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???
03/11/06 14:04
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 		 #111965 - MOSFET, constant current source?
Responding to: ???'s previous message
Suresh said:
would connecting a suitable resistor value parallel to the switch to keep the filament warm would prove an efficient way of minimising the current inrush?

Yes, that's an idea. But maybe you waste lots of current if only one lamp is on at a time?

It's better to turn-on the lamp by a MOSFET, which has an integrator (RC-low pass filter) at its input. This will allow the lamp to be turned-on so slowly, that inrush current does no longer make trouble. And at the same time, you don't suffer from wasting of supply current.

You can also turn-on the lamp by the help of a constant current source, like it's shown here:




Why are you so focused on using a relay for the swicthing? A relay would only consume additional supply current, while the MOSFET or constant current source would not waste anything relevant.

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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