Help needed desperately with PIC LCF meter

tariq7868 said:

i hav made the pic lcf meter using 16f628A, but when i turned on the meter,only one line of rectangular boxes is appearing on lcd (i.e noting changed) & nothing happening.. i have checked all the connection which are alright..
i have a doubt abt my 3.2768 crystal, which was not available and i found it by chance. the value on the crystal is written as : ECS v 3.27 - 17 ,,, ..what do u think ???

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tariq7868 said:

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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tariq7868 said:

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

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3v0 said:

Al,

Have you run Erick's code that changes the value of a single pin. I seen where you said it seemed to run away. Did it toggle the pin?

Maybe build some other tools first?

A programmer with ICD would a good tool for debugging. You could set breakpoints inside the LCD code and check the state of each line with a volt meter or a logic probe.

For 16F work a serial ICD2 is fast enough. Bill is closing out the the Inchworms ICD2's so the price is right. They are mostly a 16F877A, a few transistors, and a handful of resistors and caps. Uses code from Microchip's ICD2 so it will work with MPLAB as long as Microchip supports the ICD2.

A PICkit2 or Bills clone the Junebug is even better. It runs at USB speed and does double duty as a 3 channel logic analyzer. That would be nice for looking at the LCD control lines on the current project. 3 lines is not much but you would be suprised what you can do with it.

Peter Anderson has a PIC programed as a logic prob for under $3.


Or you can build an Mondo SuperProge which has 17 or 18 functions including LC. These use a 4 char 7 seg LED display.

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tariq7868 said:

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 with such minor things...

thnx for the help...

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lynx said:

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?!

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ericgibbs said:

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.?

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bigal_scorpio said:

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

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kasamiko said:

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?

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kasamiko said:

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?

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ericgibbs said:

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.

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bigal_scorpio said:

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.

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kasamiko said:

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

TIA

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ericgibbs said:

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.

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bigal_scorpio said:

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

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