WEBVTT 1 00:00:00.080 --> 00:00:03.080 Welcome back to the deep dive, especially to you the learner. 2 00:00:03.520 --> 00:00:05.599 You know, if you're looking to shortcut the learning curve 3 00:00:05.639 --> 00:00:10.359 of home automation and hardware hacking, you are in exactly 4 00:00:10.400 --> 00:00:10.960 the right place. 5 00:00:11.080 --> 00:00:13.439 Yeah. Absolutely, We've got a really fun one today. 6 00:00:13.480 --> 00:00:16.679 We do because I want you to imagine looking at 7 00:00:16.679 --> 00:00:19.039 the walls of your living room right now. You know, 8 00:00:19.079 --> 00:00:21.960 you see drywall, you see paint, maybe a few standard 9 00:00:21.960 --> 00:00:28.480 plastic power outlets. It all looks so, I don't know, static. 10 00:00:28.239 --> 00:00:30.359 Right, incredibly ordinary, exactly. 11 00:00:30.879 --> 00:00:34.119 But what if those plain copper wires inside the walls, 12 00:00:34.320 --> 00:00:37.000 like the ones meant to just blindly pump raw electricity, 13 00:00:37.240 --> 00:00:41.079 What if they're actually a hidden digital network, just waiting 14 00:00:41.119 --> 00:00:42.000 for you to take control. 15 00:00:42.079 --> 00:00:44.840 It really completely shifts how you view the physical structure 16 00:00:44.880 --> 00:00:47.000 you live in. I mean, you stop seeing a house 17 00:00:47.039 --> 00:00:50.200 and you start seeing this enormous programmable machine. 18 00:00:50.320 --> 00:00:53.759 Yeah, and today we are pulling back that drywall to 19 00:00:53.840 --> 00:00:56.960 explore this hidden network. We're getting into the mechanics of 20 00:00:57.000 --> 00:00:59.799 home automation by looking at excerpts from the book geek 21 00:00:59.799 --> 00:01:03.640 House Ten hardware Hacking Projects for a Round Home by 22 00:01:03.640 --> 00:01:04.959 Barry and Marcilla Press. 23 00:01:05.079 --> 00:01:06.239 It's such a great source. 24 00:01:06.560 --> 00:01:09.920 It is. Specifically, we are focusing on a section called 25 00:01:10.120 --> 00:01:11.120 X ten Under the Hood. 26 00:01:11.400 --> 00:01:13.920 Yeah. It's an incredible guy for anyone who wants to 27 00:01:14.000 --> 00:01:16.640 understand not just you know that their house can be automated, 28 00:01:16.640 --> 00:01:20.640 but exactly how that automation physically functions behind the scenes. 29 00:01:20.799 --> 00:01:24.159 Right, Okay, let's unpack this because the core premise the 30 00:01:24.200 --> 00:01:26.959 authors lay out here is brilliant. They want to help 31 00:01:27.000 --> 00:01:29.519 you take a boring, conventional house and turn it into 32 00:01:29.599 --> 00:01:31.400 a custom built geek. 33 00:01:31.120 --> 00:01:33.480 House minion, a minion that does your bidding. 34 00:01:33.560 --> 00:01:37.319 I love that, right, But before we get anywhere near 35 00:01:37.400 --> 00:01:40.879 the actual hardware, we have to issue a very serious, 36 00:01:41.319 --> 00:01:45.840 very crucial safety disclaimer. We are talking about hacking the 37 00:01:45.879 --> 00:01:48.000 actual electrical wiring of a house. 38 00:01:48.239 --> 00:01:51.439 Yeah, and that really cannot be overstated. Powerline control devices 39 00:01:51.480 --> 00:01:54.840 operate on hazardous voltages, lethal voltage. Literally, we're talking about 40 00:01:54.879 --> 00:01:56.840 one hundred and twenty to two hundred and forty volts 41 00:01:56.879 --> 00:01:59.480 of alternating current. If you do not know how to 42 00:01:59.519 --> 00:02:01.959 safely work with live home wiring, you need to stick 43 00:02:02.000 --> 00:02:05.000 strictly to the plug in modules exactly because touching the 44 00:02:05.040 --> 00:02:08.400 wrong wire at the wrong time isn't just a shock hazard, 45 00:02:08.479 --> 00:02:09.599 it can literally kill you. 46 00:02:09.919 --> 00:02:14.199 So keeping that very real physical danger in mind, we 47 00:02:14.319 --> 00:02:18.039 have a massive engineering puzzle here. How does this technology 48 00:02:18.120 --> 00:02:22.719 actually transmit a delicate digital message through copper wires that 49 00:02:22.759 --> 00:02:26.520 were let's face it only ever built to carry raw lethal. 