$20 LCR ESR Transistor checker project

[Yuriy_K]

....
in general I have a COMPLETE misunderstanding

Don't you understand that it is impossible to compare the readings of devices with autonomous power and kicking from a mains power supply?
The sensitivity of the TTester is so high that it reacts to the close presence of hands, like an antenna to influence network interference.
In all my examples, there is no mains power and there are no hand pickups.

[Vitaly_Ne]

...With such a low value, your probe capacitances and the connection methods affect the results.
How many pF the Tester shows when there is nothing connected to the probes? (keep the probes connected to the ZIF socket)

Use a 50-100pF capacitor to compare your DMM and Tester. Probably you will see a similar 'spread'.

1. The tester shows 0.05pF-0.1pF
2. measured 15nF almost the same (I think the error is normal) ..
3. I connected the cable to the ZIF - 69-75pF, which is almost similar to the measurements from others ... i.e. tester can be trusted...
then the problem is in the multimeter ... it probably can't cope ...
Okay, I'll focus on the tester.
Thanks to EVERYONE who helped

[indman]

tester can be trusted...
then the problem is in the multimeter ... it probably can't cope ...

The problem is in your multimeter, which has a large error when measuring the picofarad range. Try to measure the usual capacitance of 10-20pF on this multimeter and you will immediately see the difference in the readings.

[Vitaly_Ne]

....Don't you understand that it is impossible to compare the readings of devices with autonomous power and kicking from a mains power supply?
The sensitivity of the TTester is so high that it reacts to the close presence of hands, like an antenna to influence network interference.
In all my examples, there is no mains power and there are no hand pickups.

So I have both a multimeter and a tester powered by batteries ...
I take into account the influence of the hands, and I understand that they can influence ... but the fact is that when everything is connected and the hands are removed - for some reason, when measuring the cable, this is what happens ...
In all other measurements, the tester and multimeter are almost the same ...
Here ONLY this coaxial cable froze and confused ... it seems to me that even with "noise", there should not be such a large spread ...
But for now, I decided to trust the testimony of the tester (of course, having correctly connected it to the ZIF panel and removed my hands away)
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Tell me more please. On page 317 Your options for BGR display - ST7735_BGR_en.zip is this the final option for G328A(BGR)? Those. Can I reflash this k-version over 1.13 color?
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I have the m-firmware version 1.44 extreme .... still available

[elecdonia]

Just got mine after 3 weeks. It has an unmarked microcontroller. By the looks of it, it seems like a 32pin deal. Is there a way to know which of the clones this is ?

That is a Logic Green LGT8F328P MCU. It is said to be "almost" compatible with the Atmel ATmega328P. However the pinout is slightly different. As of yet there really isn't any fully tested OSHW Transistor Tester software for it, although this person is working on it:
     https://github.com/DurandA/transistor-tester-lgt328p

I have also read discussions stating "it may be possible to rework the PC board for Atmel ATmega328P."

[hojnikb]

Just got mine after 3 weeks. It has an unmarked microcontroller. By the looks of it, it seems like a 32pin deal. Is there a way to know which of the clones this is ?

That is a Logic Green LGT8F328P MCU. It is said to be "almost" compatible with the Atmel ATmega328P. However the pinout is slightly different. As of yet there really isn't any fully tested OSHW Transistor Tester software for it, although this person is working on it:
     https://github.com/DurandA/transistor-tester-lgt328p

I have also read discussions stating "it may be possible to rework the PC board for Atmel ATmega328P."

cool. Did anyone try this modified firmware... Does it actually work?
How does one go about flashing these things.... likely not serial, like arduinos?

[Feliciano]

We could review/update some discussion of last year about the several MCU clones populating the market, and DurandA initiative. If we re-read the discussion around those days, maybe there is something worthy to add now.

[elecdonia]

cool. Did anyone try this modified firmware... Does it actually work?
How does one go about flashing these things.... likely not serial, like arduinos?

I don’t know very much about the DurandA project on GitHub. It hasn’t been updated in 2 years. Perhaps the author went on to other projects before finishing it? There seem to quite a few unfinished projects on GitHub.

Programming LGT8F328 chips is totally different than Atmel AVR.
The AVR programming interface is known as “ISP” and uses a 6-pin cable and a programming device.
Arduino boards have a “bootloader” which works through a TTL level or USB serial port.
But to get the bootloader onto an AVR initially requires the ISP programmer.
LGT8F328 uses a totally different programming device than AVR.

Note: Transistor Testers don’t usually have a bootloader. There’s not enough flash in 32k devices like ATmega328P or ATmega324 for them to have a bootloader and still have enough room for the Transistor Tester firmware.

[.RC.]

My LCR testers turned up today.

While the chip says Atmel 328P and it did come from what should have been a reputable seller (fnirsi)  There is no crystal on the board, so I am going hmm.

[indman]

.RC.,you got a fake from FNIRSI!

[.RC.]

Well a fake there.

Then I try to use the second one I bought and it is DOA.

Not even the screen lights up when I connected a battery and tried to test a resistor.

Just not my day.

[indman]

Not even the screen lights up when I connected a battery and tried to test a resistor.

In this option, a lot depends on how thoroughly and carefully you assembled the constructor.
Before soldering parts, it is highly desirable to check their compliance with the diagram and item number.
Very rarely, but there have been cases that the ATMEGA328 was empty. Then you need a simple programmer to determine this.

[elecdonia]

Then I try to use the second one I bought and it is DOA. Not even the screen lights up when I connected a battery and tried to test a resistor. Just not my day.

