Author Topic: $20 LCR ESR Transistor checker project  (Read 3396791 times)

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Offline madires

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Re: $20 LCR ESR Transistor checker project
« Reply #8325 on: March 18, 2023, 07:43:23 pm »
A bit unrelated, I wanted to ask if you'd ever managed to solve the problem with LC add-on where it was counting too many pulses.

The m-firmware expects the base frequency of the LC meter hardware option to be within a specific range. Do you mean this?
 

Offline elecdonia

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Re: $20 LCR ESR Transistor checker project
« Reply #8326 on: March 18, 2023, 07:44:08 pm »
...A problem with a thread as huge as this is that even when you know what you're looking for, it's not always easy to find. It would be nice to have either the first post or a separate page (or web site?) that links to the current important stuff: Where the current repository is, where the most updated documentation is, where the different modifications are described (like how to wire up a display for hardware SPI for example).
For those who haven't noticed, this Transistor Tester topic is by far the largest on the eevblog "Test Equipment" board: 8,323 replies, 2,957,670  views. In fact this might be the largest topic on the entire eevblog forum.

The sheer size of this topic does suggest that adding a "table of contents" or "faq" would be a useful task.
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Offline hapless

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Re: $20 LCR ESR Transistor checker project
« Reply #8327 on: March 18, 2023, 07:53:22 pm »
A bit unrelated, I wanted to ask if you'd ever managed to solve the problem with LC add-on where it was counting too many pulses.

The m-firmware expects the base frequency of the LC meter hardware option to be within a specific range. Do you mean this?

Yes. I remember it counting too many pulses at one end of the range, probably above 500nF (but, of course, now I can't find where I saw that being stated  |O).
 

Offline elecdonia

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Re: $20 LCR ESR Transistor checker project
« Reply #8328 on: March 18, 2023, 08:01:20 pm »
I know that many are unhappy with the tester that contains the APT32F172K8T6 (TC1 in my case).
But if you don't know anything about ATmega and firmware etc., it's not that bad for ~$10 including battery and case.
Despite the small battery, it has a really good endurance.
Once the problem with KAA range is solved (2K2 resistor) there is no reason to throw it away. Imo it's worth the money.
I also have one of these LCR-style units with the APT32F172K8T6. My unit is reasonably accurate when testing R, C, L, or zener diodes.

However, I have noticed that it sometimes totally fails to correctly identify transistors by type. On a related topic it tends to display wildly inaccurate hfe values for some transistors which test consistently within the expected range by several other transistor testers which I have on hand. I will review the notes I made when I observed this discrepancy and post them.

« Last Edit: March 19, 2023, 04:59:01 pm by elecdonia »
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Offline elecdonia

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Re: $20 LCR ESR Transistor checker project
« Reply #8329 on: March 19, 2023, 02:40:59 am »
None of this is what I was asking. Looking to build, not buy. Need info.

I'm starting construction on a scratch-built DIY Transistor Tester "development system:"
« Last Edit: March 19, 2023, 04:55:39 pm by elecdonia »
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Offline Messtechniker

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Re: $20 LCR ESR Transistor checker project
« Reply #8330 on: March 19, 2023, 07:24:30 am »
I have several ATmega644 and ATmega1284 MCU chips in 40-pin DIP packages.
Good idea. If socketed, makes for easy replacement since the inputs are unprotected (for a good reason).
Also dont forget to provide an USB data output. The firmware does provide for this.
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Offline gipetto

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Re: $20 LCR ESR Transistor checker project
« Reply #8331 on: March 19, 2023, 10:57:42 am »
None of this is what I was asking. Looking to build, not buy. Need info.
I am starting construction on a DIY Transistor Tester myself:
I have several ATmega644 and ATmega1284 MCU chips in 40-pin DIP packages. Actually the mega644 is big enough in terms of flash size. Enabling all available features in the OSHW Transistor Tester software does require an MCU with more than 32k of flash.
I intend to use a larger color LCD display than what comes in the ready-made Chinese units.
I plan to build the first unit on a “perma-proto” style board.
My version will have a high-quality rotary encoder for user input.

