WEBVTT 1 00:00:00.000 --> 00:00:04.080 All right, dive enthusiasts, welcome back today. We're uh crack 2 00:00:04.160 --> 00:00:07.000 and open. Excerpts from a book that's all about getting 3 00:00:07.040 --> 00:00:11.679 hands on with electronics. Getting Started with Electronic Projects by 4 00:00:11.679 --> 00:00:12.359 Bill Pritty. 5 00:00:12.919 --> 00:00:15.720 That's right, And our mission, you know, in this deep 6 00:00:15.759 --> 00:00:18.440 dive is to go beyond just listing what's inside. We 7 00:00:18.480 --> 00:00:22.640 want to extract the real core knowledge, those surprising insights 8 00:00:22.879 --> 00:00:25.640 and practical takeaways. 9 00:00:25.280 --> 00:00:27.960 Stuff that anyone curious about building things with wires and 10 00:00:28.000 --> 00:00:29.280 components can really. 11 00:00:29.079 --> 00:00:32.560 Grab hold of, exactly starting simple, you know, and moving 12 00:00:32.600 --> 00:00:34.320 towards more complex systems. 13 00:00:34.399 --> 00:00:37.039 And this isn't just theory. It's built on some serious, 14 00:00:37.439 --> 00:00:42.159 real world experience. Bill Friddy's background is well pretty fascinating. 15 00:00:42.240 --> 00:00:44.560 It really is. Started in electronics back in the eighties, 16 00:00:44.640 --> 00:00:48.000 then telecom, aviation, r indeed defense work. 17 00:00:47.799 --> 00:00:50.159 And even found in his own technical security company. That 18 00:00:50.280 --> 00:00:53.240 kind of breath really shows through in the projects, doesn't it. 19 00:00:53.240 --> 00:00:55.759 It absolutely does. And the book's approach is I think 20 00:00:55.840 --> 00:00:56.679 perfect for learning. 21 00:00:56.719 --> 00:00:59.479 It builds step by step foundational skills first. 22 00:00:59.280 --> 00:01:02.799 Yeah, then gets in hardware software and puts them together, 23 00:01:02.880 --> 00:01:05.280 and he uses mostly through hole components. 24 00:01:05.319 --> 00:01:08.239 The bigger ones much easier to handle when you're starting out. 25 00:01:08.239 --> 00:01:10.959 Definitely friendlier than those tiny surface mount things. 26 00:01:11.040 --> 00:01:14.599 Okay, let's unpack this. He starts right where you'd expect, 27 00:01:15.439 --> 00:01:18.400 simple hands on stuff to build those fundamentals. 28 00:01:18.640 --> 00:01:23.159 Soldering especially absolutely, the very first project is incredibly accessible. 29 00:01:23.200 --> 00:01:26.840 It's about modifying an expensive you know, off the shelf 30 00:01:27.000 --> 00:01:29.719 led flashlights or headlamps. 31 00:01:29.519 --> 00:01:31.959 And the core idea just swapping LEDs. 32 00:01:32.239 --> 00:01:36.640 Basically, Yeah, replace the visible white LEDs with infrared or 33 00:01:36.680 --> 00:01:40.640 IR LEDs, which give you invisible light exactly. The result 34 00:01:40.680 --> 00:01:44.719 is a truly practical application. You create these invisible light sources. 35 00:01:44.840 --> 00:01:46.760 Okay, but why what's the use case? 36 00:01:46.799 --> 00:01:50.519 Well, think about discrete lighting maybe for nature observation at night, 37 00:01:50.879 --> 00:01:53.599 or even some leash security or gaming scenarios where you 38 00:01:53.640 --> 00:01:56.640 only want light visible to certain cameras, right. 39 00:01:56.560 --> 00:01:58.680 Because a lot of cameras can see IR light even 40 00:01:58.680 --> 00:02:00.760 if our eyes can't, like black and white cameras and 41 00:02:00.799 --> 00:02:01.519 night vision stuff. 42 00:02:01.560 --> 00:02:04.359 Precisely, it's a spectrum trick, and it's cheap. The book 43 00:02:04.400 --> 00:02:06.439 says around five bucks per project. 44 00:02:06.599 --> 00:02:09.199 Wow, and you immediately practice key skills. 45 00:02:09.479 --> 00:02:12.759 Yeah, taking something apart, desoldering, soldering the new parts in. 46 00:02:13.360 --> 00:02:15.879 It's a perfect way to get comfortable with the iron right. 47 00:02:15.759 --> 00:02:19.280 Away, straight into the fundamentals with something you can actually use. 48 00:02:19.840 --> 00:02:22.120 Love it. What's the next big concept. 