Two months ago I purchased a Transistor Tester in  “kit form” identical to the unit in your photo. I thought it was easy to assemble, but then I’m a professional EE with many years of experience.

Before starting the build I took several photos of the bare PC board since it has the labels showing where each component part is supposed to go. Then I measured the resistors with ohmmeter and put them into groups of same resistance before soldering to PC board. These resistors are small and the color bands can be difficult to read.

After assembly the LCD would turn on and display the expected screens. It was almost functional. However it was unable to enter the “self test”  mode. Then I discovered that one of the 680 ohm “probe” resistors was slightly out of spec. Details are in my previous post:

https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg4726172/?topicseen#msg4726172

I strongly recommend downloading the full Transistor Tester manual and then printing the schematic and selected pages to use while troubleshooting. I will endeavor to post a brief checklist to assist with getting these “kit form” Transistor Testers into working condition.

[Per Hansson]

Then I try to use the second one I bought and it is DOA.

Not even the screen lights up when I connected a battery and tried to test a resistor.

Just not my day.

Well duh, you have to solder the components to the PCB first!
Sorry, I'll find the door and let myself out

[alex_D]

Well a fake there.

Then I try to use the second one I bought and it is DOA.

Not even the screen lights up when I connected a battery and tried to test a resistor.

Just not my day.

Worth looking at this video for troubleshooting:-
  #108 Building and testing an eBay Transistor Tester kit
Also feel free to post some closeup photos of the assembled board in case we can spot something.

[.RC.]

Well duh, you have to solder the components to the PCB first!
Sorry, I'll find the door and let myself out

Oh, damn, I thought I must have done something wrong.   

There is another job to do.

Actually I was going to get some high precision components for the kit before I built it.

[vk3em]

I ordered a LCR-TC2 from SeeSensor on AliExpress which arrived today.
https://www.aliexpress.com/item/1005004717377243.html

PCB is marked T7 Plus v2.0 - mcu has no markings, 8 pins per side.

Note: This seller was previously known to ship Atmel based LCR testers (at least in Jan 2023) but now in April 2023 they have moved to the alternative.

[elecdonia]

I ordered a LCR-TC2 from SeeSensor on AliExpress which arrived today.
     https://www.aliexpress.com/item/1005004717377243.html
PCB is marked T7 Plus v2.0 - mcu has no markings, 8 pins per side.
Note: This seller was previously known to ship Atmel based LCR testers (at least in Jan 2023) but now in April 2023 they have moved to the alternative

That is a Logic Green LGT8F328P MCU. It is said to be "almost" compatible with the Atmel ATmega328P. However the pinout is slightly different. As of yet there really isn't any fully tested OSHW Transistor Tester software for it, although this person is working on it:
     https://github.com/DurandA/transistor-tester-lgt328p
I have also read discussions stating "it may be possible to rework the PC board for Atmel ATmega328P."

[elecdonia]

...Then I try to use the second one I bought and it is DOA.
Not even the screen lights up when I connected a battery and tried to test a resistor.
Just not my day.

After looking at your photo very closely I think I understand the problem.

[.RC.]

After looking at your photo very closely I think I understand the problem.

Yes, there is no crystal there either, or so I found out when I was going through the components.

So I visited Ms Mouser and ordered all the parts to make it as per the proper original specs.  I actually ordered twice the number (plus some other stuff I needed) as then I got free freight, as otherwise the freight was more then the component costs. Only thing I could not get was a spare dip ATMega328 as they were out of stock.

I will probably blow this unit up down the track doing something silly.   Probably worth getting another kit anyway as who knows how long these genuine Atmel kits will be around for.  It seems the prebuilt SMD units are pretty much non Atmel now, unless you are lucky. 

[vk3em]

Probably worth getting another kit anyway as who knows how long these genuine Atmel kits will be around for.

Where can you buy it from?

Luke

[elecdonia]

Yes, there is no crystal there either, or so I found out when I was going through the components.

The standard factory crystal is 8MHz. That's what my "kit form" unit came with. Only part "missing" from my unit was a 10k resistor which I had dropped on the floor (I did manage to find it).

[.RC.]

Where can you buy it from?

Luke

I generally buy from Aliexpress now.   Seems to be far cheaper then ebay for me.

I searched with this term GM328 LCR tester  -->> https://www.aliexpress.com/w/wholesale-gm328-lcr-tester.html

I did some searching and found one seller selling a kit for a far lower price then everyone else.   Then I noticed the three SMD components on the PCB were missing in the photo -->> https://www.aliexpress.com/item/32706710335.html

I also found a version that looked to be a cut down version. 

So I went for a version were multiple sellers were around a similar price.  Like -->>https://www.aliexpress.com/item/1005003127524856.html

[hoangtran]

I ordered a LCR-TC2 from SeeSensor on AliExpress which arrived today.
https://www.aliexpress.com/item/1005004717377243.html

PCB is marked T7 Plus v2.0 - mcu has no markings, 8 pins per side.

Note: This seller was previously known to ship Atmel based LCR testers (at least in Jan 2023) but now in April 2023 they have moved to the alternative.

I have the same item like this. Mod to Atmega328 with 1.48m firmware. Here is the result:
Original firmware:

M328 with 1.48m firmware

Measuring with DE5000

[Yuriy_K]

I have the same item like this. Mod to Atmega328 with ...

The value of any measuring instrument is determined by its accuracy in relation to reference values.
I did not find a similar capacitor in my arsenal. For example, the readings of such capacitors on the firmware of both authors.