$20 LCR ESR Transistor checker project

[madires]

In this case it's not a bug, it's a feature. Any base-emitter resistor(s) will screw up some measurements and make related results less meaningful. When no base-emitter diode (or two in series for a Darlington) is found V_BE and h_FE aren't displayed. For measuring the h_FE of a power BJT a higher base current would be helpful. The tester can provide just 7mA which isn't sufficient for this. So a simple trick is used to extrapolate mathematically a higher base current. This doesn't work for a power BJT with base-emitter resistor.

[n6rob]

Greetings;

I have a LCR-T4 (mega328p, 8 MHz crystal, 78L05, TL431, one button, no encoder, no up/down buttons) and I have loaded 1.47m on it successfully (also previously loaded 1.13k, but that's another story).  Anyhow, running 1.47m, and noticing some odd behaviors.

Here's what I did; per instructions I edited Makefile, config.h, and config_328.h with appropriate settings (as best I could).  If I was unsure about a software or hardware feature, then I took it out.  The unit boots, and displays fine (had to flip the display and remove the offset in the x axis of the display), and responds to the button as expected.

Observations:
The unit boots, and runs a test and comes back with an IGBT N-ch (with nothing in the test port).
I put the unit in menu mode by quickly clicking twice, I select test, it asks for a short, I install it, and then it does nothing.  I quick-click, and it returns the menu (if I long-click then it gives an error! and returns to the menu).
If I leave the short in during a normal test cycle, it says "probing..... C", it takes a while, but then shows the short across all three terminals.  (Draws a fair bit of current, about 45 mA, from the power supply, too).
It reads an resistor, LED, or an NPN, or a PNP, as an IGBT.
It reads a resistor as "no component found".

Measuring resistance (power and ISP programmer disconnected) between test pins 1 and 2, I get 39K ohms, from 2 to 3 I get an open, from 1 to 3 I measure about 1.4M ohms.  I'm going to hit Google and look for a schematic for this unit after I post this.

Any suggestions of things I should look for?  Much appreciated.

Rob

[madires]

Have you used the settings listed in the Clones file? There could be something wrong with the pin assignments for the probes. You'll find a schematic at https://disk.yandex.ru/d/yW8xa5NJgUo5z (the T4 comes in two variants).

[n6rob]

Have you used the settings listed in the Clones file? There could be something wrong with the pin assignments for the probes. You'll find a schematic at https://disk.yandex.ru/d/yW8xa5NJgUo5z (the T4 comes in two variants).

Greetings and thank you for your reply.

Yes, I referenced the Clones file when updating the configuration files.
Thanks for the link to the reference files, including schematics.  In reviewing the photos I can say that I have the T4/T3-NoStripGrid version.  That helps.  I just referenced the schematics and the pin designations in the config_328p.h file and I don't see any incorrect assignments.

Since my last post, I have reloaded the original firmware (as it came when I bought it, "MTester", no version indicated).  It exhibits some of the same problems.  I might play with the 1.13k version again (previous attempts have given the same results as the original & 1.47m firmware).

Taking a step back, I think it is likely that I have damaged something at the test ports (probably the chip).  I probably failed to discharge a cap before testing; but that is just a guess.

The next step I'll take is to disassemble the unit from the case and inspect it for damaged traces, solder bridges, or cracked solder joints.  It worked just fine for a few years; this weird behavior is more recent.
 If I learn something new, I will post back here.  Otherwise, I would consider this a case of damaged hardware.

Thanks for the help.

Rob

[madires]

Then it's most likely caused by damaged I/O pins. To verify this you can run the self test and look for strange values (or post them here).

[n6rob]

Then it's most likely caused by damaged I/O pins. To verify this you can run the self test and look for strange values (or post them here).

I de-fluxed the board, cleaned-up a few things, looked for cracks, shorts, etc.  I didn't find a smoking-gun.

I entered menu mode, select "test", it asks for a short, I install the short, and then nothing happens.  I wait a minute, click the button, and it goes back to the main menu.
I entered the menu mode, select "adjustment", and get the same result as "test".

I entered "show values" I find the following:
Ri- 20 ohms
Ri+ 22 ohms
C0 43 pF
R0 0.2 ohms
Vref 1084 mV
Vcc 5049 mV *
Acomp 0 mV

[madires]

I see. In this case replace the ATmega or get a new tester.

[blubillcanada]

I wonder how hard this project would be to port over to a Raspberry Pi Pico.
USB would make for a simple display on a PC to keep it real simple, also firmware updates would be a snap.
A significant increase in the program memory 2MB vs 32kB, more speed! & cheap too.
It can be programmed in C++ or Python
The ADC VREF is easy, LM4040 is recommended in the Pico datasheet.
pushbutton(s), 470K,  680ohm resistors and a connector would be all the external parts for a basic unit.
Optionally:

• an LCD / OLED display as is tradition (personally I like the no display terminal option as I have a PC on my workbench)
  
• keypad or rotary switch

The original tester schematic just for reference.

[madires]

That was answered already just two pages back: https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg4318561/#msg4318561
The Raspberry Pi Pico has the same drawback, it runs with 3.3V.

[n6rob]

I have no idea what version that is, but trying a OCR translation it seems to be saying that the USB port is only for user upgrades (of the firmware) and that it does not supply power.

