$25 Component Tester - Too good to be true?!

Sorry for bumping this thread I just wanted to clarify that I do not think the larger LCD needs special programming. I was going over the source and it seems to provide detection for the type of display and then configures itself accordingly. The wiki page also seems to briefly mention the possible use of a dot matrix LCD. EDIT: Just googled the LCD controller referenced in the wiki for dot matrix and it brought up pictures of many LCDs that were extremely similar to those found on these testers, definitely do not need custom firmware, the most you would need to do is program it with the proper firmware for the display controller you're using.

Also in theory it should not be hard to reprogram all you need is an AVR ISP programmer and one of these units with an ISP header which most of them seem to have.

As a side note I'm almost positive that the larger display units are using custom firmware as they display the website of the seller fish8840 although I do not think the custom firmware goes any further than that.

EDIT: There is actually a folder in the software titled fish8840, it would seem that the creator made a custom version for fish8840, interesting, wonder how much they paid him. I wonder if the hidden features noted previously would be available if it was reprogrammed with the normal firmware.
 
Last edited:
I just got one of these little gadgets, too. Works great so far. I have tried everything with it except for an inductor. But without a reference, it will be hard to say how accurate it is.

Another thing that may have been left overlooked in this thread. Make sure you use a >100 nF cap for calibration. I misread the instructions at first, and used 100nF 1% cap and after calibration it read about 96nF. After calibrating with a 12uF cap, it gave me 101.1 nF for the nominal 100nF cap which is right on the money.
 
I am considering an LED tester, and was curious if one of these would also work to test LED's down to 0.5mA... I am hoping to match some Silonex NSL32 to make an LDR attenuator, and these testers appear to be far more useful than a dedicated LED tester. Thanks.
 
restorer-john said:
they testers are good fun but in my experience with them, they are too slow, suffer from non-repeatable values and need a regulated supply to get any real consistency.
Click to expand...

Hi John.
Does this mean that it would be worthwile to hook up a 9v wall wart for power supply instead of using a 9v battery? Just curious. I plan on buying one of these next week and will look around for such a small power supply if it's a worthwile mod.

Cheers,
James
 
I have been using a 9V walwart since I got mine about two years ago. See post #7 on page #1. It can vary with the mains, but is reasonably consistent.
 
mortron said:
I am considering an LED tester, and was curious if one of these would also work to test LED's down to 0.5mA... I am hoping to match some Silonex NSL32 to make an LDR attenuator, and these testers appear to be far more useful than a dedicated LED tester. Thanks.
Click to expand...

Works for me. It tests them like regular diodes. I haven't tried it with any ultra low current LEDs though. It flashes a couple of times if its a good LED. The forward voltage estimates are on the low side, which tells me that its not feeding the LED much current.

For example, a green LED I just tested with it shows a Vf of 2.6V on the tester, but 3.0V when I give it 20mA. Still, it works better than the diode tester on my DMM.

Of course, its easy enough to test an LED with a 9V battery and a couple resistors...
 
so_ein_pech said:
Works for me. It tests them like regular diodes. I haven't tried it with any ultra low current LEDs though. It flashes a couple of times if its a good LED. The forward voltage estimates are on the low side, which tells me that its not feeding the LED much current.

For example, a green LED I just tested with it shows a Vf of 2.6V on the tester, but 3.0V when I give it 20mA. Still, it works better than the diode tester on my DMM.

Of course, its easy enough to test an LED with a 9V battery and a couple resistors...
Click to expand...

Thanks, I am trying to do some reading up on this unit. I am looking to match some items and the process for matching these LDR is:

"Match the LDR resistances using a DMM, powering the LED from 1mA to 20mA, give them time as they need a few minutes to warm up.Match the LDR resistances using a DMM, powering the LED from 1mA to 20mA, give them time as they need a few minutes to warm up."

Not sure if these units can do this. I am also curious as to how accurate these are for measuring caps and resistors... would I be better off spending $50 on a dedicated meter over this? I am not in need of most of the functions (maybe an intermediate skill level here), and my current project depends on matching caps and resistors very well.

Apologies if I derailed anything. Just trying to figure out if this would be too much for my need or something to pull the trigger on. Thanks in advance.
 
mortron said:
Thanks, I am trying to do some reading up on this unit. I am looking to match some items and the process for matching these LDR is:

"Match the LDR resistances using a DMM, powering the LED from 1mA to 20mA, give them time as they need a few minutes to warm up.Match the LDR resistances using a DMM, powering the LED from 1mA to 20mA, give them time as they need a few minutes to warm up."

Not sure if these units can do this. I am also curious as to how accurate these are for measuring caps and resistors... would I be better off spending $50 on a dedicated meter over this? I am not in need of most of the functions (maybe an intermediate skill level here), and my current project depends on matching caps and resistors very well.

