$20 LCR ESR Transistor checker project

[Feliciano]

Actually I'm busy now, so maybe someone else wants to take the lead from here.

[Kim Christensen]

I think that the issue is not the new or old version of m-firmware, but the fact that your FNIRSI clone tests electrolytes completely differently from Kim Christensen. I think that there is some other hardware difference from the standard in these clones that does not allow the firmware to function normally. Or the firmware is not yet fully adapted.

I assume the one on the right is Feliciano's unit:




EDIT: Updated to better picture. Ignore the test loop wire.
From what I can see, it looks identical to mine. I'll do some double checking of the schematic against my unit:

[Feliciano]

Yes, the one under study is the one the right. I also uploaded a high-res photo of the MCU and it's traces and external components, just in case.

Please also check the LCR-related configuration, because it seems the error is in that use-case, and with relative large capacitors.

UPDATE:
For my unit and 1.51m configuration, and for the LCR-Monitoring feature: Capacitors <22uF are quickly detected with reasonable values. Larger capacitors are either not detected or seldom detected as Inductors (normal measurements for those work properly, 'though).

Code: [Select]

#define SW_INDUCTOR
#define SW_ESR
//#define SW_OLD_ESR
#define SW_ESR_TOOL

#define SW_CAP_LEAKAGE
#define SW_MONITOR_RCL        /* R plus L, or C plus ESR */
//#define SW_MONITOR_HOLD_ESR   /* auto-hold ESR (C monitor) */
//#define SW_MONITOR_HOLD_L     /* auto-hold L (L monitor) */
#define SW_C_VLOSS


[Kim Christensen]

Feliciano or indman,
What AVR toolchain are you using? Googling shows some old ones like WinAVR and then newer stuff like Microchip Studio. I've never programmed with AVRs. Just PICs and older stuff like 68HC11, etc so it's a bit of a learning curve.

Hardware wise:
On my unit, the 78L05 is dropping out of regulation since U6, the SDB628 boost reg, is only outputting 6.5V (R18/R19 sets it to a nominal 6.6V but tolerances give me a bit less). So the 5V line was fluctuating at around 4.8-4.9V. I temporarily bridged a 100K resistor across R19 which boosted the input voltage to the 78L05 to 7.1V... Then the 5V stabilized. While it didn't make any significant difference to the capacitance readings, I did notice that it effected the battery voltage readout which leads me to believe the firmware I'm using doesn't use the TL431 reference and instead uses the 5V supply as the reference.

I did notice an error on your schematic though:

[indman]

I did notice an error on your schematic though:

I will correct this inaccuracy on my schematic, but it's not essential. I'm more interested in what is the capacitance rating of C13 and C10 on your board?
And one more question - PB1(41pin) is connected to +5V through resistor R7. It is also directly connected to somewhere else through a via hole. Where?

[indman]

Kim Christensen,Feliciano, check this new firmware for your clones. How will large capacitances be measured on it?
It would also be useful if you provided the results of hardware self-tests T1-T6 and self-correction tests A1-A6.

[Feliciano]

What AVR toolchain are you using?

I'm ussing the original that came with WinAVR2010, because if I replace it with the one I used to use, it gave me errors when trying to enable hardware SPI (which we don't use for this case anyways).

Hardware wise:
On my unit, the 78L05 is dropping out of regulation since U6, the SDB628 boost reg, is only outputting 6.5V (R18/R19 sets it to a nominal 6.6V but tolerances give me a bit less). So the 5V line was fluctuating at around 4.8-4.9V. I temporarily bridged a 100K resistor across R19 which boosted the input voltage to the 78L05 to 7.1V... Then the 5V stabilized. While it didn't make any significant difference to the capacitance readings

I also noticed the same, the boost is giving me 6.xV, but the linear regulator seems to hold 5V (haven't had time to check thouroughly). I was considering reinforcing the boost capacitor (that was giving me trouble at the begining), but now you mention the resistor mod and its effects, I will consider it too.

I did notice that it effected the battery voltage readout which leads me to believe the firmware I'm using doesn't use the TL431 reference and instead uses the 5V supply as the reference.

