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???
07/18/06 15:56
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 		 #120496 - well, it might
Responding to: ???'s previous message
This circuit will not work, unfortunately!

Absolutely and fully correct for traditionl '51 ports

However more and more derivatives now are coming out with configurable ports (Philips LPC, SILabs ...) and if such a port is configured as push-pull it will just blow the transistor instead (I was about to write 'work', but that would require a resistor between the port pin and the transistor base)

Erik



List of 49 messages in thread
TopicAuthorDate
Driving 12 Volts relay by 5 Volts microcontroller            01/01/70 00:00      
   12v relay            01/01/70 00:00      
      This will not work properly!            01/01/70 00:00      
         well, it might            01/01/70 00:00      
         pullup?            01/01/70 00:00      
            Doable, but disadvantagous            01/01/70 00:00      
               language and a comment            01/01/70 00:00      
                  Makes only 3 drivers per port            01/01/70 00:00      
      12v relay            01/01/70 00:00      
   12V relay driver for 80C52            01/01/70 00:00      
      12V relay driver for 80C52            01/01/70 00:00      
      Analysis            01/01/70 00:00      
         sure.but why? this is \"grab bag values\"            01/01/70 00:00      
            Re: Analysis            01/01/70 00:00      
               basically they are 'bleeders'            01/01/70 00:00      
                  Choosing Bleeder resistor values            01/01/70 00:00      
                     Values Are design Specific            01/01/70 00:00      
                        how to calculate?            01/01/70 00:00      
                           what you are missing is that a transistor junction            01/01/70 00:00      
                           Two ways of calculation...            01/01/70 00:00      
                              Thank you very much!            01/01/70 00:00      
                                 Nearly....            01/01/70 00:00      
                                    BC556 base current direction...            01/01/70 00:00      
                                       Three currents arround the base...            01/01/70 00:00      
                                          Yes. Its clear for me now.            01/01/70 00:00      
                                             Was a pleasure...            01/01/70 00:00      
                                                So Nice of You. Thanks again!            01/01/70 00:00      
   Didn't search first            01/01/70 00:00      
      Everything is already here. That is not the point!            01/01/70 00:00      
         Maybe it IS the point            01/01/70 00:00      
            Please read again his post            01/01/70 00:00      
               He'd have seen other alternatives            01/01/70 00:00      
                  I give up...            01/01/70 00:00      
                     don't            01/01/70 00:00      
         faq            01/01/70 00:00      
            Beat me to it            01/01/70 00:00      
            freewheling            01/01/70 00:00      
               1n4148            01/01/70 00:00      
               Heaven, no!            01/01/70 00:00      
                  as usual, the global became specific            01/01/70 00:00      
                     That's why I...            01/01/70 00:00      
                  FAQ update            01/01/70 00:00      
                     Comment            01/01/70 00:00      
                        It's fixed now. Thanks.            01/01/70 00:00      
   Alternatives            01/01/70 00:00      
   yet another way            01/01/70 00:00      
      Trouble making            01/01/70 00:00      
   the case of fault            01/01/70 00:00      
      Some thoughts            01/01/70 00:00      

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