$20 LCR ESR Transistor checker project

[amtpdb]

Hi:
Could I get anyones thoughts on this meter?
Has anyone purchased this one and been able to update it and how did you do it or is this one not to be purchased. I was looking at the ones with the larger display, but I believe it was mentioned that you cannot update it with the files mentioned here.
http://www.ebay.com/itm/291041497713?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT   Thanks for any help.
Don

[MickM]

Hi amtpdb;
   I bought one of as a gift.
The AVR is locked by the fusebits.
AVRDUDE will read it ok, but the file is length 0.

Nevertheless it is a good clone, and does ESR

Mick M

[amtpdb]

Hi amtpdb;
   I bought one of as a gift.
The AVR is locked by the fusebits.
AVRDUDE will read it ok, but the file is length 0.

Nevertheless it is a good clone, and does ESR

Mick M

Thanks Mick
Is there anything I should know before I buy it to change? Can you put a header on it easy enough to change the program and did you change the program? Did you change the atmega out? Is there one that you would consider other then this one now that you purchased it? I am a newbe, do you need to change out the resistor or anything?
I appreciate your getting back so quickly.
Don

[madires]

Thanks! Can you go into more detail on why it's limited to that? I'd be interested in helping to add support for lower and more precise inductor measurements.

Based on the hardware design the only feasable method for measuring inductance is to track the current change of the inductor when a current is applied. To measure low inductances a high test current is required but the MCU's limit is 20mA. In "safe" mode (about 7mA, limited by the 680 Ohms probe resistor) the tester can measure down to about 100µH. But there's also an "unsafe" mode which overloads the MCU's I/O pin for a short period of time and allows a measurement down to 10µH. The unsafe mode is entered if the tester doesn't detect an inductor in the safe mode and the resistance of the DUT is less than 40 Ohms. So far we haven't seen any issues with that, but the measurements in the low inductance range are not very accurate.

[JoeO]

amtpdb;

I bought 2 of these also.  Under the LCD is a DIP socketed 328P.  There is no connector to program it on the board.  You would have to remove it to modify the program.

This is the BEST design because you can buy a second 328P and program it.  Test it on the board  and if it does not work, reinsert the original 328P

[madires]

Some changes for v1.15m to improve the inductance measurement a little bit more. In inductance.c in function MeasureInductance() in the "process counters" section please change:

Code: [Select]

Offset = -4;                /* subtract processing overhead */
to

Code: [Select]

Offset = -3;                /* subtract processing overhead */

Remove or comment out the following line:

Code: [Select]

    Counter += (CPU_FREQ / 2000000);         /* add half of cycles for rounding */

And change

Code: [Select]

  if (Counter <= 500) Flag = 2;         /* signal "inductance too low" */
to

Code: [Select]

  if (Counter <= 100) Flag = 2;         /* signal "inductance too low" */

The changes above will be included in the next release.

[timb]

Some changes for v1.15m to improve the inductance measurement a little bit more. In inductance.c in function MeasureInductance() in the "process counters" section please change:

Code: [Select]

Offset = -4;                /* subtract processing overhead */
to

Code: [Select]

Offset = -3;                /* subtract processing overhead */

Remove or comment out the following line:

Code: [Select]

    Counter += (CPU_FREQ / 2000000);         /* add half of cycles for rounding */

And change

Code: [Select]

  if (Counter <= 500) Flag = 2;         /* signal "inductance too low" */
to

Code: [Select]

  if (Counter <= 100) Flag = 2;         /* signal "inductance too low" */

The changes above will be included in the next release.

Thanks, I'll give this a go today and report back!

So, one issue I've run into with reprogramming my Mega328 chips after flashing this firmware is the fact I can't reprogram them! After some head scratching I realized (after some Googling) that it's because the fuse bits are set for an 8MHz crystal and the MCU won't start at all (even for programming) without one in place.

This is about the dumbest fycking thing I've ever seen! Why the hell wouldn't Atmel have designed the chip to default to a "safe mode" using the internal oscillator during programming?

Since I don't have any 8MHz crystals laying around I'm just using male to female jumper straps to go from the xtal ports on the socket to the chip's pins during programming.

