$20 LCR ESR Transistor checker project

[madires]

Yes, a 16 MHz crystal works fine. The fuse bits are the same as for an 8 MHz quartz (external crystal, 1:1 prescaler). But you need to compile the firmware for 16 MHz (-> Makefile).

[jdev99]

I now installed a ATmega644 + 16MHz crystal, and it works great.
The only other thing I want to know is how to improve the zener test values.
A 5.1v read as 5.44v and a 12v read as 13.5v.

[madires]

Could be the test current (too low). Low wattage zeners need about 3 - 5 mA.

[jdev99]

It draws 3.7mA for the 5.1v, so it seems like there is enough current. 

[indman]

jdev99
A competent and simple solution, as indicated in the screenshot. Selection of the most optimal current and its stabilization for safe testing of high-power and middle(low)power zener diodes.
For more precise adjustment of the measured voltage on the zener diode, in k-firmware the Makefile contains lines for the input resistor divider
# Voltage divider for the external zener voltage measurement 180k / 20k = 10/1
CFLAGS += -DEXT_NUMERATOR=10
CFLAGS += -DEXT_DENOMINATOR=1
Instead of a decimal value, you can use the following numbers for smoother voltage adjustment
CFLAGS += -DEXT_NUMERATOR=100
CFLAGS += -DEXT_DENOMINATOR=10
In your case, to reduce the voltage, you can, for example, try the following values
CFLAGS += -DEXT_NUMERATOR=120
CFLAGS += -DEXT_DENOMINATOR=10

For m-firmware, similar divider settings are in the config.h file
#define ZENER_DIVIDER_CUSTOM
#define ZENER_R1         180000
#define ZENER_R2         20000

[rherber1]

I have purchased an LCR-TC2 which appears identical to that in Swainster's pics(Reply #8574 on: May 09, 2023, 05:00:09 am). My pcb is marked T7-PLUS V2.0 also and f/w is V3.1E.

My tester exhibits odd behaviour when measuring resistors of 15 Ohms and 18 Ohms in that it identifies them as Inductors with some arbitrary value of inductance and with the nominal resistance shown. If I use 12 Ohms or 22 Ohms these values are correctly identified as Resistor with the nominal values displayed.

The ability of this tester to produce an accurate value of resistance appears to be quite poor. I measured a nominal 56KOhm resistor with two different multimeters and both produce a reading of 56k6 Ohms. The TC2 produces a value of 58k07 - not what you would call close to the result of both multimeters.

[wasedadoc]

Could be the test current (too low). Low wattage zeners need about 3 - 5 mA.

No, the effect would be the opposite.  Low current through a zener gives a lower voltage across it, not higher.

[indman]

The Zener stabilization voltage may differ from the rated voltage even with the current allowed for it. Therefore, to be sure that the readings are correct, you must first provide current from the stabilized power supply through the zener diode, which is indicated in the datasheet for it, and then measure the voltage drop with a multimeter. This will be the right choice.

[madires]

I have purchased an LCR-TC2 which appears identical to that in Swainster's pics(Reply #8574 on: May 09, 2023, 05:00:09 am). My pcb is marked T7-PLUS V2.0 also and f/w is V3.1E.

My tester exhibits odd behaviour when measuring resistors of 15 Ohms and 18 Ohms in that it identifies them as Inductors with some arbitrary value of inductance and with the nominal resistance shown. If I use 12 Ohms or 22 Ohms these values are correctly identified as Resistor with the nominal values displayed.

Have you run the self-adjustment (shorting all three probe pins)? BTW, that TC2's MCU is an LGT8F328.

[rherber1]

Have you run the self-adjustment (shorting all three probe pins)? BTW, that TC2's MCU is an LGT8F328.

That procedure is not mentioned anywhere in the instruction pamphlet - so, no, I didn't do it.

Have done it now shorting 1-2-3 together and running a test. Shows 0.11 Ohms 1-2 and 0.14 Ohms 2-3. Then ran a test on the 15 Ohm resistor again and no difference - still says it is an inductor.

[madires]

Bummer! Unfortunately some of the tester clones with an alternative MCU come without the self-adjustment feature.

[csuhi17]

Have you run the self-adjustment (shorting all three probe pins)? BTW, that TC2's MCU is an LGT8F328.

That procedure is not mentioned anywhere in the instruction pamphlet - so, no, I didn't do it.

Have done it now shorting 1-2-3 together and running a test. Shows 0.11 Ohms 1-2 and 0.14 Ohms 2-3. Then ran a test on the 15 Ohm resistor again and no difference - still says it is an inductor.

https://youtu.be/KPdoprtrfBg?si=xw6ZLrNqGqUZCcVY&t=130

Did the calibration go well for you, like in the video?

It happened to me that the calibration failed, because the resistance value was higher with the short between me.
After pressing Test, it showed two or three resistances between the test points.

[slybunda]

I have purchased an LCR-TC2 which appears identical to that in Swainster's pics(Reply #8574 on: May 09, 2023, 05:00:09 am). My pcb is marked T7-PLUS V2.0 also and f/w is V3.1E.

My tester exhibits odd behaviour when measuring resistors of 15 Ohms and 18 Ohms in that it identifies them as Inductors with some arbitrary value of inductance and with the nominal resistance shown. If I use 12 Ohms or 22 Ohms these values are correctly identified as Resistor with the nominal values displayed.

