00:00:10.220 hi this blog is going to be all about 00:00:13.03000:00:13.040 capacitors the what why how and where of 00:00:16.54000:00:16.550 using capacitors I've got ten minutes 00:00:19.75000:00:19.760 let's start now okay the first type of 00:00:24.17000:00:24.180 capacitor is the electrolytic capacitor 00:00:26.99000:00:27.000 you've seen them before these things in 00:00:28.73000:00:28.740 the metal cans they've basically got an 00:00:31.10000:00:31.110 aluminium foil in them filled with a 00:00:33.13900:00:33.149 liquid electrolyte and these things are 00:00:36.56000:00:36.570 absolutely horrible they are all full 00:00:39.43900:00:39.449 capacities in in almost every respect 00:00:42.40000:00:42.410 try and avoid using them if you can but 00:00:45.68000:00:45.690 the problem is the advantage of them is 00:00:48.04900:00:48.059 that they come in massive capacitance 00:00:51.13900:00:51.149 values for their size so really yeah you 00:00:54.55900:00:54.569 really can't avoid using them for things 00:00:56.89900:00:56.909 like power supply filtering and large 00:01:00.38000:01:00.390 bypassing and things like that and in 00:01:02.68900:01:02.699 power storage and some AC coupling 00:01:05.84000:01:05.850 applications for very low frequencies 00:01:07.82000:01:07.830 it's hard to avoid these things so 00:01:09.64900:01:09.659 unfortunately there are necessary evil 00:01:11.84000:01:11.850 you've almost certainly noticed this 00:01:14.20900:01:14.219 little vent mark on the top this is 00:01:16.58000:01:16.590 actually a pressure vent that in the 00:01:18.67900:01:18.689 case of these things overheating and 00:01:20.38900:01:20.399 overloading 00:01:22.10000:01:22.110 the vent is supposed to break and 00:01:23.63000:01:23.640 release the energy so that they don't 00:01:25.21900:01:25.229 explode and our foil goes everywhere 00:01:27.46900:01:27.479 well they don't always work these 00:01:29.63000:01:29.640 suckers can explode they're dangerous be 00:01:31.88000:01:31.890 careful one of the hugest problems with 00:01:34.55000:01:34.560 these things is that they dry out over 00:01:37.19000:01:37.200 time heat can kill these things the 00:01:39.62000:01:39.630 liquid in there dries out and this 00:01:41.33000:01:41.340 increases the equivalent series 00:01:43.06900:01:43.079 resistance the ESR and really to measure 00:01:46.96900:01:46.979 this you've got to have an ESR meter not 00:01:49.76000:01:49.770 a capacitance meter an ESR meter I use 00:01:52.03900:01:52.049 this Bob Parker one thumbs up you've got 00:01:54.52900:01:54.539 to have something like this if you want 00:01:56.27000:01:56.280 to test electrolytic because the life of 00:01:58.58000:01:58.590 these things is inversely proportional 00:02:00.52000:02:00.530 to the temperature they use that so the 00:02:03.34900:02:03.359 higher the temperature the shorter the 00:02:05.27000:02:05.280 life now these will have a rated life on 00:02:08.69000:02:08.700 the datasheet at a certain temperature 00:02:10.66900:02:10.679 but you can easily shorten that life if 00:02:13.43000:02:13.440 you mount this thing near a heat sink or 00:02:16.22000:02:16.230 something like that inside your product 00:02:17.83900:02:17.849 these things need to be kept 00:02:19.87000:02:19.880 cool but don't make them too cool 00:02:21.76000:02:21.770 because then their their ESR just shoots 00:02:23.86000:02:23.870 through the roof of cold temperatures 00:02:25.21000:02:25.220 they're horrible high ESR on these 00:02:27.82000:02:27.830 things is probably the number one 00:02:29.71000:02:29.720 failure mode in consumer products if 00:02:32.41000:02:32.420 you're plasma TV fails or your digital 00:02:35.59000:02:35.600 set-top box or DVD player fails it's 00:02:37.99000:02:38.000 probably because one of these has dried 00:02:40.33000:02:40.340 out in the power supply odds-on now if 00:02:43.78000:02:43.790 you