$20 LCR ESR Transistor checker project

[hapless]

Thank you, but I see no anomaly here. You are using a capacitor. upsss is getting "if xxnF" without a capacitor, so the reading is incorrect because the tester is measuring as if there were a tank circuit with a known capacitor. I asked for the minimum value at which this keeps happening.

[indman]

Sorry, but I not absolutely understand why it is necessary?
The resonant method (SamplingADC on) works with excellent accuracy to a upper limit 2-3mH and requires mandatory connection of the capacitor parallel to the measured coil.

[hapless]

Because it should not be detecting a capacitor when there is no capacitor.

[texaspyro]

Because it should not be detecting a capacitor when there is no capacitor.

Woo hoo!  You get free capacitors!

[hapless]

Yep... Too bad they are imaginary.

[texaspyro]

Yep... Too bad they are imaginary.

Yes, but an imaginary capacitor is an inductor, so all is well and good and balance has been restored to the force.

[upsss]

What happens if you also put a 21nF cap in parallel with those coils (the one you calibrated with)?

OK, if I put the 22uH inductor in parallel with my calibration capacitor then I get the correct (~22uH) inductance displayed.  I still don't understand why only the AY-AT tester displays this "xxuH if xxuF" and requires this resonance configuration with the calibration capacitor. Also in case of the 22uH inductor when it display "40nH if 21.3nF" what does the 40nH means?

Another problem, when it displays the inductance correctly like in my example with the 47uH, on the 2nd line it displays some resonant frequency.  In this case it displays 3618kHz, what is the significance of this resonant frequency?  47uH with 21nF (my calibration capacitor) DOESN'T resonates at 3618kHz, it resonates @ ~159KHz, so what is this 3618kHz frequency? 

Any inductor will resonate with any capacitor at some frequency.  What is the significance of knowing the resonant frequency with some arbitrary capacitance, who cares? And who cares what is the Q of that resonant circuit?  Both of these parameters are totally meaningless.

[indman]

Also in case of the 22uH inductor when it display "40nH if 21.3nF" what does the 40nH means?

It means that on pins 1-3 tester included measurement by a resonant method and as the capacitor on 21.3nF wasn't connected, incorrectly defined value of inductivity in 40nH. 
Why it included a resonant method without the connected capacitor? It is necessary to understand.
Tester very sensitive in the SamplingADC mode therefore any noises on a supply, the capacity and inductivity of the connected cables create an oscillating circuit.
It is possible to measure inductivity by an old method, connecting a detail on pins 1-2 and 2-3.
Then the resonant method doesn't work, but measuring accuracy of small inductance will be low.

[bianchifan]

What is the significance of knowing the resonant frequency with some arbitrary capacitance, who cares? And who cares what is the Q of that resonant circuit?  Both of these parameters are totally meaningless.

I will not comment this..

I cannot help you regarding the sampling-ADC story 'cause I do not make use of it.
But as far as I know it was introduced by Pieter-Tjerk in mid 2015 and bases on a university project for measuring very small capacities.
Karl-Heinz explained this method in the "Transistortester-AVR" thread within the german "mikrocontroller.net", feel free to ask there for details.
It should be explained in the actual documentation too, my version from 02/2015 is too old

If you don't need to "measure" small caps and inducts don't select this func..

[mauroh]

I got interested in the SamplingADC Method for measuring small coils and made some tests...
So far it is amazing and finally I got the purpose of the additional capacitor during calibration 

To facilitate the measurements with this method I modified my super simple SMD test pads adapter to fit the 20nF capacitor.
Now I'm curious to see how the m-firmware will behave since it doesn't support this methos.

Hey Marcus, thank you again for the development of the Servo test function on the m-firmware.
In this days I used it alot to match few servos and test some ESC for brushless motors I was working on.
To better fit my needs I modifyed the sweep mode of the Servo test in the extras.c file to go all the way from 0.5ms to 2.5ms during sweep (instead of 1ms to 2ms).
If someone is interested I copyed the code below.

