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    #41
    Re: Analog ESR meter design

    Ok, I built a ~50khz, ~50% duty cycle LM555 timer circuit. That drives a transformer via a coupling capacitor. The transformer takes in 5vac and puts out about 225mV open-circuit. I used this page and the diagram on it to get my ideas from.

    I can post some pics tomorrow, but so far I have only made the capacitor testing portion. I tested a 63v 330uF NCC LXZ -> 216mV. I tested a bulged capXon KF (1000uF 25v) ---> 43mV!!!

    The 555 has no problem powering the transformer, as its 200:15 ratio. As described on this page, the transformer takes the high-voltage, high-impedance, and makes it low-voltage, low-impedance.
    Muh-soggy-knee

    Comment


      #42
      Re: Analog ESR meter design

      ESR meter for capacitor LOW ESR in circuit.
      http://radiokot.ru/konkurs/10/

      Comment


        #43
        Re: Analog ESR meter design

        Originally posted by vhr View Post
        ESR meter for capacitor LOW ESR in circuit.
        http://radiokot.ru/konkurs/10/
        Wow, good link! Never seen that one before. Interesting how the circuits aren't even in a box xD
        Muh-soggy-knee

        Comment


          #44
          Re: Analog ESR meter design

          Double WOW!, it can test any form factor CAPS, I like the way he made the testing pads for testing the surface mounted cap.
          Never stop learning
          Basic LCD TV and Monitor troubleshooting guides.
          http://www.badcaps.net/forum/showthr...956#post305956

          Voltage Regulator (LDO) testing:
          http://www.badcaps.net/forum/showthr...999#post300999

          Inverter testing using old CFL:
          http://www.badcaps.net/forum/showthr...er+testing+cfl

          Tear down pictures : Hit the ">" Show Albums and stories" on the left side
          http://s807.photobucket.com/user/budm/library/

          TV Factory reset codes listing:
          http://www.badcaps.net/forum/showthread.php?t=24809

          Comment


            #45
            Re: Analog ESR meter design

            ESR meter with indication of leakage and short circuit.
            ESR-0...75Ohm
            F-80kHz
            Vp-p<30mV
            HL1-leakage 0...100Ohm
            http://radiokot.ru/konkurs/21/

            Comment


              #46
              Re: Analog ESR meter design

              I wonder how easy it would be to replace the analog meter with a digital readout using 7400\4000 series logic
              "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
              -David VanHorn

              Comment


                #47
                Re: Analog ESR meter design

                Originally posted by Agent24 View Post
                I wonder how easy it would be to replace the analog meter with a digital readout using 7400\4000 series logic
                I think it would be quite complicated, using at least half a dozen IC's

                -Ben
                Muh-soggy-knee

                Comment


                  #48
                  Re: Analog ESR meter design

                  Here's my stab at an ESR meter. It passes a constant current sine wave thru the cap (converts square wave to sine), picks up the voltage and outputs an AC (100kHz) voltage with an amplitude approximately equal to ESR. A scale factor control would allow for compensation for true-RMS or average-reading multimeters. May as well use the meter's conversion circuitry...

                  In theory, as it is all ac coupled, it can handle a fully charged capacitor with no problems. Maximum voltage would be 630V or 1000V depending on cap limits.

                  TODOs - think about AC-to-DC conversion, think about split supplies (try and avoid them.) Ideal meter would run off either 2pc or 3pc of 1.5V AA.
                  Attached Files
                  Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                  For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                  Comment


                    #49
                    Re: Analog ESR meter design

                    The circuit in post 45, the output is rectified to feed analog meter, you may be able to just use cheap DMM that can read low DC mV range.
                    Never stop learning
                    Basic LCD TV and Monitor troubleshooting guides.
                    http://www.badcaps.net/forum/showthr...956#post305956

                    Voltage Regulator (LDO) testing:
                    http://www.badcaps.net/forum/showthr...999#post300999

                    Inverter testing using old CFL:
                    http://www.badcaps.net/forum/showthr...er+testing+cfl

                    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                    http://s807.photobucket.com/user/budm/library/

                    TV Factory reset codes listing:
                    http://www.badcaps.net/forum/showthread.php?t=24809

                    Comment


                      #50
                      Re: Analog ESR meter design

                      This my experiment with ESR meter using some scrapped parts I have in my parts bin, LM555 and 2N3904. Works pretty well compared to my SECORE LC75 for the reading range I want.
                      Attached Files
                      Never stop learning
                      Basic LCD TV and Monitor troubleshooting guides.
                      http://www.badcaps.net/forum/showthr...956#post305956

                      Voltage Regulator (LDO) testing:
                      http://www.badcaps.net/forum/showthr...999#post300999

                      Inverter testing using old CFL:
                      http://www.badcaps.net/forum/showthr...er+testing+cfl

                      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                      http://s807.photobucket.com/user/budm/library/

                      TV Factory reset codes listing:
                      http://www.badcaps.net/forum/showthread.php?t=24809

                      Comment


                        #51
                        Re: Analog ESR meter design

                        Originally posted by budm View Post
                        This my experiment with ESR meter using some scrapped parts I have in my parts bin, LM555 and 2N3904. Works pretty well compared to my SECORE LC75 for the reading range I want.
                        Cool.
                        Mind posting a schematic or link where you might have gotten the schematic? I need to build me one as well.