want the best reliability for 00:02:45.34000:02:45.350 electrolytic capacitors you need to 00:02:47.29000:02:47.300 stick to the name-brand ones and check 00:02:49.93000:02:49.940 the data sheets and use the high quality 00:02:52.72000:02:52.730 ones 00:02:53.08000:02:53.090 there's tons of fake ones and dodgy ones 00:02:55.90000:02:55.910 on the market and you can get duped into 00:02:58.51000:02:58.520 it another major problem with these 00:03:00.76000:03:00.770 things is that they have a maximum ah 00:03:03.27000:03:03.280 charge and discharge or ripple current 00:03:05.98000:03:05.990 they can handle so make sure you read 00:03:08.41000:03:08.420 the data sheets and you don't exceed 00:03:10.39000:03:10.400 that ripple current because if you do 00:03:12.76000:03:12.770 they can heat up internally and like I 00:03:15.58000:03:15.590 said shorten the life if you want really 00:03:17.71000:03:17.720 reliable designs using these things you 00:03:20.02000:03:20.030 put two or more in parallel that way 00:03:22.54000:03:22.550 they share the ripple current they share 00:03:24.31000:03:24.320 the heat and they lower the ESR and it 00:03:27.70000:03:27.710 increases your liability and system so 00:03:30.36000:03:30.370 parallel is a really good way to go and 00:03:32.89000:03:32.900 you can also get low ESR versions of 00:03:35.86000:03:35.870 these things and they're good for use in 00:03:38.50000:03:38.510 switch mode power suppliers and low 00:03:40.84000:03:40.850 dropout voltage regulators and things 00:03:42.76000:03:42.770 like that now the temperature variation 00:03:45.37000:03:45.380 of electrodes is pretty horrible can be 00:03:47.20000:03:47.210 anywhere from plus 5 to minus 40% minus 00:03:50.68000:03:50.690 50% so just watch out for it and of 00:03:53.80000:03:53.810 course they're polarized you have to put 00:03:55.78000:03:55.790 them in your circuit the right way 00:03:57.16000:03:57.170 that's a major disadvantage now they 00:04:00.79000:04:00.800 have a maximum reverse voltage of about 00:04:02.83000:04:02.840 1.5 volts anything over that continuous 00:04:05.98000:04:05.990 and you're going to damage these things 00:04:07.54000:04:07.550 permanently sometimes you're going to 00:04:09.25000:04:09.260 need a non polarized electrolytic 00:04:11.74000:04:11.750 capacitor and you can't actually buy 00:04:14.23000:04:14.240 them but if you haven't got one you can 00:04:16.51000:04:16.520 do it by putting two in series 00:04:19.12000:04:19.130 back-to-back like this with the two 00:04:21.52000:04:21.530 negatives together or the two positives 00:04:23.80000:04:23.810 together it doesn't matter which way 00:04:24.97000:04:24.980 around sometimes in high voltage 00:04:26.74000:04:26.750 applications you need to put two 00:04:30.70000:04:30.710 electrolytic capacitors in 00:04:32.15900:04:32.169 Cirie's it's not recommended but if you 00:04:34.20000:04:34.210 have to you can do it got to capacitors 00:04:37.17000:04:37.180 like this one of them could leak very 00:04:39.17900:04:39.189 badly and that will change the voltage 00:04:41.58000:04:41.590 division ratio and you'll get excess 00:04:43.86000:04:43.870 voltage across one of the capacitors and 00:04:45.77900:04:45.789 that can quickly destroy it so what you 00:04:48.26900:04:48.279 do is you put ballast resistors 00:04:50.15900:04:50.169 across the two caps and you calculate 00:04:52.73900:04:52.749 these values based on the worst-case 00:04:54.64900:04:54.659 leakage current of one of the capacitors 00:04:57.20900:04:57.219 and the maximum voltage that that 00:04:59.33900:04:59.349 capacitor can handle the other thing 00:05:01.89000:05:01.900 about electrolytic capacitors is a 00:05:03.98900:05:03.999 phenomenon called dielectric absorption 00:05:05.95900:05:05.969 and this means that the capacitor can 00:05:09.05900:05:09.069 actually rebuild its charge after you've 