$20 LCR ESR Transistor checker project

[Feliciano]

I think so. Since my Trinitron days, I always have thought on RGB as an horizontal array. A case like we're discussing would have a little horizontal misalignment, less noticeable than a vertical one. Anyways, it is what it is, and I also think for the price tag of this new TC1, we can't complain much. But know we know it's there, I guess others will start to notice it too everywhere

[indman]

But know we know it's there, I guess others will start to notice it too everywhere

You only notice this shift when the colors characters are close to each other.
Don't have too many different colors on one screen or place them far apart from each other and you won't have this problem.
In general, I am against the display of more than 2-3 color shades at the same time. This strains the eyes and leads to rapid fatigue if prolonged visual work is required.

[Feliciano]

Yeah, and the color fidelity of these display (at least the FNIRSI) is not so high either.

Besides your recommendation, I would add the color sequence and palette also plays a part. In this case, RGB is not as noticeable as RBG or GRB, and additionally the violet (if we want to match what printed on the case) tends to look blurry because in reality it's R+B.

This strains the eyes and leads to rapid fatigue if prolonged visual work is required.

Which makes me wonder: hasn't somebody considered a 20 or 24-pixel-high font? (I'd prefer that over 26, considering the memory requirements).

[indman]

Which makes me wonder: hasn't somebody considered a 20 or 24-pixel-high font? (I'd prefer that over 26, considering the memory requirements).

We already have 16x26 font, nothing prevents you from trying it. But in this case you will have to forget about the compact placement of all the information about the parts. You will have to choose what to show on the display 160x128 and what to hide.

[Feliciano]

I was thinking on something around 10x20 to not sacrify much on a 160x128 screen, but maybe to opt-out to several of the features for that woudn't be appealing to many of the 32KB-units users.

[madires]

A 10x20 font (horizontally aligned) for the ST7735 would be 8 bytes * 110 chars = 880 bytes larger than the default 10x16 font.

[indman]

madires, and if there is any magic method or trick to use several fonts of different heights in the firmware at the same time?

[madires]

No. It would require an additional abstraction layer and increase the firmware size dramatically. RAM could also become an issue.

[Gengis]

Hello to everyone  , I'm searching for some help with my tester...

I have what I think is a "standard" GM328 AY-AT chinese clone kit (writngs on the pcb: K103603BS 2578AY-AT) with 160x128 color display, it came with 1.12 k firmware and appears to work correctly. I want to modify the hardware to improve the accuracy as explained here: https://github.com/blurpy/transistor-tester (this is why I searched exactly this model) but before to order the parts I wanted to be sure I can upgrade the firmware and there started my problem:

I downloaded the current 1.51 m firmware and configured the makefile, config.h and config_328.h according to the included Clones file. Compilation gives no errors and I write the firmware to a spare ATMEGA328P microcontroller.

With the new firmware the tester turns on and the screen gets cleared correctly but it stops there, the display remains black, nothing appears on it (the backlight is of course on).
I can say the display is cleared correctly because if I change the display size or rotation in config_328.h I can make it to initialize partially while the remainder of the screen shows random color pixels.

When I press the rotary controller, the led responds by turning momentairly off, but I tried to connect my multimeter to the test leads and playing around (also if without seeing) with the rotary encoder, and do not see any voltage activity, so I think it's not just a problem of display/color settings, it seems to me the tester is stuck at some point of the initialization and does not respond.

I also tried to write the "mega328_color_kit.hex" prebuilt firmware available here: https://github.com/kubi48/TransistorTester-source/tree/master/trunk/mega328_color_kit but it displays a blanc (white) screen and nothing more. I tried also the "OrigChina.hex" in the same folder but also that displays the blanc screen.

Also searching for "black screen/display" in this thread did not produce useful answers and this looks strange to me because my model seems pretty common and documented. Anyone has suggestions?

[madires]

For 1.51m please also download cap.c-1.51m.tgz (replacement for buggy cap.c). Have you also programmed the EEPROM with the .eep file?

[Feliciano]

I would check again the pinouts of the MCU against the LCD and then to the config file. Some clone makers make modifications to the clone they base their design on.

[Gengis]

For 1.51m please also download cap.c-1.51m.tgz (replacement for buggy cap.c). Have you also programmed the EEPROM with the .eep file?

I will try the replacement file, and no, I have not used the .eep file at all, I did not read anything about it until now . I searched in the pdf manual and see I have to load also that file...

I would check again the pinouts of the MCU against the LCD and then to the config file. Some clone makers make modifications to the clone they base their design on.

I also was worried about the presence of some difference in my particular clone, but the fact that I am able to selectivey initialize parts of the display seems to me a sign that the communication between MCU and LCD is working well...

Thank you very much, I'll do the homework and come back with the results 

[Feliciano]

Has somebody succeded on remaping some ports of a damaged MCU?

Background: An unprotected m328p damaged by a charged capacitor became very slow, then detects a 4V Cell, then enters SeltTest but doesn't finish. I measure low resistance from PC0 to GND, all the ports shows a few mV, except for PB0 which shows around 140mV (with PC0 disconnected).

For this particular clone PC3 is free, so maybe I could rewire PC0 to it. But if PB0 is damaged too, I think there's no hope. Anyways I kindly ask about your experience on the matter before discarding this one.

