$20 LCR ESR Transistor checker project

[oitar]

Could you please repeat the Zener test (with a Zener <10V and another one >10V) and measure Vcc (5V) with a DMM? Is Vcc stable?

Sorry about the mess on the desk! See attached measurement of an 8.2 V Zener with the dmm over the diode.One with the dmm over the VCC.
Another with a 16 V Zener. And one with empty test terminals.
I can put a trace scope on the VCC if needed, but it looks pretty steady.

[indman]

However the issue persists: 1. Zener diodes over 10 V are measured perfectly, below 10 V(or thereabout) are shown as ~1/4th of their voltage.
Please be aware that this is NOT A FIRMWARE ISSUE, since it had a similar behaviour with the original Chinese firmware.

In this case, show us the compiled firmware and the configuration files you used.
It will also be nice if you show the results of hardware tests T1-T6 from the Selftest item.

[oitar]

However the issue persists: 1. Zener diodes over 10 V are measured perfectly, below 10 V(or thereabout) are shown as ~1/4th of their voltage.
Please be aware that this is NOT A FIRMWARE ISSUE, since it had a similar behaviour with the original Chinese firmware.

In this case, show us the compiled firmware and the configuration files you used.
It will also be nice if you show the results of hardware tests T1-T6 from the Selftest item.

See attached makefile, config.h, config_644.h, .hex file, and .eep file in one archieve.
Second archieve has screenshots of each stage of Self Test, as well as the Show Values screen.
The T4 stage did not show any values, but flickered very quickly, before asking to "remove short".
Didn't want to upload a video. Hope this is what you needed?

[indman]

Second archieve has screenshots of each stage of Self Test, as well as the Show Values screen.

Well, a hardware problem was immediately discovered in the T2-T3 tests. In the photo, I highlighted with a red question the values ​​that indicate a problem with the measuring resistors or controller ports. The values ​​in these tests should always be of the same order and close in value. Now you must remove all the extra wires that you use for the ZIF panel and also power the tester not from an external source, but from a 3.7V battery. Then repeat tests T1-T6 and show us the results.
Show us also a good quality photo of the reverse side of your clone where is the microcontroller and parts?

[indman]

I completely forgot one more thing. Such poor readings in the T2-T3 tests can be caused by a faulty SRV05-4 protective assembly. Remove it for a while and repeat the hardware tests again.

[madires]

Sorry about the mess on the desk! See attached measurement of an 8.2 V Zener with the dmm over the diode.One with the dmm over the VCC.
Another with a 16 V Zener. And one with empty test terminals.
I can put a trace scope on the VCC if needed, but it looks pretty steady.

So Vcc is stable and the problem is somewhere else. Please follow indman's suggestions next.

[oitar]

I completely forgot one more thing. Such poor readings in the T2-T3 tests can be caused by a faulty SRV05-4 protective assembly. Remove it for a while and repeat the hardware tests again.

Thanks, I will try removing the OV protection.
With the battery back, and Self Test performed(all T readings are basically the same), the zener/resistor issue is still present.

[oitar]

Thanks, I will try removing the OV protection.
With the battery back, and Self Test performed(all T readings are basically the same), the zener/resistor issue is still present.
[/quote]

No luck with the DZ1 chip removed, I'm afraid! Re-did the tests, similar results.

[indman]

No luck with the DZ1 chip removed, I'm afraid! Re-did the tests, similar results.

Have the test results not changed at all, exactly the same as before?
One more question - why did you change the port for the Test button from PD2 to PD0?

[vk3em]

ha ha, well I now have gone from zero testers a month ago to two and another currently on a plane.  Then I bought six resistors for $2.57 each and six for $1.60 each to "fix up the kits" Along with a couple of precision voltage regulators and a couple of precision voltage references.

Wow, that's expensive! A local online shop sells 0.1% TH resistors (Yageo) in single quantity for around EUR 0.25 - 0.30 (680 and 470k are 0.27).

E96 resistor values are more common in 0.1% than E12 where 0.1% values are non standard. Look for 681 Ohms (instead of 680) and 475 kOhms (instead of 470k).

