This is very old thread, however I have a need to build some simple, cheap and more or less reliable ESR tester fast...
I have look and read this thread and dr. Le Hung website about ESR. Few things I have noticed:
- The schematic is almost identical to dr. Le Hung ESR part.
- Notification on this forum ESR is not able to do in-circuit measurement, while dr. Le Hung device is.
- Dr. Le Hung do not expose source (hex only for ATmega88PA) as it sold the device.
- The 47uF discharge capacitor need to be non-polarized? This is not commonly available part easily found in local stores.
Upper force me to believe many things could be improved for this Arduino open source version.
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If hardware is almost identical, identical features this ESR tester should have. I.e in-circuit measurements (up to ~300mV test voltage) is possible to achieve.
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As I'm only amateur, my knowledge in electronic is limited. However, if 47uF is jut discharge capacitor, I believe it could be used two 100uF 100V in series el. capacitors (with the diodes protection) - the circuit to make non-polarized capacitor from two polarized. This kind of capacitor configuration double its own ESR, however if it serves only to discharge it before test, this is not crucial. Even better, any, especially larger capacitors should be discharged before test in order to protect MCU.
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The most important feature for an ESR is to have measures with at least two freq. I have not found at dr. Le Hung documentation that his device can do that as well (only measurement at 100KHz).
Anyone with more experience can elaborate about for this circuit?
If not, is there some DIY circuit with commonly available parts is proven to be able for in-circuit measurements as well as can test in at least two freq.?
Thanks in advance.