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Post by DarioG on Feb 3, 2020 17:51:41 GMT
It was almost time to create mine - after watching so many Ads on chinese resellers' sites! So, here it goes first draft, and a more complete version is coming soon: youtu.be/6KU4qVwkbCoI built it as a Layered daughterboard for Arduino (how they call them? oh, I can't remember, I actually HATE ivrea and arduino!!) just because I had those PCBs at a hand. I made it compatible to some stuff found on the net, and wrote the software from scratch after reading some documentation (and the usual awful code out there...) More to come!
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Post by du00000001 on Feb 3, 2020 18:02:38 GMT
They are called shields as they shield the controller PCB from spilled coffee
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Post by DarioG on Feb 3, 2020 18:11:19 GMT
ahah true, thanks! I remembered "sketch" but at times I confuse the 2 words and anyway... I loved the joke
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Post by DarioG on Feb 3, 2020 23:13:25 GMT
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Post by du00000001 on Feb 3, 2020 23:39:44 GMT
Got a bit sea sick from the video. Anyway, looks like one day I might be able to "inherit" a nice piece of tutorial about component testing. Although I'm preferring English over Italian
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Post by DarioG on Feb 4, 2020 9:14:54 GMT
it's note easy to make good documentation video, I'd need a help in that but okay, this is just a hobby! I am trying to figure out how to check capacitors and more than else inductors
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Post by DarioG on Feb 5, 2020 10:46:20 GMT
SCR are ok too now
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Post by du00000001 on Feb 5, 2020 14:07:06 GMT
Re "it's not easy ..." A tripod would do Magic Re capacitor/inductor measurements: There are some schematics etc. in the net. If you're very lucky, you might come up with the schematics of some Hameg RLC tester. They really know how. Important for capacitors: apply a DC bias (min. 1 V) - overlaid by the AC measurement voltage (with a typical frequency of 1 kHz). My guess: professional approaches measure the Phase shift caused by the capacitor. Important for inductors: a DC bias is counter-productive. Which basically leaves you with an AC voltage imposed and a current measurement.
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Post by DarioG on Feb 5, 2020 15:50:50 GMT
a tripod, yep, but this one is a Eyetoy webcam with no hole for such Same for the smartphone. And I did not want to use the camera... I've been able to measure capacitors by simple charge/discharge and, well, they're good enough for this scope/proof for design. Considering that the ADCs have a somewhat low impedance and I didn't plan extra part... The range seems to be around 1nF -> 10uF. Indeed I could improve that or, yep, use AC signaling and readout: given such a powerful PIC, everything can be thought of Now I just want to measure "some" impedance, I will work a bit more on it. Oh, and Mosfets, just to take a look. PS: also has to be born in mind that "it's smart enough to autodetect" everything, so far!
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Post by du00000001 on Feb 5, 2020 16:01:46 GMT
The "universal adapter" for some kind of not-too-heavy camera would be some dual-sided adhesive tape or alike Measuring capacitors per charge/discharge time will give nothing but a coarse estimate of the capacitance. If that one is voltage-dependent, the resulting value is nothing more than a vague guess. If this is sufficient, . . . Re auto-detect: starting with voltages and currents that won't destroy "a thing", you can try out. Although electrolytic caps (especially Ta caps) are not exactly made for auto detection as they react really bad on reverse polarity and their memory of such events lasts forever. In the past, we had Ta caps that once experienced reverse polarity for a very short time: they burst in flames - - - some years later. Could be tracked back to the one-time reverse polarity.
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Post by DarioG on Feb 5, 2020 16:12:13 GMT
Interesting this one about reverse polarity! I assume it only happens with Ta, but I get the point. In any case, I repeat (don't get me wrong) this is just "free experimenting", I'm not getting paid for it. I just wanted to try "how" this all could be done: I took a look at the (yes, awful) code I found out there, and at some documents, and then went on my way... First, the 6 combinations are tested via the 680ohm R (meaning some 3.5mA) and later decisions are taken and further tests are done. A constant current generator could be useful for measuring resistors... but this PIC has no op-amp inside. Oh well. A frequency meter is going to be easy and much easier than the rest just need to think about "how to autodetect" it!
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Post by du00000001 on Feb 5, 2020 17:09:43 GMT
All electrolytic capacitors are quite vulnerable vs. reverse polarity. But only the Ta ones may burst in flames. (Al capacitors might blow part off the electrolyte via the vent - or "eject" the case. Nb was chosen because these caps cannot burn while otherwise somewhat similar to Ta.) Even if that's a "hobby project", others might learn from that. Or you may want to publish some tutorial some day. And yes - a reasonable component tester might require some external components to supplement the PIC's abilities A frequency meter has another issue when considering somewhat "universal applicability": in might require a pre-amp and scaler in the input path as higher frequencies tend to have quite low amplitudes. You want to auto-detect that frequency-measurement is requested? Check the respective outputs for pulses when the PIC isn't yet up to output "something". Measurements of somewhat reasonable frequencies won't take long - depending on the number of pulses you want to have to decide on this mode.
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Post by DarioG on Feb 5, 2020 17:48:28 GMT
Yeah, just after I replied I realized that, as the PIC is waiting for user to start a measurement, it can of course check the 3 input pins and if any activity is detected, switch to Frequencymeter mode Will do that soon. And yes, like the rest, I'm okay with square wave at the moment (though in theory I could at least use ADC, in this case...) As for a tutorial, oh well yes, will consider that... Back to electrolytics, yes I know that they're vulnerable but I assumed you said "just a few tens mSec testing with reverse polarity may make them explode!" which would sound kinda crazy to me. But ok. And, thinking back at the measurement, do you actually believe that measuring "reactance" would be a more precise method than charge/discharge timing? I am not so sure about this... I can understand that one method may fit better some capacitor values and others in other cases but...
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Post by DarioG on Feb 5, 2020 18:48:36 GMT
nice it took about 15min work to get frequencymeter working!
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Post by DarioG on Feb 6, 2020 12:01:00 GMT
+-1 error is expected (especially when counting in software)
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