50 00:02:26.199 --> 00:02:28.319 Power, right, It's not a data cable, no. 51 00:02:28.800 --> 00:02:31.120 So to understand this we have to look at the 52 00:02:31.120 --> 00:02:34.919 foundational level of what engineers call the ISO seven layer 53 00:02:35.000 --> 00:02:38.080 communications model, which is essentially the physical layer. 54 00:02:38.199 --> 00:02:40.479 Yeah, the physical layer's layer one. Before you can get 55 00:02:40.479 --> 00:02:43.319 two computers to talk, you need a framework that separates 56 00:02:43.400 --> 00:02:47.199 the physical reality of the wire from the grammar of 57 00:02:47.240 --> 00:02:48.479 the actual message. 58 00:02:48.639 --> 00:02:50.919 Right. The physical layer doesn't care what the message means 59 00:02:50.919 --> 00:02:51.439 at all. 60 00:02:51.439 --> 00:02:53.719 Not even a little bit. It's strictly about the physics 61 00:02:53.719 --> 00:02:55.960 of moving a bit of information, a single one or 62 00:02:55.960 --> 00:02:57.719 a zero, from point A to point B. 63 00:02:58.039 --> 00:02:59.759 And the challenge for the creators of the X ten 64 00:02:59.759 --> 00:03:03.800 pro was doing this reliably using cheap electronics over an 65 00:03:03.840 --> 00:03:06.840 electrical grid that was never designed to carry data. So 66 00:03:06.919 --> 00:03:10.039 their solution was to literally piggyback on the alternating current. 67 00:03:10.319 --> 00:03:13.840 Exactly in North America, the power grid operates at sixty hertz. 68 00:03:13.919 --> 00:03:14.919 Okay, so that means. 69 00:03:14.800 --> 00:03:18.039 That means the electrical current isn't just flowing constantly like 70 00:03:18.159 --> 00:03:21.360 water in a pipe. It's alternating. It's surging back and 71 00:03:21.400 --> 00:03:25.520 forth sixty times every single second. It's this massive rhythmic 72 00:03:25.719 --> 00:03:26.719 wave of energy. 73 00:03:26.840 --> 00:03:30.759 And the XTEN system uses that surging sixty hrtz wave 74 00:03:31.199 --> 00:03:33.879 as its transportation vehicle. Like whenever it wants to send 75 00:03:33.919 --> 00:03:36.199 a one bit, it transmits a one hundred and twenty 76 00:03:36.280 --> 00:03:39.479 kilohertz tone, which is basically just a very high pitched 77 00:03:39.479 --> 00:03:40.759 electronic squeal. 78 00:03:40.479 --> 00:03:43.080 Yeah, tiny squeal, and it blasts. 79 00:03:42.639 --> 00:03:45.879 That tone into the wire for a tiny one millisecond burst. 80 00:03:46.520 --> 00:03:49.479 So the physical presence of that high frequency tone equals 81 00:03:49.479 --> 00:03:52.400 a one, and the absolute absence of the tone equals 82 00:03:52.400 --> 00:03:52.800 a zero. 83 00:03:52.879 --> 00:03:55.400 But the real genius here isn't the tone itself, it's 84 00:03:55.479 --> 00:03:58.520 exactly when the system decides to send that burst, the 85 00:03:58.599 --> 00:04:02.240 timing right the timing, It uses a mechanism called zero crossing. 86 00:04:02.639 --> 00:04:07.159 As that massive sixty herds alternating current rhythmically rises and falls, 87 00:04:07.520 --> 00:04:10.680 it constantly crosses the zero voltage point in the middle. 88 00:04:10.479 --> 00:04:12.759 Because it's going from positive to negative exactly. 89 00:04:12.800 --> 00:04:18.279 So the X ten transmitter waits for that exact quiet moment, specifically, 90 00:04:18.439 --> 00:04:20.920 it waits for the rising line voltage to cross zero, 91 00:04:21.279 --> 00:04:24.160 and it fires its one millisecond tone burst within two 92 00:04:24.240 --> 00:04:26.360 hundred microseconds of that exact crossing. 93 00:04:26.680 --> 00:04:29.759 Wow, that is just so elegant. And then right after that, 94 00:04:29.839 --> 00:04:31.360 just to be sure the bit wasn't I don't know, 95 00:04:31.480 --> 00:04:34.040 mangled by some random spark in the wire, it does 96 00:04:34.040 --> 00:04:35.120 a built in error check. 