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???
02/24/07 22:48
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#133639 - No you missed that it is the coil...
Responding to: ???'s previous message
Mike:
No. You missed that it is the relay coil that is in series with the switch, the combination of which is across the +12 volt supply. The relay coil has some resistance to it and this limits the current to some finite amount. Say the coil was 120 ohms then the current would nominally be limited to 12V/120ohms = 100mA when the switch is closed.

Of course there could be situations where the +12 volt supply comes from a low current source such as a LM7812 that may be current limited to 1A and the relay was come type of huge contactor with a 2.4 ohm coil in which case the current draw through the coil would be more than enough to swamp out the supply and limit the source so that it outputs decidedly less than +12 volts.

Michael Karas


List of 51 messages in thread
TopicAuthorDate
How its happen?            01/01/70 00:00      
   correction            01/01/70 00:00      
   my 2 cents            01/01/70 00:00      
   What is exactly RLY fuction?            01/01/70 00:00      
      Effect of relay            01/01/70 00:00      
         Isn't it called EMI?            01/01/70 00:00      
            Sure - radiated and conducted            01/01/70 00:00      
               Ok, thought so :)            01/01/70 00:00      
                  Maybe it's a test?            01/01/70 00:00      
                     Not very kind to operator :)            01/01/70 00:00      
         A diode helps.            01/01/70 00:00      
            But immunity is best!            01/01/70 00:00      
         Arcing machine            01/01/70 00:00      
            RF oscillations            01/01/70 00:00      
               School experiment            01/01/70 00:00      
   Ok, we posted in the same minute :)            01/01/70 00:00      
      This time it was Andy and AGAIN same time :)            01/01/70 00:00      
      I'll build in some random delay next time :-)            01/01/70 00:00      
   the solution will be here            01/01/70 00:00      
   I'm puzzled            01/01/70 00:00      
      It damps out the relay voltage spikes?            01/01/70 00:00      
         not much, if any - 33pF?            01/01/70 00:00      
            Should be a printing error.            01/01/70 00:00      
   let's focus            01/01/70 00:00      
      Of course it is possible.            01/01/70 00:00      
      why focus            01/01/70 00:00      
         because......            01/01/70 00:00      
            Part more susceptable to EMI?            01/01/70 00:00      
            'experiment' all you want            01/01/70 00:00      
            prevent problems            01/01/70 00:00      
      where did we not focus?            01/01/70 00:00      
         conclusion            01/01/70 00:00      
            You are a funny guy...            01/01/70 00:00      
               chips is different            01/01/70 00:00      
                  already answered            01/01/70 00:00      
                  That's the definition of "Unreliable"!!            01/01/70 00:00      
                  pure unadulterated male cow manure            01/01/70 00:00      
                     The Relay            01/01/70 00:00      
                        The purpose of a Watchdog            01/01/70 00:00      
                           Woof            01/01/70 00:00      
                              Grrr            01/01/70 00:00      
                                 Watchdog Hit Report            01/01/70 00:00      
                  Some hints...            01/01/70 00:00      
                     The decoupling Cap            01/01/70 00:00      
                        With shortest leads to Vcc and GND pins            01/01/70 00:00      
                     What software,Kai?            01/01/70 00:00      
                        Target            01/01/70 00:00      
                           yes            01/01/70 00:00      
                     Thankyou Kai            01/01/70 00:00      
   isn't it obvious?            01/01/70 00:00      
      No you missed that it is the coil...            01/01/70 00:00      

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