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Help needed desperately with PIC LCF meter

Discussion in 'General Electronics Chat' started by bigal_scorpio, May 2, 2008.

  1. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    I cannot identify the crystal from that number.

    A common problem with LCD's....
    is the R/W pin connected to 0V.?
    do you have a contrast pot on the LCD.?
     
  2. tariq7868

    tariq7868 New Member

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    to program the ic pic 16f628A for Lcf meter , can anybody plz tell what config bit to set ? i am using mepwin 500 universal programmer and it gives me some options to set the config word (see in the attached image)

    so which of the check boxes i should tick ???
     

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  3. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    All this information is on the Header of the asm file.!

    Look at these two images.

    A '1' means its checked a '0' is not..OK
     

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  4. dave

    Dave New Member

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  5. tariq7868

    tariq7868 New Member

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    gosh! Thanks alot for replying that fast...i am also having the same trouble just as al was having ...ie no just a single line of boxes on the lcd...so eric can you plz also upload the asm file for lcd testing as well as led toggler (RA3 pin toggler) u uploaded( the previous upload seems to be damaged ?? thnx

    note tht i have grounded R/W and have a contrast pot..


    thnx a lot
     
  6. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Here is the LCD test asm... 'AlsLCD1.asm':)

    Where in this thread is the 'Led Toggler' program you refer to.??
     
  7. tariq7868

    tariq7868 New Member

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    RA3 is the unused pin in the lcf meter, so i thought i should also test it by toggling led slowly just to confirm whether my pic is starting/working or not...just as u and others suggested..actually i m really new to microcontroller and so far have done programming for 8051 (in C) so thats why i hav to bother u :eek: with such minor things...

    thnx for the help...
     
  8. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    I will look at the program for the toggle.
     
  9. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    A short asm program.

    All that it does is set all PORTB pins high for 0.5sec and then low for 0.5s,,, repeating forever.

    No LCD programming.
     

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  10. lynx

    lynx Member

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    Hi

    i had that LCF meter working fine for long time..
    recently i decided to remove the rotery switch and keep the instrument
    as L meter everything went fine and it was measuring ok but after i tried
    to put it in a plastic box, it fails to measure correctly.. especially very
    small inductors!

    a once measured 3.3uH inductor now the instrument show it is 17mH
    and the measurement hardly stays steady..

    looking at the board and components..couldn't find something wrong...
    any ideas what might has happend?!
     
  11. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Referring to the circuit in the pdf.

    When you removed the rotary switch, did you change or remove IC3b/c or d.??

    If you removed IC3b/c, what did you connect to IC3d pin8.?
     
  12. bigal_scorpio

    bigal_scorpio Active Member

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    Hi Eric and Lynx,

    Just wondering if since maybe its a while since using the LC meter if you remembered to short the leads before measuring inductors to null the reading?

    Also I have noticed that even though the LCD may look OK, when the battery is failing the readings can vary dramatically.

    Hope this helps.......Al
     
  13. lynx

    lynx Member

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    Ηι!

    thanks both of you for your replies! :)


    no i haven't removed anything else other than the rotary switch..
    the cables are connected so the instrument can work as L meter


    yes i'm shorting the leads so i can null the instrument with the push button...

    no..the battery is new...


    when the cables are shorted and the instrument is nulled or when i probe an inductor...
    the frequency and the inductance doesn't stay steady instead it starts to raise
    for example:

    17584Hz
    37.694uH

    17596Hz
    43.576uH

    17609Hz
    51.799uH

    and so on... and also the measurement is not the correct one
     
    Last edited: Feb 28, 2011
  14. kasamiko

    kasamiko Member

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    I'm planning to built this project too but reluctant due to the fact of the hard to find XTAL..does the 3.2768MHz crystal matters for the accuracy of this meter? Can I used a much standard values like 4,8,10,12 or 20Mhz instead of 3.2768MHz by changing the xtal value in the source code?
     
    Last edited: Mar 1, 2011
  15. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    The 3.2768MHz crystal is essential, any other frequency will not give the correct readings.
    The program is written only for a 3.27MHz crystal.
     
  16. bigal_scorpio

    bigal_scorpio Active Member

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    Hi mate,

    As Eric says, the frequency is very important. However there may be a quick and easy solution to your problem.

    If you can get a cheap or even broken battery clock (the type that has just one battery and fingers) you should find the exact crystal in it to use.

    I have seen a lot of these and they are usually available for about a pound here in the UK, so they should be available where you are I think?

    Hope this helps.......Al

    BTW the Crystal in them tends to be cylindrical but this is of no matter. But be careful removing them they are quite delicate.
     
  17. lynx

    lynx Member

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    i think you forgot about me :p any opinions concerning my problem? :)
     
  18. kasamiko

    kasamiko Member

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    how about modifying the code and change the clock to 4mhz? is that possible? or as simple as that?

    oh..never mind...here's the good news below...:D


    You mean the cheap quartz clock? like this?

    [​IMG]

    yes i got a lot of this lying around with exhausted battery....:D are all of them uses same crystal frequency??

    i was thinking it was 32,768 Hertz or 32.768 Khz???

    TIA
     
    Last edited: Mar 2, 2011
  19. bigal_scorpio

    bigal_scorpio Active Member

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    Ooops, you are correct Kasamiko, I must be having one of those days.

    Until I actually looked again at the drawing I was convinced that the freq was 32.768khz. Doh! Plans scuppered, but I will see if I have a 3.768mhz crystal in my bits box and if I have I will send it to the guy free. It was my bad that got his hopes up after all.

    Al
     
  20. kasamiko

    kasamiko Member

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    :D :D

    I'll try my luck on some local distributors....

    Wished me luck...
     
  21. lynx

    lynx Member

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    you guys keep ignoring my posts..why? there's nothing could
    advice me for the problem?

    this instrument is rather simple other than the PIC there are
    a couple of resistors and capacitors, i can't see what can cause
    such mulfunction..
     

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