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???
03/19/06 15:12
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#112495 - power dissipation calculations?
Responding to: ???'s previous message
Hello Kai,

here i would like to recall the circuit,


I read the description of the above inrush current limitting circuit given by you but couldnt understand fully since iam not clear on how you managed to calculate the following:

Kai said,
When the lamp is switched-on, current through it is limited to about 0.2A and up to about 2.0W will drop across the transistor, but only for a very short time.
If the current through 3R0 resistor reachs about I = 0.6V / 3Ohm = 0.2A


from reading the above note, i tried to calculate how you have said that 2W would be dissipated in the transistor (BD135) and, the 3R resistor would have drop of .6V. BUT couldnt get clear with that. also with "what would be the voltage drop in the bulb in that circuit" since i think it would not drop 12V fully on it.
So, it would be helpful for me if you could provide me with few details on those issues.

Thanking you,
Suresh.

List of 57 messages in thread
TopicAuthorDate
inrush current + suitable voltage sour            01/01/70 00:00      
   Inrush current of lamp            01/01/70 00:00      
      Current inrush            01/01/70 00:00      
         NTC?            01/01/70 00:00      
            Soft-start            01/01/70 00:00      
               8 reed SW parallely + 21.12A / at 12VDC            01/01/70 00:00      
                  Car battery???            01/01/70 00:00      
                  inrush current            01/01/70 00:00      
                  totally irrelevant            01/01/70 00:00      
                  No testing needed, standardly            01/01/70 00:00      
                     replies            01/01/70 00:00      
                        Reply to "replies"            01/01/70 00:00      
                           the difference between "cheap" and "inex            01/01/70 00:00      
                           current limit resistor            01/01/70 00:00      
                              are you just grasping for straws?            01/01/70 00:00      
            NTC, yes            01/01/70 00:00      
               Filaments            01/01/70 00:00      
                  In the days of radios for AC and DC            01/01/70 00:00      
                     Thanks            01/01/70 00:00      
            resistor parallel to Switch!            01/01/70 00:00      
               MOSFET, constant current source?            01/01/70 00:00      
                  not for my use            01/01/70 00:00      
                     Ok, but...            01/01/70 00:00      
                        but i think            01/01/70 00:00      
                           Relays            01/01/70 00:00      
                              yes ofcourse            01/01/70 00:00      
                                 here we go again            01/01/70 00:00      
                                    Even more!!            01/01/70 00:00      
                                       werlcome to the club            01/01/70 00:00      
                                       reply            01/01/70 00:00      
                                          why did you not say so?            01/01/70 00:00      
                                          You made a fool of us!            01/01/70 00:00      
                                             reply            01/01/70 00:00      
                                                That's no fun!            01/01/70 00:00      
                                                   Suresh, I hope you had fun            01/01/70 00:00      
                                                   reply            01/01/70 00:00      
                                                      yeah 6 days later.            01/01/70 00:00      
                  Hello Kai,            01/01/70 00:00      
                     Look at here            01/01/70 00:00      
                        Thank you very much Kai.            01/01/70 00:00      
                           It just strikes me            01/01/70 00:00      
                              yes you are right            01/01/70 00:00      
                                 Reed switch problems            01/01/70 00:00      
                                    Current rating?            01/01/70 00:00      
                                       I recall long ago something about a "sti            01/01/70 00:00      
                                       Reed problem            01/01/70 00:00      
                                          Glueing together            01/01/70 00:00      
                                             Reed problems            01/01/70 00:00      
                                                reed relayrs            01/01/70 00:00      
                           power dissipation calculations?            01/01/70 00:00      
                              bulb voltage drop            01/01/70 00:00      
                                 Thanks            01/01/70 00:00      
                                 (.2*bulb resistance            01/01/70 00:00      
                                    The bulb            01/01/70 00:00      
                              Constant current during inrush moment            01/01/70 00:00      
                                 Thanks a lot Kai            01/01/70 00:00      
         Choke would be huge            01/01/70 00:00      

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