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Capacitor Substitution Box! - The Learning Circuit

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Language: en

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the following program is brought to you
00:00:02.180 00:00:02.190 by element14 the electronic design
00:00:04.849 00:00:04.859 community where you can connect and
00:00:06.740 00:00:06.750 collaborate with top engineers from
00:00:08.780 00:00:08.790 around the world join now at
00:00:10.580 00:00:10.590 element14.com hi I'm Karen and this is
00:00:14.150 00:00:14.160 the learning circuit today we're going
00:00:15.740 00:00:15.750 to build the capacitance substitution
00:00:17.810 00:00:17.820 box once the kid is assembled it can be
00:00:23.870 00:00:23.880 really useful you can plug it into your
00:00:26.060 00:00:26.070 circuit in place of a capacitor that you
00:00:28.130 00:00:28.140 maybe don't have that value lying around
00:00:29.779 00:00:29.789 or you can use it to try out different
00:00:31.849 00:00:31.859 values of capacitance to see which works
00:00:34.069 00:00:34.079 best just gather up your tools because
00:00:36.680 00:00:36.690 this kit comes with everything else you
00:00:38.209 00:00:38.219 need the capacitors in this kit are all
00:00:40.490 00:00:40.500 nonpolar mostly ceramic and mylar so
00:00:43.970 00:00:43.980 this means that once the box is built
00:00:46.069 00:00:46.079 you can plug it into your circuit in
00:00:47.869 00:00:47.879 either orientation and it'll work just
00:00:49.700 00:00:49.710 fine this kid has capacitors with values
00:00:52.220 00:00:52.230 from 100 Pico farad's up to 0.1
00:00:54.319 00:00:54.329 microfarads let's take a look at them
00:00:56.540 00:00:56.550 and see how to read the markings to
00:00:58.099 00:00:58.109 figure out each capacitors value if we
00:01:01.069 00:01:01.079 look at the assembly instructions page
00:01:02.569 00:01:02.579 of the manual we can see which capacitor
00:01:04.759 00:01:04.769 goes in each place on the board so I
00:01:06.980 00:01:06.990 noticed something a little funny with
00:01:08.750 00:01:08.760 the PCV and our capacitance substitution
00:01:11.780 00:01:11.790 box kits we had also made one of the
00:01:15.260 00:01:15.270 resistance substitution boxes before
00:01:17.390 00:01:17.400 which is made by the same manufacturer
00:01:19.429 00:01:19.439 and it looks like they decided to save a
00:01:22.100 00:01:22.110 little bit of money and use the same PCB
00:01:24.200 00:01:24.210 so all of the capacitor places are
00:01:27.140 00:01:27.150 marked with R and a number typically on
00:01:29.690 00:01:29.700 a PCB it would marked with C and a
00:01:31.399 00:01:31.409 number so it looks like maybe they
00:01:33.740 00:01:33.750 cheated it a little bit and decided to
00:01:35.240 00:01:35.250 save some money rather than having
00:01:36.730 00:01:36.740 proper corresponding labels but it'll
00:01:39.859 00:01:39.869 still work the same markings on
00:01:41.660 00:01:41.670 capacitors can vary depending on the
00:01:43.490 00:01:43.500 manufacturer and what type of capacitor
00:01:45.560 00:01:45.570 it is you usually want to look for a
00:01:47.569 00:01:47.579 series of three numbers to figure out
00:01:49.249 00:01:49.259 the value the first two numbers are the
00:01:51.260 00:01:51.270 first two digits of the value and the
00:01:52.789 00:01:52.799 third is a multiplier a letter at the
00:01:55.039 00:01:55.049 end shows the tolerance if you see 101 K
00:01:58.730 00:01:58.740 the K doesn't mean thousand it means a
00:02:01.399 00:02:01.409 tolerance of plus or minus 10% here's a
00:02:04.039 00:02:04.049 chart that shows what other letters mean