97 00:04:35.319 --> 00:04:37.120 Yeah, the inverse rule right on. 98 00:04:37.079 --> 00:04:39.040 The very next half of the wave, when the voltage 99 00:04:39.040 --> 00:04:41.959 crosses zero on the way down, it sends the exact 100 00:04:42.079 --> 00:04:44.959 inverse or complement of the bit. So if it blasted 101 00:04:44.959 --> 00:04:47.199 the tone to say one on the way up, it 102 00:04:47.240 --> 00:04:49.800 guarantees a moment of silence to say zero on the. 103 00:04:49.720 --> 00:04:53.399 Way down, precisely. Now, that inverse rule doesn't magically fix 104 00:04:53.519 --> 00:04:56.879 errors if they happen, but it's a brilliant diagnostic tool. Yes, 105 00:04:56.920 --> 00:05:00.040 so well, let's the receiving lamp or switch immediately. I 106 00:05:00.160 --> 00:05:02.720 know if a bit got corrupted in transit, if it sees, say, 107 00:05:02.839 --> 00:05:05.519 two tones back to back, it knows the rule was 108 00:05:05.560 --> 00:05:07.439 broken and the data is just garbage. 109 00:05:07.560 --> 00:05:09.839 I picture the whole thing like an extreme sport, you know, 110 00:05:10.240 --> 00:05:14.920 like you've got this massive, surging, lethal sixty hertze electrical 111 00:05:14.959 --> 00:05:17.360 ocean wave that could easily crush you, oh for sure. 112 00:05:17.480 --> 00:05:20.519 And the X ten system is trying to perfectly surf 113 00:05:20.639 --> 00:05:23.879 a tiny one hundred and twenty killer hertz ripple right 114 00:05:23.959 --> 00:05:26.519 on the lip of that wave exactly at the moment 115 00:05:26.560 --> 00:05:27.720 it crests the zero line. 116 00:05:27.759 --> 00:05:29.720 That's a really good analogyh. 117 00:05:29.199 --> 00:05:31.839 Wait, if I run the math on that you're telling me, 118 00:05:31.879 --> 00:05:34.240 it sends exactly one bit of data perhaf cycle of 119 00:05:34.279 --> 00:05:37.879 the PowerWave. Yes, at sixty herdz. That means the raw 120 00:05:37.920 --> 00:05:41.720 transmission speed is a mere sixty bits per second. Isn't 121 00:05:41.759 --> 00:05:44.399 that incredibly slow for a computer. I mean, a standard 122 00:05:44.399 --> 00:05:47.160 dial up modem from the nineties was thousands of times 123 00:05:47.240 --> 00:05:47.920 faster than that. 124 00:05:48.040 --> 00:05:50.879 It is slow. But what's fascinating here is that this 125 00:05:51.160 --> 00:05:55.120 agonizingly slow speed isn't a mistake. It is a highly 126 00:05:55.160 --> 00:05:56.879 deliberate engineering trade off. 127 00:05:56.920 --> 00:05:58.839 Wait, really deliberately slow. 128 00:05:59.000 --> 00:06:03.399 Yeah, because in any digital communication network, timing is everything. Usually, 129 00:06:03.439 --> 00:06:07.519 microchips need complex, expensive internal quartz clocks to keep their 130 00:06:07.560 --> 00:06:10.720 signals perfectly synchronized with each other. Right, But by tying 131 00:06:10.759 --> 00:06:13.879 the data bursts strictly to the physical zero crossings of 132 00:06:13.879 --> 00:06:17.160 the AC power line, the X ten devices don't need 133 00:06:17.199 --> 00:06:18.560 to generate their own timing. 134 00:06:18.959 --> 00:06:22.399 Oh, I see the sixty hertz power grid itself, like 135 00:06:22.439 --> 00:06:26.439 the literal hum of the utility company, acts as a massive, 136 00:06:26.680 --> 00:06:30.600 free and incredibly precise clock for every single device in 137 00:06:30.639 --> 00:06:31.000 the house. 138 00:06:31.199 --> 00:06:35.360 Exactly. They essentially outsource the system's internal clock to the 139 00:06:35.360 --> 00:06:38.639 power company, and that brilliant shortcut meant they could strip 140 00:06:38.680 --> 00:06:42.240 the expensive timing components out of the hardware, which keeps 141 00:06:42.240 --> 00:06:44.839 the cost of the receivers incredibly low. 142 00:06:45.120 --> 00:06:49.079 That is clever, but I mean it completely shifts the burden. Right. 143 00:06:49.160 --> 00:06:51.839 If your transmission speed is locked into glacial sixty bits 144 00:06:51.879 --> 00:06:55.360 per second, you cannot afford long chatty messages no one 145 00:06:55.360 --> 00:06:58.720 at all. Every single microsecond is precious real estate. So 146 00:06:58.759 --> 00:07:01.439 how does it format the data so the receiver understands 147 00:07:01.480 --> 00:07:02.959 it without getting confused? 148 00:07:03.120 --> 00:07:05.639 So that moves us up a step in the ISO model, 149 00:07:05.800 --> 00:07:08.800 straight into the link and presentation layers. If the physical 150 00:07:08.839 --> 00:07:10.800 layer is the raw sound of a voice, the link 151 00:07:10.839 --> 00:07:12.120 layer is the grammar. 152 00:07:11.879 --> 00:07:13.680 The stuttering grammar. As we'll see right. 