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???
04/11/06 14:56
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 		 #114100 - I guess I know what happens...
Responding to: ???'s previous message
Jon, voltage drop across 0.33Ohm resistors (Rsense) becomes too high! Think about how little your Ugs is!! So, before the current reaches the limit controlled by Uref, the MOSFET tends to turn-off again resulting in an instability and oscillation.

Try to increase the Ugs of IRL540 to at least 5V, or even more. Then the strange ringing at Rsense should disappear!

Kai

List of 111 messages in thread
TopicAuthorDate
Using L6506            01/01/70 00:00      
   Two sensing resistors            01/01/70 00:00      
      Oops...            01/01/70 00:00      
         Diodes            01/01/70 00:00      
            internal vs external diodes            01/01/70 00:00      
               Yes, but depends            01/01/70 00:00      
   Still having problems with this.            01/01/70 00:00      
      Scope plots?            01/01/70 00:00      
         Plots and Diodes            01/01/70 00:00      
            On the scope plots...            01/01/70 00:00      
               I don't see photos at all            01/01/70 00:00      
                  That's all I can see:            01/01/70 00:00      
                     Ok, bad links... try this            01/01/70 00:00      
                        Ahh, much better!!            01/01/70 00:00      
                           Some Explanation            01/01/70 00:00      
                              I guess I know what happens...            01/01/70 00:00      
                                 Explaination            01/01/70 00:00      
                                    I guess.. I don't follow...            01/01/70 00:00      
      Switch mode            01/01/70 00:00      
         1.6 mH / Phase            01/01/70 00:00      
      Additional questions            01/01/70 00:00      
         Additional Answers            01/01/70 00:00      
            More decoupling needed            01/01/70 00:00      
         One more            01/01/70 00:00      
            5.1 zener            01/01/70 00:00      
         Two more            01/01/70 00:00      
            RE: Two more            01/01/70 00:00      
               They should stay rather cool            01/01/70 00:00      
                  Right now            01/01/70 00:00      
      I don't understand...            01/01/70 00:00      
         Not Calculation... measurement            01/01/70 00:00      
            Peak versus DC?            01/01/70 00:00      
               Measurements            01/01/70 00:00      
                  What you see is not the motor current!            01/01/70 00:00      
                     Rsense            01/01/70 00:00      
                        Pumping enery into inductance            01/01/70 00:00      
                           Current sensing            01/01/70 00:00      
                              3 amps/phase - unipolar config            01/01/70 00:00      
                     That would be the motor current            01/01/70 00:00      
                        I think your am-meter is not working cor            01/01/70 00:00      
                           Amps            01/01/70 00:00      
                              A scope plot would clear the situation            01/01/70 00:00      
                                 set the scope to differential mode            01/01/70 00:00      
                                    Shunt resistor            01/01/70 00:00      
                                       Parallel them            01/01/70 00:00      
                                          Ok, but first            01/01/70 00:00      
                                             Hmm...            01/01/70 00:00      
                                                Time constants            01/01/70 00:00      
                                                   Stepper Motor Datasheet            01/01/70 00:00      
                                             Connecting mistake?            01/01/70 00:00      
                                                Take care with it            01/01/70 00:00      
                                                   Sparks?            01/01/70 00:00      
                                                      Protection earth            01/01/70 00:00      
                                                         Dual channel scope            01/01/70 00:00      
                                                         Power Supply            01/01/70 00:00      
                                                            Have a nice lunch!            01/01/70 00:00      
                                                            Another idea            01/01/70 00:00      
                                                               Scope plot            01/01/70 00:00      
                                                                  yup            01/01/70 00:00      
                                                                     RE:yup            01/01/70 00:00      
                                                               RE: Another Idea            01/01/70 00:00      
                                                                  It explains why your DC current is ...            01/01/70 00:00      
                                                                     Yes...            01/01/70 00:00      
                                                                     Same setup            01/01/70 00:00      
   Where is this coming from...            01/01/70 00:00      
      Analysis            01/01/70 00:00      
   I can't !#$#@ believe it!            01/01/70 00:00      
      New Scope Plots            01/01/70 00:00      
         Ringing            01/01/70 00:00      
            RE:Ringing            01/01/70 00:00      
               save the trouble            01/01/70 00:00      
                  He already does!            01/01/70 00:00      
                     Additionally            01/01/70 00:00      
               Yes, in HF boards            01/01/70 00:00      
                  Looks the same.            01/01/70 00:00      
                     5k + 2n and 10k+ 1n please            01/01/70 00:00      
                        Vsense Plots            01/01/70 00:00      
                           Aha!            01/01/70 00:00      
                              And...            01/01/70 00:00      
                           Filtered Plots            01/01/70 00:00      
                              Sense of filtering            01/01/70 00:00      
                                 More Torque            01/01/70 00:00      
         Differential mode            01/01/70 00:00      
   Back at it again.            01/01/70 00:00      
      Hmmm...            01/01/70 00:00      
      Free wheeling schemes            01/01/70 00:00      
         TVS value?            01/01/70 00:00      
            Surely not            01/01/70 00:00      
               Not my marriage... my dad's            01/01/70 00:00      
                  Success with fishing on the weekend?            01/01/70 00:00      
                     Yes... I did get to go            01/01/70 00:00      
                        Comments            01/01/70 00:00      
                           Start with a 1.5KE6V8A            01/01/70 00:00      
                              No change with 1.5KE6V8A            01/01/70 00:00      
                                 No difference with other values            01/01/70 00:00      
                                    Last hope...            01/01/70 00:00      
                                       Same motor - different drive            01/01/70 00:00      
   Plots of current system            01/01/70 00:00      
      More plots            01/01/70 00:00      
   By golly, we're making headway now            01/01/70 00:00      
      Need of free wheels            01/01/70 00:00      
         Looking Back and Forward            01/01/70 00:00      
            A bit strong...            01/01/70 00:00      
               Strong            01/01/70 00:00      
                  Didn't work :((            01/01/70 00:00      
                     As I recommended earlier...            01/01/70 00:00      
                        Yes, but...            01/01/70 00:00      
                           Keep an exe on heat dissipation!            01/01/70 00:00      
                              Only slight decrease in FET temp            01/01/70 00:00      
                        Yes, but...            01/01/70 00:00      
   You can switch both            01/01/70 00:00      

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