Luke

[oitar]

Have the test results not changed at all, exactly the same as before?
One more question - why did you change the port for the Test button from PD2 to PD0?
[/quote]
They look pretty identical...

I could never get the Test Button to operate properly via the U3(as in my board) chip. I re-programmed it as stated, but could not get it to go low on pin8(i.e. PD2 on the MCU). So using it before only woke-up the tester, but could not enter the menu, so only usable way was to program it as "continuous".
I know replacing it with the 2 transistors will be better(also gaining a port), that's coming next, but I don't think this affects the measurements.

Tomorrow I will check the battery port if it can measure low voltage, since it is adjacent to the zener port. And the zener port is indeed failing in [low] voltage measurement. As to the weird resistor results- no idea what to do yet.

[indman]

They look pretty identical...
I could never get the Test Button to operate properly via the U3(as in my board) chip. I re-programmed it as stated, but could not get it to go low on pin8(i.e. PD2 on the MCU).

These strange and incorrect test data quite convincingly hint at a hardware problem with your tester. It is very likely that your controller is damaged or defective. Try the 2-transistor control option. If you have already checked the 680Ω and 470kΩ resistors and they are OK to I have no more ideas how to fix this problem.

[Obelix2007]

... no idea what to do yet.

... my suggestion is to swap the "small" Atmega324 for a 644 or 1284!!

Greeting Horst

[oitar]

[/quote]

... my suggestion is to swap the "small" Atmega324 for a 644 or 1284!!

Greeting Horst
[/quote]

Very nice job, doubt it I'll be able to do it, without damaging the pcb. Add to it the "Chipgate".
..And where's the fun, if you don't [try and] get to the bottom of things
I set the zener input as a Battery Test(TP_BAT), and changed the BAT_LOW to 1 mV- so the CPU doesn't switch off. Next I put it on Continuous mode, and connect a multiturn pot, instead of a zener. I have attached the results of measuring the voltage at the pin(AFTER ALL DIVIDERS- RIGHT ON THE INPUT PIN) to ensure proper voltage reaches the ADC. You can see that the measuring pin is receiving the right voltage, and the displayed reading is pretty consistent- increasing by 0.03 for each input volt, until the "magic" 1 V threshold is passed, after which the measurement is correct, and the reading increases by 0.11/V.

My knowledge of AVR's is not much, but doesn't this look like hardware configuration issue, rather than a blown port- which would be "clipping" over/under certain voltage.

And a stupid question(all trolling welcome ): Why is the AREF pin connected to GND via a capacitor(and not directly, or via dc ref)?

[indman]

oitar,it would be nice if you made a short video showing the process of turning on the tester and the self-test procedure. Only with the condition of using very short jumpers to short the ZIF 1-2-3 test contacts.
I would also like to see what fuses are currently installed for your chip? Exactly those that are now being read from your chip.

Why is the AREF pin connected to GND via a capacitor(and not directly, or via dc ref)?

You can remove this capacitor entirely. What it is for is explained in detail in the documentation from Karl-Heinz:
"The new software version can use ADC voltage scaling. The switching speed depends on the external capacitor C1 on AREF (pin 21 of the ATmega328). To avoid slowing down by more than necessary, the capacitance of this capacitor must be reduced to 1nF. You can remove the capacitor C1 altogether."

[oitar]

oitar,it would be nice if you made a short video showing the process of turning on the tester and the self-test procedure. Only with the condition of using very short jumpers to short the ZIF 1-2-3 test contacts.
I would also like to see what fuses are currently installed for your chip? Exactly those that are now being read from your chip.

Why is the AREF pin connected to GND via a capacitor(and not directly, or via dc ref)?

Indman, thank you for your help!

I made a video, including Start-up, Test, Adjustment, 2 zeners test, and Fuse-read. I is almost 5 min long, and about 11 MB after recoding.
Couldn't upload it here, due to the 4 MB limit, please check the link to my GDrive. Otherwise let me know if I should cut it to 3 pieces maybe.

https://drive.google.com/file/d/1_b-A_LHtR5gFB1j11Iy09tIkvR9vuGX2/view?usp=sharing

[oitar]

You must "share to all" this file so that others can watch it. It is not necessary to cut the video into parts.
[/quote]

Sorry, should work now! If I play it online it's upside down and reversed, but vlc plays it fine.