153 00:07:13.720 --> 00:07:16.040 It dictates how you frame the messages. So a listening 154 00:07:16.079 --> 00:07:18.800 outlet knows exactly when a command is starting and stopping, 155 00:07:19.399 --> 00:07:22.319 and X ten handles this using a very specific start code, 156 00:07:22.600 --> 00:07:26.199 which is the sequence one one zero, so three. 157 00:07:26.000 --> 00:07:29.600 Tone bursts followed by silence exactly. But wait a second. 158 00:07:29.839 --> 00:07:33.199 If the start code is one one zero, that means 159 00:07:33.199 --> 00:07:36.319 the first two cycles are sending a one followed immediately 160 00:07:36.319 --> 00:07:39.079 by another one. But the physical layer rules we just 161 00:07:39.120 --> 00:07:43.079 talked about absolutely demand that every bit is followed by 162 00:07:43.079 --> 00:07:46.199 its exact inverse. If you send a one on the 163 00:07:46.319 --> 00:07:49.680 rising wave, you must send a zero on the falling wave. 164 00:07:49.879 --> 00:07:52.399 You're exactly right, and that is the absolute beauty of 165 00:07:52.399 --> 00:07:54.920 the start code. The first two cycles of that sequence 166 00:07:55.000 --> 00:07:58.240 intentionally violate the protocol's own foundational rule. 167 00:07:58.439 --> 00:08:01.199 Oh wow, they make their own rule on purpose. 168 00:08:01.279 --> 00:08:05.800 Yes, they are mathematically invalid sequences. In engineering, we call 169 00:08:05.879 --> 00:08:07.519 this out of band signaling. 170 00:08:07.319 --> 00:08:11.399 Because it's impossible for actual valid data to ever accidentally 171 00:08:11.439 --> 00:08:12.399 generate that pattern. 172 00:08:12.519 --> 00:08:15.839 Exactly, because those first bits purposefully break the laws of 173 00:08:15.839 --> 00:08:19.360 the physical layer, the receiving device instantly knows, without a 174 00:08:19.399 --> 00:08:21.600 shadow of a doubt that it isn't looking at random 175 00:08:21.600 --> 00:08:24.680 electrical noise and it isn't looking at regular data. It's 176 00:08:24.720 --> 00:08:27.399 like a flare in the sky exactly. It's a guaranteed 177 00:08:27.399 --> 00:08:30.120 flare that says a new message is starting right now. 178 00:08:30.639 --> 00:08:33.600 It prevents the receiver from mistaking a random fragment of 179 00:08:33.639 --> 00:08:35.840 a passing message for the start of a command. 180 00:08:35.960 --> 00:08:39.240 Okay, so the start code flashes that signal, the outlet 181 00:08:39.279 --> 00:08:43.399 snaps to attention. Logically, once it's listening, you'd have to 182 00:08:43.440 --> 00:08:45.840 tell it two things, right, who you're talking to and 183 00:08:45.879 --> 00:08:46.799 what you want it to do. 184 00:08:47.039 --> 00:08:50.519 That's exactly how it's structured. Immediately following that start code, 185 00:08:50.799 --> 00:08:54.559 the system transmits exactly nine bits of data, just nine bits, 186 00:08:54.639 --> 00:08:57.960 just nine. The first four bits represent the house code, 187 00:08:58.039 --> 00:09:02.440 which is assign a letter from the next five bits 188 00:09:02.519 --> 00:09:05.480 represent either the key code, which is a number from 189 00:09:05.519 --> 00:09:09.399 one to sixteen targeting a specific lamp, or they represent 190 00:09:09.480 --> 00:09:10.279 a function. 191 00:09:10.039 --> 00:09:12.720 Code, and the function code is the actual action like on, 192 00:09:12.840 --> 00:09:16.039 off or dim. But because you only have nine bits 193 00:09:16.080 --> 00:09:18.600 to work with, you can't fit the who and the 194 00:09:18.639 --> 00:09:21.639 what in the same block, Like you can send lamp 195 00:09:21.679 --> 00:09:23.519 B twelve or you can send B turn on, but 196 00:09:23.559 --> 00:09:25.720 you can't send them together. So how do you build 197 00:09:25.759 --> 00:09:27.720 a full command out of this? Do you just chain them? 198 00:09:27.960 --> 00:09:30.759 You do, but the reality of sending data over a 199 00:09:30.799 --> 00:09:33.679 power line makes it much clunkier than just chaining them. 200 00:09:34.039 --> 00:09:37.600 The electrical grid is so inherently noisy. The protocol demands 201 00:09:37.600 --> 00:09:40.200 extreme redundancy to ensure the message survives. 