$20 LCR ESR Transistor checker project

[f1rmb]

Hi,

Anyone have any idea what might be causing mine to display an underscore at the end of the text?

The attached photos demonstrate what is happening, that underscore is always present after the last character.

It's just the LCD cursor.

Cheers.
---
Daniel

What would cause it to be displayed? It doesn't blink and on other units I've seen that are the same as this one it doesn't show up.

Maybe you may give us more details, e.g what is the firmware version running on your tester.

Cheers.
---
Daniel

[Alex1]

Hi, its running version 1.11k which is what it came with. Would it be a software thing or can the cursor showing up be hardware related?

[madires]

Hi, its running version 1.11k which is what it came with. Would it be a software thing or can the cursor showing up be hardware related?

I think that there's a problem with the initialization of the LCD module which causes the cursor to be displayed. The cursor should be disabled by default. It's just a single bit in the "display on/off" command.

[Alex1]

I think that there's a problem with the initialization of the LCD module which causes the cursor to be displayed. The cursor should be disabled by default. It's just a single bit in the "display on/off" command.

Hi, so there could be something wrong with the LCD module itself? The LCD board has "1602a v2.0" on the back of it if that makes a difference.

Thanks.

[madires]

Hi, so there could be something wrong with the LCD module itself? The LCD board has "1602a v2.0" on the back of it if that makes a difference.

Or maybe a flipped bit in the firmware. You could check that with another character display.

[Alex1]

Hi, what does a "flipped bit" mean? Does it mean something went wrong when they flashed the chip with the firmware?

[madires]

Hi, what does a "flipped bit" mean? Does it mean something went wrong when they flashed the chip with the firmware?

Yes, something like that. A flipped bit is a bit which should be 0 but changed into 1 for whatever reason, or vice versa.

[coromonadalix]

Some lcd  dont have u3 the 8 pins soc ic, usually an tc7660 dc dc  converter and caps ...   for the contrast voltage (normally pin 3 of the lcd)  had a few problems in the past until i found that some lcd need an negative voltage, some don't    ....

Maybe thats your problem ??

[madires]

Some lcd  dont have u3 the 8 pins soc ic, usually an tc7660 dc dc  converter and caps ...   for the contrast voltage (normally pin 3 of the lcd)  had a few problems in the past until i found that some lcd need an negative voltage, some don't    ....

Maybe thats your problem ??

I don't think so. Have you seen his pictures a few posts ago? The contrast is fine.

[tom666]

Anyone have any idea what might be causing mine to display an underscore at the end of the text?
The attached photos demonstrate what is happening, that underscore is always present after the last character.

I may be wrong. But underscore indicates the uncalibrated tester. This applies to firmware by Karl-Heinz Kübbeler.

[madires]

I may be wrong. But underscore indicates the uncalibrated tester. This applies to firmware by Karl-Heinz Kübbeler.

Ah, I missed that feature (was added in v1.10k).

[firepower]

I get a C at the end of "testing...C" is that also mean uncalibrated?

[tom666]

I get a C at the end of "testing...C" is that also mean uncalibrated?

I recently received from the author of software this answer:
The character "C" is output on line 2 of the tester, when the capacity measurement begin. It helps a little to analyse, where the time is wasted for the measurement cycle.

[madires]

I get a C at the end of "testing...C" is that also mean uncalibrated?

I recently received from the author of software this answer:
The character "C" is output on line 2 of the tester, when the capacity measurement begin. It helps a little to analyse, where the time is wasted for the measurement cycle.

The measurement of caps with a large µF value needs some time. To indicate that that tester hasn't crashed and that the user should be patient, the 'C' is displayed. Since the capacitance measurement is time critical, a progress bar or whatever wouldn't be easy to implement.

[JohnPen]

Having done the stupid thing of turning down the contrast on my nice new tester I can no longer see anything to bring it back up.  It has the 1.12K s/w and is a GM328 model. Has anyone any suggestions how to recover??
John

[firepower]

Do you have an AVR ISP, could try erasing eerom that stores the setting , that should default it. Or program default values. I have same model GM328A with smd micro, but have updated my firmware from factory original. When I get home I go through the menu and see how many button presses is needed to get to contrast menu.

Thanks for info about C tom666 and madires

Long press menu:
Transistor
Frequency
f-Generator
10-bit PWM
C+ESR@TP1:3
R+L
Capacitor
Rotary encoder
Selftest
Contrast
Show data
Switch Off
Then Back to Transistor.

Try long press, 9 short presses, long press then many short until  display contrast comes back
It usually dark > light > black > dark etc

[JohnPen]

Thanks for the info Firepower.  I eventually managed to step correctly to the Contrast  menu item and managed to recover the display.  Because I had problems getting the count right with the appropriate button duration press I cheated a little by using a scope to identify the frequency generator menu setting (pin 1 and 2 for scope) and then the 10 PWM  to get close enough to be sure of getting Contrast.  I had found pressing the button my duration's didn't always get me where I thought I was on the invisible menu!  One thing is certain I am not touching contrast again.  I am a bit surprised that a Master Reset doesn't bring it back to a default display setting it must start there at the very first power up.