49 00:02:21.759 --> 00:02:26.080 He tackles, ah, A true cornerstone of electronics, the LM 50 00:02:26.120 --> 00:02:27.280 five five five time. 51 00:02:27.159 --> 00:02:30.000 Er ic, the five five five. Yeah, that thing's legendary 52 00:02:30.199 --> 00:02:31.759 but around since the seventies, right it. 53 00:02:31.719 --> 00:02:35.680 Has, and it's still incredibly popular, just so versatile, a 54 00:02:35.759 --> 00:02:37.800 real warhorse chip you see everywhere, and. 55 00:02:37.800 --> 00:02:40.120 The book uses it to show two really different things 56 00:02:40.159 --> 00:02:42.919 it can do. Yeah. First up, an infra red beacon. 57 00:02:43.280 --> 00:02:46.280 Yeah, this builds on the ir LED idea but makes 58 00:02:46.280 --> 00:02:48.560 it flash. It uses the five to fifty five and 59 00:02:48.599 --> 00:02:49.680 it's as stable. 60 00:02:49.400 --> 00:02:53.039 Mode astable meaning unstable. Why you just keep switching exactly. 61 00:02:53.080 --> 00:02:56.639 It's free running like an oscillator, continuously switching on and 62 00:02:56.680 --> 00:02:58.360 off without needing an external trigger. 63 00:02:58.439 --> 00:03:00.240 And you control how fast it flashed. 64 00:03:00.280 --> 00:03:03.000 With just a few external parts, a couple of resistors 65 00:03:03.000 --> 00:03:06.199 and a capacitor. They set the timing, the flash rate, 66 00:03:06.639 --> 00:03:07.560 the onof. 67 00:03:07.240 --> 00:03:09.840 Duration, simple components controlling the chip's brain. 68 00:03:10.120 --> 00:03:13.039 Well, the chip has some clever internal bits, comparators and 69 00:03:13.159 --> 00:03:16.960 an RS flip flop, which is basically the simplest kind 70 00:03:17.000 --> 00:03:18.560 of digital memory. It just remembers a. 71 00:03:18.560 --> 00:03:23.159 State, so changing those resistor values changes the whole flashing pattern. 72 00:03:23.599 --> 00:03:26.080 That really shows how you customize a chip's behavior. 73 00:03:26.240 --> 00:03:28.879 It does, and even the case is simple using common 74 00:03:28.919 --> 00:03:32.520 plumbing pipe parts. The insight isn't the specific size, but 75 00:03:32.639 --> 00:03:34.000 using easy to find stuff. 76 00:03:34.240 --> 00:03:36.719 Okay, so that's a stable mode making it flash. Yeah, 77 00:03:36.759 --> 00:03:38.919 how does he use the same chip for the motion alarm? 78 00:03:39.000 --> 00:03:40.280 That sounds completely different. 79 00:03:40.400 --> 00:03:43.319 It is a completely different setup, often called a modified 80 00:03:43.360 --> 00:03:46.840 monastable mode. And what's fascinating is it doesn't even use 81 00:03:46.879 --> 00:03:49.280 the full five five five. It basically just uses the 82 00:03:49.439 --> 00:03:51.319 internal RS flip. 83 00:03:51.000 --> 00:03:53.439 Flop part, just a piece of the chip. How does 84 00:03:53.479 --> 00:03:54.680 that become a motion sensor? 85 00:03:54.960 --> 00:03:57.960 It's triggered mechanically a simple mercury switch, kind of like 86 00:03:58.000 --> 00:03:59.680 the tilt sensors and old car alarms. 87 00:04:00.039 --> 00:04:03.120 Uh okay, like a little blob of mercury rolling around. Yeah. 88 00:04:03.479 --> 00:04:06.639 When motion disturbs it, the switch momentarily grounds the five 89 00:04:06.680 --> 00:04:10.759 fIF five's trigger input. That pulse sets the RS flip flop, 90 00:04:10.919 --> 00:04:13.719 drives the output high, and bang turns on a buzzer. 91 00:04:13.919 --> 00:04:17.439 So instead of oscillating, it just waits and when tilted, 92 00:04:17.720 --> 00:04:20.199 it fires once the buzzer stays. 93 00:04:19.879 --> 00:04:23.439 On, stays on until it's reset. Yeah again, common pipe 94 00:04:23.480 --> 00:04:26.279 for the case, keep it hidden, and nice practical touches 95 00:04:26.319 --> 00:04:28.879 like a little diode for a verse polarity protection. 96 00:04:28.839 --> 00:04:31.360 Similar things that make it more robust. Definitely, it really 97 00:04:31.439 --> 00:04:34.199 hammers home the versatility of that five point fifty five 98 00:04:34.639 --> 00:04:38.199 flashing beacon. One minute hid an alarm the next, same chip, 99 00:04:38.319 --> 00:04:40.040 just connected differently. Amazing. 100 00:04:40.519 --> 00:04:44.480 Moving on, the book then transitions into projects that combine 101 00:04:44.519 --> 00:04:48.279 the physical electronics with computing power. This is where things 102 00:04:48.279 --> 00:04:51.759 get really interesting. I think creating custom instruments. 