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    #81
    Re: Cheaper ESR meter

    It looks like it does not have fine resolution to show anything well at 1 Ohm. What is this meter? 50uA, 100uA, 200uA?
    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

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      #82
      Re: Cheaper ESR meter

      Tascam 38 reel to reel tape recorder vu meter
      Part no. 5296003300
      Not been able to find out mA rating.
      I have 2 of them and both are the same.
      I do have another analog meter from a Precision 10
      Analyser (car diagnostic meter) with volts, amps, dwell etc... Shall try this
      one out later.

      Comment


        #83
        Re: Cheaper ESR meter

        I will doubt that VU meter from TASCAM is sensitive enough, I did try using some of those VU meters and they did not work well, I had to drive them harder to get full scale. The 50micro-Amp works well for me to see 1 Ohm range at 1/4 of the scale.
        http://s807.photobucket.com/albums/y...t=DSC00980.jpg
        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


          #84
          Re: Cheaper ESR meter

          Ok I shall try and source a more suitable meter and report back.
          I have also built this on a breadboard but what diodes are used on the 555 timer esr circuit?

          Comment


            #85
            Re: Cheaper ESR meter

            I use 1n4148, 1n914.
            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


              #86
              Re: Cheaper ESR meter

              Ok shall try those, I have 1n4148's, shall see what else I can use in place of the others.

              Comment


                #87
                Re: Cheaper ESR meter

                http://en.wikipedia.org/wiki/VU_meter
                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


                  #88
                  Re: Cheaper ESR meter

                  Thanks, which would be better out of the following:
                  1, 10 or 100 mA meter?
                  I don't think any of these will be of any use as
                  1 mA is equivalent to 1000 uA and mA is a larger SI unit.
                  Last edited by notallbad; 11-08-2012, 11:16 AM.

                  Comment


                    #89
                    Re: Cheaper ESR meter

                    You need sensitive meter such as 50uA or 100uA which needs less current to drive it full scale, so if yoy use 1mA (1000uA!) you will need the circuit that can drive 1mA to get to to show full scale.
                    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


                      #90
                      Re: Cheaper ESR meter

                      Originally posted by gs3 View Post
                      Hmmm, it seems that page www.qsl.net/iz7ath/web/02_brew/15_lab/06_esr/ is down now. I found the google cached page but it does not show the graphics which are the most important part. Maybe it will come online again soon.

                      At any rate, here is my version as it stands now. Still a work in progress though. Notice some values are not final yet and some labels are not consecutive etc. But I will answer any questions.

                      The ESR meter has two test probes to connect it to the capacitor under test without removing it from the circuit. This injects a signal of about 100 Khz and under 100 mv(pp). This low level signal will not be enough to trigger semiconductors in parallel with the capacitor and most components one can expect would have higher resistance and would not interfere with the measurement.

                      The circuit is a bridge of four resistors which is normally balanced and the capacitor is placed in parallel with one of the legs which introduces an imbalance which is amplified by an OpAmp. The lower the ESR, the greater the imbalance and the higher the reading.


                      OpAmp A, first from the left, divides the 9V power supply into two halves so we have +4.5 and -4.5 with respect to the center point which becomes our virtual ground. This symmetrical power supply is required by the opamps which follow.

                      Second opamp, B, is the basis for the 100 Khz oscillator. In practice I have noticed that the frequency tends to be not close to 100Khz, probably due to component tolerance values, so it is best to check it and trim values to bring the frequency close to 100 Khz. While this is not essential, it permits better comparisons between units built. At the output of this opamp we should have a square wave between -4 and +4 V pp.

                      The transistor which follows serves several purposes. It shifts the level of the signal so it is always positive, between 0 and +4 and it isolates the load that follows from the output of the opamp which does not have a low enough output impedance to drive the bridge directly.

                      At the collector of the transistor we find the bridge which is the central part of the unit. The two upper resistors are much larger in value than the two lower ones so that the voltage which is put to the capacitor under test is a small fraction of the output of the transistor. Any imbalance in this bridge is amplified by the next opamp, C. Let us analyze the different cases carefully.

                      1- When the leads are open, not connected to anything, the bridge is balanced and the output of the opamp will be a constant zero volts.
                      2- When we connect a good capacitor we are shorting one branch of the bridge to ground in AC only, not in DC. Therefore the output will be an AC waveform with no DC component, i.e. it will be centered at 0 V and swing up and down from 0V.
                      3- When we further short the capacitor, then the branch of the bridge is shorted to ground in DC also and the output of the opamp will be shifted upwards so that it has a positive DC component. Now the entire waveform will be above 0 V.

