$20 LCR ESR Transistor checker project

[Davo013]

it's a kinda strange that 1uF/8,2uF it works,
from 10uF/220uF it crashes,
from 330uF.3300uF it work
From 4700uF it crashes 
tried different voltages etc

but when it's on with a cap from 470uf and i replace it with a 220uf it works
you could have a point there with esr while booting the regulator is 5v 30mA

There.s another 3.5v but that one for the display

i used my thermal cam also and nothing remarkable to see,,,

[Kim Christensen]

You could use a scope on the 5V rail to see if the voltage dips when the unit crashes. Interesting that they used the HT7150-1 with it's 30mA spec vs the MCP1702 which is good for 250mA. You could also measure the current draw to see if it's close to the limit. Just a guess.

[Yuriy_K]

it's a kinda strange that 1uF/8,2uF it works,
from 10uF/220uF it crashes,
from 330uF.3300uF it work
From 4700uF it crashes 
tried different voltages etc

Can you show the display readings of the Show data menu item after Selftest?

When examining your circuit, I noticed a significant difference in U4. What is the voltage between GND and GND0?

When performing Selftest, it is necessary to disconnect all measuring wires, except for the short jumper shown in the photo below. In the k-firmware, a series of short pulses is used when measuring the ESR, and long wires can affect the measurements and readings of the ESR. As I showed on my homemade T-tester.

[madires]

Looks like a hardware issue. Have you swapped C10 and C12 by any chance?

[indman]

Looks like a hardware issue.

I drew the schematic diagram of this clone because I have this device and have studied all its features well.
In red color I showed the improvements that are very necessary to make so that the device works stably!!!
It is especially important to replace the weak and low-quality stabilizer HT7150 with a stronger MCP1702!!!
C10 can be removed from the circuit altogether, its absence will not affect the operation of the circuit, but C12 is important and preferably of high quality!!!
Yuriy_K made a correct comment on the calibration procedure. Initially, you need to disconnect all long conductors and calibrate with a short jumper and then check the details on the same contacts. If longer conductors are needed, then the calibration procedure must be repeated and the parts checked only on these contacts.
It is also very important to correctly complete all calibration steps and use high-quality calibration capacitors, because the correct operation of the device depends on this. All these nuances are discussed in detail in the author's manual, read very carefully, otherwise you will constantly have questions and problems.

[Per Hansson]

Davo013: I think you have reversed the position of C10 and C12, compare this picture of mine, it is important that the AREF capacitor is of the correct type

https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg1371182/#msg1371182

[indman]

  it is important that the AREF capacitor is of the correct type

As I wrote above, all the latest k-firmware and m-firmware work perfectly without this capacitor C10 at the AREF pin!

[Davo013]

You could use a scope on the 5V rail to see if the voltage dips when the unit crashes. Interesting that they used the HT7150-1 with it's 30mA spec vs the MCP1702 which is good for 250mA. You could also measure the current draw to see if it's close to the limit. Just a guess.

Nah i'm just going to order some other parts this versions sucks haha

it's a kinda strange that 1uF/8,2uF it works,
from 10uF/220uF it crashes,
from 330uF.3300uF it work
From 4700uF it crashes 
tried different voltages etc

Can you show the display readings of the Show data menu item after Selftest?

When examining your circuit, I noticed a significant difference in U4. What is the voltage between GND and GND0?

When performing Selftest, it is necessary to disconnect all measuring wires, except for the short jumper shown in the photo below. In the k-firmware, a series of short pulses is used when measuring the ESR, and long wires can affect the measurements and readings of the ESR. As I showed on my homemade T-tester.

I'm aware of the inductance of the alligator clips, i made screens from the show data & made screens from the calibration also

Looks like a hardware issue. Have you swapped C10 and C12 by any chance?

Good one!, but no, i took them both of the board and measured them when I noticed that they where shifted..

Looks like a hardware issue.

I drew the schematic diagram of this clone because I have this device and have studied all its features well.
In red color I showed the improvements that are very necessary to make so that the device works stably!!!
It is especially important to replace the weak and low-quality stabilizer HT7150 with a stronger MCP1702!!!
C10 can be removed from the circuit altogether, its absence will not affect the operation of the circuit, but C12 is important and preferably of high quality!!!
Yuriy_K made a correct comment on the calibration procedure. Initially, you need to disconnect all long conductors and calibrate with a short jumper and then check the details on the same contacts. If longer conductors are needed, then the calibration procedure must be repeated and the parts checked only on these contacts.
It is also very important to correctly complete all calibration steps and use high-quality calibration capacitors, because the correct operation of the device depends on this. All these nuances are discussed in detail in the author's manual, read very carefully, otherwise you will constantly have questions and problems.

You made the schematic!
Ah Cool Nice work! 
I'm going to order those regulators, are those the right ones?
MCP1702T-5002E
LM4040AIM3X-5.0

Weird that the regulaor doesn't has a regulator cap... just an 10uF elco can make a difference in stabilty
 The manual what you are talking about, is that ttester.pdf?

Davo013: I think you have reversed the position of C10 and C12, compare this picture of mine, it is important that the AREF capacitor is of the correct type

https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg1371182/#msg1371182

It's the same one, the other cap 1nF has a bigger package size 0805
Which class has it to be? i have some over here but i really don't know which class they are..
Maybe test 'm with a heat source for stability? those frikkin things never have markings...

  it is important that the AREF capacitor is of the correct type

As I wrote above, all the latest k-firmware and m-firmware work perfectly without this capacitor C10 at the AREF pin!

So ditch C10 lol

[indman]

I'm going to order those regulators, are those the right ones?
MCP1702T-5002E
LM4040AIM3X-5.0
Weird that the regulaor doesn't has a regulator cap... just an 10uF elco can make a difference in stabilty
The manual what you are talking about, is that ttester.pdf?