00:05:11.61000:05:11.620 shorted it you know 1020 percent 00:05:13.61900:05:13.629 recovery something like that so in high 00:05:15.98900:05:15.999 voltage applications that can actually 00:05:17.36900:05:17.379 be dangerous so be wary of it next up we 00:05:20.64000:05:20.650 have tantalum capacitors these things 00:05:23.24900:05:23.259 these little resin dipped ones or the 00:05:25.52900:05:25.539 surface mount tantalum caps and these 00:05:28.14000:05:28.150 are another necessary evil in a lot of 00:05:31.40900:05:31.419 cases you avoid using them if you can 00:05:33.80900:05:33.819 the first problem with tandems is that 00:05:35.73000:05:35.740 the tantalum material itself is actually 00:05:37.67900:05:37.689 a fairly rare metal it requires lots of 00:05:40.35000:05:40.360 mining and this can lead to very high 00:05:43.11000:05:43.120 prices and shortage of tantalum ah if 00:05:46.95000:05:46.960 you use quite a few years back there's a 00:05:48.62900:05:48.639 huge tantalum shortage in the market 00:05:50.90900:05:50.919 simply marketing to complete and utter 00:05:52.95000:05:52.960 chaos and they're talking about it 00:05:54.57000:05:54.580 happening again soon the other major 00:05:56.73000:05:56.740 problem with tandems is that they're 00:05:58.23000:05:58.240 famous for blowing up and bursting into 00:06:01.26000:06:01.270 flames the damn things are flammable and 00:06:03.23900:06:03.249 this is generally considered a bad thing 00:06:06.35000:06:06.360 tantalum is also just like Electro's 00:06:08.96900:06:08.979 they hate high pulse and ripple currents 00:06:11.76000:06:11.770 so watch the datasheet and don't go 00:06:13.82900:06:13.839 anywhere near those limits but it's not 00:06:16.55900:06:16.569 all doom and gloom with Tanna lumps they 00:06:18.11900:06:18.129 do have some good aspects if you use 00:06:20.27900:06:20.289 them with inside their specs they're 00:06:21.86900:06:21.879 actually very reliable much more 00:06:24.20900:06:24.219 reliable than Electro's in some cases 00:06:26.01000:06:26.020 but just like Electro's they're they're 00:06:27.95900:06:27.969 pretty horrible caps generally all right 00:06:30.57000:06:30.580 they're they're very low leakage though 00:06:31.86000:06:31.870 that's another good thing about them but 00:06:33.45000:06:33.460 you'll generally find them in just 00:06:34.95000:06:34.960 pretty much power supply decoupling and 00:06:37.11000:06:37.120 large value uh energy reserves things 00:06:40.49900:06:40.509 like that 00:06:41.27900:06:41.289 you're very common for FPGA decoupling 00:06:44.07000:06:44.080 these days that now there are 00:06:45.87000:06:45.880 different types of tan limbs these days 00:06:48.54000:06:48.550 as the technology gets better organic 00:06:50.64000:06:50.650 and polymer tatum's and look at using 00:06:53.40000:06:53.410 those as substitutes but they're rarer 00:06:55.26000:06:55.270 and more expensive now thankfully the 00:06:57.93000:06:57.940 ceramic technology these days is eating 00:07:00.45000:07:00.460 away the need to have tantalum 00:07:02.85000:07:02.860 capacitors now another type of main 00:07:04.95000:07:04.960 capacitor are these film capacitors 00:07:07.32000:07:07.330 plastic film capacitors and they come in 00:07:10.05000:07:10.060 two major types one of the main types of 00:07:12.45000:07:12.460 plastic film capacitors are the 00:07:14.28000:07:14.290 polyester type there are general-purpose 00:07:16.11000:07:16.120 ones you use for bypassing AC coupling 00:07:18.96000:07:18.970 filtering applications things like that 00:07:21.00000:07:21.010 you can get quite stable ones their main 00:07:22.98000:07:22.990 advantages that they have a high 00:07:24.90000:07:24.910 capacitance per unit volume due to their 00:07:28.38000:07:28.390 high dissipation factor you wouldn't use 00:07:30.30000:07:30.310 polyester in high poles high current or 00:07:33.48000:07:33.490 