Email: Password: Remember Me | Create Account (Free)

Back to Subject List

Old thread has been locked -- no new posts accepted in this thread
???
03/20/10 11:45
Read: times


 		 #174349 - Gate current
Responding to: ???'s previous message
Chico Magalhães said:


So, I got there is no current in the gate, am I doing this right?

Also, as I seen there is no current in gate I made another test, put a potentiometer as voltage divisor and the swipper/cursor connected to IRF's gate, and could control the brigthness of the light bar, the IRF got a bit hot this time, but I think the raise in temperature is normal, but dont know if is right to put a potentiometer in the IRF's gate.



The gates have a capacitance that has to be charged. You're only looking at the steady state current, which is indeed very small, however if you are really switching these things hard, you need AMPS of gate current.

FETs work in a "linear" mode, just the same a Bipolar transistor - which you have explored with the pot

Steve

List of 120 messages in thread
TopicAuthorDate
IRF640 noob test            01/01/70 00:00      
   Gate current            01/01/70 00:00      
   "empirical" learning...            01/01/70 00:00      
      read the material...            01/01/70 00:00      
         I believe he is using a MOSFET here            01/01/70 00:00      
            kit            01/01/70 00:00      
               It is DC output            01/01/70 00:00      
               POOF BOOM            01/01/70 00:00      
   what about this circuit?            01/01/70 00:00      
   IRFZ48N and a circuit, this one can fit?            01/01/70 00:00      
      A little bit easier link            01/01/70 00:00      
         Thanks Per            01/01/70 00:00      
            The longest road from a to b            01/01/70 00:00      
               The problem is...            01/01/70 00:00      
                  Sorry            01/01/70 00:00      
                     Hope, you will find the time...            01/01/70 00:00      
                        RGB Controller            01/01/70 00:00      
                           do you need it that bright            01/01/70 00:00      
                              Bar and some info            01/01/70 00:00      
                                 sure you can            01/01/70 00:00      
                                    Hard to adjust intensity by changing voltage            01/01/70 00:00      
                           Simple scheme...            01/01/70 00:00      
                              Very nice!            01/01/70 00:00      
                                 HC32 and not KTC32            01/01/70 00:00      
                                 Answers...            01/01/70 00:00      
                                    maybe another CI?            01/01/70 00:00      
                                       Yes most hc is ok            01/01/70 00:00      
                                          Same HCs to switch ULN2803?            01/01/70 00:00      
                                       Logic Level MOSFET            01/01/70 00:00      
                     you can - wth a caveat            01/01/70 00:00      
   Can I ask a color question?            01/01/70 00:00      
      Start a new thread            01/01/70 00:00      
         Interpolate in RGB or HSV but not in your tabulated index.            01/01/70 00:00      
            linear interpolations...            01/01/70 00:00      
               Standard interpolation            01/01/70 00:00      
                  that depends            01/01/70 00:00      
         right subject            01/01/70 00:00      
      your premises are wrong            01/01/70 00:00      
      If you answer a question...            01/01/70 00:00      
         Just tests, no MOSFETs yet...            01/01/70 00:00      
            The ULN2803 will ruin your colors!            01/01/70 00:00      
               when doing color            01/01/70 00:00      
               miss the point... the point is the color generation...            01/01/70 00:00      
                  Help with what?            01/01/70 00:00      
                  already answered            01/01/70 00:00      
                  Have you seen my link?            01/01/70 00:00      
                     Yes, but dont helps...            01/01/70 00:00      
                        as usual            01/01/70 00:00      
                           not "SPECIFIC, SPECIFIC, SPECIFIC"            01/01/70 00:00      
                              Use another look-up table...            01/01/70 00:00      
                                 Thats it!            01/01/70 00:00      
                                    Copy from a professional solution...            01/01/70 00:00      
                                       Youtube has some nice videos...            01/01/70 00:00      
                              you've got it wrong and what are you doing            01/01/70 00:00      
                                 I care Erik!            01/01/70 00:00      
                                    why are you "going through steps"?            01/01/70 00:00      
                                       Kai videos?            01/01/70 00:00      
                                          Already been told            01/01/70 00:00      
                                             HSV            01/01/70 00:00      
                                                Now I'm confused            01/01/70 00:00      
                                                   Still never telling what you do want            01/01/70 00:00      
                                                      you are going for an intensity ratio ...            01/01/70 00:00      
                                                      I see no contradiction...            01/01/70 00:00      
                                                         I think it was incrementing of the index that was the proble            01/01/70 00:00      
                                                            Chico, are you getting it            01/01/70 00:00      
                                                               Words            01/01/70 00:00      
                                                                  He should have enough information now...            01/01/70 00:00      
                                                                     that is often the problem ...            01/01/70 00:00      
                                                                        Words fail me...            01/01/70 00:00      
                                                                  How to add            01/01/70 00:00      