Apologies if I derailed anything. Just trying to figure out if this would be too much for my need or something to pull the trigger on. Thanks in advance.
Click to expand...

Hmm... I think you are overthinking this. Sounds like a job for a battery, a couple of resistors, and, of course, a DMM.
 
Has anyone tried writing (or modifying) any code for these testors?

I think I read somewhere that accuracy could be improved with more detailed calibration, and using more samples for the calculations. This should also improve the repeatability.

I suspect that selected replacement of some components with precision parts could improve performance and/or accuracy. Precision parts could be hard-wired in for the calibration(s).

Just wondering - - -
 
ghazzer said:
Has anyone tried writing (or modifying) any code for these testors?

I think I read somewhere that accuracy could be improved with more detailed calibration, and using more samples for the calculations. This should also improve the repeatability.

I suspect that selected replacement of some components with precision parts could improve performance and/or accuracy. Precision parts could be hard-wired in for the calibration(s).

Just wondering - - -
Click to expand...

I don't believe anyone here has, or at least they've never mentioned it here. As I've said previously all you really need is an AVR ISP programmer and you're off to the races, the code is all available on the wiki.

I have looked at it briefly but was deterred by the amount of code and how to go about compiling it.
 
I can't see much reason to not want to try one of these units, but am concerned over the accuracy of the measurements. As I understand it is dependant on the calibration, but am wondering the following:

- How well explained is the operation of the various functions of this unit? Does one need to be quite advanced with electronics to do this?

- How consistent is the measurement on this? Like if you kept measuring the same cap every 15 minutes - would it always measure the same?

- How accurate is this as a % point? 1%?? 5%?

- Would this be a wise choice for someone in need of capacitance measurement and not able to buy a $200 Fluke or comparable DMM?

Thanks
 
I got one of these about a month ago. I decided to get a preassembled version with surface mount capacitors and resistors. I decided to use a wall wart for power but didn't realize the one I used was a 10 V AC not DC unit. I couldn't get it to work. I then used a 9 V battery with the same result. In checking the voltage between pins 7 and 22 on the IC plug, I got only about 1.5 volt. I then adjusted the LCD contrast and got a very faint image showing a low battery state. So, I thought I had killed it with the AC input or it came with a defective part.
I really wanted to get one of these working so I got another in kit form with through hole capacitors and resistors. It took several hours to assemble. I had another wall wart with a 10V DC output and everything worked fine. So, I used my new transitor tester to check the transistors on the first unit. I found a bad 2N5401 transistor. Fortunately, I had a spare so I put it in the first unit and it came back to life! So, I now have two working units.
I decided to do some comparative testing to try to attempt an assessment of precision and accuracy. Using a new 1 uF +/- 10% capacitor I got the following after putting both units through the selftest/calibration procedure and using the same power source.
The first unit gave the following for three tests: 996.6 nF, 995.9 nF, and 996.1 nF
The second unit gave the following for three tests: 1007 nF, 1004 nF, and 1007 nF.
So, from my perspective these units (at least for capacitors) have quite respectable accuracy and repeatability. Not bad for units that cost about $13 each.
 
Has anyone tried reprogramming on of these? And if so did you just write the hex and eeprom files or did you re-make it? Whenever I run the makefile I get a bigger hex file that won't fit on the chip...

EDIT: Got help from the German forum where this was created and found that in order to compile it you need AVR-GCC 4.8.1 or newer but WinAVR only comes with 4.3.3 so I had to manually update it and then it worked fine. The problem with the previous version was that the output hex was too large for the flash on the Mega328p
 
Last edited:
Thanks for the link. The blog contains a wealth of information, but at 98 pages it will take me at least a week to wade through it. Sounds like some users may have adapted the H/W for other uses, and there are newer versions of the S/W available.
 
ghazzer said:
Thanks for the link. The blog contains a wealth of information, but at 98 pages it will take me at least a week to wade through it. Sounds like some users may have adapted the H/W for other uses, and there are newer versions of the S/W available.
Click to expand...

If anyone figures out the easy steps for downloading the latest revision of the software and loading it, please post that here. I will if I end up being the first to try and succeed.
 
You must log in or register to reply here.

Similar threads

kotofei
Opinion on the Tenma 72-8150 cap tester please
Replies
9
Views
3K
SET12
SET12
Dmannnnn
Solar CE Capicitor Tester
Replies
3
Views
927
Dmannnnn
Dmannnnn
H
To identify a passive component
Replies
8
Views
213
gdmoore28
gdmoore28
opt80
Too Good To Be True
Replies
3
Views
623
opt80
opt80
A
Are there any DMMs that are around $120 or less that are good?
2
Replies
22
Views
2K
Ceallach
C
Back
Top Bottom