IIUC, for Vref you can choose to read the TL431, or use the internal Vcc/2 of the ATmega (which I'm currently using):

Code: [Select]

/*
 *  2.5V voltage reference for Vcc check
 *  - default pin: PC4 (ATmega 328)
 *  - should be at least 10 times more precise than the voltage regulator
 *  - see TP_REF in config-<MCU>.h for port pin
 *  - uncomment to enable and also adjust UREF_25 below for your voltage
 *    reference
 */

//#define HW_REF25


/*
 *  Typical voltage of 2.5V voltage reference (in mV)
 *  - see datasheet of the voltage reference
 *  - or use >= 5.5 digit DMM to measure the voltage
 */

#define UREF_25           2495

#define TP_REF           PA3       /* test pin for 2.5V reference and relay */


[Kim Christensen]

Kim Christensen,Feliciano, check this new firmware for your clones. How will large capacitances be measured on it?
It would also be useful if you provided the results of hardware self-tests T1-T6 and self-correction tests A1-A6.

Thanks. I'll update my unit in a bit. Need to sort out my dodgy AVR programming hardware first. Was using AVRdude and ponyser, a serial port bit-banger which was glacially slow via a USB to serial adapter. I knew it would be slow trying to bitbang via USB-->Serial but it was much slower than I expected. 
Going to try an older computer that has a legacy serial port, but gotta get it up and running 1st.

Meanwhile, here the test results from the previous firmware you gave us. I'll post another test result after updating with your latest firmware:
Just ignore my nose/mouth reflection.

[Feliciano]

I did notice an error on your schematic though:

I will correct this inaccuracy on my schematic, but it's not essential. I'm more interested in what is the capacitance rating of C13 and C10 on your board?
And one more question - PB1(41pin) is connected to +5V through resistor R7. It is also directly connected to somewhere else through a via hole. Where?

Besides what Kim Christensen reported earlier, R7 goes between pin 41 and Vcc. On that side of the PCB, pin 41 also goes to the tip of EN test point. Therefore, EN don't go to the Crystal array, that part of the schematic need rework. /Reset is pulled high by R14. And regarding C13 C10, it would have to be removed to be measured, because on circuit it detects a diode in both cases (and I ran some wires over it, so it would require extra work for my case). FWIW, with a DMM C13 measures 100nF or 470nF and I couldn't get a reading for C10.

[Kim Christensen]

Kim Christensen,Feliciano, check this new firmware for your clones. How will large capacitances be measured on it?
It would also be useful if you provided the results of hardware self-tests T1-T6 and self-correction tests A1-A6.

Ah... So much faster/reliable using a legacy serial port.
OK, here's the updated capacitance readings. Looks pretty much the same as the last version:

Cap       "Auto"   "LCR mon"
1uF        1.083    1.079
10uF      10.35    10.33
39uF      37.75    38.35
120uF    103.6    124.6
270uF    162.0    272.9
680uF    342.2    625.6
1000uF  525.3    960.7
3900uF  3240     3790

I used the same capacitors as last time. Here's the previous readings for easy reference:

Cap       "Auto"   "LCR mon"
1uF        1.039    1.038
10uF      9.929    9.953
39uF      36.29    37.02
120uF    99.79    120.1
270uF    155.6    262.5
680uF    328.3    599.5
1000uF  392.9    932.0
3900uF  3017     3657

And the new self tests/corrections:

[Feliciano]

Kim Christensen,Feliciano, check this new firmware for your clones. How will large capacitances be measured on it?
It would also be useful if you provided the results of hardware self-tests T1-T6 and self-correction tests A1-A6.

Thanks. Your binaries probe there's something in the configuration that affects measurements of large capacitors (large meaning >22uF for my configuration).

As study subject I keep using the "SANYO" 1000uF/35V:

• With my 1.51m, the normal measurement shows values close to 1000uF, but the LCR monitoring some cycles detect nothing, some cycles goes bananas and reflect an 8uH inductor. To rise the boost converter output to 7V and/or to enable/disable the TL431 ref makes no big difference in that regard
• With your 1.51m binaries, the normal measurement shows 430uF, and the LCR monitoring shows 1300uF the first time, and 880uF afterwards

I attach the calibration and test results, with test leads.

[Kim Christensen]

I also noticed the same, the boost is giving me 6.xV, but the linear regulator seems to hold 5V (haven't had time to check thouroughly). I was considering reinforcing the boost capacitor (that was giving me trouble at the begining), but now you mention the resistor mod and its effects, I will consider it too.