202 00:09:40.480 --> 00:09:41.639 Okay, so what does that look like. 203 00:09:41.679 --> 00:09:43.879 You don't just transmit the address and then the command. 204 00:09:44.240 --> 00:09:47.159 The rules state that every single message block must be 205 00:09:47.200 --> 00:09:50.799 transmitted twice back to back with no gaps. Wow, And 206 00:09:50.840 --> 00:09:53.399 then you have to leave a mandatory three cycle gap 207 00:09:53.399 --> 00:09:55.600 of empty silence before you can send the next part. 208 00:09:55.679 --> 00:09:58.559 Okay, so the final instruction is basically a highly redundant 209 00:09:58.600 --> 00:10:01.559 stutter to turn on one light. It's not sending B 210 00:10:01.759 --> 00:10:05.919 twelve on. It's literally broadcasting B twelve B twelve long 211 00:10:06.000 --> 00:10:07.799 gap beyond ye on. 212 00:10:08.120 --> 00:10:11.399 Yes, it requires at least four separate message blocks to 213 00:10:11.440 --> 00:10:13.759 complete one single functional command. 214 00:10:13.600 --> 00:10:15.799 And at sixty bits per second, that actually takes a 215 00:10:15.840 --> 00:10:17.159 noticeable fraction of a second. 216 00:10:17.240 --> 00:10:20.799 It does. And the downside is that if any single 217 00:10:20.840 --> 00:10:23.919 piece of that four part transmission gets swallowed by electrical noise, 218 00:10:24.240 --> 00:10:27.519 the receiving lamp might flicker erratically, or it might just 219 00:10:27.559 --> 00:10:28.559 ignore you entirely. 220 00:10:28.960 --> 00:10:32.440 Just to put this in perspective for everyone listening, imagine 221 00:10:32.480 --> 00:10:36.159 trying to type an urgent email but your keyboard physically 222 00:10:36.159 --> 00:10:40.519 restricts you to typing one single letter per second sounds awful, 223 00:10:40.679 --> 00:10:43.440 It gets worse, and the rules of the email program 224 00:10:43.519 --> 00:10:46.559 state you have to type the recipient's entire name twice, 225 00:10:47.360 --> 00:10:50.600 pause for three seconds, and then type the actual body 226 00:10:50.600 --> 00:10:55.720 of the message twice. That is the agonizing, stuttering digital 227 00:10:55.720 --> 00:10:57.159 reality this protocol lives in. 228 00:10:57.399 --> 00:11:00.399 It is slow, and the grammar is incredibly rich, but 229 00:11:00.440 --> 00:11:02.519 it had to be designed that way because the environment 230 00:11:02.519 --> 00:11:04.799 it was deployed in is outright hostile. 231 00:11:04.360 --> 00:11:06.720 Which leads right into the next major hurdle. We have 232 00:11:06.759 --> 00:11:11.879 this rigidly structured grammar intentionally rule breaking, star codes, massive repetition. 233 00:11:12.159 --> 00:11:15.759 So why do these X ten signals still sometimes just vanish? 234 00:11:16.080 --> 00:11:18.360 Why do you press the button and nothing happens exactly? 235 00:11:18.399 --> 00:11:20.519 Why does the lamp in the bedroom do absolutely nothing? 236 00:11:20.759 --> 00:11:23.440 What's because the actual physical copper wiring of your house 237 00:11:23.519 --> 00:11:24.679 is essentially an obstacle. 238 00:11:24.679 --> 00:11:28.240 Course it is an incredibly harsh environment for a delicate 239 00:11:28.399 --> 00:11:31.960 one hundred and twenty killerhertz data signal, and the first 240 00:11:32.200 --> 00:11:36.200 major physical obstacle is a house's power transformer itself, the 241 00:11:36.240 --> 00:11:39.000 one outside well. The high voltage power coming from the 242 00:11:39.080 --> 00:11:42.200 utility pole comes into your breaker panel, and then it 243 00:11:42.200 --> 00:11:45.480 gets split into two separate one hundred and twenty volt rails. 244 00:11:45.639 --> 00:11:47.759 Right, So half the circuits in your house draw from 245 00:11:47.799 --> 00:11:49.399 one rail and the other have draw from. 246 00:11:49.320 --> 00:11:52.840 The other rail exactly, and the power transformer sitting between 247 00:11:52.840 --> 00:11:56.360 those two rails is highly efficient at passing that raw 248 00:11:56.440 --> 00:12:00.279 sixty hertz power. But to the tiny high frequency X 249 00:12:00.360 --> 00:12:03.639 ten signal, that transformer behaves completely differently. 250 00:12:03.840 --> 00:12:04.399 It blocks it. 251 00:12:04.559 --> 00:12:07.960 Yeah, it has what engineers call high impedance to that 252 00:12:08.000 --> 00:12:09.080 specific frequency. 