(For the record, I'm an MSP430 and ARM programmer mainly, so the concept of setting these type of things via fuses is very alien to me. It seems especially dumb to have clock settings done this way since you can basically lock yourself out of the chip unless you happen to have a HV programmer laying around. I much prefer setting the clock speed via software registers, which has the added advantage of dynamic frequency selections to save power!)


Sent from my Smartphone

[madires]

Since I don't have any 8MHz crystals laying around I'm just using male to female jumper straps to go from the xtal ports on the socket to the chip's pins during programming.

Some ISP programmers provide a clock signal for those cases.

[timb]

Yeah, I've only got a Bus Pirate and hand-built ArduinoISP Shield (with 16MHz crystal installed). I guess I could generate an 8MHz clock with my function generator? Still a pain the ass though.


Sent from my Smartphone

[con-f-use]

Am I mistaking or is the MCP1700 rated at 6V input, but connected to the 9V battery?

[madires]

Am I mistaking or is the MCP1700 rated at 6V input, but connected to the 9V battery?

The recommended LDO voltage regulator is a MCP1702 which supports an input voltage up to 13.2V.

[con-f-use]

Thank you, I thought so. I have another set of question, if you're a not fed up already:

As I was skimming through the svn repository, I was a bit con-f-used by the following passage in the Makefile:

# The WITH_UART option enables the software UART  (TTL level output at Pin PC3, 26).
# If the option is deselected, PC3 can be used as external voltage input with a
# 10:1 resistor divider.
#CFLAGS += -DWITH_UART

# With option TQFP_ADC6 or/and TQFP_ADC7 you can use the additional pins of the TQFP or
# the QFN package for external analog input. You should install a 10:1 voltage dividers
# on the selected pin(s).
# If both pins are defined, both voltages are measured with the voltage measure function.
# But for zener diode measurement the ADC6 pin is used, if both pins are defined.
CFLAGS += -DTQFP_ADC6
CFLAGS += -DTQFP_ADC7

# For ATmega8/168/328 processor the option WITH_VEXT can only be set, if the PC3 pin
# is not used for serial output (WITH_UART option).
# For ATmega644/1284 processor the UART has a separate pin.  Therefore the external input
# at pin ADC3 can be enabled separate by setting the WITH_UART option.
CFLAGS += -DWITH_VEXT

So you can measure Zeners or a voltage on ADC6 and additionally another external voltage on ADC7. Do you have to set -DWITH_VEXT for that? I assume not as VEXT says it "can only be set if the PC3 pin is not used." It would be annoying having to abstain from UART to measure voltages.

PC3 gives UART output. If you don't set  -DWITH_UART, you can set -DWITH_VEXT and get an extra voltage input, right? Does that make three  extra voltage inputs, when  -DTQFP_ADC6 and  -DTQFP_ADC7, -DWITH_VEXT are set and -DWITH_UART is not?

Why is there even -DWITH_VEXT and -DWITH_UART? Wouldn't one of them suffice if you can't use VEXT with UART enabled? If you disable UART and VEXT, does PC3 do nothing?

Finally, why is the voltage reference only used for measuring the battery voltage? I'd imagine the whole thing would be more accurate if you calibrated against the optional external voltage reference.

[madires]

So you can measure Zeners or a voltage on ADC6 and additionally another external voltage on ADC7. Do you have to set -DWITH_VEXT for that? I assume not as VEXT says it "can only be set if the PC3 pin is not used." It would be annoying having to abstain from UART to measure voltages.

Yes, you should set WITH_VEXT if you're using ADC6 and/or ADC7 together with WITH_UART. Just the combination of WITH_VEXT and WITH_UART without TQFP_ADC6 or TQFP_ADC7 set doesn't work. TQFP_ADC6 and TQFP_ADC7 are switches for re-defining the pins used for the external voltage measurement.

PC3 gives UART output. If you don't set  -DWITH_UART, you can set -DWITH_VEXT and get an extra voltage input, right? Does that make three  extra voltage inputs, when  -DTQFP_ADC6 and  -DTQFP_ADC7, -DWITH_VEXT are set and -DWITH_UART is not?

