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???
01/12/05 08:23
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 		 #84812 - How Can It Work....
Responding to: ???'s previous message
Your circuit that has the NPN transistor to switch the 3.3V to the ISP header has 3.3V on the collector of the transistor. You are driving the base with a signal from the microcontroller (a 3.3V part) so that signal cannot go higher than 3.3V. The emitter of the NPN transistor will always be one Vbe drop below the base voltage if the transistor is to be ON. DUH.

This is why it works the way you see. One fix is indeed the circuit type shown by Ijaz.

Michael Karas


List of 34 messages in thread
TopicAuthorDate
LPC932A1 ICP problem.            01/01/70 00:00      
   One problem sovled another came up.            01/01/70 00:00      
      LPC932A1 ICP problem            01/01/70 00:00      
      Some comments            01/01/70 00:00      
         Transistor and base resistor changed.            01/01/70 00:00      
            values            01/01/70 00:00      
               Did you analyze the circuit?            01/01/70 00:00      
                  Re: ' '            01/01/70 00:00      
                     A possible solution            01/01/70 00:00      
                        HCT driven with RS232.            01/01/70 00:00      
                           Professional Programmer? Which?            01/01/70 00:00      
                              the horses mouth            01/01/70 00:00      
                                 ICP Programmer            01/01/70 00:00      
                                    More info on the ICP programmers list            01/01/70 00:00      
                                       More info on the ICP programmers list            01/01/70 00:00      
                                          www.elnec.com            01/01/70 00:00      
                                             ISP ICP            01/01/70 00:00      
                                                Scratch Advantech too            01/01/70 00:00      
                                                I checked out with elnec.com,            01/01/70 00:00      
                                                    I checked out with elnec.com too            01/01/70 00:00      
                                                      Double-check at elnec.com            01/01/70 00:00      
                                                         Double-check at elnec.com            01/01/70 00:00      
                                                            Send them the chip            01/01/70 00:00      
                                                               ICP Programmer (Elnec)            01/01/70 00:00      
                  0.7V drop            01/01/70 00:00      
                     Re: 0.7V drop            01/01/70 00:00      
            How Can It Work....            01/01/70 00:00      
               Terrible circuit...            01/01/70 00:00      
   New(er) ICP specs            01/01/70 00:00      
      New(er) ICP specs            01/01/70 00:00      
         ICP Programmers            01/01/70 00:00      
      ICP specs            01/01/70 00:00      
         ICP Programmer from ZLG            01/01/70 00:00      
            maybe....            01/01/70 00:00      

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