103 00:04:51.319 --> 00:04:54.000 Right, like turning your computer into an ascilloscope using its 104 00:04:54.000 --> 00:04:55.759 sound card. I remember hearing about that. 105 00:04:56.319 --> 00:04:59.519 It's a brilliant concept in its simplicity, isn't it? Using 106 00:04:59.560 --> 00:05:03.160 the an a digital conversion that's already built into most computers. 107 00:05:03.199 --> 00:05:06.519 Though the author does recommend using an external USB sound card. 108 00:05:06.720 --> 00:05:08.879 Why external better quality. 109 00:05:08.680 --> 00:05:12.399 Better quality generally, and it avoids any risk of accidentally 110 00:05:12.480 --> 00:05:16.399 damaging your main computers built in sound hardware safer makes sense. 111 00:05:17.000 --> 00:05:20.319 But there's a frequency limit, right. Sound cards aren't super fast. 112 00:05:20.160 --> 00:05:23.680 Correct, You're limited by the sampling rate. The Nyquist theorem 113 00:05:23.759 --> 00:05:26.240 tells us you can only accurately measure frequencies up to 114 00:05:26.319 --> 00:05:29.319 half that rate. So yeah, it's not for high frequency 115 00:05:29.439 --> 00:05:30.360 RF stuff. 116 00:05:30.079 --> 00:05:34.000 But okay for audio frequencies, maybe some lower speed digital signals. 117 00:05:33.560 --> 00:05:37.680 Exactly perfectly capable for a lot of hobbyist electronics. But 118 00:05:38.279 --> 00:05:40.800 and this is key, you can't just plug your circuit 119 00:05:40.920 --> 00:05:42.120 straight into the sound card. 120 00:05:42.199 --> 00:05:45.120 You need an interface, ah, some hardware in between. 121 00:05:45.600 --> 00:05:51.360 Why protection protection, yes, but also signal conditioning. This interface 122 00:05:51.399 --> 00:05:53.959 hardware does a few things. If you use the sound 123 00:05:53.959 --> 00:05:57.240 card to generate signals, there's an output buffer to isolate 124 00:05:57.279 --> 00:06:00.079 the card, okay, But for using it as a scope, 125 00:06:00.120 --> 00:06:03.800 the input section is crucial. It uses things like oppams 126 00:06:03.879 --> 00:06:06.079 to give you high input impedance. 127 00:06:05.680 --> 00:06:07.399 Meaning it doesn't mess with the circuit you're trying to. 128 00:06:07.319 --> 00:06:10.360 Measure precisely, it doesn't load it down. It also usually 129 00:06:10.360 --> 00:06:11.279 includes AC. 130 00:06:11.240 --> 00:06:15.600 Coupling, which removes any steady DC voltage. Let's you focus 131 00:06:15.600 --> 00:06:16.399 on the changing. 132 00:06:16.160 --> 00:06:19.560 Signal, right and sure as only the AC part gets analyzed. 133 00:06:19.800 --> 00:06:22.600 And the book also mentions handling standard aciliscope probes. 134 00:06:22.680 --> 00:06:24.319 Yeah, the X one and X ten settings. 135 00:06:24.399 --> 00:06:27.040 Yes. Scope robes often have that X ten setting, which 136 00:06:27.240 --> 00:06:31.040 cuts the signal by ten but increases impedance. The DIY 137 00:06:31.040 --> 00:06:35.480 hardware includes circuitry to compensate for that attenuation, so the reading. 138 00:06:35.199 --> 00:06:37.439 On the screen is correct regardless of the probe setting. 139 00:06:37.480 --> 00:06:40.240 That's the idea, keeps the level consistent for the sound card. 140 00:06:40.879 --> 00:06:43.920 There's also a neat trick mentioned, using a voltage reference 141 00:06:43.920 --> 00:06:46.399 and capacitors to shift the signal so it fits within 142 00:06:46.439 --> 00:06:49.480 the sound card's input range, then removing that offset later. 143 00:06:49.959 --> 00:06:50.839 Clever stuff. 144 00:06:51.079 --> 00:06:54.120 So you build this interface, plug in your USB sound card, 145 00:06:54.600 --> 00:06:55.439 connect it all up. 146 00:06:55.800 --> 00:06:59.800 Then what software, yep, software is where the magic really happens. 147 00:07:00.199 --> 00:07:03.480 The book mentions several options, and these aren't just basic 148 00:07:03.519 --> 00:07:04.279 scope displays. 149 00:07:04.360 --> 00:07:06.000 Oh what else can they do? 150 00:07:06.199 --> 00:07:09.680 Many add powerful features signal generators so your setup can 151 00:07:09.680 --> 00:07:14.680 create test signals, audio spectrum analyzers to see the frequency content. 