$20 LCR ESR Transistor checker project

[elecdonia]

If  I had a custom PCB made using AY-AT design but altered the board substituting the ATMega328 with a ATmega1284p package, it should just work right?
assuming I compile the the firmware for the ATmega1284p and I would have 4 times the flash?

I've been thinking about the same thing. In fact there are ATmega644 and ATmega1284 devices sitting on my workbench right now. They are housed in 40-pin DIP packages.

I plan to scratch-build a Transistor Tester on a "perma-proto" board with a 40-pin MCU socket.

Another of my ideas is to design a separate analog section to interface with the 3 test pins. 
It will have a high-resolution A-D converter and dedicated low-resistance drivers for the test pins.
All signals to/from the MCU will then be logic level. This way it won't matter whether the MCU operates at 5V or 3.3V. 
Eventually I might make the test voltages/currents for the 3 test pins programmable: Ideally 0-100V and 0-2A.

[Aldo22]

To conclude, the fix is:
1) Cut the PC board foil leading to pin K and then connect 2K2 resistor from junction of D2 and C14 to pin K,

Thank you!
There isn't much space for a 1206 SMD, but it works.
This is my first attempt at SMD soldering. 

[Per Hansson]

A question for Madires:
I had a device with a seemingly working Rohm 1SR159-200 diode rectifying the output from a switch mode transformer but it provided unexpected low output voltage.
In the end I found that the diode had failed in such a way that it became a regular diode, not a ultra fast diode!
I first replaced it with a UF4007 and it got me much closer to the expected output voltage.
So I bought a even faster diode (Diotec ES1D) that should exceed the originals specifications on paper and I got the expected output voltage!
My question is if this type of testing (speed of the diode) could be implemented in the transistor tester?

[indman]

A question for Madires:
I had a device with a seemingly working Rohm 1SR159-200 diode rectifying the output from a switch mode transformer but it provided

And what test results do you see now with this diode on a transistor tester? What is the CpF? What are the results compared to a serviceable ES1D? 

[Per Hansson]

And what test results do you see now with this diode on a transistor tester? What is the CpF? What are the results compared to a serviceable ES1D? 

The bad Rohm 1SR159-200 with trr value from datasheet: <50ns (23ns typical)
Uf=570mV
9.3pF - 3.6pF @ 0 - 5V
Ir=0.18µA

A new Diotec ES1D with trr value from datasheet: <15ns
Uf=541mV
24pF - 15pF @ 0 - 5V

But to do a proper test I should desolder one of the other Rohm diodes from the unit and measure those, since the Diotec has better specs in the datasheet.
But first I want to hear what madires thinks too

[gipetto]

If  I had a custom PCB made using AY-AT design but altered the board substituting the ATMega328 with a ATmega1284p package, it should just work right?
assuming I compile the the firmware for the ATmega1284p and I would have 4 times the flash?

I recall years ago seeing one of the first avr transistor tester prototyped on a dip atmega32a. i think the page is only accessible on the web archive. however the support for that mcu seems to not be listed any more.
If you want any help in designing the pcb and keeping it open source i can offer it. I'd like it to have an isp header, something that is missing from most designs. If nothing else i can check for mistakes.

[madires]

My question is if this type of testing (speed of the diode) could be implemented in the transistor tester?

The ATmega's slow ADC plus some processing time would limit that measurement to about 30µs, I'd guess. The reverse recovery time of a classic 1N400x can be somewhere between 30 and 2µs (UF400x: 50/75ns). So it wouldn't help much.

[Yuriy_K]

The reverse recovery time of a classic 1N400x can be somewhere between 30 and 2µs (UF400x: 50/75ns). So it wouldn't help much.

There is no need to add anything, both authors clearly show the dependence of the diode capacitance on its speed.

[indman]

The reverse recovery time of a classic 1N400x can be somewhere between 30 and 2µs (UF400x: 50/75ns). So it wouldn't help much.

There is no need to add anything, both authors clearly show the dependence of the diode capacitance on its speed.

Then why is the lower capacitance 1SR159-200 diode not working properly?

[Yuriy_K]

Then why is the lower capacitance 1SR159-200 diode not working properly?

Because, Ir=0.18µA

[indman]

Then why is the lower capacitance 1SR159-200 diode not working properly?

Because, Ir=0.18µA

According to the datasheet 1SR159-200, the allowable Reverse Ir can reach 10µA

[Per Hansson]

My question is if this type of testing (speed of the diode) could be implemented in the transistor tester?

The ATmega's slow ADC plus some processing time would limit that measurement to about 30µs, I'd guess. The reverse recovery time of a classic 1N400x can be somewhere between 30 and 2µs (UF400x: 50/75ns). So it wouldn't help much.

Thank you for the explanation madires!