253 00:12:09.360 --> 00:12:12.080 Let me clarify that term for a second. Impedance is 254 00:12:12.159 --> 00:12:15.399 essentially electrical resistance. That change is based on the frequency 255 00:12:15.440 --> 00:12:15.840 of the wave. 256 00:12:16.080 --> 00:12:16.480 Correct. 257 00:12:16.600 --> 00:12:19.279 So to the massive sixty herz power wave, the transformer 258 00:12:19.320 --> 00:12:22.000 looks like a wide open highway, but to the delicate 259 00:12:22.080 --> 00:12:24.960 one hundred and twenty kiloberts data tone, that exact same 260 00:12:25.000 --> 00:12:27.799 transformer suddenly acts like a thick par wall. 261 00:12:28.000 --> 00:12:31.519 That's a perfect analogy. The signal simply cannot pass easily 262 00:12:31.519 --> 00:12:33.480 from one side of your breaker panel to the other. 263 00:12:34.000 --> 00:12:36.399 If you plug a transmitter into an outlet on rail 264 00:12:36.440 --> 00:12:39.200 A and the lamp is on rail B, the signal 265 00:12:39.279 --> 00:12:42.840 might degrade so severely bouncing against that brick wall that 266 00:12:42.879 --> 00:12:45.120 the lamp never even hears the start code. 267 00:12:45.279 --> 00:12:46.399 So how do you fix that. 268 00:12:46.480 --> 00:12:48.879 You basically have to build a detour. You go into 269 00:12:48.919 --> 00:12:51.360 the breaker panel and install a coupler or a repeater. 270 00:12:51.799 --> 00:12:54.960 It catches the signal on one rail bypasses the transformer 271 00:12:55.080 --> 00:12:57.799 entirely and shuttles it directly over to the other rail. 272 00:12:57.879 --> 00:12:59.960 Okay, but even once you build that bridge, the eye 273 00:13:00.000 --> 00:13:04.639 obstacles don't stop because ironically, modern electronics are actually the 274 00:13:04.720 --> 00:13:06.120 natural predators of this data. 275 00:13:06.200 --> 00:13:08.320 Oh this is one of the biggest headaches in home automation. 276 00:13:08.799 --> 00:13:11.080 Think about switching power supplies. 277 00:13:10.679 --> 00:13:12.080 Like the power bricks for laptops. 278 00:13:12.159 --> 00:13:15.039 Yeah, the power bricks on your computer, your flat screen TV, 279 00:13:15.519 --> 00:13:19.759 basically any modern digital device. Inside those power supplies are 280 00:13:19.799 --> 00:13:23.200 capacitors designed to smooth out and filter the electrical power. 281 00:13:23.799 --> 00:13:27.039 But to a high frequency one hundred and twenty Killerherz signal, 282 00:13:27.399 --> 00:13:31.080 those specific capacitors act as a zero impedance black hole. 283 00:13:31.200 --> 00:13:35.200 Wait, a black hole, meaning there is literally zero resistance. 284 00:13:35.480 --> 00:13:36.840 The signal just falls right in. 285 00:13:37.159 --> 00:13:40.039 It completely eats the signal. You could buy a brand 286 00:13:40.120 --> 00:13:42.720 new flat screen TV, plug it into the wall, and 287 00:13:42.799 --> 00:13:45.519 suddenly the automated lights in the living room completely stop 288 00:13:45.559 --> 00:13:46.480 responding just. 289 00:13:46.480 --> 00:13:49.679 Because the TV is physically swallowing the data tones right 290 00:13:49.679 --> 00:13:50.679 out of the copper wiring. 291 00:13:50.879 --> 00:13:53.840 It literally absorbs the signal before it can reach the lamp. 292 00:13:53.919 --> 00:13:56.759 That is wild. So what's the solution to solve that? 293 00:13:56.879 --> 00:14:00.639 You have to deploy inline filters. You plug little box, 294 00:14:00.639 --> 00:14:03.960 which is basically specialized inductor coil, into the wall, and 295 00:14:04.000 --> 00:14:05.600 then plug the TV into the box. 296 00:14:05.720 --> 00:14:08.320 Ah, so it acts like a nightclub bouncer. Yeah, it 297 00:14:08.360 --> 00:14:11.320 happily lets the bulky sixty hertz power flow right into 298 00:14:11.360 --> 00:14:14.639 the TV, but it violently blocks the one hundred and 299 00:14:14.679 --> 00:14:17.120 twenty kill herds of data from entering the TV and 300 00:14:17.159 --> 00:14:17.720 getting eaten. 301 00:14:17.919 --> 00:14:20.799 Exactly. But wait, if your signal isn't getting blocked by 302 00:14:20.840 --> 00:14:24.440 a transformer or absorbed by a television, it's probably getting 303 00:14:24.519 --> 00:14:26.039 shouted over because. 