152 00:07:14.519 --> 00:07:16.839 Like seeing the different notes in a sound sort of. 153 00:07:16.879 --> 00:07:21.560 Yeah, and even things like a ZRLC meter for measuring impedance, resistance, 154 00:07:21.680 --> 00:07:23.240 inductance capacitance. 155 00:07:23.480 --> 00:07:26.240 Wow. Okay, even if the author didn't build the extra 156 00:07:26.360 --> 00:07:29.759 jig for that, the software capability is there. Your DIY 157 00:07:29.839 --> 00:07:31.839 tool gets way more powerful. 158 00:07:31.639 --> 00:07:35.920 Exactly, and functions like a sweep generator are incredibly useful. 159 00:07:36.000 --> 00:07:38.560 It automatically sweeps through frequency go for. 160 00:07:38.560 --> 00:07:41.680 Testing filters right, seeing how they respond at different frequencies. 161 00:07:41.720 --> 00:07:45.839 Perfect for that, or testing amplifier response. The software really 162 00:07:45.839 --> 00:07:50.199 completes the picture, turning fairly simple hardware into a quite 163 00:07:50.279 --> 00:07:52.120 capable test instrument. 164 00:07:52.360 --> 00:07:55.079 So you can turn your computer into a basic lab instrument. 165 00:07:55.879 --> 00:07:58.160 Very cool. Yeah. Building on that, the book then moves 166 00:07:58.199 --> 00:08:01.199 into radio frequency or RF projects. 167 00:08:01.319 --> 00:08:03.360 Yeah, RF, which you know, for a lot of people 168 00:08:03.399 --> 00:08:04.839 feels a bit like black magic. 169 00:08:04.959 --> 00:08:07.160 It does have that reputation. Yeah, but you're saying it's 170 00:08:07.160 --> 00:08:08.439 just electronics principles. 171 00:08:08.720 --> 00:08:11.639 It absolutely is. Just follows the rules of physics. And 172 00:08:11.720 --> 00:08:14.879 the first RF project provides a really critical tool, a 173 00:08:15.040 --> 00:08:16.319 calibrated RF source. 174 00:08:16.360 --> 00:08:18.120 Why do you need a calibrated source? What does it do? 175 00:08:18.439 --> 00:08:22.360 Its job is to outprint a known stable RF signal 176 00:08:22.720 --> 00:08:25.040 like fifty meli hurts in the example, at a very 177 00:08:25.040 --> 00:08:28.600 precise power level. This becomes your reference point, a reference 178 00:08:28.600 --> 00:08:32.480 for what for calibrating other RF measurement tools like the 179 00:08:32.639 --> 00:08:35.360 RF power meter project that comes next. You need a 180 00:08:35.399 --> 00:08:37.919 known input to calibrate the meter accurately. 181 00:08:38.080 --> 00:08:40.480 Gotcha. So how does it make this known signal? 182 00:08:40.840 --> 00:08:44.360 It uses a stable component, a crystal oscillator to get 183 00:08:44.399 --> 00:08:48.320 the exact frequency then to get the precise power level. 184 00:08:48.399 --> 00:08:52.840 It uses a simple but effective circuit called a pipad attenuator. 185 00:08:52.240 --> 00:08:54.360 Pipad like the Greek letter yeah. 186 00:08:54.399 --> 00:08:56.879 The resistors are arranged kind of like a PI symbol. 187 00:08:57.039 --> 00:08:59.279 It's just a few resistors used to trim the output 188 00:08:59.360 --> 00:09:02.519 power down to a standard reference level, often zero dB. 189 00:09:02.600 --> 00:09:05.120 And zero dBm is one milli wont. 190 00:09:05.039 --> 00:09:08.759 Correct a standard RF power unit. Very convenient reference. The 191 00:09:08.759 --> 00:09:12.000 PCB design for this also shows good RF practices, like 192 00:09:12.320 --> 00:09:15.080 using lots of vias those little plated holes to connect 193 00:09:15.159 --> 00:09:16.840 ground planes together for stability. 194 00:09:16.919 --> 00:09:18.759 Little details matter in RF. 195 00:09:18.519 --> 00:09:20.679 They do, and the book also shows how you can 196 00:09:20.720 --> 00:09:24.120 add external attenuators fixed or even programmable ones to get 197 00:09:24.159 --> 00:09:26.440 different known power levels out of that source. 198 00:09:26.840 --> 00:09:30.120 Programmable meaning you can control the attenuation. 199 00:09:29.679 --> 00:09:32.600 Level electronically exactly, which is key because you can then 200 00:09:32.639 --> 00:09:35.120 control it with something like a beagle bone. 201 00:09:34.840 --> 00:09:37.720 Which leads nicely into the RF power beater hardware I 202 00:09:37.759 --> 00:09:38.600 assume it does. 203 00:09:38.960 --> 00:09:42.159 This project is all about measuring the strength of RF signals. 