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???
03/05/06 15:00
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 		 #111292 - Soft-start
Responding to: ???'s previous message
Jan said:
Or, maybe a suitable NTC?

Yes, theoretically.
But voltage drop across NTC after turn-on highly depends on temperature developping in the NTC and this can differ from type to type and mounting condition to mounting condition. As consequence identical lamps protected by individual NTCs would no longer shine equally bright.


Jan said:
I have also seen somewhere a dimmer-like triac-based circuit, exactly aimed at "pre-heating" of incandescent lamp filaments.

Yes, this is a suitable and widely used methode, especially for stage and public address applications.
Another methode, especially for lamps driven by DC voltages, is to provide a soft-start, where the voltage dropping at lamp rises rather slowly. A LM317 can ideally be used for this.

Another beautiful sort of soft-start is to drive the lamp by a constant current source, like in here:





Kai

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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