                      At the output of the opamp we separate the AC and the DC components. First we see a low pass filter, composed by a resistor and capacitor, which allows the DC component to drive the base of the transistor which controls an LED. This LED will light if the capacitor under test is shorted or has high leakage current.

                      The AC is allowed through a high pass filter, formed by a capacitor (which blocks the DC component) and a resistor, into the input of the last opamp which is a rectifier. The lesser the ESR of the capacitor under test, the greater the rectified voltage will be. I adjust the circuit so that the maximum voltage out of the rectifier is about 1 volt. Then I have inserted a diode in series with the instrument. The purpose of this is to expand the range of the instrument in the low ESR values and compress it in the higher ones. As the voltage rises, at first the needle hardly moves, but as the voltage passes 0.6 volts, the needle moves faster. This means the lower 0.6 volts hardly move the needle and the upper 0.4 volts are expanded to almost the entire range of the instrument.

                      By adjusting the output to less than 1 V we could make the instrument even more sensitive.

                      I have built a couple of prototypes using cheap galvanometers I had in my junk box. I have considered modifying the design to use a bar of LEDs but I decided not to do this for two main reasons. One is that a galvanometer can usually be found cheaper and gives more resolution than a bar of, say, 10 LEDs. Another is that a galvanometer will use much less battery power which is an important consideration when using 9 volt batteries.

                      I am still considering adding a circuit which will make the LED flash briefly at intervals as long as the instrument is turned on. This will remind us to switch it off and therefore save batteries.
                      Originally posted by gs3 View Post
                      I made a small PCB but this design does not exactly match the schematic because I have introduced changes. The resistors in series with the ammeter depend on the particular instrument. As I say, I have made several but no two exactly alike. I am trying to make some final improvements and then give it final form. The you have to assemble several to make sure they all work well and within tolerance in spite of component variation etc.

                      I thnk this could be cheaply manufactured in China and sold at a low price. Similar to those analogue (or even digital!) multimeters that cost $2.

                      One of the guys at the other forum built the PCB to fit inside one of those meters and transformed it from multimeter to ESR meter.
                      Originally posted by notallbad View Post
                      So, I built the meter as per link on post #1, prototyped on a breadboard using 1% 1/4w resistors throughout and a VU meter.
                      Supply voltage is provided by a 9v dc mains adapter.
                      +4.5v and -4.5v confirmed at IC TL084 Pins 4 and 11 measured across Pin 1.
                      With probes open, no LED and no movement on the meter.
                      When probes shorted the LED illuminates as expected and full deflection on the meter is achieved by adjusting the pot.

                      Issues I'm having:
                      When connecting a cap to test probes the deflection on the meter is more than full deflection (when probes shorted).
                      This may be correct but my logical thinking thinks otherwise.

                      I would like to confirm 100khz at the probes, I do have an oscilloscope (S51B) with probe but unsure how to use it.
                      I built it based on this site: http://www.qsl.net/iz7ath/web/02_bre..._esr/index.htm and I am using a DMM to measure the current. It always shows maximum current flow. Some issue I find many others share with building based on this design. I wonder what it must be, and what rectifies the issue.

                      Comment


                        #91
                        Re: Cheaper ESR meter

                        Originally posted by helion View Post
                        I built it based on this site: http://www.qsl.net/iz7ath/web/02_bre..._esr/index.htm and I am using a DMM to measure the current. It always shows maximum current flow. Some issue I find many others share with building based on this design. I wonder what it must be, and what rectifies the issue.
                        Found that I connected pin 10 instead of pin 9. Fixed now.

                        Comment


                          #92
                          Re: Cheaper ESR meter

                          Originally posted by gregmcc View Post
                          I've build the ESR meter from here and can't seem to get it to work. I would appreciate a few pointers.


                          IC1A is generating a square wave. The collector is TR1 is shown here

                          and the collector of TR2 is here

                          If I short the cap out the RED should come on but it doesn't. The pins 5 and 6 of IC1 are both 0V

                          Any tips of where I could be going wrong. Any more scope screenshots of points would be helpfull.

                          i have built this one too,, but i make any change for transistor just 2..i remove that transistor have collector is connected to transistor bc557.. and use small vu meter.. and i think that my project is success... make sense that bold line is not a ground but it is connected to pin 1 IC tl 084.. first i think is like you that i think this circuit is not function,, but about two to three times trial and error i find that it functional esr meter and cheap one also...

                          maybe u can use this schematic that i think more useful with any change...
                          Attached Files
                          "There is no shortcut to be successful. No pain, no gain."

                          Best Regards
                          Rudi
                          Thank You

                          Comment


                            #93
                            Re: Cheaper ESR meter

                            parts list creative electronics esr meter ,THANKS

                            Comment


                              #94
                              Re: Cheaper ESR meter

                              Anyone have pcb size for esr TL084???

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