mrx23

Could someone upload a working compiled firmware (.HEX) for the PIC16F628A which is based on the newest LCFmet790.asm firmware?

(newest firmware)

Thank you!

ericgibbs

hi,
Are you just wanting the hex file, rather than the asm source code.?

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ericgibbs

hi,
The hex file is attached, had to use the '.txt' extension to get it uploaded, just change it back to '.hex'.

This is the 628A version.

Attached Files

LCFmet790_2.txt (6.9 KB, 3 views)

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Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

mvs sarma

I tried to make a zip file of all the relevant files derived using MPlab.

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mrx23

Thank you for the code!
Have you build this LCF meter with 628A?

bigal_scorpio

Hi to all,

Just to confirm that I have built the meter with the 628A, and it works fine!

But don't make the same mistake I did, make sure you ground the R/W pin on the LCD, which is only obvious in the schematic and NOT obvious on the circuit drawing....DOH!

But thanks to the help from this forum, especially Eric, it worked in the end and is the best thing I have ever built, now I can use all those chokes that are in my bits box but had no markings!

Al. (bigal_scorpio)

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mrx23

So you don't have the "CAPICATOR TIME OUT" hanging at startup?

Did you use the modification (correction) for the schematic from here?
P.E. LCF Meter Modifications

How accurate is this LCF meter at high capacities? Like >1000uF

Thx

bigal_scorpio

Hi mrx23,

Yes I have the hangup, but I found a way round it, I turn on the meter in L mode and then switch to C and it works ok then, have you found a different way of preventing the hangup?

As to the measurements of large caps I have measured quite a few 3300uF and they were within 50 in every case, except one which I new was faulty (swelled top) and that measured 150uF hehehe.

I was more interested in chokes when I built the meter, as I mentioned I have a lot of them that are not marked and never been able to measure before, now I have them all measured and marked up, which will save me a good bit of cash as before I always had to buy them for different projects, and its not just the cost of the components its the cost of postage and the hassle of having to wait for them coming

Anyway if you need to discuss anything further or have any tips for the meter feel free.

Regards.........Al

BTW if you want to see some really weird cap readings look in an old Grundig Sky Digibox, or an Amstrad 400! I measured a duff 10uF from an Amstrad that thought it was 1200uF - still trying to figure out how a cap can fail and get a bigger capacitance!

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Nigel Goodwin

As it measures how long it takes to charge, presumably the capacitor was leaking, so took longer to charge?.

But you're using the wrong device, you want an ESR meter to check electrolytic capacitors, measuring the value is rarely of much help.

I've recently started using a Peak ESR meter, these read both capacitance and ESR - as expected, mostly the capacitance is in tolerance, and the ESR is far too high.

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bigal_scorpio

Hi Nigel,

Peak ESR meters look good but a bit pricy for my budget. I just bet someone who was good with electronics and especially Pics could come up with a design for a homebrew one Hint Hint

All the best..........Al

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mrx23

Unfortunately I don't have any solution for this problem.
This problem is written here:
:: EPE Chat Zone *:: *Radio Bygones Message Board ::: LCF meter
I think it's a problem with the firmware adaptation from 628 to 628A.

But maybe I know the reason for that:
When the LCF meter first starts it will store the default frequency values to the EEPROM, and the second start it tries to read them.
So I think there is a problem with a EEPROM handling with the 628A source code. (628 and 628A have differences in EEPROM HW)

Try to start up while pressing the Nulling button, it will enter the correction subroutine you can set a number (0-100%) (check the article) and it would store the result in EEPROM, so set the number, SW off, turn back in while pressing the NULL button and check that is the number stored. (not 100 like normally).

If the problem is not with the EEPROM, than we could put some line in the source code so it will start up in inductance mode.
Eliminating this error.

I'm just planning to build this LCF meter.

You can't measure a cap in circuit! You have to solder out to get an accurate read.
And you have to keep the measuring wires SHORT!
Not like in the original article (crocodile clips
You can use ESR incircuit with power off.

The best way is to put 2 female banana sockets on the instrument.

It would be awesome to ad an ESR meter to the CLF (but it would be very complicated I think)
And It is not really necessary for hobby, it's for pro servicing.

I really don't like that the Ext. Freq input is not isolated from the MCU and it's just for 5V TTL. I will do some modification to that (like transistor isolation...)

How accurate is this devices with 100nF ceramic caps?

bigal_scorpio

Hi again mrx23,

I didn't mean integrating the ESR into the CFL meter, I reckon it should be a much easier task for someone skilled to just build one as a standalone device.

As to the lockup problem, I will find out if the "A" is causing the problem later today, as I will program a NON "A" 628 and swap it over!

While I'm at it I will test some small cap values too.

See you later...........Al

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bigal_scorpio

Hi mrx23,

Just progged a 628 (notA) and swapped it into the meter and you were right in the assumption of the timeout being caused by the subtle differences between the 628 and 628A.

Now there is no timeout, the setup loop and even the null loop seems faster too.

As for testing caps, my strip of 100n tested from 97.75 to 101.5 the strip of 10n tested at 9.765 to 10.3 and the 1ns tested 0.98 to 1.020.

I also tested some 22ps and they were all between 21 and 22.2.

Pretty good as far as I can see, I am highly satisfied and now with no timeouts its even better Everyone should have one!

I still think someone should have a go at designing an ESR meter though, they may have been mainly used in a professional capacity (pun intended) at one time but as with most other things when they become cheap enough and readily available then they are adopted by a greater number of the average persons in the street, otherwise we'd still be lighting candles and I'de be chiselling this into a piece of stone in a cave hehehehe.

So if anyone fancies a challenge!

All the best.........Al

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mvs sarma

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mrx23

Now we have the source off the problem, we need to eliminate it.
628A is an upgrade to the 628. It's cheaper and it's easier to get.

Did you try to Save the calibration (0-100) number? (with the A version)
We still don't know that is it an EEPROM error.
Let it automaticaly exit this calibration subroutine (5sec), then power off as I sad.

Here are the comparisons between the A upgrade and the not A.
The biggest difference I think is the Timer1. Maybe this is the source of the problem.
Ericgibbs please could you help?

Attached Files

628 to 628A.pdf (211.3 KB, 10 views)