                                                                     You don't have paletted device so stop thinking about index            01/01/70 00:00      
                                                                        only 125 colors            01/01/70 00:00      
                                                                           Smooth? Sudden? This make no sense!            01/01/70 00:00      
                                                                              I'm tired from guessing, Chico...            01/01/70 00:00      
                                                                           So you haven't read what we have posted?            01/01/70 00:00      
                                                         Thats it Kai...            01/01/70 00:00      
                                                            place my 125 unchangeable colors in a nice sequence in this            01/01/70 00:00      
                                                               Lacks words for me!            01/01/70 00:00      
                                                                  You need more levels.            01/01/70 00:00      
                                                                  See previous suggestions!            01/01/70 00:00      
                                                            only 32 words            01/01/70 00:00      
                                                            what is "nice sequence"? and for what purpose?            01/01/70 00:00      
                                                            A Color Sequence            01/01/70 00:00      
                                                               Gives color jumps            01/01/70 00:00      
                                                                  Missing backslash in previous post            01/01/70 00:00      
                                                                  Look at the example cited earlier            01/01/70 00:00      
                                                                     not a good one            01/01/70 00:00      
                                                                        Starting point?            01/01/70 00:00      
                                                                           my thought is            01/01/70 00:00      
                                                                              Did I get you?            01/01/70 00:00      
                                                                                 sort of            01/01/70 00:00      
                                                                                    Thanks!            01/01/70 00:00      
                                                                                    You are so full of yourself...            01/01/70 00:00      
                                                                                       "web safe" colors available in standard VGA color palette            01/01/70 00:00      
                                                                                          right, you compensate for this by ...            01/01/70 00:00      
                                                                                             Note that candela hides the eyes spectral response            01/01/70 00:00      
                                                                                                true, and            01/01/70 00:00      
                                                                                                   But he doesn't want his solution to be better - just differe            01/01/70 00:00      
                                                                                                      I give up suggesting better and simpler ...            01/01/70 00:00      
                                                                                       with "binary weighing" he gets 32738 colors            01/01/70 00:00      
                                                                                          Number of colors            01/01/70 00:00      
                                                                                             for a LED sign: none            01/01/70 00:00      
                                                                                             Solve modulation first, then bother about constant-intensity            01/01/70 00:00      
                                                                                                not if you do as I suggested            01/01/70 00:00      
                                                                                                   You'll see a lot if slow-stepping changes            01/01/70 00:00      
                                                                                       How naive I was...            01/01/70 00:00      
                                                                                          I do not know, but ...            01/01/70 00:00      
                                                                                             I still say...            01/01/70 00:00      
                                                                                          Everything depends on needs - simplification often ok            01/01/70 00:00      
                                                                                             Gamma            01/01/70 00:00      
                                                                                             If I were Chico...            01/01/70 00:00      
                                                                     Another Color Sequence...            01/01/70 00:00      
                                                                        Yet another sequence...            01/01/70 00:00      
                                                                           another (better) approach            01/01/70 00:00      
                                                               Oops....Sawtooth File Deleted            01/01/70 00:00      
                                                                  On its way...            01/01/70 00:00      
                                                                     Received and RePosted            01/01/70 00:00      
                                                                        RE: wake up the cat            01/01/70 00:00      
                                                                           Walking the RGB cube as described earlier            01/01/70 00:00      
                                                                              the way to do it            01/01/70 00:00      

Back to Subject List