high frequency applications at the other 00:07:35.73000:07:35.740 major type of cap is polypropylene now 00:07:38.46000:07:38.470 these have much higher performance due 00:07:40.44000:07:40.450 to their lower dissipation factor and 00:07:42.18000:07:42.190 their higher dielectric strength you use 00:07:44.52000:07:44.530 them for high voltage high frequency 00:07:46.71000:07:46.720 high current pulse applications and 00:07:49.41000:07:49.420 things like that so really grunty 00:07:51.15000:07:51.160 capacitors but their major disadvantages 00:07:53.58000:07:53.590 you can only get them in small values 00:07:55.86000:07:55.870 here's a good tip polypropylene and 00:07:58.26000:07:58.270 polyester capacitors have roughly 00:08:00.59000:08:00.600 opposite temperature characteristics so 00:08:03.87000:08:03.880 if you actually put the two in two types 00:08:06.00000:08:06.010 in parallel you can get a reasonably 00:08:08.01000:08:08.020 stable or a much more stable temperature 00:08:11.34000:08:11.350 characteristic the other major type of 00:08:13.74000:08:13.750 film capacitor is the polyethylene 00:08:15.75000:08:15.760 sulfide and these are mainly used in SMD 00:08:18.93000:08:18.940 caps because the other ones are mainly 00:08:20.31000:08:20.320 through-hole and these are very stable 00:08:22.68000:08:22.690 and close tolerance caps now the other 00:08:25.89000:08:25.900 type of capacitor out there is a mica 00:08:28.68000:08:28.690 and these are very exotic kind of things 00:08:31.53000:08:31.540 that are used really for only ultra high 00:08:33.71900:08:33.729 stability ultra close tolerance 00:08:36.33000:08:36.340 applications so if you need a mica 00:08:39.33000:08:39.340 you're going to know it I can't do this 00:08:41.27900:08:41.289 blog without mentioning mains rated 00:08:44.12000:08:44.130 capacitors now you can't just use any 00:08:47.28000:08:47.290 old capacitor when you're hooking these 00:08:49.44000:08:49.450 things directly on the mains for like 00:08:51.27000:08:51.280 suppression these special mains Raider 00:08:53.01000:08:53.020 ones come in two different types two 00:08:54.87000:08:54.880 different classes Class X and class Y 00:08:57.36000:08:57.370 now Class X 00:08:59.11000:08:59.120 comes in two types x1 and x2 x1 are 00:09:02.56000:09:02.570 rated for higher voltage higher pulse 00:09:05.88000:09:05.890 applications but either can be used 00:09:07.93000:09:07.940 generally and they are designed x-class 00:09:10.90000:09:10.910 are designed to go directly across the 00:09:13.03000:09:13.040 mains they're not designed for anywhere 00:09:16.15000:09:16.160 that can be accessed by people something 00:09:18.94000:09:18.950 for safety and things like that 00:09:20.59000:09:20.600 that's where class y comes in class Y 00:09:23.32000:09:23.330 capacitors are used between either of 00:09:26.14000:09:26.150 the mains lines and protective earth and 00:09:28.69000:09:28.700 you've got to make sure you use the 00:09:30.16000:09:30.170 right type and these the advantage of 00:09:33.01000:09:33.020 these capacitors is that they're 00:09:34.30000:09:34.310 self-healing what it means is that if 00:09:36.61000:09:36.620 you get a tiny little overload and spark 00:09:38.76900:09:38.779 inside the capacitor basically what it 00:09:41.32000:09:41.330 does is itself extinguishes itself and 00:09:44.05000:09:44.060 just breaks it and you lose a tiny 00:09:45.94000:09:45.950 amount of capacitance miniscule but it 00:09:48.31000:09:48.320 means the thing doesn't overload or 00:09:50.01900:09:50.029 short or explode or something like that 00:09:52.36000:09:52.370 and you've got to make sure you use 00:09:54.31000:09:54.320 these right type of capacitors if you 00:09:56.41000:09:56.420 don't your products won't get approved 00:09:58.48000:09:58.490 and they can kill someone
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