                        Comment


                          #52
                          Re: Analog ESR meter design

                          Good job!
                          Muh-soggy-knee

                          Comment


                            #53
                            Re: Analog ESR meter design

                            Thanks, here is the Diagram & BOM. I am going to make smaller board to fit into old RadiShack Analog meter, since proof of ciruit is verified and it works.
                            Attached Files
                            Last edited by budm; 09-28-2012, 04:39 PM.
                            Never stop learning
                            Basic LCD TV and Monitor troubleshooting guides.
                            http://www.badcaps.net/forum/showthr...956#post305956

                            Voltage Regulator (LDO) testing:
                            http://www.badcaps.net/forum/showthr...999#post300999

                            Inverter testing using old CFL:
                            http://www.badcaps.net/forum/showthr...er+testing+cfl

                            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                            http://s807.photobucket.com/user/budm/library/

                            TV Factory reset codes listing:
                            http://www.badcaps.net/forum/showthread.php?t=24809

                            Comment


                              #54
                              Re: Analog ESR meter design

                              By the way, for more bias stability of Q1, you can add 100 Ohms between Emitter and Ground and bypass it with 0.47uF cap, and if you want adjustable gain, then put that 0.47uF cap in series with 500 Ohm trimpot for gain adjustment.
                              Never stop learning
                              Basic LCD TV and Monitor troubleshooting guides.
                              http://www.badcaps.net/forum/showthr...956#post305956

                              Voltage Regulator (LDO) testing:
                              http://www.badcaps.net/forum/showthr...999#post300999

                              Inverter testing using old CFL:
                              http://www.badcaps.net/forum/showthr...er+testing+cfl

                              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                              http://s807.photobucket.com/user/budm/library/

                              TV Factory reset codes listing:
                              http://www.badcaps.net/forum/showthread.php?t=24809

                              Comment


                                #55
                                Re: Analog ESR meter design

                                Rev2 with added Adj gain and bias stabilizer for Q1.
                                Attached Files
                                Never stop learning
                                Basic LCD TV and Monitor troubleshooting guides.
                                http://www.badcaps.net/forum/showthr...956#post305956

                                Voltage Regulator (LDO) testing:
                                http://www.badcaps.net/forum/showthr...999#post300999

                                Inverter testing using old CFL:
                                http://www.badcaps.net/forum/showthr...er+testing+cfl

                                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                http://s807.photobucket.com/user/budm/library/

                                TV Factory reset codes listing:
                                http://www.badcaps.net/forum/showthread.php?t=24809

                                Comment


                                  #56
                                  Re: Analog ESR meter design

                                  Originally posted by budm View Post
                                  Rev2 with added Adj gain and bias stabilizer for Q1.
                                  Thanks for the update, just what i was looking for

                                  Comment


                                    #57
                                    Re: Analog ESR meter design

                                    Originally posted by budm View Post
                                    Thanks, here is the Diagram & BOM. I am going to make smaller board to fit into old RadiShack Analog meter, since proof of ciruit is verified and it works.
                                    Thanks.
                                    I think I will be building one as well sometime this week.

                                    Comment


                                      #58
                                      Re: Analog ESR meter design

                                      Just to make sure: this meter isn't capable of testing caps in circuit, or?

                                      Maybe in next revision you could add diodes + bleed resistor to protect the circuit if a charged cap is connected?

                                      Comment


                                        #59
                                        Re: Analog ESR meter design

                                        Even the meters that can test in-circuit can still be fooled by paralleled capacitors or other components, as always, the best test for just about anything is out-of-circuit.

                                        I don't see a huge reason for testing in-circuit anyway. When doing a recap it's usually because you have crap brands and some have already failed.

                                        In such a case it's more sensible to replace the lot anyway for better reliability in the future. Testing their ESR becomes more of an informational postmortem exercise.


                                        Still, I guess it's better to have the feature and not want it than want it and not have it.
                                        "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                        -David VanHorn

                                        Comment


                                          #60
                                          Re: Analog ESR meter design

                                          agent24 is correct, if you have a bunch of caps in parallel, the bad one will not show up as having the high ESR. I always test component out off the circuits.
                                          @sebr: I did add the 1N4007 Diodes to the test terminal, you can add it if you worry about accidentally attach a charged caps to the tester, and if you want more complex, you can add the cap and a bleeder resistor also.
                                          Attached Files
                                          Last edited by budm; 10-02-2012, 04:30 PM.
                                          Never stop learning
                                          Basic LCD TV and Monitor troubleshooting guides.
                                          http://www.badcaps.net/forum/showthr...956#post305956

                                          Voltage Regulator (LDO) testing:
                                          http://www.badcaps.net/forum/showthr...999#post300999

                                          Inverter testing using old CFL:
                                          http://www.badcaps.net/forum/showthr...er+testing+cfl

                                          Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                          http://s807.photobucket.com/user/budm/library/

                                          TV Factory reset codes listing:
                                          http://www.badcaps.net/forum/showthread.php?t=24809

                                          Comment

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