00:02:05.660 00:02:05.670 different tolerances let's find the
00:02:07.789 00:02:07.799 capacitor for r1 which according to the
00:02:09.889 00:02:09.899 instructions is 100 Pico farad's so
00:02:12.860 00:02:12.870 we're looking for one with them
00:02:13.890 00:02:13.900 accuse of 101 now if we remember how
00:02:16.949 00:02:16.959 capacitance works it's directly relative
00:02:19.410 00:02:19.420 to the amount of surface area within the
00:02:21.270 00:02:21.280 capacitor so if we're looking for a
00:02:23.100 00:02:23.110 small value capacitor it's probably also
00:02:25.410 00:02:25.420 going to be small in size
00:02:26.729 00:02:26.739 let's look yep our smallest capacitor
00:02:37.289 00:02:37.299 says 101 so that's what we need for our
00:02:39.599 00:02:39.609 one now that might not necessarily be
00:02:41.910 00:02:41.920 true for the rest of them but it's a
00:02:43.800 00:02:43.810 good place to start okay I'm gonna start
00:02:45.869 00:02:45.879 this one on and then continue finding
00:02:47.520 00:02:47.530 and placing the rest of the capacitors
00:02:49.289 00:02:49.299 now this board was designed for
00:02:51.330 00:02:51.340 resistors so placing the leads into the
00:02:53.789 00:02:53.799 holes can be a little bit tricky so just
00:02:55.500 00:02:55.510 do your best
00:02:57.360 00:02:57.370 [Music]
00:03:39.520 00:03:39.530 now that all the capacitors are soldered
00:03:41.990 00:03:42.000 in place let's populate the rest of the
00:03:44.060 00:03:44.070 components first solder on the switch in
00:03:46.910 00:03:46.920 the sw3 spot next take your red and
00:03:56.870 00:03:56.880 black wires cut one and a half inches
00:03:59.600 00:03:59.610 off of each and set that aside for later
00:04:03.010 00:04:03.020 take the larger pieces of red and black
00:04:05.510 00:04:05.520 wire and strip the ends we want to tin
00:04:08.150 00:04:08.160 the ends by adding a small amount of
00:04:09.830 00:04:09.840 solder solder the red wire to red on the
00:04:16.370 00:04:16.380 PCB and the black wire to black on the
00:04:18.830 00:04:18.840 PCB
00:04:26.290 00:04:26.300 tie the wires together in a knot as
00:04:28.540 00:04:28.550 close as possible to the PCB
00:04:34.120 00:04:34.130 now take the rotary switches bend the
00:04:37.060 00:04:37.070 tabs down
00:04:40.060 00:04:40.070 insert the switches into the PCB
00:04:44.580 00:04:44.590 and solder them into place
00:04:53.310 00:04:53.320 now take your small pieces of wire trim
00:04:56.490 00:04:56.500 and tin the ends and solder them to the
00:04:59.460 00:04:59.470 wiper pin and then up to the switch it
00:05:02.400 00:05:02.410 doesn't matter which color goes on which
00:05:04.050 00:05:04.060 side
00:05:09.540 00:05:09.550 next thread the wires through the hole
00:05:12.059 00:05:12.069 in the faceplate
00:05:16.670 00:05:16.680 next take the alligator clips and remove
00:05:19.080 00:05:19.090 the rubber thread the rubber onto the
00:05:21.540 00:05:21.550 wires then take the alligator clips and
00:05:24.330 00:05:24.340 solder them to the ends of the wires
00:05:26.089 00:05:26.099 replacing the rubber back onto the clip
00:05:32.200 00:05:32.210 00:05:36.499 00:05:36.509 push the faceplate all the way on place
00:05:39.779 00:05:39.789 the washers on the shaft of each knob
00:05:41.610 00:05:41.620 and then secure with a nut
00:05:52.370 00:05:52.380 now we need to add the knobs so that the
00:05:54.980 00:05:54.990 line is pointing at the wiper placing
00:05:57.560 00:05:57.570 the knobs are a little tricky we need to
00:05:59.900 00:05:59.910 make sure that the wipers underneath are
00:06:02.240 00:06:02.250 pointing to the correct pin and that we
00:06:04.850 00:06:04.860 know which one is which so I'm going to
