$20 LCR ESR Transistor checker project

[oitar]

I saw something interesting...
Look at the 2 short videos. I'm measuring the voltage on the AREF pin(the one with the cap), while testing the 8.2V, and then the 12V zeners.
In the first case(8.2V) the voltage never goes over 4.3V at the beginning of every measurement, and drops further during the test.
In the 12V case the AREF clearly goes over 5V at the beginning of each measurement.

[indman]

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.

[snapper]

Adapter to upgrade the T-Tester with ATMEGA328 DIP28 to ATMEGA644 TQFP.
Idea and implementation by Boleslaw Jamroz from Poland,
I have only developed a circuit board for the cumbersome threading adapter
that simplifies the construction much ;-)
https://www.mikrocontroller.net/topic/transistortester-avr?goto=7398047#7381379

[.RC.]

I found I had a small boost converter here.   It seems like it would work to supply voltage for zener diodes.

[.RC.]

My inductor measurements seem to be out as it seems to measure higher then the inductors say they are.   Are there any adjustments for inductance?

[indman]

Are there any adjustments for inductance?

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.

[carrascoso]

Hello everyone.

I have a GM328 with the buzzer modification.
With v1.47m it works perfectly for me.
But with v1.49m, it's always ringing, and I've tried various things and it's always the same.

What could be the problem?

[madires]

My inductor measurements seem to be out as it seems to measure higher then the inductors say they are.   Are there any adjustments for inductance?

Please see the README file, section 'Inductors'!

[madires]

I have a GM328 with the buzzer modification.
With v1.47m it works perfectly for me.
But with v1.49m, it's always ringing, and I've tried various things and it's always the same.

What could be the problem?

Which buzzer related options have you enabled? Which pin have you set for BUZZER_CTRL (_PORT and _DDR) ? Is that pin also used for something else? Does the buzzer start ringing at power-on or when running a specific function?

[carrascoso]

I have not activated any function for the buzzer.
The buzzer starts to sound as soon as the equipment is turned on

[madires]

Have you enabled HW_BUZZER? BUZZER_ACTIVE or BUZZER_PASSIVE? Which pin have you set for BUZZER_CTRL (_PORT and _DDR)? Or have you just connected the buzzer to some pin without enabling anything?

[carrascoso]

Thank you, Madires, I already solved it.

What difference is there in the operation of BUZZER_ACTIVE or BUZZER_PASSIVE

[madires]

BUZZER_ACTIVE: buzzer with integrated oscillator (makes sound when power is applied)
BUZZER_PASSIVE: simple piezo disc (needs external oscillator)

[.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).