204 00:09:42.240 --> 00:09:44.559 Okay, what's the core component doing the measurement? 205 00:09:44.679 --> 00:09:48.879 It uses a specialized chip, an RMS RF power detector. 206 00:09:49.120 --> 00:09:52.679 The book mentions one from linear technology the LTC five 207 00:09:52.840 --> 00:09:54.799 five eighty two RMS detector. 208 00:09:54.799 --> 00:09:55.879 What's the advantage. 209 00:09:55.960 --> 00:09:58.320 What's great about this type of chip is it hugely 210 00:09:58.360 --> 00:10:03.159 simplifies things. It outputs a DC voltage that's directly proportional 211 00:10:03.240 --> 00:10:05.559 to the RMS power of the RF signal coming in, 212 00:10:05.720 --> 00:10:06.840 so you. 213 00:10:06.759 --> 00:10:09.399 Don't have to deal with the high frequency RF signal 214 00:10:09.440 --> 00:10:12.039 directly in software. You just read a DC voltage precisely. 215 00:10:12.399 --> 00:10:15.440 The chip does the complex RF to DC conversion. The 216 00:10:15.519 --> 00:10:18.399 software just needs to read that relatively slow changing DC 217 00:10:18.559 --> 00:10:20.080 voltage much easier. 218 00:10:20.240 --> 00:10:23.200 And how does that DC voltage get into the beagle Bone? 219 00:10:23.240 --> 00:10:25.480 It gets fed into one of the beagle Bon's analog 220 00:10:25.600 --> 00:10:28.639 input pins. But there's a crucial detail here. 221 00:10:28.879 --> 00:10:30.240 Uh oh, what's the catch? 222 00:10:30.600 --> 00:10:34.360 The beaglebones analog inputs have a maximum voltage limit around 223 00:10:34.440 --> 00:10:37.639 one point eight volts. The power detector chip can output 224 00:10:37.679 --> 00:10:40.559 more than that, maybe up to two point four v ah. 225 00:10:40.879 --> 00:10:43.159 So you'd fry the beagle Bone input potentially. 226 00:10:43.240 --> 00:10:46.320 Yes, So you need a simple voltage divider just two 227 00:10:46.360 --> 00:10:49.720 resistors to scale the detector's output voltage down into the 228 00:10:49.720 --> 00:10:52.440 safe range. The beagle Bone can read like zero point 229 00:10:52.519 --> 00:10:55.080 six to one point two volts in the example. 230 00:10:55.240 --> 00:10:59.519 Okay, simple fix. So hardware built connected now software to 231 00:10:59.519 --> 00:11:00.720 make sense of that voltage. 232 00:11:00.840 --> 00:11:04.320 Right. The book details setting up the beagle Bone, installing 233 00:11:04.360 --> 00:11:08.120 Debian Linux, getting development tools like no js, and using 234 00:11:08.159 --> 00:11:10.279 a library called bone script. 235 00:11:09.919 --> 00:11:12.559 Bone script that's JavaScript for the beagle Bone hardware. 236 00:11:12.639 --> 00:11:15.279 Yeah, makes it easy to control the pens using JavaScript. 237 00:11:15.360 --> 00:11:17.840 They use the cloud nine ID, which is cool because 238 00:11:17.840 --> 00:11:19.919 it can run right on the beagle Bone itself. Makes 239 00:11:19.960 --> 00:11:21.440 it a self contained development box. 240 00:11:21.519 --> 00:11:23.360 Okay, so the software runs on the beagle Bone. How 241 00:11:23.360 --> 00:11:24.240 do you interact with it? 242 00:11:24.279 --> 00:11:26.799 See the power reading through a web interface? This is 243 00:11:26.799 --> 00:11:28.879 pretty neat. They use something called socket dot io. 244 00:11:29.159 --> 00:11:32.519 Socket dot io that lets a web page talk to 245 00:11:32.600 --> 00:11:35.120 the code running on the beagle Bone exactly. 246 00:11:35.200 --> 00:11:38.440 It creates a real time communication channel between an HTML 247 00:11:38.480 --> 00:11:41.440 web page you open in your browser. That's your graphical interface, 248 00:11:41.759 --> 00:11:45.559 your GUI, and the JavaScript program running on the beagle Bone. 249 00:11:45.759 --> 00:11:48.279 So the web page is the control panel in display. 250 00:11:48.480 --> 00:11:51.080 You got it. The JavaScript program on the beagle Bone 251 00:11:51.200 --> 00:11:54.960 continuously reads the analog input voltage from the RF detector. 252 00:11:55.399 --> 00:11:58.000 Then it applies a calibration calculation. 