00:06:07.460 00:06:07.470 give you a little cheat if you rotate
00:06:09.650 00:06:09.660 this there's a little ball that you can
00:06:11.570 00:06:11.580 see if you have it pointing straight
00:06:13.220 00:06:13.230 down then on not one that's pointing at
00:06:17.180 00:06:17.190 r8 so you can have your line on your
00:06:19.340 00:06:19.350 knob pointing to 820 Pico farad's on
00:06:22.400 00:06:22.410 knob two if you put the ball facing
00:06:25.850 00:06:25.860 straight down that's pointing to our 20
00:06:29.210 00:06:29.220 and you can have your knob pointing to
00:06:31.070 00:06:31.080 point zero three three microfarads
00:06:42.000 00:06:42.010 00:06:49.910 00:06:49.920 00:06:52.529 00:06:52.539 to show off the capacitor substitution
00:06:55.900 00:06:55.910 box I've built a little circuit so that
00:06:57.820 00:06:57.830 we can see the difference between our
00:06:59.290 00:06:59.300 lowest value capacitor and our highest
00:07:01.540 00:07:01.550 value capacitor let's take a look in my
00:07:04.089 00:07:04.099 circuit I have my switch which has power
00:07:06.249 00:07:06.259 coming to it from my desktop power
00:07:08.710 00:07:08.720 supply now that supplies power to both
00:07:11.320 00:07:11.330 the LED which has the safety resistor
00:07:13.839 00:07:13.849 and that goes back out to ground of the
00:07:15.969 00:07:15.979 power supply and then there's also these
00:07:18.399 00:07:18.409 two leads that I have hooked up to my
00:07:20.790 00:07:20.800 capacitance substitution box now what
00:07:23.980 00:07:23.990 will happen is when I turn this switch
00:07:26.050 00:07:26.060 on the power supply will be powering the
00:07:28.930 00:07:28.940 LED and it will be charging the
00:07:30.850 00:07:30.860 capacitor when I turn this off the
00:07:33.670 00:07:33.680 capacitor and LED are still in parallel
00:07:37.990 00:07:38.000 so the capacitor will actually be
00:07:39.790 00:07:39.800 powering the LED so let's see what
00:07:42.700 00:07:42.710 happens I have my multimeter hooked up
00:07:45.820 00:07:45.830 also to read my capacitor to see what's
00:07:48.700 00:07:48.710 going on in there
00:07:49.779 00:07:49.789 so I have it set to my lowest value I'm
00:07:52.749 00:07:52.759 gonna turn this on charges it up to 3
00:07:55.809 00:07:55.819 volts let's see how fast that discharges
00:07:58.680 00:07:58.690 pretty fast now I'm gonna turn off my
00:08:02.050 00:08:02.060 power supply I'm going to switch to
00:08:06.070 00:08:06.080 micro farad so now I'm at my highest
00:08:07.870 00:08:07.880 capacitance value let's apply power to
00:08:10.930 00:08:10.940 the circuit okay didn't take very long
00:08:14.080 00:08:14.090 to charge up if I turn the circuit off
00:08:16.480 00:08:16.490 let's see how fast that point 1 micro
00:08:19.209 00:08:19.219 farad capacitor discharges
00:08:26.869 00:08:26.879 whoo much slower so that's the
00:08:30.420 00:08:30.430 difference now the capacitor is in the
00:08:32.759 00:08:32.769 capacitance substitution box are all
00:08:34.440 00:08:34.450 fairly small values if I had some
00:08:36.899 00:08:36.909 capacitors on hand that were say a
00:08:38.579 00:08:38.589 thousand microfarads or ten thousand
00:08:41.070 00:08:41.080 microfarads the LED would have actually
00:08:43.230 00:08:43.240 stayed on longer beaten powered by the
00:08:44.940 00:08:44.950 capacitor so what uses do you think you
00:08:48.030 00:08:48.040 can find for the capacitance
00:08:49.889 00:08:49.899 substitution box tell us about them on
00:08:52.110 00:08:52.120 the element14 community on element14.com
00:08:54.920 00:08:54.930 /the learning circuit happy learning

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