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???
08/05/09 16:26
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 		 #168186 - hot... depends
Responding to: ???'s previous message
Kai Klaas said:
Anurag said:
7809 is just a 'very very' little warm, with a small heat sink.

...that each relay draws about 40mA which results in 8 x 40mA = 320mA when all are on? 320mA usually makes more than "very very little warm".

Depends on how much voltage the 7809 drops. If the "unregulated 12V source" is "soft" enough, it might quite well drop only around 2V or maybe even less, depending on circumstances. That's around half a watt, not necessarily running it hot.

JW



List of 44 messages in thread
TopicAuthorDate
Mechnical Relay or Triac            01/01/70 00:00      
   Relays Or Triacs            01/01/70 00:00      
      Isolation            01/01/70 00:00      
      Relay or Triac            01/01/70 00:00      
         Pull-in vs hold current?            01/01/70 00:00      
         Relays Suggestions            01/01/70 00:00      
      Agree            01/01/70 00:00      
         optotriac            01/01/70 00:00      
            Relay Vs Triac            01/01/70 00:00      
               multimeter is reading 'hold' current?            01/01/70 00:00      
               a simple "kick and hold" circuit            01/01/70 00:00      
                  RE: a simple "kick and hold" circuit            01/01/70 00:00      
                     Thanks            01/01/70 00:00      
                     no            01/01/70 00:00      
                        I see!            01/01/70 00:00      
                     You are absolutely right...            01/01/70 00:00      
                  What are the values of R and C ?            01/01/70 00:00      
                     To be calculated!            01/01/70 00:00      
                     About...            01/01/70 00:00      
               Here are some calculations ..might be helpful            01/01/70 00:00      
                  RE: some calculations            01/01/70 00:00      
                     To Andy            01/01/70 00:00      
                        current measurement            01/01/70 00:00      
                           Schematic            01/01/70 00:00      
                              Re-Drawn Schematic            01/01/70 00:00      
                                 ASCII Art            01/01/70 00:00      
                     Relay supply            01/01/70 00:00      
                  To Kiran            01/01/70 00:00      
               latching relay            01/01/70 00:00      
                  Latching relays are cost effective            01/01/70 00:00      
                     One thing to consider            01/01/70 00:00      
                        latching relay : status updated on bootup            01/01/70 00:00      
                           Ay be a mix will be fine            01/01/70 00:00      
                           I just found a relay which needs lot lesser current            01/01/70 00:00      
                           That's too late!            01/01/70 00:00      
                              My Circuit            01/01/70 00:00      
                                 But didn't you mention...            01/01/70 00:00      
                                    hot... depends            01/01/70 00:00      
                                       Agreed!            01/01/70 00:00      
                                          Thanks ALL.            01/01/70 00:00      
                                       Low voltage drop            01/01/70 00:00      
                                          Good luck!            01/01/70 00:00      
                              random phase?            01/01/70 00:00      
                                 The same what the manufacturer meant...            01/01/70 00:00      

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