304 00:14:25.759 --> 00:14:30.519 The electrical grid inside a home is incredibly noisy, very noisy. 305 00:14:30.799 --> 00:14:35.279 Fluorescent lamps, for instance, are terrible offenders. The electrical arc 306 00:14:35.360 --> 00:14:38.919 inside a fluorescent tube actually dies and re strikes itself 307 00:14:38.960 --> 00:14:41.919 at every single zero crossing of the power. 308 00:14:41.639 --> 00:14:45.159 Line, which is the exact microsecond or x ten signal 309 00:14:45.240 --> 00:14:47.000 is trying to quietly surf the wave. 310 00:14:46.960 --> 00:14:50.679 Exactly, So every time that fluorescent tube sparks, it blasts 311 00:14:50.799 --> 00:14:54.679 wide band high frequency noise all over the grid, and I. 312 00:14:54.559 --> 00:14:56.159 Imagine large motors are just as bad. 313 00:14:56.240 --> 00:15:00.000 Oh yeah, anything with commutators and brushes like a vacuum 314 00:15:00.120 --> 00:15:04.080 cleaner or a blender, generates chaotic electrical spikes. And remember, 315 00:15:04.120 --> 00:15:07.039 the wires don't stop at your house. Even your neighbor's 316 00:15:07.200 --> 00:15:10.559 X ten system can bleed over through the shared utility 317 00:15:10.600 --> 00:15:14.399 transformer and start randomly turning your kitchen lights on and off. 318 00:15:14.600 --> 00:15:16.960 Here's where it gets really interesting. Think of the X 319 00:15:17.000 --> 00:15:19.600 ten signal like someone trying to whisper a delicate secret 320 00:15:19.639 --> 00:15:23.879 code across a massive echoing house. Okay, except while they' 321 00:15:23.879 --> 00:15:27.000 whispering someone else is running a blender. Your television is 322 00:15:27.000 --> 00:15:29.679 physically absorbing the sound waves out of the air, and 323 00:15:29.720 --> 00:15:32.519 the guy next door is shouting his own secret codes 324 00:15:32.559 --> 00:15:33.480 through the open window. 325 00:15:33.759 --> 00:15:36.799 If we connect this to the bigger picture, this entire 326 00:15:36.879 --> 00:15:41.600 struggle is the ultimate illustration of the clash between the messy, 327 00:15:41.960 --> 00:15:48.080 chaotic analog real world and the rigid needs of digital communication. Right, 328 00:15:48.600 --> 00:15:53.279 the digital world demands perfection, but the analog power grid 329 00:15:53.399 --> 00:15:56.840 is a violent storm of energy. Making the two cooperate 330 00:15:56.919 --> 00:15:58.919 takes a lot of engineering duct tape. 331 00:15:59.039 --> 00:16:00.960 So let's say you've a play all that duct tape. 332 00:16:01.000 --> 00:16:03.639 You've installed the repeaters, You've plugged in the bouncers to 333 00:16:03.720 --> 00:16:06.399 protect the signal from your TV. You've waited for the 334 00:16:06.399 --> 00:16:09.879 blender to stop, and your whispered digital signal actually arrives 335 00:16:09.919 --> 00:16:11.559 safely at the physical wall switch. 336 00:16:11.679 --> 00:16:13.639 You're still not out of the woods. 337 00:16:13.440 --> 00:16:16.360 Right, because if you have installed the wrong hardware modules 338 00:16:16.360 --> 00:16:20.080 behind the dry wall, you might actually destroy your expensive appliances. 339 00:16:20.440 --> 00:16:23.519 This is a critical distinction the authors make. When you 340 00:16:23.559 --> 00:16:26.799 buy these automated switches, you have to understand the fundamental 341 00:16:26.840 --> 00:16:30.320 difference between simple appliance modules and dimmer switches. 342 00:16:30.480 --> 00:16:31.799 Okay, break that down for us. 343 00:16:31.879 --> 00:16:35.159 An appliance module is essentially a digital relay. It has 344 00:16:35.200 --> 00:16:39.320 a physical mechanical contact inside it violently clicks on or 345 00:16:39.399 --> 00:16:42.600 violently clicks off. It doesn't modify the electricity. It just 346 00:16:42.720 --> 00:16:43.840 acts as a simple gait. 347 00:16:44.039 --> 00:16:46.279 But dimmers are completely different animals, right. 348 00:16:46.399 --> 00:16:49.039 Dimmers don't use mechanical clicks that use a solid state 349 00:16:49.080 --> 00:16:52.759 semiconductor called triac, and a triac doesn't just lower the 350 00:16:52.799 --> 00:16:55.639 voltage smoothly like turning down a water faucet. 