Yuriy_K: I desoldered a working Rohm 1SR159-200 diode now but unfortunately it measures almost identical to the bad one:
Uf=545mV
10pF - 3.5pF @ 0 - 5V
Ir=0.20µA

I thought it could be a nice addition to measure the reverse recovery speed (trr) since this was a pretty tricky failure mode, but if the ADC is too slow then that is not possible of course...

[indman]

Per Hansson,What operating voltage is present on this diode in the circuit?

[Per Hansson]

Per Hansson,What operating voltage is present on this diode in the circuit?

The output from the transformer is 50v p-p at ca 100kHz, see attached screenshot.

[indman]

The operating voltage exceeds the test voltage by 10 times, so it has been repeatedly repeated in this and other topics that this tester cannot provide a 100% probability of detecting all faults.

[Yuriy_K]

Yuriy_K: I desoldered a working Rohm 1SR159-200 diode now but unfortunately it measures almost identical to the bad one:
Uf=545mV
10pF - 3.5pF @ 0 - 5V
Ir=0.20µA

I thought it could be a nice addition to measure the reverse recovery speed (trr) since this was a pretty tricky failure mode, but if the ADC is too slow then that is not possible of course...

I made a comparison of similar characteristics of US1M and 1SR159-200. Compare for yourself, I can’t understand where Ir=0.18µA  comes from at 5v. Probably problems with the diode, it is a pity that there is no unused diode to compare with the used ones.

[Per Hansson]

I made a comparison of similar characteristics of US1M and 1SR159-200. Compare for yourself, I can’t understand where Ir=0.18µA  comes from at 5v. Probably problems with the diode, it is a pity that there is no unused diode to compare with the used ones.

Notice how there is very little difference of reverse current at 200v vs the minimum the datahseet shows at 50v.
So if we extrapolate down to 5v it is easy to see how the reverse current value could still be valid.

The operating voltage exceeds the test voltage by 10 times, so it has been repeatedly repeated in this and other topics that this tester cannot provide a 100% probability of detecting all faults.

Sure, but it still provides relevant data, I'm sure it could test reverse recovery time too even at that low voltage.
But as madires says if the speed of the ADC is not enough that will limit the lowest trr value we can see.
And just to provide a different way to visualize it:
Diotec ES1D in-circuit output voltage: 17.87v
Rohm 1SR159-200 in-circuit output voltage: 17.83v
Diotec UF4007 in-circuit output voltage: 17.30v
Bad Rohm 1SR159-200 in-circuit output voltage: 14.4v

[9voltbrain]

Can anyone chime in on the differences between the LCR-T7 and LCR-T4? I'm mostly interested in getting some ballpark measurements on the inductors I have lying around here. As long as I get +/- 20uH I'm happy. I don't want to get the LCR-T7 because of the built in rechargeable battery. It's just annoying to me having to keep it charged and dealing with it going bad eventually. Do you have to recalibrate the T4 every time you take the 9v battery out?

There is also another meter available from where I usually buy stuff called M162, but I can't find any info on it. Anyone tried it? It's like 3x the price of the other ones. Picture below.

[Feliciano]

Have you looked at indman's table of ctester clones?

[elecdonia]

There is also another meter available from where I usually buy stuff called M162, but I can't find any info on it. Anyone tried it? It's like 3x the price of the other ones. Picture below.

That is a gorgeous display. Someone with talent designed it and wrote the code for it.

Regarding testing small inductors, have you considered the LC100-A?
It measures L and C only (nothing else). I’ve had one for years. It is an excellent companion for a Transistor Tester because it uses a totally different measurement process. I found that the LC100-A does a great job measuring L <10uH and C <50pF. Here’s a topic that discusses them:

https://www.eevblog.com/forum/testgear/lc100-a-a-precise-lc-meter-for-3-75$/msg4599424/#msg4599424

[Messtechniker]

The M162 is not a transistor checker.
You might want to go here:
https://www.eevblog.com/forum/testgear/new-jyetech-m162-lcr-meter-(april-2022)/msg4136254/#msg4136254

[Yuriy_K]

As long as I get +/- 20uH I'm happy.
...
Do you have to recalibrate the T4 every time you take the 9v battery out?

Three years ago I made a firmware for T4 for another forum. In it, to measure small inductances and capacitances, it is necessary to replace the crystal with 16 MHz. Since then, much of the software has changed and expanded. In the archive, the changes are in New, but this firmware is not tested, I do not have T4.
The calibration is retained when the battery is replaced.

Examples of measuring small inductances are in my posts.

[hojnikb]

hello; new here with these whole cheap LCR tester... Which one should one buy these days? There seems to be lots of different versions available (like TC1, TC2, T7 etc)....

Is there a list of all these clones and pros/cons of each one? 

[hojnikb]

hello; new here with these cheap LCR testers... Which should one buy these days? There seems to be lots of different versions available (like TC1, TC2, T7 etc)....

Is there a list of all these clones and pros/cons of each one? 

[madires]

Feliciano posted a link to a list just four posts earlier.