$20 LCR ESR Transistor checker project

[.RC.]

What do you think for whom and why does the respected madires wasting his precious time and write detailed instructions(manual) in which he considers all the nuances of measuring resistors, capacitances, inductances and other details? I think for those who want to explore the possibilities of the project, and not just for themselves.

Thanks for the help.   I simply did not see the reandme file in amongst the files in the download.  I did not ask the question frivolously.  I noticed in the .c files there are large amounts of explanatory text and I have been using that to fiddle around.  I searched through inductor.c and I did see something there, I also searched google for #define SW_INDUCTOR, and also searched this thread for the same. Coming up with nothing of consequence.

The reason I asked is the fnirsi clone (which is surprisingly accurate) seems to giving me a closer measurement on inductance and we simply cannot have a unit with a completely fake atmel chip doing that.

Anyway, I am now off to start a thread on how can I find a $50 oscilloscope, and what oscilloscope should I buy.

Thanks again.

[.RC.]

Have a matching pair now.

A tip for anyone building these.  The zif socket, you need to pull the lugs out a bit as you solder them otherwise the socket will rattle with use (found this out on the first built one).  I carefully used a pair of side cutters to gently pull on each lug as I soldered it. They pulled out about another 0.5mm or a tad more. 

Pics of results side by side with same component.

[Obelix2007]

... the socket will rattle with use

... nice tip about the ZIF sockets (cheap China replica)!

... and, did you find a $50 oscilloscope??

Regards Horst

[.RC.]

Nah, no time now for a $50 oscilloscope.  I have been too busy reading a readme file, changing configuration settings, compiling,  uploading, cursing when it says I have tried to compile too much for the atmega328.   Wondering why my screen was all screwed up.   Found I had a hashtag in the wrong spot. More compiling.   Now I have pretty colours everywhere, found out I have to save after doing the adjustment test, also found out why no capacitor was needed when doing the calibration.

These units are freaking amazing for AU$25.  The software and hardware inventors are up there with Ken Thompson and Steve Wozniak.

[.RC.]

I hope madires does not mind me doing this, but I added some new colours to my scheme.  I found the green to be too bright and tended to wash out the other colours on my screen as I have gone for pastel colours on a black background.  I also found the red too dark to see easily.

So I created

#define COLOR_PALE_GREEN    0x9fec    /* RGB 99FF66 */
#define COLOR_PALE_RED        0xfb6d    /* RGB FF6F6F */

I used this website to convert the hex colour I chose to the RGB565 form the tester uses http://www.rinkydinkelectronics.com/calc_rgb565.php

[.RC.]

Here it is using the normal green and red.

[Feliciano]

A little bit of fun: here's the last damaged capacitor I've tested. The kind of failure it developed fools K-firmware by looking a Xtal.

[oitar]

oitar, it is likely that ADC scaling is not working properly. Therefore, I propose several options for further action:
1. Remove capacitor C1 and repeat measurements without it. Does anything change?
2. Compile a new firmware, where the PA6 port will be assigned to measure the zener diodes. Apply external voltage(necessarily through a resistor divider) in the same way as you did before and check the response of this port.
3. You can try to upload firmware 1.13k.

1. Did not produce any noticeable change
2. Done, similar results to the original port. In fact that's what I did earlier, using the "Battery Votage" testing pin. They all have a problem with voltages below 1V(at the pin).
Did the following test by commenting off most lines between 156 and 163 in ADC.c:
/* get voltage of reference used */
  //if (Ref == ADC_REF_BANDGAP)      /* bandgap reference */
  //{
  //  U = Cfg.Bandgap;                 /* voltage of bandgap reference */
  //}
  //else                             /* Vcc as reference */
  //{
    U = Cfg.Vcc;                     /* voltage of Vcc */   
  //}

i.e. forcing VCC reference all the time.

Result: Both zener, and resistor measurements are now proportional, albeit with much bigger error. Also the "Adjustment" menu item keeps completing with Error.

Looks like I need much more digging, regarding bandgap calculation.

3. Haven't had a chance to check 1.13k yet.

[alex_D]

I have noticed a battery charge graphic at the bottom on some photos in this thread, looked in config.h but can't see the option to enable it 

[indman]

3. Haven't had a chance to check 1.13k yet.

Be sure to try this k-firmware and I will also suggest another option for m-firmware that you can easily check.
Turn on the #define ADC_LARGE_BUFFER_CAP setting, replace C1 with a 100nF capacitor and compile a new firmware with this setting.
Will there be any changes for the better?

