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???
04/13/06 16:42
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 		 #114237 - Dual channel scope
Responding to: ???'s previous message
You can solve this situation by a dual channel scope, where you connect each probe to one end of the shunt, but where both ground tips are connected to 0V of motor. Then choose the "channel a minus channel b" option, as Erik mentioned.

I must apologize for not mentioning this grounding issue earlier, but I do always use a scope with galvanically isolated probes!

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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