Another option would be to replace the 78L05 with a 5V LDO regulator of the same pinout. The only negative I see with increasing the boost voltage, is reduced battery life as a bit more power is dissipated in the 5V linear reg, but it's the simplest of the options.
BTW, I measured the current draw off the battery at various voltages. Fluctuated at bit as it did it's thing:
3.10V = 155-200mA
3.80V = 120-150mA
4.14V = 107-132mA

[Feliciano]

As by your measurements, I don't mind disipating additional 100mW or so as long as the equipment work properly.

(Perhaps a more precise schematic could help).

[indman]

Besides what Kim Christensen reported earlier, R7 goes between pin 41 and Vcc. On that side of the PCB, pin 41 also goes to the tip of EN test point. Therefore, EN don't go to the Crystal array, that part of the schematic need rework. /Reset is pulled high by R14. And regarding C13 C10, it would have to be removed to be measured, because on circuit it detects a diode in both cases (and I ran some wires over it, so it would require extra work for my case). FWIW, with a DMM C13 measures 100nF or 470nF and I couldn't get a reading for C10.

OK! I updated the circuit diagram again, it remains to clarify where the PD0 (9pin) port of the controller is connected?
C13 - I believe that on your board it is set to 100nF. C10 should be 1nF, in principle it can be safely removed from the board, this should not affect the measurement results in original firmware. But it is advisable to check this!

And the new self tests/corrections:

The results of your tests indicate that the +5V voltage is poorly stabilized. You need to replace the 7805 with a better LDO.

[Yuriy_K]

From what I can see, it looks identical to mine. I'll do some double checking of the schematic against my unit:

Several years ago I assembled my testers on the ATMega 644. Now I don’t remember why, but I had to change some of the capacitance values. Here in your diagram I indicated my values...

Added. In the Hiland M644 C13, according to your circuit, the manufacturer initially installed 220nF.

[Feliciano]

it remains to clarify where the PD0 (9pin) port of the controller is connected?

Pin 9 goes to RxD, pin 10 to TxD and pin 7 of U8. And the rest of U8 part of the schematic seems right.

C13 - I believe that on your board it is set to 100nF. C10 should be 1nF, in principle it can be safely removed from the board, this should not affect the measurement results in original firmware. But it is advisable to check this!

IIUC, C13 is the Capacitor used for Adjustement, and C10 is the bypass Capacitor of the Aref, right? Yuriy_K thinks these Capacitors should be higher, though.

[indman]

C13 is the Capacitor used for Adjustement ?

Yes, this capacitor must be high quality and stable. In the config.h setting, you can disable this installed capacity so as not to unsolder it from the board. Instead, you can use an external high quality capacitor for the Adjustement procedure. Then you will need to measure this capacity 3 times in a row before the Adjustement procedure.

C10 is the bypass Capacitor of the Aref, right?

C10 is the setting of the ADC voltage scale switching speed. For correct operation of autors firmware, its capacity should not exceed 1nF. As I wrote above, it can be removed from the board and this should not affect the test results in any way.

P.S The circuit diagram has been updated once again in my post #9226

[madires]

One thing I did notice with this version is that there is a discrepancy in the capacitance measured depending on what mode it is operating in. Does your unit also show vastly different capacitance readings between "Probing..." mode and "LCR Monitor" mode for certain values? I did perform both a "Test" and an "Adjustment" thinking that was the issue but it wasn't. For example this is what I measured in uF:

Cap       "Auto"   "LCR mon"
1uF        1.039    1.038
10uF      9.929    9.953
39uF      36.29    37.02
120uF    99.79    120.1
270uF    155.6    262.5
680uF    328.3    599.5
1000uF  392.9    932.0
3900uF  3017     3657

There's something very wrong! The values in the normal probing cycle and in the C or RCL monitor should be nearly the same. For electrolytic caps a small difference (about 1%) is normal. This is caused by the different checks run in both modes before the capacitance measurement. Despite discharging and offset compensation a small charge difference can build up and lead to a small error. Anyway, both modes use exactly the same capacitance measurement functions. Your problem could be related to the power supply or some component drawing excessive current.