351 00:16:55.759 --> 00:16:56.240 It doesn't. 352 00:16:56.360 --> 00:16:59.840 No, it actually violently chops off a portion of the 353 00:17:00.600 --> 00:17:03.000 wave it waits a fraction of a second after the 354 00:17:03.080 --> 00:17:06.079 zero crossing, and then suddenly slams the power on. 355 00:17:06.599 --> 00:17:09.200 So it's rapidly chopping the electrical wave of one hundred 356 00:17:09.200 --> 00:17:10.279 and twenty times a second. 357 00:17:10.440 --> 00:17:15.279 Yes, and that constant truncation introduces chaotic new frequency components 358 00:17:15.279 --> 00:17:16.480 into the power line. 359 00:17:16.720 --> 00:17:20.039 But wait, if dimmers are that effective at controlling light levels, 360 00:17:20.240 --> 00:17:23.240 why bother with basic on off switches at all? Wouldn't 361 00:17:23.279 --> 00:17:26.079 it be easier to just use dimmers universally across the 362 00:17:26.119 --> 00:17:28.680 whole house. Then you always have the option to dim 363 00:17:28.680 --> 00:17:29.680 whatever is plugged in. 364 00:17:29.880 --> 00:17:32.119 You really can't, and it comes entirely down to physics. 365 00:17:32.119 --> 00:17:35.119 You have to understand the critical difference between resistive loads 366 00:17:35.200 --> 00:17:39.759 and reactive loads. A standard old school incandescent light bulb 367 00:17:39.920 --> 00:17:42.640 is a resistive load. It's literally just a piece of 368 00:17:42.680 --> 00:17:45.279 wire that gets hot and glows. It doesn't care if 369 00:17:45.279 --> 00:17:48.279 the power wave is smoothly rolling or violently chopped up. 370 00:17:48.279 --> 00:17:51.000 It just takes whatever energy it gets and clows a 371 00:17:51.079 --> 00:17:52.079 little less brightly. 372 00:17:52.240 --> 00:17:56.599 So TRIACs work beautifully for pure resistive loads exactly. 373 00:17:56.799 --> 00:17:59.960 But most modern devices plugged into our walls aren't just hot, 374 00:18:00.119 --> 00:18:01.400 glowing wires. 375 00:18:01.079 --> 00:18:04.640 Right, Things like fan motors, fluorescent tubes or high end 376 00:18:04.759 --> 00:18:08.839 halogen lamps with internal magnetic transformers. Those are reactive loads, right. 377 00:18:09.000 --> 00:18:13.359 Yes, they contain magnetic coils or capacitors that expect a smooth, 378 00:18:13.519 --> 00:18:15.559 continuous wave of power to function. 379 00:18:15.759 --> 00:18:17.920 So to put it, simply, feeding a chopped up wave 380 00:18:17.920 --> 00:18:20.079 from a dimmer to a motor is like trying to 381 00:18:20.079 --> 00:18:23.279 push a child on a swing by randomly and violently 382 00:18:23.359 --> 00:18:26.880 jerking the chains instead of giving them smooth, rhythmic pushes. 383 00:18:26.960 --> 00:18:29.759 That's exactly what happens. The magnetic field inside the motor 384 00:18:29.880 --> 00:18:34.519 collapses and spikes unpredictably. The motor will stall, it'll violently overheat, 385 00:18:34.599 --> 00:18:37.519 and eventually it will burn out. Wow, a transformer will 386 00:18:37.519 --> 00:18:41.039 start buzzing loudly and destroy itself. You must only ever 387 00:18:41.160 --> 00:18:43.480 use dimmer modules on pure resistive loads. 388 00:18:43.799 --> 00:18:46.599 It sounds like a hardware hacker's absolute nightmare if you 389 00:18:46.640 --> 00:18:47.680 don't know what you're doing. 390 00:18:47.599 --> 00:18:48.200 It really is. 391 00:18:48.400 --> 00:18:51.920 But if you follow the rules, if you meticulously map 392 00:18:51.920 --> 00:18:55.200 out your resistive and reactive loads, if you filter your 393 00:18:55.200 --> 00:19:00.000 TVs and bridge your transformer, you get the ultimate payoff. Yeah, 394 00:19:00.160 --> 00:19:03.960 total automated control. That's the dream, And the book finishes 395 00:19:04.000 --> 00:19:06.000 this deep dive by showing how you can give this 396 00:19:06.160 --> 00:19:09.359 entire sprawling ecosystem a brain by tying it all together 397 00:19:09.400 --> 00:19:09.799 with a PC. 398 00:19:10.079 --> 00:19:12.000 Right, Because the ultimate goal isn't just to use a 399 00:19:12.039 --> 00:19:14.720 remote control, it's to automate. And to do that you 400 00:19:14.839 --> 00:19:18.319 use a computer interface controller like the X ten cmlven. 401 00:19:17.720 --> 00:19:19.640