Mauro

//Sweep mode Servo test MAX Limits

{
  uint16_t          Temp;     /* temp. value */

  /*
   *  hints:
   *  - the OCF0A interrupt flag is  cleared automatically
   *  - interrupt processing is disabled while this ISR runs
   */

  /* toggle values for PWM */
  #define SERVO_LEFT_MAX     (((CPU_FREQ / 10000) * 5) / 16)   /* 1.0ms */ 
  #define SERVO_RIGHT_MAX    (((CPU_FREQ / 10000) * 25) / 16)   /* 2.0ms */
  //#define SERVO_LEFT_NORM     (((CPU_FREQ / 10000) * 10) / 16)   /* 1.0ms */  //Mauro
  //#define SERVO_RIGHT_NORM    (((CPU_FREQ / 10000) * 20) / 16)   /* 2.0ms */   //Mauro

  /*
   *  update PWM pulse length (Timer1)
   */

  Temp = OCR1B;               /* get current compare value */

  if (SweepDir == 1)          /* forward */
  {
    Temp += SweepStep;        /* add step */

    if (Temp >= SERVO_RIGHT_MAX)  /* exceeded upper limit */    //Mauro
    {
      Temp = SERVO_RIGHT_MAX;     /* limit */               //Mauro
      SweepDir = 2;                /* change direction */
    }
  }
  else                        /* backward */
  {
    Temp -= SweepStep;        /* substract step */

    if (Temp <= SERVO_LEFT_MAX)   /* exceeded lower limit */   //Mauro
    {
      Temp = SERVO_LEFT_MAX;      /* limit */
      SweepDir = 1;                /* change direction */   //Mauro
    }
  }

  OCR1B = Temp;               /* set new compare value */

  #undef SERVO_LEFT_MAX
  #undef SERVO_RIGHT_MAX
  //#undef SERVO_LEFT_NORM   //Mauro
  //#undef SERVO_RIGHT_NORM   //Mauro
}

[madires]

To facilitate the measurements with this method I modified my super simple SMD test pads adapter to fit the 20nF capacitor.
Now I'm curious to see how the m-firmware will behave since it doesn't support this methos.

Just as a side note, the 664/1284 dev kit got a relay for switching the parallel cap for the SamplingADC automatically. I don't know if Karl-Heinz has added that hardware option already to the firmware. I'm busy with the touch screen.

[tdriver]

I have the ay-at tester, and 2 new 10mH UU9.8 common line filter I measured, show only half the value (5mH , 1.2ohm) why?
everything else seems to work fine.

tester has latest karl-heinz firmware, but Chinese firmware showed the same value.

[madires]

2 * 5mH = 10mH 

[tdriver]

thank you, I suspected this, but wasn't sure.   

[scdreger]

So I received mine from Amazon (link: https://www.amazon.com/gp/product/B06WW6QNFZ/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1) yesterday and soldered it up.

The unit turns on (red LED, backlight on display etc.) but the screen appears blank (although lit up). I've read that it could be the contrast setting but I'm not sure how to adjust it blind. I believe you turn it on with a 2 second press to enter menu mode and then keep clicking to move through the different menu items. Can someone tell me how many times to press to get to the contrast setting? Any help would be greatly appreciated.

[casinada]

You should carefully check everything, connections, resistor values, transistors etc. There is no trimpot to adjust the contrast on this version. Make sure the voltages are correct and the microcontroller is connected the right way. If everything is assembled correctly it should work. The contrast can only be changed by software and or compiling the firmware. 

[hapless]

OK, if I put the 22uH inductor in parallel with my calibration capacitor then I get the correct (~22uH) inductance displayed.  I still don't understand why only the AY-AT tester displays this "xxuH if xxuF" and requires this resonance configuration with the calibration capacitor. Also in case of the 22uH inductor when it display "40nH if 21.3nF" what does the 40nH means?

As indman explained, it means that the tester thinks that it sees a coil and a capacitor when there is no capacitor present due to very high sensitivity. The question is, what prompts it to do so? This is why I suspected the protection diodes, as they add capacitance to the input. Also, I see you have a dangling programming header. See if you can fix it so it won't move during measurement. Place it and its cable away from the test points or noise sources.

Another problem, when it displays the inductance correctly like in my example with the 47uH, on the 2nd line it displays some resonant frequency.  In this case it displays 3618kHz, what is the significance of this resonant frequency?  47uH with 21nF (my calibration capacitor) DOESN'T resonates at 3618kHz, it resonates @ ~159KHz, so what is this 3618kHz frequency?

I can't even tell if it's intentional. That line looks like it may be displaying by mistake. This frequency it displays is the resonance of your inductor with the capacitance of your tester's inputs.

Any inductor will resonate with any capacitor at some frequency.  What is the significance of knowing the resonant frequency with some arbitrary capacitance, who cares? And who cares what is the Q of that resonant circuit?  Both of these parameters are totally meaningless.