Then it should be possible to update the firmware directly via avrdude.

Do you have any suggestions for how to set avrdude (in Linux command line)?  I'm not sure how to set the "-c" switch (i.e. which programmer) as I am connecting my computer USB directly to the USBC connector on the board.

~$ lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 046d:c534 Logitech, Inc. Unifying Receiver
Bus 001 Device 019: ID 1a86:7523 QinHeng Electronics CH340 serial converter
Bus 001 Device 002: ID 05e3:0608 Genesys Logic, Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

I tried this...

~$ avrdude -c ttl232r -p m328p
avrdude: ft245r_open(): invalid device identifier '        '

avrdude done.  Thank you.

[madires]

Adding the port argument might help, e.g. -P /dev/ttyACM0. But I don't know which programmer needs to be set for the CH340.

[n6rob]

Adding the port argument might help, e.g. -P /dev/ttyACM0. But I don't know which programmer needs to be set for the CH340.

Okay.  I played around with a few port designations and programmer options but was never successful. 

I wrote to the seller asking for instructions and a schematic.  They replied and said they were working on getting me the info.  If I learn anything I will share it here.

Thanks for the help.

[carrascoso]

Hello everyone.
I like to try out the different options Madires adds to our little meter.
The last thing was the continuity meter that is already working thanks to the help of Indman.

Now I have assembled the circuit for the LOPT/FBT measurement but it does not work.
I have reviewed the assembled circuit and in principle it is fine, but it does not go beyond screen 1, both with or without the coil being tested.
It always emits a small constant and intermittent sound.

Perhaps, as in the case of continuity, some other adjustment must be made or activated.
Please if someone can help me to solve the problem.

Thank you

 

[madires]

Could you please post your settings for the ring tester? Do you have a scope to check the trigger pulse and the rings?

[carrascoso]

Could you please post your settings for the ring tester? Do you have a scope to check the trigger pulse and the rings?

[madires]

And the settings for RINGTESTER_PORT, RINGTESTER_DDR and RINGTESTER_OUT? Is the port pin set in RINGTESTER_OUT used by any other setting too?

[carrascoso]

The three that you tell me are activated

[madires]

You have
 #define RINGTESTER_OUT   PD5       /* pulse output */
and
 #define BUZZER_CTRL      PD5       /* control pin (low: off / high: on) */
while
 #define HW_RING_TESTER
and
 #define HW_BUZZER

So ring tester and buzzer are enabled and are using the same port pin. Try another pin or disable the buzzer (also remove the buzzer).

[Yuriy_K]

Information for users of my firmware. The reaction to a short-circuited coil is shown in the pictures on the right.

[indman]

The reaction to a short-circuited coil is shown in the pictures on the right.

This method does not guarantee 100% detection of short-circuited coil.Example in the photo below. You should always have a sample of a similar, serviceable throttle to compare readings. The simplified version of LOPT/FBT also cannot guarantee accurate detection of short-circuited turns and is very dependent on the core material. It is better to use specialized devices for this purpose.

[masster]

Does anyone have the schematic for the tester clone known as Kuman Multifunction Transistor Checker or DROK Transistor tester?
https://www.amazon.com/kuman-Multifunction-Transistor-Automatic-Identification/dp/B075DDXV11
http://www.kumantech.com/kuman-multifunction-transistor-tester-with-18-inch-lcd-tft-display-mega328-npn-pnp-automatic-identification-transistor-diodes-dual-diode-scr-res_p0435.html

[indman]

masster Look at my resource https://disk.yandex.ru/d/yW8xa5NJgUo5z the "Fish8840TFT" folder

[firewalker]

masster Look at my resource https://disk.yandex.ru/d/yW8xa5NJgUo5z the "Fish8840TFT" folder

The folder with the MK-328 is the firmware the device came with?

Alexander.

[indman]

firewalker No, if there is a factory firmware, it will be located in the "Firmware/Original" folder

Hi,
I know there are a lot of different models, anyway have you saw this one ?
What is the purpose of USB interface ?
I try to use it to supply the module, it shows around 7 V, but didn't measure a simple resistor.

https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg4291063/#msg4291063

Surprises from Chinese friends continue!
This clone of T4 is not based on the original ATmega328, but so far on a processor known only to FNIRSI.
The marking on the ATMega328PU-TH case is a fake, since the pins of this chip does not match either ATMel or LGT8F328P.
The K2 button is used to enter BootLoader mode.

[masster]

Quote from: indman on Yesterday at 11:53:56 pm>masster Look at my resource https://disk.yandex.ru/d/yW8xa5NJgUo5z the "Fish8840TFT" folder

Quite a treasure you have there. Well organized and very full of resources.

Just a short observation though. On the schematic it is missing the LED between R6 and Q3.


I am confronting myself with the following problem: while the tester is working fine, when I press the TEST button, the current consumption is 220 mA (!!) and the battery voltage is reported wrong (7.72V instead of 8.9V). Transistor Q1 gets very hot. Alcohol evaporates almost instantly on it, in comparison with the other components. If I supply 6V instead of 9V, the current consumption drops to about 70mA, still too much IMO. Could it be a faulty capacitor C1?