[indman]

Have the test results not changed at all, exactly the same as before?
They look pretty identical...

1.Here is a clear example of the fact that it is very useful to make a video that explains a lot.
I asked you if the readings of the hardware tests have changed? You said they haven't changed.
And on your video, I see that the results of hardware tests now look quite standard, which indicates that the controller's measurement ports are in perfect order.
2. Who prompted you to set the fuse values ​​that you now have?
Set the fuses as I showed in the screenshot, make sure they are registered correctly and do not touch them again!
3. We will deal with the measurement of zener diodes separately, after you set the fuses correctly.

[oitar]

[/quote]
1.Here is a clear example of the fact that it is very useful to make a video that explains a lot.
I asked you if the readings of the hardware tests have changed? You said they haven't changed.
And on your video, I see that the results of hardware tests now look quite standard, which indicates that the controller's measurement ports are in perfect order.
[/quote]

My apologies, should've made it more clear in my previous post:

Thanks, I will try removing the OV protection.
With the battery back, and Self Test performed(all T readings are basically the same), the zener/resistor issue is still present.

No luck with the DZ1 chip removed, I'm afraid! Re-did the tests, similar results.
[/quote]

[/quote]
2. Who prompted you to set the fuse values ​​that you now have?
Set the fuses as I showed in the screenshot, make sure they are registered correctly and do not touch them again!
[/quote]

I put the values I've saved from the original F/W. Mentioned earlier that I had to unbrick it, because of wrong fuse values. After managing to parallel-program it in-circuit, decided that the original values are the safest.

[/quote]
3. We will deal with the measurement of zener diodes separately, after you set the fuses correctly.
[/quote]

The fuses are now exactly as you suggested. I made a number of Test/Adjustments, no improvement on the displayed results. Should I make a new video?

[indman]

The fuses are now exactly as you suggested. I made a number of Test/Adjustments, no improvement on the displayed results. Should I make a new video?

No, you don't need to make a video yet.
What will be the results when measuring zener diodes from the "Zener" menu item?
Remove diode D5 from the circuit and measure the Fluke voltage at the point I showed with the red arrow when measuring the 8.2V and 12V zener diode.

[oitar]

[/quote]
No, you don't need to make a video yet.
What will be the results when measuring zener diodes from the "Zener" menu item?
Remove diode D5 from the circuit and measure the Fluke voltage at the point I showed with the red arrow when measuring the 8.2V and 12V zener diode.
[/quote]

Done.
While measuring 8.2V zener: at the highlighted point voltage is 0.892V(LCD showing 2230mV). While measuring the 12V zener(LCD showing 12.17V): 1.30V.
That's similar to the test I did yesterday with the D5 diode still in. You can see the 12V point( in the spreadsheet I posted ) is identical to the new measurement(with D5 out).

I re-run the test, using the Battery Test pin( PA5 ). Since this pin is connected to the battery, but via a 1MOhm resistor, one can short it progressively to GND without overloading the bat, to achieve all voltages between 0 and Vbat. The LCD reading behavior is identical to PA4: once the pin voltage crosses 1V downwards, the reading becomes way lower than the actual value. So the whole PA port is affected, and I'm sure this is the reason for the strange resistor measurements.

This pretty much confirms that I have a damaged/defective ADC then?

[indman]

What will be the results when measuring zener diodes from the "Zener" menu item?

You didn't answer this question.
Show me a photo of the clone from the details side of how it looks at this point in time.

[Yuriy_K]

This pretty much confirms that I have a damaged/defective ADC then?

Why did they do it in config_644.h

[indman]

Yuriy_K, In his config.h, the setting of a dedicated port for checking zener diodes is disabled
//#define ZENER_SWITCHED
, so the settings that you have shown do not affect the operation of the tester in this mode.

[oitar]

What will be the results when measuring zener diodes from the "Zener" menu item?

You didn't answer this question.
Show me a photo of the clone from the details side of how it looks at this point in time.