Thanks John

[bob808]

I finished mine today. And it works great!
I had some issues with a few shorts on the pcb due to the nature of it's fabrication but I sorted that out (with one fried transistor only) and I loaded both firmwares. I will have to play some more with them, but so far I like it.
I testes some germanium diodes and I have a big Vf compared to my multimeter (~0.6V vs ~0.25) but the rest of the parts check out ok.
I didn't manage to install 0.1% 680R and 470K resistors, I will upgrade those in the future.
I did use a 1702-5002 regulator and lt1004-2.5 voltage reference.
I was interested mainly in having a transistor tester for matching transistors, but the extra features are handy.
I still need to put some conformal coating on the back of the pcb so it doesn't oxidise but I'll do that after I upgrade the resistors.
So far good job and a big thank you to the creators!

[montarbo]

I finished mine today. And it works great!
I had some issues with a few shorts on the pcb due to the nature of it's fabrication but I sorted that out (with one fried transistor only) and I loaded both firmwares. I will have to play some more with them, but so far I like it.
I testes some germanium diodes and I have a big Vf compared to my multimeter (~0.6V vs ~0.25) but the rest of the parts check out ok.
I didn't manage to install 0.1% 680R and 470K resistors, I will upgrade those in the future.
I did use a 1702-5002 regulator and lt1004-2.5 voltage reference.
I was interested mainly in having a transistor tester for matching transistors, but the extra features are handy.
I still need to put some conformal coating on the back of the pcb so it doesn't oxidise but I'll do that after I upgrade the resistors.
So far good job and a big thank you to the creators!

Nice work.
Mind sharing the PCB file in PDF with 1:1 scale and part list. Thanks ahead.

[madires]

Just a brief update about the m-firmware. There will be two editions in the future. The current firmware, supporting ATmega168/328 with a 2x16 HD44780 character display, will be called classic edition. The second edition (no name yet) supports the ATmega328 with character and graphic displays. For the start, HD44780 and ST7565R drivers are included. The UI automatically adapts to the available number of lines. Later on I'll add support for ATmega644/1284, fancy pinout and additional display controllers. If you like to support the development, I would appreciate samples of LCD modules with other controllers. V1.18m of both editions will be released within the next week or so.

[neslekkim]

Later on I'll add support for ATmega644/1284, fancy pinout and additional display controllers.

Are there pcb's available for these?

[madires]

Later on I'll add support for ATmega644/1284, fancy pinout and additional display controllers.

Are there pcb's available for these?

Not yet, AFAIK.

[bob808]

I finished mine today. And it works great!
I had some issues with a few shorts on the pcb due to the nature of it's fabrication but I sorted that out (with one fried transistor only) and I loaded both firmwares. I will have to play some more with them, but so far I like it.
I testes some germanium diodes and I have a big Vf compared to my multimeter (~0.6V vs ~0.25) but the rest of the parts check out ok.
I didn't manage to install 0.1% 680R and 470K resistors, I will upgrade those in the future.
I did use a 1702-5002 regulator and lt1004-2.5 voltage reference.
I was interested mainly in having a transistor tester for matching transistors, but the extra features are handy.
I still need to put some conformal coating on the back of the pcb so it doesn't oxidise but I'll do that after I upgrade the resistors.
So far good job and a big thank you to the creators!

Nice work.
Mind sharing the PCB file in PDF with 1:1 scale and part list. Thanks ahead.

I attached the brd file. I think you should find the parts with values in it.
One piece of advice, I used 2.5mm pitch non polarised caps. If you want to use 5mm ones just be sure they have longer leads.
I can't even remember how I started this project, I may have gotten the eagle project and modify it.
Also do size the contrast resistor according to your LCD. (it's noted as 470ohms in the project, RLCD2)
Anyway, have fun.
PS I can't remember what the second set of connectors is for (Pin 26). I don't care, I really need this gizmo to test transistors mostly.

[tom666]

I like to do things as simple as possible and so I decided for this variant of tester. This is a version of my PCB design in minimal form (VSCT = Very Simple Componet Tester  ).

Features of Tester are preserved and identical to the standard version, but without auxiliary power circuit - it is necessary to use manual switching power on and off. I recommend compile software with blocked the auto power off (#CFLAGS += -DPOWER_OFF) - disable auto power off.

Crystal and 2.5V reference voltage source (which may to some extent contribute to improvements in measurement precision) has been omitted.

LCD contrast trimmer 10k was replaced by 2k7 resistor connected between the GND and the LCD contrast adjustment pin.

I chose commonly available LDO stabilizer 78L05.

Fuse setting:
ATmega168, ATmega168p:
lfuse:0xe2 hfuse:0xdc efuse:0x01 (0xf9)

ATmega328, ATmega328p:
lfuse:0xe2 hfuse:0xd9 efuse:0x04 (0xfc)

[montarbo]

I think you should find the parts with values in it.

Well thanks a lot for sharing the brd file, any chance to get one with top view? just to get the parts list would be appreciated.

BR