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  1. #1
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    pic esr meter

    Dear all,

    here is nice project a pic based ESR meter

    http://saint.419.removed.us/esrtest.html

    Regards
    Fragrance

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    PIC Based Low Cost ESR meter

    Have you built it, and did it work?



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    Re: PIC Based Low Cost ESR meter

    Hello Neelandan,
    I've been looking at your circuit this evening and it looks like an interesting project. I've tried to correlate the schematic to your board layout and I'm having some problems with parts placement. There are parts on the schematic that I can't locate on the board layout and parts and pads shown on the board layout that I can't identify in the schematic.

    My first problem is that the schematic shows RA2 (pin 4 of the PIC) connected thru a 330K resistor to the base of the transistor that switches the 4.7K resistor in and out of the circuit. The board layout shows RA5 (pin 7) connected thru a resistor to this transistor (marked Q3 on the board layout). I suspect that pins 4 and 7 of the PIC have been reversed on the schematic. Can you confirm this?

    Also, the board layout has circuitry associated with the Vref pot (Q6, a diode, and a few resistors) that doesn't appear on the schematic. Would it be possible to get a board layout that identifies the values of all of the components including the switch locations? Perhaps a picture of your finished board? It's obvious that you have put a lot of time and effort into this project and the fact that you have shared it is appreciated. I'd like to have a go at building it but the documentation as is just doesn't give enough detail to where I feel comfortable charging ahead.

    Thanks again -- Mike



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    Re: PIC Based Low Cost ESR meter



    These corrections were mailed to me by someone who built it.

    You might find that it answers some of your queries.


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    PIC Based Low Cost ESR meter

    @neelandan
    If i am correct, i too remember to have seem a PIC based Auto fare meter in your page. Did you ever built it?



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    Re: PIC Based Low Cost ESR meter

    Some of the projects on that page have been for engineering students as part of their academic studies. The emphasis, there, has been on the programming and interfacing of a microcontroller to do some significant task.

    The ESR meter was built to demonstrate interfacing an LCD in "byte" mode (ie, eight wide data path) and using the internal ADC of the PIC microcontroller.

    The auto fare meter was built to demonstrate the use of the internal eeprom and interfacing with a smart card.

    They are useful if you are trying to learn to program PIC microcontrollers. If you are looking to build an ESR meter or a smart card operated fare meter, you might be disappointed.



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    Re: PIC Based Low Cost ESR meter

    Quote Originally Posted by neelandan
    The auto fare meter was built to demonstrate the use of the internal eeprom and interfacing with a smart card. They are useful if you are trying to learn to program PIC microcontrollers. If you are looking to build an ESR meter or a smart card operated fare meter, you might be disappointed.
    Sorry...i didnt get what you mean to say by this? "usefull to learn but dissapoint if i build"



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    Re: PIC Based Low Cost ESR meter

    Quote Originally Posted by pranam77
    "usefull to learn but dissapoint if i build"
    They are useful if you are building similiar systems, and modify the program and circuits to get what you want.

    Since they are student projects, they are not very good examples of an ESR meter or fare meter.



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    PIC Based Low Cost ESR meter

    Ok...you mean..As the said circuits are mere student projects, one cannot expect professional performance.



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    Re: PIC Based Low Cost ESR meter

    Quote Originally Posted by pranam77
    circuits are student projects, one cannot expect professional performance.
    Or coding to professional standards.

    For measuring capacitance (in the ESR meter) the calibration is by adjusting the delay of the timing loop by padding it with goto's and nop's. The more accurate way to do it would be to measure the time taken for the capacitor to charge, and then devide it by a value stored in eeprom. This approach would require the students to get into floating point arithmetic on the PIC, something beyond the scope of their course.

    It has been documented there, mainly to inspire other similiar people to build on these and design a better gadget.



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    Re: PIC Based Low Cost ESR meter

    Apart from the code quality, expectable performance of the measurement circuit should be considered. The project specification
    is rather limited. I think, existing DIY LCR meter designs should be preferred if instrument performance is intended. In my
    opinion, a complex impedance measurement approach, as used in most commercial instruments, is most promising.



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    Re: PIC Based Low Cost ESR meter

    I've just started an ESR repository...
    take a look !
    ESR-Repository


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    Re: PIC Based Low Cost ESR meter

    Finding ESR as a function of frequency is very useful. Some approaches are better than others.

    However DMM's use special ASIC's to do this very low cost. One would do well to research and reverse engineer these patents and products.

    ESR is a critical value that indicates quality, performance and aging of a component such batteries, capacitors, Lasers, power LEDs, MOSFETs, etc and can change with frequency in non-ideal ways.

    Deciding how to measure is more important. The ESR is frequency dependant, and step response is another method. ESR will also change with DC current.

    Generally ESR is measured at 10KHz, 100KHz & 1MHz but depends on application. It could also be DC or GHz.

    DMM's are inexpensive and could be used as peripheral but are proprietary and usually not an open standard or as precise.
    A best design is easily achieved with good test specs™
    A better question deserves a better answer. ™
    ... so include all your acceptance criteria ( values, % tolerance) and assumptions in your question or any design.

    ... Tony Stewart EE since 1975
    - slightly north of Toronto



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    Re: PIC Based Low Cost ESR meter

    hi,
    here twographs : esr vs frequency, it doesn not change lot with frequency...
    and esr vs temperature, a little change also.
    regards,



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