Yes, if you find an original and high-quality MCP1702T-5002E, then you can refuse the external LM4040AIM3X-5.0, it is not needed just like the C10
The manual for k-firmware is ttester.pdf, you wrote it correctly.

[Davo013]

I'm going to order those regulators, are those the right ones?
MCP1702T-5002E
LM4040AIM3X-5.0
Weird that the regulaor doesn't has a regulator cap... just an 10uF elco can make a difference in stabilty
The manual what you are talking about, is that ttester.pdf?

Yes, if you find an original and high-quality MCP1702T-5002E, then you can refuse the external LM4040AIM3X-5.0, it is not needed just like the C10
The manual for k-firmware is ttester.pdf, you wrote it correctly.

Lol

[indman]

Davo013, I looked at your photos from the ShowData archive. Your clone now has Atmega installed, which is of Chinese origin and is not of the highest quality. This can be clearly seen from the internal resistance of the measuring ports. Even if you replace the +5V stabilizer, problems with capacitance measurement may remain with a 50% probability. Therefore, read my recommendations, which I outlined in detail in this post, especially points 4 and 5
https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg5552775/#msg5552775

[Phil1977]

It´s the same issue I mentioned in this thread 2 pages ago, with a different type of tester.

I have a 1000uF cap between terminal 1 and 3. I switch the tester on, it says "Bat12V ok, testing..." and a few seconds later it switches off.

I attached the scope to the 7550 voltage regulator. The yellow line is the 12V-intermediate voltage in my tester (Battery level), the cyan line is the output of the 7550. I would really like to exchange the IC for something better, but the scope is quite convinced that that´s not the problem:




The first page of the "Show Data" screen is:

Version: 1.12k
R0=0.18 0.17 0.17Ohm
Ri_high=15.9Ohm
Ri_low=13.1Ohm

Any other ideas? I think about adding programming pins to the device, reprogram the AVR, (re-)set the fuses and as last resort exchanging the AVR against an original one.

[indman]

Phil1977, you need to watch for short-term dips in the supply voltage, which are not so easy to detect, although this can be done on your device. In addition, you need to look at the noise characteristics of the power supply, as done in the photo that I will show below. For example, oscillograms are shown if a cheap Chinese 7550 and a high-quality MCP1702 are installed. Look carefully at these photos, the inscriptions are in Russian, but I think you’ll figure it out.  7550 stabilizers also come in different quality, this is also shown in the photo.

[indman]

Any other ideas? I think about adding programming pins to the device, reprogram the AVR, (re-)set the fuses and as last resort exchanging the AVR against an original one.

Yes, these are the things that helped solve the problem. You are not the first to encounter this effect of the Chinese industry. Take it calmly.

[Phil1977]

I don't think it´s the voltage regulator. I did some more measurements with AC mode and zoomed into the worst voltage drop before the power off. It´s slightly more than 20mV over 100us.

With another device of the same type I added a few high quality decoupling caps directly at the AVR, and it didn't change a thing. If the voltage drop shown in the measurement would be responsible, it should easily have been solved by 100nF COG and 4.7uF X7R.

I´m not angry, these little gems are wonderful even if they have a few bugs. I just want to report it because it seems to be the right place here :-)

[indman]

I don't think it´s the voltage regulator.

Quite agree, if you have not quite a bad 7550 installed. So now connect the programmer and set the fuse to ExtentedFuse=FD.

[Yuriy_K]

Davo013
I have good and bad news for you. The screenshots are normal, but the information in your T-tester is not always displayed correctly. I highlighted the unnecessary information in red.
My conclusion is that the ATmega is defective.

I can advise to temporarily replace U1 with any 5V stabilizer - on wires. Solder parallel to C16 10 uF. Solder the power leads of the ATMega itself.

[Phil1977]

My conclusion is that the ATmega is defective.

How do you came to this conclusion? By the "1"-numbers in the "Show-Data"-display at the 3 resistances?

[Yuriy_K]

How do you came to this conclusion? By the "1"-numbers in the "Show-Data"-display at the 3 resistances?

I didn't understand the question. I'll explain my conclusion in more detail on the screenshot below. The text constant "RH/RL" (line 381) should end with the code "00" - the end sign. But on the screen we see a continuation in the form of "left half of the resistor - code 04" and a continuation of the text constant of line 380. This can only happen if the ATMega328 is not working correctly...

[indman]

My conclusion is that the ATmega is defective.

This is not a fact. This effect can occur if the firmware was written with an error. Look at the photo of Davo013 with firmware Rev.804 from my archive - there is no such effect there
https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg5580231/#msg5580231

[Yuriy_K]

In his screenshots it's not constant either, but it does happen. So I'm right...

[Phil1977]

Can you tell typical good values for the internal resistance and capacitance?

And what I also can not understand is that the continuos C+ESR measurement works flawlessly with exactly the same hardware that is crashing in the standard universal test:

[indman]

I've explained before - automeasuring a capacitor is one of the longest processes in terms of time and load power supply, because it also searches for and detects other components in front of it!
And in C/ESR mode, the algorithm is immediately set to measure only capacitance.
The original ATMEL AVRs had an internal resistance in the 20-22 ohm range. Chinese knockoffs and new generation controllers can have this range from 12 to 18 ohms. 

[Yuriy_K]

Davo013
To eliminate any errors during compilation, I checked it on my color display beforehand. The original font is terribly straining for the eyes, so I remade it for my own. Here are the results of checking various capacitors. All tests passed normally. There are no extraneous symbols. I rebuilt the firmware for your display, check the results...

[Davo013]

Thnx Bro!
I will check in the morning, i had a terrible tuff day…