It makes sense to build on this existing project. I have yet to find the original post in this thread about it.
https://github.com/madires/Transistortester-Warehouse/blob/master/Hardware/DevKit-644.kicad.tgz
 
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Offline madires

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Re: $20 LCR ESR Transistor checker project
« Reply #8332 on: March 19, 2023, 11:27:32 am »
Yes. I remember it counting too many pulses at one end of the range, probably above 500nF (but, of course, now I can't find where I saw that being stated  |O).

Larger capacitance means lower frequency (lower limit is 10 kHz). The base frequency is around 595 kHz (L_i 82µH, C_i 1nF), the theoretical measurement range is 3.3 fF - 3.5 µF, and what you get with the example circuit in the repo is 10 fF - 33 nF (120 nF with signal clean-up). A different LC oscillator circuit might extend that range.
 

Offline madires

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« Last Edit: March 19, 2023, 11:31:50 am by madires »
 
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Offline Aldo22

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Re: $20 LCR ESR Transistor checker project
« Reply #8334 on: March 19, 2023, 11:45:34 am »
I also have one of these LCR-style units with the APT32F172K8T6. My unit is reasonably accurate when testing R, C, L, or zener diodes.

However, I have noticed that it sometimes totally fails to correctly identify transistors by type. On a related topic it tends to display wildly inaccurate hfe values for some transistors which test consistently within the expected range by several other transistor testers which I have on hand.

Hi!

I've updated my list with some transistor measurements.
Do you see a problem with these numbers?
I don't have enough knowledge to judge that.

 

Offline indman

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Re: $20 LCR ESR Transistor checker project
« Reply #8335 on: March 19, 2023, 03:26:13 pm »
Aldo22, Check these items from the list, if there are any in your household?
https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg4610314/#msg4610314
 
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Offline Aldo22

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Re: $20 LCR ESR Transistor checker project
« Reply #8336 on: March 19, 2023, 03:47:26 pm »
Aldo22, Check these items from the list, if there are any in your household?
https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg4610314/#msg4610314
Thank you!
No, I don't have any of these.
All I have is in the list above (21 types).

I found that calibration is really important with this device.
If it is not freshly calibrated, it sometimes even recognizes a transistor as a resistor.
After the calibration, however, it recognizes it correctly.
Maybe even the battery status makes a difference (just a guess).

I am sure that the tester with the APT32F172K8T6 has weaknesses (like other devices?).
I just think it's not completely useless and not that bad for $10.
 

Offline hapless

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Re: $20 LCR ESR Transistor checker project
« Reply #8337 on: March 19, 2023, 08:14:01 pm »
Quote
10 fF - 33 nF
That's... a disappointingly short range. What's involved in the cleaning up of the signal? (I thought it came as a simple square wave at the output of the comparator.)
 

Offline elecdonia

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Re: $20 LCR ESR Transistor checker project
« Reply #8338 on: March 19, 2023, 09:39:03 pm »
Aldo22  Check these items from the list, if there are any in your household?
I'll test these transistors and JFETs with my Transistor Testers and post a spreadsheet of my results here. I have large quantities of the parts listed below:
Quote
3.Some BJT transistors (for example,2N5089,MPSA12,MPSA13, etc.) are defined as thyristors or resistors.
4.Some JFET transistors (e.g. J112,J113,2N5457, etc.) are not defined at all or are defined as BJT.
I have 3 LCR-style units at this time: One with ATmega324, another with LGT8F328P, and another with APT32F172K8T6.
All have the Chinese firmware they came with. Eventually I'll put different FW into my ATmega324 unit (probably upgrading to ATmega644 at same time) but I haven't done that yet.
I also have 2 AY-AT style units and one GM328A (monochrome graphic LCD). All have Atmel ATmega328P MCU with original Chinese firmware.
« Last Edit: March 19, 2023, 09:44:55 pm by elecdonia »
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Offline madires

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Re: $20 LCR ESR Transistor checker project
« Reply #8339 on: March 19, 2023, 09:46:04 pm »
That's... a disappointingly short range. What's involved in the cleaning up of the signal? (I thought it came as a simple square wave at the output of the comparator.)

The LM311 based LC oscillator circuit has a known issue with the signal starting around 30 nF (spurs at falling/rising edges). Another comparator or a 4093 will do the job. But starting around 120 nF the oscillator becomes unstable. It's no big deal as the LC oscillator is meant for measuring low value capacitance/inductance (below the normal range of the tester).
 