[indman]

Has somebody succeded on remaping some ports of a damaged MCU?

No, it is better not to waste your precious time on these experiments, and immediately throw such a controller in the trash. This will save you from possible problems and unexpected results in the operation of the device. That's my opinion and a wealth of experience.

[madires]

I haven't tried that yet. Suprisingly I never managed to damage an ATmega all these years. Anyway, two or three users have remapped ADC pins (also cut traces and so on) after damaging one, and it seems to work fine for them. Personally I agree with indman. You never know what else is damaged by the overvoltage. If you can't replace the ATmega for some reason remapping might be worth a try.

[Feliciano]

Note: I also have been lucky of not damaging one CTester yet, knock on wood. My mistake was to sell ALL the ATmegas I showed to my friends/customers

The thing would it be to find an original m328p these days, and the cost/risk of finding it overseas and bringing it here. That's the only reason for considering to workaround this convenient Wei-M8-Shell. For sure it would be (literally) a black box of potential surprises, but hey, just for the sake of it, I already remaped PC0 to PC3. The benefit was a reasonable response time, but now instead of a Cell it detects a MOS, so maybe there's more internal damage, and I don't notice any another apparent B or C spare port on the schematic. Anyways, I realize the change is not as easy as replacing the port on the config.h, as now the usual 1-3 menu entries show 4-3 instead, and the final step of the adjustment asks for a capacitor between 2-3, so something else would be needed to be modded on the config, and I don't know whether it would be related with the MUX0, MUX1 that is referred there (and I haven't tracked that to other parts of the k-firmware code):

Code: [Select]

#else /* PROCESSOR_TYP */
//############### default for mega8, mega168 and mega328
 #define ADC_PORT PORTC
 #define ADC_DDR DDRC
 #define ADC_PIN PINC
 #define TP1 PC3
 #define TP2 PC1
 #define TP3 PC2
 // Port pin for external Voltage measurement (zener voltage extension) PC3
 #define TPext ((1<<MUX1) | (1<<MUX0))
 // Port pin for 2.5V precision reference used for VCC check (optional) PC4
 #define TPREF (1<<MUX2)
 #define TPRELAY PC4
 // Port pin for Battery voltage measuring PC5
 #define TPBAT PC5 /* identical to ((1<<MUX2) | (1<<MUX0)) */
 // option WITH_VEXT can be set automatically, if WITH_UART is unset
 #define TPCAP -1
#endif /* PROCESSOR_TYP */


[Gengis]

I'll do the homework and come back with the results

I'm back just to confirm that my tester's black screen was caused by my not writing the .eep file into the microcontroller's eeprom.

Thank you again

[rogerdammit]

Ah, got it. Here are the values I get:
T2: 13 18 23
T3: -44 -88 -49

These results are poor, especially in the T3 test. The results in tests T2-T3 should be close to 0 and not differ from each other by more than 5 units. Check the values ​​of the measuring resistors 680 Ohm and 470 kOhm.
You can compare the results of your tests with similar tests of other participants on page 369.
You also need to remove all the conductors that you connected for the ICSP interface and repeat selftest!

No idea what happened but I picked up my tester after a week and suddenly all the issues are gone.  Calibrates properly and the open circuit high capacitance issue is gone.

Wasn’t looking forward to resoldering all the connections so happy it fixed itself. Thanks for the help!

[tonedeak99]

Hi what a great thread. Im just a hobbyist looking for an esr meter for capacitors. Mostly in circuit. Would you recommend one of the many clones such as the LCR-Tx’s?  I loved inman’s clone comparison chart.  Any features that are important to look for?

 I cant afford a nicer DER D-5000 or peak atlas meters. Just want an affordable way to see if caps are bad and need replacing. Probably mostly power supply caps and audio amp caps.

Thanks!

[madires]

There are better options for low-cost in-circuit ESR checking, e.g. https://www.eevblog.com/forum/projects/5-transistor-esr-meter-design/.

[indman]

I cant afford a nicer DER D-5000 or peak atlas meters. Just want an affordable way to see if caps are bad and need replacing. Probably mostly power supply caps and audio amp caps.

I advise you to take a closer look at this model of smart tweezers MS8911 - it is relatively inexpensive and will easily perform the tasks you need. 

[tonedeak99]

Thank you both. As for the smd tweezers I seem to run into more thru hole caps than smds. But they seem pretty fantastic. Ill keep those in mind if I need an smd cap tester in the future.

[Feliciano]

Question to the group:
According to your experience, and given the difficulty of finding an original one, which of the non-ATmegas is better or worse? LGT8F328 or APT32F172K8T6? (perhaps considering the typical firmware variation found for each one, as we know there are better adaptations than others).

[indman]

Feliciano, is your question not quite clear to me? The LGT8F328 can be easily replaced by the ATMega328 as it is almost identical in pinout.
APT32F172K8T6 cannot be replaced by anything and there is no working firmware for it!

[Feliciano]

I know, but I mean: if you don't have an ATmega unit or IC spare on your drawer, and you would have to compromise with one of the knock-off, to be used "as is". Which one would you pick, or which to avoid the most? Currently, I could buy either one (of the two), to be pass to a friend.

In fact, I read some old post of yours with a list of limitations, but I don't know which one has more handycaps than the other.