This is a very cheap ESR meter. Initially published in the Italian magazine Nuova Elettronica as an accesory to use with an analog multimeter. Shown in this page and discussed in Spanish here.
It is extremely simple to build. It only has an TL084 quad opamp IC, a couple transistors and a few other pasive components. Not much else. I have made some modifications of my own to improve it. I removed one transistor which was not needed and I modified the output part so it would be more sensitive in the lower ESR values. I have built several prototypes and they all work well but I am still tinkering with some improvements and do not consider the design finished yet. My PCB design is tiny (33 x 38 mm) with full size components and you only need to add a 9V battery and an analog ammeter or external multimeter. I made the box with a bit of PVC conduit and the whole thing cost me close to nothing.
One thing it has over others and which I consider indispensable is that it will light an LED if the capacitor is shorted or has high leakage. While it may not be as precise as digital ones costing many times more, it is more than enough for quick capacitor checks when doing repairs. You do not need exact values because if a capacitor is bad its ESR has gone way out of range, not just increased by a bit.
You can build it as shown in the page I linked to above or wait and I will post my modifications as soon as I get around to it. Mine is definitely more sensitive but, as I say, I build them as prototypes and tinker with them to the point where no two are alike. i will try to come up with a final design and then I will probably make a page with all sorts of explanations on how it works and how to build it and use it.
It is extremely simple to build. It only has an TL084 quad opamp IC, a couple transistors and a few other pasive components. Not much else. I have made some modifications of my own to improve it. I removed one transistor which was not needed and I modified the output part so it would be more sensitive in the lower ESR values. I have built several prototypes and they all work well but I am still tinkering with some improvements and do not consider the design finished yet. My PCB design is tiny (33 x 38 mm) with full size components and you only need to add a 9V battery and an analog ammeter or external multimeter. I made the box with a bit of PVC conduit and the whole thing cost me close to nothing.
One thing it has over others and which I consider indispensable is that it will light an LED if the capacitor is shorted or has high leakage. While it may not be as precise as digital ones costing many times more, it is more than enough for quick capacitor checks when doing repairs. You do not need exact values because if a capacitor is bad its ESR has gone way out of range, not just increased by a bit.
You can build it as shown in the page I linked to above or wait and I will post my modifications as soon as I get around to it. Mine is definitely more sensitive but, as I say, I build them as prototypes and tinker with them to the point where no two are alike. i will try to come up with a final design and then I will probably make a page with all sorts of explanations on how it works and how to build it and use it.
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