253 00:11:58.039 --> 00:12:00.840 Based on that reading you got from the calibrator source earlier. 254 00:12:01.240 --> 00:12:05.320 Right, it knows what voltage corresponds to zero DBBM, so 255 00:12:05.360 --> 00:12:08.000 it calculates the power level and dBm based on the 256 00:12:08.000 --> 00:12:11.639 current voltage reading. Then it sends that dBm value over 257 00:12:11.720 --> 00:12:14.679 socket dot io to the web page, which displays. 258 00:12:14.240 --> 00:12:16.480 It almost like a live meter reading in your browser. 259 00:12:16.679 --> 00:12:19.440 Pretty much. Yeah, updated frequently. And if you included that 260 00:12:19.480 --> 00:12:21.519 programmable attenuator we mentioned. 261 00:12:21.440 --> 00:12:23.159 H can the webpage control that too? 262 00:12:23.320 --> 00:12:27.159 Yes, the guy can have controls like sliders or buttons 263 00:12:27.159 --> 00:12:30.000 that correspond to the attenuator's settings. You change a setting 264 00:12:30.000 --> 00:12:32.519 on the web page, click apply or load, and. 265 00:12:32.480 --> 00:12:34.279 The JavaScript on the beagle bone gets the. 266 00:12:34.200 --> 00:12:38.039 Message and toggles the correct digital output pins connected to 267 00:12:38.080 --> 00:12:41.000 the attenuator to set the new attenuation level, so you 268 00:12:41.000 --> 00:12:44.440 can control the input level being measured right from the browser. 269 00:12:44.519 --> 00:12:49.080 Wow, that's a really powerful combination. Specialize RF hardware a 270 00:12:49.120 --> 00:12:52.399 small Linux computer do in the processing a web interface 271 00:12:52.399 --> 00:12:54.120 for control and display. Very neat. 272 00:12:54.279 --> 00:12:57.240 It really shows how you can integrate these different pieces 273 00:12:57.480 --> 00:13:00.879 taking a physical RF signal, measuring it, process it, presenting it. 274 00:13:01.039 --> 00:13:03.440 Okay. The final major section of the book seems to 275 00:13:03.440 --> 00:13:08.360 shift gears again into wireless communication. Building a network. 276 00:13:08.480 --> 00:13:11.200 Yeah, using Zigbie sensors, specifically Zigbi. 277 00:13:11.240 --> 00:13:14.639 That's like low power wireless stuff for smart homes. 278 00:13:14.440 --> 00:13:18.799 And things exactly the low power mesh networking capabilities. Usually 279 00:13:19.360 --> 00:13:21.919 the goal here is to create something like a wireless 280 00:13:21.960 --> 00:13:25.759 security system using these small ZIGBRF modules. 281 00:13:25.879 --> 00:13:27.799 How do you start with those? They need setting up 282 00:13:27.919 --> 00:13:28.240 they do. 283 00:13:28.360 --> 00:13:31.600 The process starts with configuring the modules. You use software 284 00:13:31.639 --> 00:13:34.960 from the manufacturer often called XCTU, connect the modules to 285 00:13:35.000 --> 00:13:38.679 a computer, usually via USB adapters installed drivers. 286 00:13:38.240 --> 00:13:40.200 And then tell each module what its job is. 287 00:13:40.559 --> 00:13:43.399 Pretty much, you set up their roles. One module needs 288 00:13:43.480 --> 00:13:46.240 to be the coordinator. That's the central hub the network, 289 00:13:46.320 --> 00:13:50.279 the boss kind of yeah, and the others become end units. 290 00:13:50.320 --> 00:13:53.039 These are your remote sensor nodes. But the really key 291 00:13:53.120 --> 00:13:56.320 step in the configuration, especially for this project, yes, is 292 00:13:56.399 --> 00:13:59.840 enabling a feature called digital ioline passing. 293 00:14:00.279 --> 00:14:03.639 Ioline passing, what on earth is that sounds important? 294 00:14:03.840 --> 00:14:06.879 It is the insight that makes this whole project much simpler. 295 00:14:07.279 --> 00:14:10.480 It means if a digital input pin on a remote 296 00:14:10.720 --> 00:14:15.080 end unit module changes state, say a sensor pulls it low, okay, 297 00:14:15.279 --> 00:14:19.000 then the corresponding digital output pin on the coordinator module 298 00:14:19.159 --> 00:14:22.480 automatically changes state to match it wirelessly. 299 00:14:22.559 --> 00:14:26.679 Wait, so the module itself handles the radio transmission to 300 00:14:26.799 --> 00:14:30.480 mirror the input state over the air onto the coordinator's output. Yes, 301 00:14:30.559 --> 00:14:32.960 you don't have to write code to constantly pull the sensors. 