The frequency display is actually useful. It shows the conditions under which the test was performed. This way, if you insert the same inductor into a different tester that tests under a different frequency, you won't be mislead into thinking that one of the testers is lying to you. I can't comment on the usefulness of knowing Q under a random frequency. There's probably a use case for it, I just can't think of one off the top of my head.

The unit turns on (red LED, backlight on display etc.) but the screen appears blank (although lit up). I've read that it could be the contrast setting but I'm not sure how to adjust it blind. I believe you turn it on with a 2 second press to enter menu mode and then keep clicking to move through the different menu items. Can someone tell me how many times to press to get to the contrast setting? Any help would be greatly appreciated.

The number of menu items depends on the features that were compiled into the firmware. It would probably be easier (and, perhaps, somewhat educational?) to just reprogram the chip.

[scdreger]

The unit turns on (red LED, backlight on display etc.) but the screen appears blank (although lit up). I've read that it could be the contrast setting but I'm not sure how to adjust it blind. I believe you turn it on with a 2 second press to enter menu mode and then keep clicking to move through the different menu items. Can someone tell me how many times to press to get to the contrast setting? Any help would be greatly appreciated.

The number of menu items depends on the features that were compiled into the firmware. It would probably be easier (and, perhaps, somewhat educational?) to just reprogram the chip.
[/quote]

Thanks for the reply. As I understand it, my Chinese board doesn't allow connection for updates although I think I could use my Arduino to update it. I need to learn how to do that ... I'll look into it.

You should carefully check everything, connections, resistor values, transistors etc. There is no trimpot to adjust the contrast on this version. Make sure the voltages are correct and the microcontroller is connected the right way. If everything is assembled correctly it should work. The contrast can only be changed by software and or compiling the firmware.

Thanks, I double checked everything. I was especially suspicious of the SMDs as that was my first time soldering them, but continuity testing shows each pin or terminal connected to the next point on the PCB.

The only thing I found suspicious was the TL431 showing a dead short between pin 1 and 3,  but I'm a newb so I'm not sure if this is expected behavior. Can someone help me determine if that indicates a problem?

[upsss]

The only thing I found suspicious was the TL431 showing a dead short between pin 1 and 3,  but I'm a newb so I'm not sure if this is expected behavior. Can someone help me determine if that indicates a problem?

These two pins are supposed to be shorted, that is how you get 2.5v output, see schematic.

[scdreger]

The only thing I found suspicious was the TL431 showing a dead short between pin 1 and 3,  but I'm a newb so I'm not sure if this is expected behavior. Can someone help me determine if that indicates a problem?

These two pins are supposed to be shorted, that is how you get 2.5v output, see schematic.

Ok thanks for the help and the schematic. 

[casinada]

Please post some pictures 

[upsss]

So I received mine from Amazon (link: https://www.amazon.com/gp/product/B06WW6QNFZ/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1) yesterday and soldered it up.

The unit turns on (red LED, backlight on display etc.) but the screen appears blank (although lit up). I've read that it could be the contrast setting but I'm not sure how to adjust it blind. I believe you turn it on with a 2 second press to enter menu mode and then keep clicking to move through the different menu items. Can someone tell me how many times to press to get to the contrast setting? Any help would be greatly appreciated.

Your tester has a color display so it doesn't have a contrast setting.  The contrast setting exist only on mono display like in the T3/T4 version.  As far as reprogramming the processor you either have to remove it and plug into a proper programmer or solder a programming connector as you can see in my picture.

[hapless]

Speaking of contrast setting, I just noticed that it appears in the menu (but does nothing, of course) when PCD8544 is used with m firmware.

[scdreger]

Issue resolved! It turns out I damaged a pad when assembling. 

One of the ground terminals on the D.C. Jack lifted a pad on the pcb as I inserted it. I had tested for damage, so I thought. Ground traces run on the bottom of the pcb in one direction but on top of the pcb it goes to the center pin of the rotary encoder and continues on from there.

When I was testing resistance to ground all the connections originating from the bottom of the pcb measured .2 ohms/ short but I realized all the ones originating from the top were measuring more than 500K ohms. I soldered in a jumper from the good bottom ground connection directly to the center pin of the rotary encoder and it's fixed. 

[madires]

Speaking of contrast setting, I just noticed that it appears in the menu (but does nothing, of course) when PCD8544 is used with m firmware.

The contrast setting for the PCD8544 changes V_LCD, but you're right about nothing's happening. The driver didn't set the maximum value. I have fixed that. Also I agree that you don't need to change V_LCD in most cases. Should we make it an option?