[madires]

I have noticed a battery charge graphic at the bottom on some photos in this thread, looked in config.h but can't see the option to enable it 

That's a mod by a user, and is already on my to-do list.

[madires]

2. Done, similar results to the original port. In fact that's what I did earlier, using the "Battery Votage" testing pin. They all have a problem with voltages below 1V(at the pin).

When the voltage at the ADC pin is below the voltage of the internal band-gap reference the tester switches to the band-gap reference for better resolution and accuracy (both OSHW firmwares do this). Most likely there's a problem around the AREF pin. We use a small cap at the AREF pin to buffer the reference voltage (switched between Vcc and internal band-gap).

[vk3em]

Yesterday I ordered another unit which just might contain the ATmega324. These things are cheap enough that I'll keep at it until I get the one I want!

Call me a sucker for punishment, but after recently failing with my purchase of the LCR-TC2 from this vendor (I wanted an ATmega324 but got the LGT8F328P), I've taken a gamble on the LCR-TC1 model from the same vendor. https://www.aliexpress.com/item/1005004717377243.html

What gives me hope?

LCR-T7 / LCR-TC1:color screen / M644 chip, two functions are the same! T7 is slightly faster! The TC1 screen is slightly larger and they are all powered by lithium batteries. In addition to measuring resistance, capacitance, inductance, diodes, MOS transistors, thyristors, it can also measure additional voltage regulators, infrared decoding (limited to for Hitachi format)
Self test with automatic calibration

In the LCR-TC2 description, it does not mention M644 (since it was delivered with LGT8F328P that makes sense) nor does it mention "Self test with automatic calibration" - this also makes sense as firmware for the LGT8F328P (in my case V3.1e) cannot fit the code for self-calibration. V3.1E firmware is also horrifically buggy, cannot reliability measure ESR, or Darlington transistors, etc. I will definitely be modifying my LCT-TC2 with LGT8F328P to the ATmega328P.

I can only presume (hope) M644 mentioned in the details of the LCR-TC1 description refers to ATMega644 and so far this is the only specific mention of M644 within an advertisement that I can find. Lets see when it arrives.

Luke

Nope - It's a fail, its not a M644. I guess you just cant trust AliExpress sellers (Note: I have a message response from the seller confirming prior to sale, the device contains an M644 chip!). Not sure if its a fake 328P. 

[.RC.]

I assume it is a fake as the chip has totally identical markings to the chip on my Fnirsi, right down to the DOM. There is no external crystal.  Also R1 and R4 (two of the important 470K and 680R resistors) are entering the chip at the same position as mine which is different to the photos of boards with real 328P chips that I have seen.

Here is a real 328p board.  https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg1016677/#msg1016677

[vk3em]

Thanks. The TC1 firmware identifies as "M-Tester" and the TC2 firmware identifies as "LCR-TC2 v3.1E".

"Short the three test sockets, press the multi-function button shortly, and the tester will automatically calibrate.
No other operations are required after disconnecting the short wiring according to the prompt during the calibration process."

Neither of the units seem to allow entry into a self-calibration mode, despite both providing the calibration shorting pins.

I'll do some side by side comparison to see how they perform, but it looks like I have no choice now but to build the GM-328 kit which came with a genuine Atmel MEGA 328P. I feel like I am walking in your footsteps ! In the future, I will try to convert the TC2 with its LGT8F328P to a MEGA328.

Its a pity because AliExpress SeeSensor has good ratings, and they obviously did sell genuine Atmel units, but not now, and not even if you ask them to confirm!

Luke

[.RC.]

I feel like I am walking in your footsteps

My footsteps seem to be like that monastery in the movie Where Eagles Dare.

You have a destination this monastery atop a cliff edged mountain.   Most sensible people take the nice safe cable car to the top.   I am often the fool you see scrambling up the cliff face, because I rushed in and never saw the cable car. 

[moghaddam]

I also have a T7 (pictured attached, fake obviously). It was working fine, but since a few days ago, when I try to test anything, it randomly detects it as resistor or mostly inductor. I can't remember what was the last thing that I tested. I checked all the diodes (in circuit) and they all looks ok. I don't have a hot-air gun, so I have not tried to desolder caps to check them one by one. I just checked for short, and seems none of them are shorted.

My question may have already been answered, but at least I didn't manage to find it in the last couple of days that I'm reading through this thread (10 years old thread, really impressive ). I was wondering maybe someone has already had this issue and could give me some hint to do further troubleshooting.

I'm not professional. Just a hobyist trying to learn electronics.