302 00:14:33.039 --> 00:14:35.200 Of course, it packets back and forth saying sensor x 303 00:14:35.279 --> 00:14:35.600 is open. 304 00:14:35.759 --> 00:14:39.679 Exactly. That's the power of ioline passing. The Zigbie module 305 00:14:39.720 --> 00:14:43.519 firmware handles all that wireless communication invisibly. Your main controller, 306 00:14:43.559 --> 00:14:45.559 the beagle doone connected to the coordinator. 307 00:14:45.759 --> 00:14:48.080 It just has to watch the output pins on the 308 00:14:48.120 --> 00:14:49.080 coordinator module. 309 00:14:49.200 --> 00:14:52.399 Right, those pins are now effectively mirroring the state of 310 00:14:52.440 --> 00:14:56.080 the remote sensors. It hugely simplifies the software you need 311 00:14:56.120 --> 00:14:57.320 to write on the beagle bone. 312 00:14:57.480 --> 00:15:00.799 That is clever. What kind of network work setup or 313 00:15:00.879 --> 00:15:03.480 topology does the book use to make that work? A 314 00:15:03.600 --> 00:15:07.320 star topology jar like everything talks directly to the center. Yeah. 315 00:15:07.360 --> 00:15:10.120 In a star network, all the end units communicate directly 316 00:15:10.200 --> 00:15:13.559 only with that central coordinator, like spokes on a wheel. 317 00:15:13.799 --> 00:15:17.159 Not like a mesh network where messages can hop between nodes. 318 00:15:17.399 --> 00:15:20.879 Right, Mesh networks can be more robust, messages find other 319 00:15:21.000 --> 00:15:24.159 paths if one node fails. But the book chooses the 320 00:15:24.159 --> 00:15:27.240 star topology here specifically because. 321 00:15:26.960 --> 00:15:30.799 Let me guess that ioline passing feature works best or 322 00:15:30.840 --> 00:15:32.879 maybe only in a STAR setup. 323 00:15:33.080 --> 00:15:35.919 You got it. That's the crucial trade off. The massive 324 00:15:35.960 --> 00:15:39.200 software simplification gained by using ioline passing in a STAR 325 00:15:39.279 --> 00:15:43.279 network was prioritized for this specific project's goals, even if 326 00:15:43.360 --> 00:15:44.799 MESH offers other advantages. 327 00:15:45.120 --> 00:15:47.600 Okay, makes sense. What about the actual hardware, the sensor 328 00:15:47.600 --> 00:15:48.080 boards and. 329 00:15:48.039 --> 00:15:51.960 Things well beyond the XB modules themselves, which are physically 330 00:15:51.960 --> 00:15:55.879 identical but configure differently, You need some custom electronics. The 331 00:15:55.919 --> 00:15:58.799 book details building things like a zone monitor. 332 00:15:58.480 --> 00:16:01.960 Board, a zone being like an area you're protecting a. 333 00:16:01.879 --> 00:16:04.960 Group of sensors exactly, And this board uses a pretty 334 00:16:04.960 --> 00:16:08.399 clever technique to monitor the actual sensors connected to it. 335 00:16:08.559 --> 00:16:10.080 Oh, what's the clever bit. 336 00:16:10.200 --> 00:16:13.200 It uses LM three thirty nine comparators. We talked about 337 00:16:13.200 --> 00:16:15.399 comparators earlier with the five point fifty five. They just 338 00:16:15.440 --> 00:16:16.159 compared two. 339 00:16:16.080 --> 00:16:16.960 Voltages, right. 340 00:16:17.200 --> 00:16:19.559 The clever part is how they're used with end of 341 00:16:19.600 --> 00:16:23.559 line EOL resistors. These are resistors you place physically at 342 00:16:23.559 --> 00:16:25.799 the very end of the sensor wiring loop. 343 00:16:26.000 --> 00:16:28.279 Okay, why put a resistor way out there? 344 00:16:28.480 --> 00:16:31.600 By arranging the circuit as a voltage divider, including that 345 00:16:31.639 --> 00:16:35.759 EOL resistor, the comparators can actually detect three different states 346 00:16:35.799 --> 00:16:38.639 on the sensor wiring loop, not just open or closed. 347 00:16:38.759 --> 00:16:40.200 Three states like what. 348 00:16:40.279 --> 00:16:44.639 Normal contacts closed wirecut an open circuit, and wire shorted 349 00:16:44.679 --> 00:16:46.720 together like someone trying to bypass the sensor. 350 00:16:46.879 --> 00:16:49.559 Uh So it can spot tampering, not just as simple 351 00:16:49.600 --> 00:16:50.960 break exactly. 