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Offline elecdonia

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Re: $20 LCR ESR Transistor checker project
« Reply #8340 on: March 20, 2023, 06:05:08 pm »
I like DIP because of the ease of swapping out the chip. What would be the advantage of an ATmega324 over ATmega328 to pay a premium for a tester based on it?
ATMega324 has more I/O ports than ATMega328 DIP. Therefore, you simply have more chanses and options for connecting peripheral sources for the tester. I don’t see any more advantages. :)
My thoughts about selecting MCU chips for scratch-built DIY Transistor Testers and also for upgrading/customizing "factory built" Transistor Testers:

The OSHW Transistor Tester requires the MCU to have GPIO ports which fully support 5V logic levels for both input and output.
There simply aren't many alternatives to the Atmel/Microchip AVR family.
The trend is for newer/faster/larger/cheaper MCU chips to operate only at 3.3V (although some can accept 5V logic signals as inputs on selected pins)
     To review: Since the Transistor Tester generates its test signals directly from MCU GPIO pins this means the MCU must be able to output a full 5V from its GPIO pins.

And with the OSHW Transistor Tester software gradually growing in features and size this makes it desirable to select an MCU with 64k (ATmega644) or 128k (ATmega1284) flash program memory. Fortunately I already have ATmega644 and ATmega1284 on hand in 40-pin DIP packages  I will use them for my scratch-built Transistor Tester.

ATmega324 TQFP-44 (square SMT package) has 44 pins vs. mega328P (TQFP-32) with only 32 pins
-   The additional pins are useful GPIO ports.
-   ATmega324 can be directly replaced by ATmega644. No alteration of PC board is needed.
-   So far none of the $1 USD Chinese MCU chips come in 44-pin TQFP.
-   Therefore a Transistor Tester which contains a 44-pin TQFP MCU is very likely to have a real ATmega324 (or ATmega644) MCU.
-   In contrast, there are at least 2 different $1 USD Chinese MCU which come in 32-pin TQFP packages.
-   This means Transistor Testers with 32-pin MCU chips could have any one of 3 different MCU chips (Atmel ATmega328P, Lucky Green LGT8F328P, or AptChip APT32F172K8T6.

« Last Edit: March 20, 2023, 09:11:52 pm by elecdonia »
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Offline ayubando

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Re: $20 LCR ESR Transistor checker project
« Reply #8341 on: March 20, 2023, 07:11:50 pm »
About to finish an exact build like this, with an atmega 1284, protoboard and an ili9488 3.5 inch screen
 
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Offline Aldo22

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Re: $20 LCR ESR Transistor checker project
« Reply #8342 on: March 21, 2023, 10:47:15 am »
Aldo22, Check these items from the list, if there are any in your household?
https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg4610314/#msg4610314
Hi!
Could it be that the APT32F172K8T6 version has a problem with lower hFE values (~<50) on BJT transistors?
It also identifies some of my fishy A42 as resistors (4 of 10).
The same could be the case with your MPSA12 and MPSA13.
« Last Edit: March 21, 2023, 04:01:52 pm by Aldo22 »
 

Offline elecdonia

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Re: $20 LCR ESR Transistor checker project
« Reply #8343 on: March 21, 2023, 05:40:06 pm »
Could it be that the APT32F172K8T6 version has a problem with lower hFE values (~<50) on BJT transistors?
It also identifies some of my fishy A42 as resistors (4 of 10). The same could be the case with your MPSA12 and MPSA13.
I plan to measure the emitter and/or collector currents during the test. This will likely require a small value current sensing resistor (1 to 10 ohms) and my oscilloscope. To the best of my knowledge the duration of hFE (gain) measurement is rather brief. Therefore it can't be measured with a DVM.

When I look at my Transistor Tester results I observe widely differing collector (or emitter) currents reported by the Transistor Testers with Chinese MCU/firmware compared to units with Atmel AVR MCU running OSHW firmware. The gain of a BJT depends quite a bit on the collector current it is measured with. This is especially true for power transistors. Curiously NPN transistors have considerably lower gain at low currents vs. high currents compared to PNP transistors where the hFE is relatively stable over a wide range of collector currents.