[Kim Christensen]

madres,

If "both modes use exactly the same capacitance measurement functions", shouldn't they both give the same reading even if there was a hardware fault?
The readings are highly consistent and repeatable in both modes. So there must be some differences between the two measurement modes firmware wise, because code is the only thing that changes between modes.
My unit was working Ok with the original Chinese firmware, but that firmware had a bit of a bug where it wouldn't consistently measure ESR so I decided to try changing the firmware. ie: It would randomly give me vloss only and other times give both vloss and ESR.
In the end if I can't figure it out, I'm OK with just using my unit in LCR monitor mode when measuring capacitors. But it'd be nice if it worked properly in both modes.

[Feliciano]

If "both modes use exactly the same capacitance measurement functions", shouldn't they both give the same reading even if there was a hardware fault?
The readings are highly consistent and repeatable in both modes. So there must be some differences between the two measurement modes firmware wise, because code is the only thing that changes between modes.

+1

madires:

As Kim says, if allegedly being the same algorithm for normal measurements and for LCR monitoring, I don't understand why the big inconsistence,

and on the other hand, why indman's configuration reflect way so different values than mine's for both scenarios. Maybe he set a very different compensation or default values? (because his readings varies a lot after adjustment, but still doesn't reach the expected values), and more important, why his LCR monitoring somehow works and mine doesn't.

Code: [Select]

#define CAP_FACTOR_SMALL      -25    /* -2.5% */
#define CAP_FACTOR_MID        -15    /* -1.5% */
#define CAP_FACTOR_LARGE      10     /* +1.0% */

Maybe Kim Chirstensen wants to try my attached binaries for a separate comparison.

Lastly, regarding the power supply, I modded the booster to 7V, and upgraded C9 from 100nF to 1uF.  For my config I didn't notice major difference. As shown in the photos versus my previous posts.

[Kim Christensen]

Maybe Kim Chirstensen wants to try my attached binaries for a separate comparison.

Here's my results with your firmware. I had the same thing as you. Looks better in auto probing mode, but now LCR Monitor mode is messed up with larger caps:

Cap       "Auto"   "LCR mon"
1uF        1.054    1.053
10uF      10.64    10.64
39uF      42.48    -----
120uF    144.5    -----
270uF    312.7    -----
680uF    740.4    -----
1000uF  1144    8.36uH 0.0R
3900uF  5212     8.36uH 0.0R

----- = no reading

I also noticed that if I short the leads in LCR monitor mode, then it reads 0.05R 8.36uH.

[Feliciano]

Anyway, both modes use exactly the same capacitance measurement functions.

You know the code better. Could it be the LCR monitor uses a particular pin that the normal testing function doesn't use, and we, or a least me defined it wrong?

Kim: Your equipment and mine behave the same. Have you tried the LCR monitor of 2hry firmware posted few pages back?

[madires]

If "both modes use exactly the same capacitance measurement functions", shouldn't they both give the same reading even if there was a hardware fault?
The readings are highly consistent and repeatable in both modes. So there must be some differences between the two measurement modes firmware wise, because code is the only thing that changes between modes.

Again, the same capacitance measurement function is called in both cases. The only difference is the frontend function (user interface).

As Kim says, if allegedly being the same algorithm for normal measurements and for LCR monitoring, I don't understand why the big inconsistence,

Neither do I. It's the first time that such an issue is reported. I've checked a 1000µF electrolytic in normal probing mode, C monitor and  RCL monitor running 1.51m and the values are fine. I think there is something else wrong.

[madires]

You know the code better. Could it be the LCR monitor uses a particular pin that the normal testing function doesn't use, and we, or a least me defined it wrong?

The monitor functions use probes #1 and #3, You could check if the probe pins and the resistor pins are all correct and that there are no additional components (besides the input protection).

[Feliciano]

I tried again 2hry's binaries, observing similar behaviour as indman's.

I also checked the configuration against the schematic, and seems correct. There is something else we're overlooking, or the schematic still doesn't match the PCB and/or values. (BTW: I think C26 is not on the PCB, the one near pin 17 is C8. Before modding, I measured a total of 600nF from Vcc to GND).

indman or 2hry: please compare my config against yours, so we can figure out why the same firmware work so different, and get the best of each settings. (Of course madires is welcome to have a look at it as well).