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

DewDude thinks that there are other features (frequency counter, function generator, PWM generator, etc) hidden behind some button combinations or durations. This may depend on which ATMega chip & S/W program your tester has.

He is awaiting arrival of his tester, anxious to give it a full checkout.
 
As Steve mentioned; I read a post on YouTube relating to one of the MK168 testers where the poster mentioned this:

A few minutes ago I discovered that there's more to these meters than meets the eye. Press and hold the test button for a few seconds. Short presses switch options, long presses select them.
Choices:
Transistor (usual tester)
Frequency (counter)
f-Generator (generate 2MHz, 1MHz, 500kHz, 250kHz, 153.8462kHz, 100kHz, 50kHz, 25kHz, 10kHz, 5kHz, 2.5kHz, 1kHz, 443.017Hz, 441.989Hz, 439.9956Hz, 250Hz, 100Hz, 50Hz, 10Hz, 1Hz)
10-bit PWM (10% to 100% in 1% steps)
C+ESR@TP1:3(don't know)

Also, powering up with the three probes shorted enters self test mode and zeroes the resistance of the probes.
Click to expand...

The shorting probes trick I had known about; but I haven't seen any mention of the others. I also haven't really been following any of this as in depth as I could have. I know they're based on ATMega Microcontrollers. I bought one in a "kit" form with a programmed controller for $15. It uses the ATMega328, which I'm not 100% sure is that much newer than the AT168. They do have some that use larger LCD with actual schematic symbol pinouts; but again, no idea if that's the result of newer hardware or just additional software.

I also have no idea if there's one universal build of this software; or if it's been customized by someone. There's a standard codebase out there; as the work developed from someone's first version. (The market for assembled versions of these grew from the existance of the software).

It is possible to upgrade the software; but I'm not 100% sure of what's involved or if you need specific builds. The software is being improved constantly, giving more accurate readings. ESR was apparently the work of further refinement of the software.

Mine doesn't have the fancy screen like SteveAndBell's has; although I looked at those; it has just the basic 2 line LCD. It's either working it's way through China or sitting on a boat; so it'll be at least another week before it shows up and I can start punching buttons.
 
I've never seen these before. I ordered a Mega328 Transistor Tester Diode Triode Capacitance ESR Meter from ebay. I'll post back in a few weeks and let you know how it works.
 
SteveAndBell said:
Yep, I'll give mine a 'test' tonight and see if it allows access to the hidden options too. I'll report back...
Click to expand...

If your unit has those and you're able to test the frequency counter; please let me know if it's a real-time update and what it's resolution is like. I hadn't read that blurb until after I ordered my tester and one of those $12 frequency counters. I'm wondering if I wound up getting the counter for no reason in the long run.
 
dewdude said:
If your unit has those...
Click to expand...

Hmm, holding down the button doesn't do anything however shorting all three probes and pressing the test button takes it straight into a 'SelfTest' mode :yes: It runs through five different tests and then displays 'Release Probes' reminding me of my alien abduction. Anyway, it continues on by itself then asks for a 100nf (0.1uf) Cap to continue which I don't have handy so I guess it will stay this way until I find/go get one.

I'm a bit relieved there's some sort of calibration though because earlier in the evening I tested a 22pf ceramic and it displayed 35pf :sigh: Fingers crossed I can get it closer to the mark. Will update when the calibration's done.
 
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Ok. Then it maybe limited to certain builds; it's also possible the guy on youtube was makin stuff up.

Good to know the calibaration needs a .1uf cap; because I don't have any either! I got a .15; and several .22s, but no .1s - guess I'll be stealing one from something. Wish I'd known...I just made a digikey order and got some .1s for my signal gen! I can probably slip a .15 somehwere in a non-vital circuit...like the audio-oscillator coupling.
 
Calibration 'Schmalibration' :)

OK, got the 100nf cap and gave it a go. The process was quick & easy but the 22pf Ceramic I tested a few days ago that read 35pf now reads 45pf :sigh: The good news however is that it's more accurate for larger caps, within 1.5% tolerance. Video of the process can be seen here: http://youtu.be/k7UinIf7HR4

Not great that it can't do everything perfectly but as others have said it's good enough for basic tests and should be fine to indicate the general state of aging filter caps and/or completely unidentifiable components which is the main reason I wanted a tester in the first place.

If anyone has any other experiences or knowledge on these tricky little devices then please post them up here. I'm already thinking there'll be firmware updates and/or complete replacements for my unit in the not-too-distant future :yes:
 
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Is that 35nƒ an OLD cap? I thought they were standardizing on 22,33,47,68,etc.

If your tester consistently reads that cap as 45nƒ, I would satisfy me. The readings with mine tend to bounce around a bit on the smaller caps and resistors, and I was hoping that the newer S/W would improve on that. Measuring 0.33Ω emitter resistors is an adventure, so I do it with 4 or 5 in series.
 
ghazzer said:
Is that 35nƒ an OLD cap? I thought they were standardizing on 22,33,47,68,etc.

If your tester consistently reads that cap as 45nƒ, I would satisfy me. The readings with mine tend to bounce around a bit on the smaller caps and resistors, and I was hoping that the newer S/W would improve on that. Measuring 0.33Ω emitter resistors is an adventure, so I do it with 4 or 5 in series.
Click to expand...

You can still get some very odd values. They're not cheap; but you can get them. My signal gen had values like .025 and .05...which I could get...but not at the prices they wanted. .022 and .047 is close enough for me!

Smallest resistor I have down here is a 1ohm 5% which my DMM told me was a 1.2ohm - it reads the clip leads as .1 or .0; it doesn't know what it wants to do. I'll let you know how mine works with it. I don't think I have anything smaller than 1ohm...but I did buy one of those Jameco grab-bags that came with...probably resistors i'll never even use...including some of those fancy 0-ohm resistors (seriously...a resistor body with a black band. damn fancy jumper)

I'll probably make a mouser/digitkey/someone order before I get my tester; so I'll order some really small value resistors and let you know how they measure.
 
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SteveAndBell said:
Most probably but with the brief research I did before buying mine it seems there are many people doing crazy things with component testers similar to this from building different versions from scratch to redeveloping software for existing units. Ahhh, the beauty of OpenSource... and lots of spare time:yes:
Click to expand...

I might just have to pick one up, I have played with arduino before, could be a fun little tool. Any idea on the accuracy on the transistor tester?
 
Hmm, holding down the button doesn't do anything however shorting all three probes and pressing the test button takes it straight into a 'SelfTest' mode It runs through five different tests and then displays 'Release Probes' reminding me of my alien abduction.
Click to expand...

LOL SteveAndBelk! alien abduction.. mate that was good.... lol

Here's another one of his excellent projects...

http://www.audiokarma.org/forums/showthread.php?t=601392
 
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I'd say that the accuracy is PDG, especially for the price. The GO/NOGO has been right on for all the spare transistors I have tested and some known bad ones (seems I never throw anything out). I compared the gain readings with an RCA transistor tester that I borrowed from Merrylander. The new tester reads a little bit higher, but it is consistently "a little bit higher".

I have not tried testing a transistor in-circuit as I have another toy for that.

Steve's tester has a newer chip and probably a more recent S/W update, so I am hoping he gets even better results.
 
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