Capacitor Tutorial (Electrolytic, Tantalum, & Plastic Film)

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Capacitor Tutorial (Electrolytic, Tantalum, & Plastic Film)

Post by exxos » Mon Oct 08, 2018 9:46 pm

Dave jones video - back in video #33... Very compact and informative video from 2009...










Dave mentions problems with ceramics, abiet rare, but he doesn't mention electrolytics can also suffer in similar ways. Examples you can actually end up in a situation where a electrolytic acts as a microphone! And no I did not just make that up either. Actually saw this problem personally around 25 years ago. In actual fact Dave is tapping board in I think one of these later oscilloscope videos recently because they can actually pick up noise..I haven't seen him do a video on that issue, but obviously he is aware of it..


In this next video he talks about other issues in ceramics which can happen. I think it did watch this video while ago. The thing to remember is the problem is worse the smaller the package. Generally when you get up to 1206 sizes and above, the capacitance versus voltage ratio ends up being pretty good. If you went down to the tiny 0402's etc, then you will likely have issues. I never use smaller than 0805.. and always try to use 1206 or larger where possible. Generally 5V with no DC offsets with my stuff, so its not a massive problem.





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Re: Capacitor Tutorial (Electrolytic, Tantalum, & Plastic Film)

Post by sandord » Tue Oct 09, 2018 10:19 pm

I dreamt of caps last night (after many hours of sifting through many, many different types of caps on mouser.com). Now I'm afraid I will be having nightmares, this is all way too interesting :D

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Re: Capacitor Tutorial (Electrolytic, Tantalum, & Plastic Film)

Post by exxos » Wed Oct 10, 2018 11:23 am

sandord wrote:
Tue Oct 09, 2018 10:19 pm
I dreamt of caps last night (after many hours of sifting through many, many different types of caps on mouser.com). Now I'm afraid I will be having nightmares, this is all way too interesting :D
Yeah, I don't think people realise how long it takes to choose a capacitor. For me, its choosing right spec vs price (of course physical constraints also a factor) , then by the time I made my mind up on a list, some of them would go out of stock for 6 months, and I have to start again. Farnell has gotten terrible for that over the past couple of years. I started using mouser more for parts lately as the lead-time on parts is getting silly. Mostly been buying caps in like 100-500 packs so I can actually keep stuff in stock for longer and save time in not having to keep looking for alternatives.
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Re: Capacitor Tutorial (Electrolytic, Tantalum, & Plastic Film)

Post by sandord » Wed Oct 10, 2018 10:25 pm

exxos wrote:
Wed Oct 10, 2018 11:23 am
Yeah, I don't think people realise how long it takes to choose a capacitor. For me, its choosing right spec vs price (of course physical constraints also a factor) , then by the time I made my mind up on a list, some of them would go out of stock for 6 months, and I have to start again. Farnell has gotten terrible for that over the past couple of years. I started using mouser more for parts lately as the lead-time on parts is getting silly. Mostly been buying caps in like 100-500 packs so I can actually keep stuff in stock for longer and save time in not having to keep looking for alternatives.
Well, I'm very glad you've educated me a bit before I hit the order button (Commodore 1084S recap). Still working on the list. It's kind of satisfying, reminds me of filling in fireworks order lists as a kid (in Holland we're only allowed to buy them during the last two days or so of the year so I was really really excites weeks in advance).

I actually added some tantalum caps to the 1084S cap list and now I understand why they are so expensive: they make excellent fireworks :lol:

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Re: Capacitor Tutorial (Electrolytic, Tantalum, & Plastic Film)

Post by exxos » Wed Oct 10, 2018 10:32 pm

sandord wrote:
Wed Oct 10, 2018 10:25 pm
I actually added some tantalum caps to the 1084S cap list and now I understand why they are so expensive: they make excellent fireworks :lol:
Yeah. like 20 years ago I was reading how Tantalum was the "future".. I had them in some PSU type thing, had electrolytics in there, swapped them for Tantalum and they burst into flames and burnt my whole board to a black melted mess. So thought, no thanks :P Stuck with electrolytes the whole time, now moving over to ceramics slowly as they are pushing 100uF in recent years. True have to look after ceramics as they can break easily, but think I will take the cracking risk over certain flames anyday :P
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Re: Capacitor Tutorial (Electrolytic, Tantalum, & Plastic Film)

Post by stephen_usher » Tue Oct 16, 2018 8:25 pm

What's puzzled me for a while is why the markings for the different types of capacitors are different. e.g. electrolytics have a black bar on the negative connection but tantalum ones have the black bar on the positive connection. This seems to me the best way to confuse and cause exploding caps. Why can't the markings be consistent?
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Re: Capacitor Tutorial (Electrolytic, Tantalum, & Plastic Film)

Post by exxos » Tue Oct 16, 2018 9:33 pm

Because that would be to easy and the world would be a better place.
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