352 00:16:51.200 --> 00:16:56.919 Each state normal open, short produces a distinctly different voltage 353 00:16:56.960 --> 00:16:59.639 at the comparator inputs. The system can tell them apart. 354 00:16:59.840 --> 00:17:03.279 It's a classic very effective security technique. 355 00:17:02.960 --> 00:17:06.200 Very neat. So these zone monitor boards connect to the sensors, 356 00:17:06.599 --> 00:17:10.119 check their status using the EOL resistors and comparators, and 357 00:17:10.160 --> 00:17:13.279 then feed that into the remote xp end unit. That's 358 00:17:13.319 --> 00:17:13.799 the idea. 359 00:17:13.960 --> 00:17:17.839 And there's also a separate board described an optically isolated 360 00:17:17.839 --> 00:17:18.559 output board. 361 00:17:18.640 --> 00:17:20.519 Optically isolated like using light. 362 00:17:20.720 --> 00:17:24.359 Yeah, it uses components called opto isolators. They transfer a 363 00:17:24.400 --> 00:17:27.720 signal using an internal LED and photo transistor, so there's 364 00:17:27.759 --> 00:17:29.240 no direct electrical connection. 365 00:17:29.359 --> 00:17:30.160 Why is that important? 366 00:17:30.559 --> 00:17:35.359 Safety? This board provides outputs that can control external devices sirens, lights, 367 00:17:35.440 --> 00:17:38.480 maybe motors. These might run on much higher voltages, even 368 00:17:38.519 --> 00:17:42.279 mains power. The opto isolation keeps the low voltage beagle 369 00:17:42.319 --> 00:17:45.079 bone and Zigbie stuff electrically separate and safe from the 370 00:17:45.160 --> 00:17:46.279 high voltage. 371 00:17:45.880 --> 00:17:47.880 Side crucial if you're switching mains power. 372 00:17:48.119 --> 00:17:52.559 Absolutely, and the book correctly stresses, you know, high voltage 373 00:17:52.559 --> 00:17:56.759 work needs a qualified electrician, but this board gives you 374 00:17:56.839 --> 00:18:00.160 that safe interface point maybe to control relays which which 375 00:18:00.160 --> 00:18:01.319 then switch the big loads. 376 00:18:01.519 --> 00:18:06.319 Makes sense. Okay, so hardware sorted, network configured. Bringing it 377 00:18:06.359 --> 00:18:09.440 all together is the software on the beagle bone talking 378 00:18:09.480 --> 00:18:11.160 to that coordinator XP. Right. 379 00:18:11.240 --> 00:18:13.519 The software set up on the beagle Bone involves, you know, 380 00:18:13.559 --> 00:18:16.519 installing some necessary libraries, like for talking to the serial 381 00:18:16.599 --> 00:18:20.240 port where the XP coordinator is connected. But the core 382 00:18:20.400 --> 00:18:23.000 logic it's incredibly. 383 00:18:22.480 --> 00:18:24.920 Streamlined because of that iolne passing exactly. 384 00:18:25.240 --> 00:18:27.720 The beagle Bone doesn't need to worry about ZIBI packet 385 00:18:27.759 --> 00:18:30.279 formats or addresses for the basic alarm function. 386 00:18:30.440 --> 00:18:32.559 It just needs to read its own input pins, which 387 00:18:32.559 --> 00:18:34.880 are connected to the coordinator's output Precisely. 388 00:18:35.000 --> 00:18:37.799 You use bone script in JavaScript again to find which 389 00:18:37.839 --> 00:18:41.599 beagle Bone pins are connected to those coordinator XP outputs. 390 00:18:42.039 --> 00:18:44.480 And the really efficient part is using interrupts. 391 00:18:44.599 --> 00:18:47.000 Interrupts, yeah, instead of constantly checking the pins. 392 00:18:47.160 --> 00:18:49.440 Yeah, think of it like setting an alert. You tell 393 00:18:49.440 --> 00:18:51.279 the beagle bone, hey, let me know immediately if the 394 00:18:51.319 --> 00:18:53.000 voltage on this pin goes low. 395 00:18:53.000 --> 00:18:55.519 So it's not wasting time checking checking, check it right. 396 00:18:55.640 --> 00:18:58.160 It can do other things or just sit idle the 397 00:18:58.240 --> 00:19:01.000 moment an input pin goes low, which which happens automatically 398 00:19:01.079 --> 00:19:04.000 when a remote sensor triggers its end unit thanks to 399 00:19:04.079 --> 00:19:08.680 ioline passing, the beagle Bone hardware generates an interrupt. 400 00:19:08.400 --> 00:19:11.079 And that interrupts triggers some code. 401 00:19:10.759 --> 00:19:14.119