No, either you got PC3 or ADC6/ADC7.

Why is there even -DWITH_VEXT and -DWITH_UART? Wouldn't one of them suffice if you can't use VEXT with UART enabled? If you disable UART and VEXT, does PC3 do nothing?

Both are options. If you don't set any of them, both are disabled and PC3 is unused.

Finally, why is the voltage reference only used for measuring the battery voltage? I'd imagine the whole thing would be more accurate if you calibrated against the optional external voltage reference.

No, the external voltage reference is used to determine the offset of Vcc (5V). That offset is used for all measurements.

[hapless]

Why is there even -DWITH_VEXT and -DWITH_UART? Wouldn't one of them suffice if you can't use VEXT with UART enabled? If you disable UART and VEXT, does PC3 do nothing?

I'm afraid I might be at least partially responsible for that by virtue of suggesting that when I have no use for serial output, I would rather not waste the microcontroller's resources on generating extra data and noise on the PC3 pin. Prior to this option being available in the make file, I had to go into the source and comment out the #define lines for VEXT because unsetting WITH_UART would result in the device trying to measure voltage every time I accidentally held the test button in a little longer. Very annoying when you have no zener extension.

[AlessandroAU]

Hey Alessandro

That's the "LCR T3" design.

Any chance you can read the flash and EEPROM and email to me ?

These ones use an older version of the firmware but I'm trying to figure out that display so it can be upgradeable.

That one you have has a 6pin ISP pin pad but it's reversed on the component side



Sent from my iPhone using Tapatalk

I tired to read the chip using my tl866. I can get the chip ID fine, but when I try to read from it just appears blank. Some form of copy protection?

[pol098]

In case anyone is interested in the graphics versions: they are described and sold within China on a Web site in Chinese only:
http://fish8840.taobao.com/ I prefer to open it in Google Chrome, which offers to translate it automatically, or on a right-click. I don't know whether the many sources of these devices buy from fish8840 (in which case they'd be all be of equal quality) or make their own copies.

Presumably fish8840 is the originator of the Chinese hardware versions (although they themselves may be imitated!), and weiweitm adapted the software. The reason for production of a graphics version given is that a text-only display in Latin characters is difficult for Chinese people, which makes sense; there are traditional and simplified Chinese, and English-language versions. There are two versions, an older one with a green display, and a later one with a slightly larger blue display; both are sold, with the blue one a little more expensive. The pictures don't show a crystal visible on the board; it could be there but hidden. As far as I can tell the later board was released in March 2014; the only software appears to be weiweitm's version 2.1 (with no mention of providing source code). I don't know if there is any provision at all for software updates (socketed chip, header, any intention to produce downloadable updates). There is a picture of an elegantly cased version, branded Yiwanjia, but no indication (such as price) that it exists.

Foreigner Markus F is acknowledged. The translation is difficult to understand in detail; I think Translate's "shelves without shell" are uncased boards!

Web pages of the two hardware versions (Chinese):
Larger screen, blue, backlit 25/3/2014, software shows as 2.1 on pictures:
http://item.taobao.com/item.htm?spm=a1z10.5.w4002-2323427594.16.IhvBUf&id=36323329572
Smaller green graphics screen version:
http://item.taobao.com/item.htm?spm=a1z10.5.w4002-2323427594.19.IhvBUf&id=37659767669

[madires]

Foreigner Markus F is acknowledged. The translation is difficult to understand in detail; I think Translate's "shelves without

Evidently the firmware is based on Karl-Heinz' source code. So much for proper credits.

[hapless]

I suspect that they are simply ignorant of the fact that someone other than "Foreigner Markus F." needs to be credited. Maybe if you or K.-H. contacted them and told them what needs to be done, this could be easily corrected. Just a thought.

[Alex1]

I bought one of the blue testers http://www.ebay.co.uk/itm/New-Transistor-NPN-PNP-MOSFET-Diode-Tester-Capacitor-ESR-Resistor-Meters-UK-Ship-/271551234681 the other day and its a great piece of kit for the price but I had to carry out some modifications to get it to behave.