I'm getting real close to measuring a whole bunch of different BJT and JFET with several different Transistor Testers.
« Last Edit: March 22, 2023, 10:34:36 pm by elecdonia »
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Offline gipetto

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Re: $20 LCR ESR Transistor checker project
« Reply #8344 on: March 21, 2023, 08:10:05 pm »
sounds like there's some kind of hardware bug with the mcu. the rp2040 for instance had an adc bug, but could be compensated for by notching out some spikes in software. link here although it's off topic.
https://www.hackster.io/news/raspberry-pi-confirms-it-is-investigating-a-flaw-in-the-raspberry-pi-pico-rp2040-adc-95c393b55dfb
 

Offline Aldo22

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Re: $20 LCR ESR Transistor checker project
« Reply #8345 on: March 22, 2023, 09:49:07 am »
When I look at my Transistor Tester results I observe widely differing collector (or emitter) currents reported by the Transistor Testers
I only have a TC1 with the APT32F172K8T6 and a Fnirsi DSO-TC2.
The DSO-TC2 reports a range of Ic from ~2.5mA (mostly for NPN) to  ~5.5mA (mostly for PNP) afaics, while the TC1 always shows ~6 mA (see my list above).
If you have a look a these curves, this might explain the big difference in some cases, e.g. for MPSA 42.
https://www.biophysicslab.com/2021/04/27/testing_transistor_hfe/
In most cases, however, 6mA seems to be a reasonable (average) value.

EDIT: Not quite true. The DSO-TC2 sometimes reports Ie.

A42, C1815
« Last Edit: March 22, 2023, 10:20:46 am by Aldo22 »
 

Offline elecdonia

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Re: $20 LCR ESR Transistor checker project
« Reply #8346 on: March 22, 2023, 10:33:34 pm »
I only have a TC1 with the APT32F172K8T6 and a Fnirsi DSO-TC2.
The DSO-TC2 reports a range of Ic from ~2.5mA (mostly for NPN) to  ~5.5mA (mostly for PNP) afaics, while the TC1 always shows ~6 mA (see my list above).
If you have a look a these curves, this might explain the big difference in some cases, e.g. for MPSA 42.
   https://www.biophysicslab.com/2021/04/27/testing_transistor_hfe/
In most cases, however, 6mA seems to be a reasonable (average) value. EDIT: Not quite true. The DSO-TC2 sometimes reports Ie. A42, C1815
That URL contains an excellent article about testing BJT gain. The curves shown are typical of NPN devices.

Note: My APT32F172K8T6 TC1 does this:
- Pressing "Start" button 4 times in quick succession (from off) causes my TC1 to display: FNIRSI-TC1 BOOTLOADER.
- It displays FNIRSI-TC1  for ~2 seconds just after entering self-test mode by pressing "Start" with a short between 1-2-3.

I wonder if FNIRSI makes these APT32F172K8T6  TC1 units?
(It is also possible the actual maker "borrowed" the FNIRSI name to try to make their knock-off product look more legitimate.)
« Last Edit: March 23, 2023, 01:57:23 am by elecdonia »
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Offline Aldo22

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Re: $20 LCR ESR Transistor checker project
« Reply #8347 on: March 22, 2023, 11:18:14 pm »
I wonder if FNIRSI makes these APT32F172K8T6  TC1 units?
I doubt it - I suspect the actual manufacturer "borrowed" the FNIRSI name to try to make their product look more legitimate.
Note: Pressing "Start" button 4 times in quick succession does cause my TC1 to display: FNIRSI-TC1 BOOTLOADER.
Yes, it also shows "Fnirsi-TC1" in self-test mode for me.
I'm not sure either. "Fnirsi" is not written anywhere else, neither on the case nor on the circuit board.
In any case, the DSO-TC2 has a different level of quality.
 
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Offline .RC.

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Re: $20 LCR ESR Transistor checker project
« Reply #8348 on: March 23, 2023, 11:45:31 pm »
I have ordered a through hole DIY kit.  Is it worth it doing the things in this mod just for general use?  https://github.com/blurpy/transistor-tester
 
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Offline wandows

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Re: $20 LCR ESR Transistor checker project
« Reply #8349 on: March 24, 2023, 02:02:15 am »



is this a full version of the LCR ESR Transistor Tester Project?
 


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