, what it is actually!! But to switch heavy or even inductive loads, there's nothing better. Corroding of contacts by sparking is minimal.

Such contact material is totally unsuited to switch light loads, or even dry loads, where no power is switched at all. Dry loads are best be switched by gold contacts and certain alloys resting in inert gas ambient. Silver and silver alloy contacts can be used for light loads but not for dry loads. Unfortunately, these expensive relay contacts are heavily eroded by even the least sparking.

When I was younger I repaired stage amps. The most often damage was the relays used to switch-on and -off loudspeaker at output of amp. After some time, they are not able to let pass music without producing noise and having set outs. It turned out, that contact material was unsuited. Exchanging them by relays having good silver alloy contacts could fix the damage.


List of 34 messages in thread
monitoring mains voltage      Per Guldmann      02/13/06 04:38      
   Opto with capacitor      Oliver Sedlacek      02/13/06 06:33      
      re opto with cap      Per Guldmann      02/13/06 07:09      
         Some protective components required      Oliver Sedlacek      02/13/06 09:56      
            Fire risk      Kai Klaas      02/14/06 07:14      
   Transformer        Andy Neil      02/13/06 07:49      
      thats the best chioce      Abhishek Singh      02/13/06 07:51      
      There's nothing wrong      Per Guldmann      02/13/06 08:40      
         Space      Andy Neil      02/13/06 09:32      
   please do not go aargh      Erik Malund      02/13/06 08:48      
      Opto isolator = LDR + Neon?      Andy Neil      02/13/06 09:20      
      10mA?      Oliver Sedlacek      02/13/06 09:53      
         Hmmm      Per Guldmann      02/13/06 10:12      
            Why not...      Steve M. Taylor      02/13/06 17:03      
               Neon + Photodiode      Andy Neil      02/14/06 00:31      
                  Loosing brightness      Kai Klaas      02/14/06 06:05      
   Transformer isolation is needed!      Kai Klaas      02/13/06 19:42      
      Previously, on      Andy Neil      02/14/06 00:29      
         Safety first      Per Guldmann      02/14/06 03:11      
            Transformer      Kai Klaas      02/14/06 05:58      
               Sorry      Kai Klaas      02/14/06 07:18      
                  two places to look      Erik Malund      02/14/06 07:26      
                  Annoying, isn't it?!      Andy Neil      02/14/06 08:23      
                     Thanx!      Per Guldmann      02/14/06 08:35      
                        maybe Amveco 6200 series?      Erik Malund      02/14/06 08:37      
                        Transformers      Anders Sandström      02/14/06 11:01      
                     Could also be used      Kai Klaas      02/14/06 10:05      
   an Idea        Mahmood Elnasser      02/14/06 10:42      
      The simplest ideas are the best      Jez Smith      02/14/06 14:58      
         Poor dads      Mahmood Elnasser      02/14/06 23:12      
            Tainted food      Kai Klaas      02/15/06 08:25      
      Yes, but...      Kai Klaas      02/14/06 20:01      
         Low current      Mahmood Elnasser      02/14/06 22:50      
            Exactly!      Kai Klaas      02/15/06 08:40      

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