1.
It would sometimes display "VCC=x.xV" underneath the battery voltage and according to ttester_eng110k.pdf this should only happen if there is a voltage reference installed, which this one does not have. The voltage it would show changed every measurement along with the test result, a 2.2k pull-up resistor from VCC to pin 27 fixed this.

Missing precision voltage reference Usually the software should detect the missing voltage reference with the unconnected pin PC4. In this case no VCC=x.xV message should appear in row 2 of the LCD on power on. If this message appear without the reference, you should connect a 2:2k resistor to the PC4 input and VCC.

It was almost like it was switching between the internal reference and what ever pin 27 was floating at, for example the battery voltage would randomly go from reading 8.5v to 7v and then 9v. The test results were only accurate when the uC detected no reference was installed.

2.
The AMS1117-5.0 voltage regulator was missing bypass capacitors on its output so I paralleled up a 100nF and 22uF as per the datasheets recommendation. Looking on my oscilloscope I noticed a slightly cleaner output and a much better transient response. Not sure if this makes any difference to measurements though.

3.
C1 was missing on the AREF pin so I installed a 1nF as per the manuals suggestion (I have firmware version 1.11k).

4.
On mine the wire to the green front cover connector had a dry solder joint so I redid it, on closer inspection each connector has a small hole on the end for the wires to thread through but for some reason they were ignored during manufacturing.

5
The track routing for AGND at pin 22 took a separate and very scenic route around the PCB before it met up with pin 7 and the uC's decoupling capacitor, effectively isolating it from said capacitor. So I soldered a 100nF ceramic directly across pins 20 and 22 in an attempt to reduce the effects of the long trace on the analog sections supply rails.

This image shows the additional capacitor and the long route from AGND to the regulator and factory decoupling cap on pin 8 GND.



Too anyone who has one of these, have you noticed that the ESR measurements tend to change depending on which way around you have the probes? Seems to be related to the temperature of the capacitor and my fingers heating it slightly, the warmer the cap the lower the ESR reading.

[pol098]

... Maybe if you or K.-H. contacted them and told them what needs to be done, this could be easily corrected ...

It might even be interesting for somebody (I think it would have to be someone who knows Chinese) to contact the people making the Chinese graphics devices and software, welcome their activity, and suggest that they could add their contributions to the shared software, that they would get useful feedback from here (e.g. Alex1's recent detailed contribution should be helpful to them), and that a system could be set up to distribute updates? They could even sell pre-programmed ATmega328s to those who don't want to do it themselves.

I hope this doesn't step on the toes of the legitimate developers here, not my intention, just a "more the merrier" idea.

[amtpdb]

I just purchased the one listed below. Does anyone have any suggestions on what should be done to make it more accurate or better? By this I see that some of you replaced resistors and caps, reprogrammed the chip (where is the latest update?).
Thanks for any help. I have been following this thread for some time but still  don't know too much about electronics but want to learn! That is one reason I purchase this item.
Thanks

http://www.ebay.com/itm/291041497713?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[madires]

It might even be interesting for somebody (I think it would have to be someone who knows Chinese) to contact the people making the Chinese graphics devices and software, welcome their activity, and suggest that they could add their contributions to the shared software, that they would get useful feedback from here (e.g. Alex1's recent detailed contribution should be helpful to them), and that a system could be set up to distribute updates? They could even sell pre-programmed ATmega328s to those who don't want to do it themselves.

That's a good idea! I always encourage contributors and users to send bug reports, add-ons, modifications and so on.

[Alex1]

@madires Looking on a scope during a capacitance test it seems that this tester will apply a high reverse voltage directly across the capacitor during one half of the cycle, which for an electrolytic is bad.

Should it be placing such a reverse voltage across the capacitor?

Below shows my scope which is DC coupled to the output of the tester with a 1200uF capacitor connected across it. Shouldn't this cause the capacitor to break down during one half of the test cycle?



2v/div 500ms/div

[texaspyro]

It's not long enough or high enough of a voltage/current to do any damage.

[Alex1]

It's not long enough or high enough of a voltage/current to do any damage.

But wouldn't it be safer to limit the test voltage to something under a capacitors reverse breakdown voltage of 1.5v?