[madires]

A common fault is a toasted SRV05-4.

[Aldo22]

My question may have already been answered, but at least I didn't manage to find it in the last couple of days that I'm reading through this thread (10 years old thread, really impressive ). I was wondering maybe someone has already had this issue and could give me some hint to do further troubleshooting.

I would calibrate it first and then check again.
Have you done anything in the K-A-A range?
I have the same board and you should add a resistor anyway.
I have done that as well.
You can find information about the problem in the forum.

See also: https://www.eevblog.com/forum/testgear/...

And you most likely have an APT32F172K8T6 like I do, not an Atmega.

[hapless]

I flashed a tester that I've had for a while with the 1.49m code and noticed a problem with too high h_FE. It also doesn't stay consistent, changing from time to time. The following fixes it:

Code: [Select]

/* ************************************************************************
 *   workarounds for some testers
 * ************************************************************************ */


/*
 *  Disable hFE measurement with common collector circuit and Rl as
 *  base resistor.
 *  - problem:
 *    hFE values are way too high.
 *  - affected testers:
 *    Hiland M644 (under investigation, possibly poor PCB design)
 *  - uncomment to enable
 */

#define NO_HFE_C_RL
However, this is not some fancy M644. It's a GM328-3V from 2014. A very simple, straightforward design. It does have a converter from 3V to 5V. It has the same issue when powered from the ISP port, which bypasses the DC-DC converter completely. I removed the surge suppressor, too, thinking that it might be fried. Same problem. The tester is rock-solid stable with 1.13k firmware, but with 1.49m sometimes it shows 0pF between probes during self-test while other times is the usual 47-51pF. Not sure where to look for further problems there. Could the problem lie with the way 1.49m measures common collector current or is it definitely something with the hardware? I can't seem to find any hardware problems on the probe side of the chip. Connecting ISP header adds some capacitance, but that's the only thing I can see that's even remotely suspect. Any ideas welcome at this point because I'd like this particular unit to be running the latest M firmware, not K.

[Yuriy_K]

I can't seem to find any hardware problems on the probe side of the chip.
...
 Any ideas welcome at this point because I'd like this particular unit to be running the latest M firmware, not K.

Compare the Show Values with the photo to see if there are significant differences.

[moghaddam]

Thanks for your suggestions guys.

@madires I just checked the SRV05-4 forward voltages. Seems they're all in range (0.6-0.8V).

@Aldo22 It doesn't get calibrated (as shown in the picture posted in my original question) and only detects an inductor between 2-3 when I short 1-2-3 together. I know I had tested some diodes between K-A and changed diodes while the tester was on, so that could easily be the case. I will definitely add the 2K2 resistor to the board.

I read the answer you linked as well as your other similar answer with even more details at https://www.eevblog.com/forum/testgear/%2420-lcr-esr-transistor-checker-project/msg4692413/#msg4692413. There it says:

Unmodified (but working) LCR- units with APT32F172K8T6 MCU and the poorly designed U7 circuit will display 5-8V “zener voltage” with the 1k resistor connected to K-A. This is because DC-DC converter U7 actually does function as a constant current source (until it gets damaged).

When I put the 1K resistor, it detects it as an 8V Zener. Also I tried measuring a 3V Zener and it detects it correctly as 3.2V Zener and it doesn't get hot at all. So is it safe to assume the U7 current limiting is still working?

[Aldo22]

@moghaddam:
I can't tell you more as I soldered the resistor in before I had a problem.
I had the information from here.

[madires]

The tester is rock-solid stable with 1.13k firmware, but with 1.49m sometimes it shows 0pF between probes during self-test while other times is the usual 47-51pF.

0 pF can happen when some values don't add up during the measurement. You could try ADC_LARGE_BUFFER_CAP to increase the delay for switching the ADC's reference voltage.

[hapless]

I can't seem to find any hardware problems on the probe side of the chip.
...
 Any ideas welcome at this point because I'd like this particular unit to be running the latest M firmware, not K.

Compare the Show Values with the photo to see if there are significant differences.

Please see the attached image. Looks reasonably close? Maybe I'm missing something there.

The tester is rock-solid stable with 1.13k firmware, but with 1.49m sometimes it shows 0pF between probes during self-test while other times is the usual 47-51pF.

0 pF can happen when some values don't add up during the measurement. You could try ADC_LARGE_BUFFER_CAP to increase the delay for switching the ADC's reference voltage.

Doesn't seem to change anything... I'll try to recompile again later, just in case. The actual cap measures around 1.1nF.