The ability of this tester to produce an accurate value of resistance appears to be quite poor. I measured a nominal 56KOhm resistor with two different multimeters and both produce a reading of 56k6 Ohms. The TC2 produces a value of 58k07 - not what you would call close to the result of both multimeters.

thats odd, your tester seems to be a bit like my T7 from the inside but your missing the crystal oscillator: https://www.eevblog.com/forum/testgear/t7-tester-410146/msg5276989/

[indman]

thats odd, your tester seems to be a bit like my T7 from the inside but your missing the crystal oscillator: https://www.eevblog.com/forum/testgear/t7-tester-410146/msg5276989/

There is an X2 quartz crystal on the board, but it is small. What this tester lacks is this normal ATMEL chip and the original authors firmware!

[NF6X]

I posted photos of the "AITRIP" brand T7 tester I just got from Amazon in slybunda's T7 thread. Mine has an APT32F172K8T6 microcontroller, and I don't see any crystal or resonator on it. I presume they're using an internal RC oscillator on the microcontroller. When I short 1-2-3, it identifies itself as "FNIRSI-TC1", and does not show a firmware version number.

[indman]

NF6X,you bought the most unsuccessful model of a Chinese clone from FNIRSI.
If for clones with LGT8F328 installed, you can replace it with the classic ATmega328 and with a little effort get a completely working version with authors firmware, then your controller in case of failure cannot be replaced with anything.

[jdev99]

jdev99


For m-firmware, similar divider settings are in the config.h file
#define ZENER_DIVIDER_CUSTOM
#define ZENER_R1         100000        // R17     
#define ZENER_R2         12000          // R18

After measuring the resistors out of circuit, and adjusting above mentioned values, it is now pretty good.
Values below 5v is a bit low, but everything up to 39v is 99% accurate.
I have a TC1, with ATmega644 and "ComponentTester-1.51m" firmware.
Thank you very much for all excellent advice and effort you guys are putting into this little tester. 

[rherber1]

Bummer! Unfortunately some of the tester clones with an alternative MCU come without the self-adjustment feature.

It certainly seems that this version doesn't have a self test function.

I also tried the factory reset switch on the bottom and it doesn't seem to do anything.

[rherber1]

I have purchased an LCR-TC2 which appears identical to that in Swainster's pics(Reply #8574 on: May 09, 2023, 05:00:09 am). My pcb is marked T7-PLUS V2.0 also and f/w is V3.1E.

My tester exhibits odd behaviour when measuring resistors of 15 Ohms and 18 Ohms in that it identifies them as Inductors with some arbitrary value of inductance and with the nominal resistance shown. If I use 12 Ohms or 22 Ohms these values are correctly identified as Resistor with the nominal values displayed.

The ability of this tester to produce an accurate value of resistance appears to be quite poor. I measured a nominal 56KOhm resistor with two different multimeters and both produce a reading of 56k6 Ohms. The TC2 produces a value of 58k07 - not what you would call close to the result of both multimeters.

thats odd, your tester seems to be a bit like my T7 from the inside but your missing the crystal oscillator: https://www.eevblog.com/forum/testgear/t7-tester-410146/msg5276989/

This board accepts either the larger xtal in a can or the tiny ceramic version. Mine appears to use the latter.

[rherber1]

thats odd, your tester seems to be a bit like my T7 from the inside but your missing the crystal oscillator: https://www.eevblog.com/forum/testgear/t7-tester-410146/msg5276989/

There is an X2 quartz crystal on the board, but it is small. What this tester lacks is this normal ATMEL chip and the original authors firmware!

You might be right about the ATMEL chip and original firmware.

I asked another guy who owns a similar unit and his definitely correctly identifies a 15 Ohm resistor as "Resistor". So perhaps my unit is an imperfect clone of the other "clone". see pic of his unit.

[wasedadoc]

.. see pic of his unit.

Tell the other guy that some of those testers can be switched between Chinese and English text by holding down the Start button  for an extended period.

[slybunda]

My T7 measured a 10ohm thermistor as 11.7 ohm, but thats gonna vary with room temps but was detected as a resistor

[NF6X]

It's unfortunate that the clone I got doesn't support the open source firmware, but I think it'll still be suitable for my "is this still a transistor?" testing purposes. Maybe I'll buy or build an Atmel-based one later. This was just the first one I tried buying from Amazon, and I knew there was a pretty high chance that I'd be getting a non-Atmel-based one in January, 2024. So, I'm not too disappointed about it.

Does the open source firmware implement the IR remote control decoder feature? I don't specifically need that feature, but it's kind of neat.

I hope there will eventually be an open source toolchain and English documentation for the APT32F family, so we can easily hack the things it shows up in.

[madires]

The m-firmware supports the detection/decoding of about 15 IR RC protocols (or 22 with the  SW_IR_RX_EXTRA option). You can also transmit about 15 protocols. The firmwares of the Chinese tester clones are all based on the OSHW firmwares (mostly k-firmware), but the manufacturers ignore the obligation to publish their modified versions.

[NF6X]

Thank you for your explanation. Now I feel more motivated to buy or build hardware which works with the open source code, and maybe even contribute to the open source tester ecosystem in some small way.