We're back. Welcome to John Park's workshop. It's me. I'm John Park. Here we are. Awesome. All right. First of all, I want to say thank you to everyone who came by last night for the unboxing on AidaBox 19. That was loads and loads and loads of fun. And I really appreciate that I get to do wacky stuff like that. Thanks to all of you. Thanks for supporting our community, buying cool stuff in the AidaFruit store, getting AidaBox's, things like that. It really helps. So, let's see. What else I wanted to let you know this will be a probably slightly more freeform show today or maybe you might think of it as a throwback to earlier shows where I used to sometimes just build something on air. Because I think what I want to do today, I've got a couple of things, normal things to do, some things I'm not doing. I didn't prepare a, or actually I didn't make a like a one minute clip of the last John Park's product pick of the week. So, I don't have a recap to play of that. But I am going to build something. I'm going to take a crack at just the most basic use of our ortho snap apart keyboard on an RP2040 feather from scratch. So, I'll be putting some software on there. I'll be doing a little bit of the soldering of header pins and wiring and looking at diagrams. So, it'll be that kind of thing. Hope you dig it. Thank you C Grover for letting me know. Microphone's peaking a little high. I think I had goosed that up yesterday when I was dealing with audio difficulties. But let's get to it. So, first of all, product jobs. Yeah. That's what I wanted to say. AidaFruit job board. Did you know about this thing? We've got it and it's right here. And if you head on over to jobs.adafruit.com, then you may see something like this. Here's a job opening for a software developer in CC++ Python Arduino. And it is at a company called playlightpong.com. Light Pong. I wonder what Light Pong is all about. I can take some guesses. This is in Chicago. It is a contract job. They're looking for software develop to join the team. Need assistance writing and maintaining a framework for the handheld game device. Ooh. All right. I'm going to click on the link then. Let's see what this is. Playlightpong.com. And ah. Hey. That looks cool. It's one-dimensional Pong. Really neat. All right. Well, that sounds super interesting. So, if you're in the market for a job, and it looks like it's probably an on-site gig, is my guess. They're in Chicago. So, you might want to check that out. You just go to jobs.adafruit.com. We have free postings. We have free job postings and free resume postings. So, head over there and check that out. Let's see. So, next thing I did mention that. Let me switch this screen out here real quick. The product pick of the week was on Tuesday. I don't have a recap video, but I'll give it away. It was this 2.7-inch sharp memory display. Really cool display. A neat display technology. And that was the product pick on display. If you want to go check out that video, I'll be posting the one-minute recap later, and they'll probably play it on Ask an Engineer next week. Maybe not. We might miss that one, because I'll have another show by then. But those were half off during the show, which is a good reason to tune in on Tuesdays for that show, because you get a deep, deep, deep discount. And actually, the other thing is, this sharp memory display I mentioned is featured in that Playdate handheld game machine. A lot of handheld game machines I mentioned today. That is available today for pre-order. So, I'm not affiliated with them. I don't make any money for saying that. I don't have one. If I get one, I'm that close to pre-ordering one. It's between that and a Euro-Rack module I want. But if you want to get one of those, if I get one, I'm going to pay for it. I'm not making any money to get that or getting a free one. But they look cool, and they use that really snazzy monochrome display. Very retro. So, go check that out. And let's see. Next up, let's check in with our Discord. If you're wondering where the chat is at, this is it. We've got a Discord server with, I think, something like 25,000 members or something like that. There's probably a robot command you can type in to ask the number of members in there. It's like, question mark members? I don't know. I won't test that, but maybe one of you will. And head to theatafru.it, that's our URL shortener, atafru.it slash Discord. You'll get an instant, whoa, we've got 30,100 plus members. Thanks, Mr. Certainly. Instant invite, if you head to the live broadcast chat channel, that's where we're hanging out right now. But we have a whole bunch of other channels from everything from announcements, pet photos, off topic, help with CircuitPython, Arduino 3D printing, help with audio, Raspberry Pi, and on and on. Much members, Andy Calloway, that's right. So head on over there. That's where a lot of the chat's happening. I also see some people over in the YouTube chat. Hey, F-A-Z. Hey, Ronald Bone. Nice to see you, Gary T. Welcome. Thanks for joining us. Let's see. How about, looks like no questions. Everything's good. Lars is lurking. You know what? Lars is back there, and Lars has a untitled goose game goose sitting on his head for some reason. Not sure why. You see that? Right there? I don't know why. I don't know what's going on. I think my daughter had something to do with that. Okay, so next up, let's do a little CircuitPython Parsec. Why don't we? Let's get all set up for that, huh? All right, I'm game. For the CircuitPython Parsec today, I want to show how you can read a capacitive touch pin or pad on a CircuitPython device. So here I have a CircuitPython, or rather, here I have a Circuit Playground Bluetooth, and this will work on nearly every microcontroller board that has capacitive touch pins, which is most of them. And the way that this works, you'll see that when I touch one of these pads here, it is both lighting up a little LED right on the device to let me know that I've pressed it, and I'm printing out to my little serial REPL display there, cap pad touched, cap pad released. So that works entirely on capacitance. In fact, it doesn't even require contact. You could put a piece of paper over that. It still works. And it's a super useful way to do input. Here's how it works in CircuitPython. And here's how it works in CircuitPython. It's really simple. I'm importing the board so that I get pin definitions. I'm importing touch IO. That's what we use for the capacitive touch. And in this case, I'm also importing digital IO just so I can light up that LED. Then I set up one of the pins as a touch IO pin with this command touch IO dot touch in, and in parentheses, the number of the pin. I'm using board A5 in this case. Then I'm setting up the LED. I'm setting up a little state variable called last touch. So I know when I've touched and released. And then during the main loop of the program, here's all that happens. We watch that touch pin value. When that value goes high, it means it's been touched. And then I can do some things. In this case, print out the cap pad is touched. And then I'm also lighting up that LED and flipping my state change variable. When I release, it says if the touch value is zero or not, so if not touch pin dot value, and my state variable is true, then we've released it, we turn off the LED and we print released. So that is how you can set up a capacitive touch pin in Circuit Python. And that is your Circuit Python, our sec. Once again, by the way, I want to say thank you to your good friend and mine, Mr. Todd Bot, Todd Bot in our Discord, who has a great Circuit Python tips and tricks page, which is one of my one-stop shopping places to go and grab cool tips that I can share with you all. And that is on Todd Bot's GitHub. So if someone can put that in the chat, that would be great. I can put it in if no one finds it or just Google for GitHub, Todd Bot, you'll find it. Dexter Starboard says Funhouse has CapTouch, that's right. The CapTouch pads on the Funhouse, in fact, are exposed out front on these little three ravens or crows here. I forget which they are. Those are capacitive touch pads, and you can see there's silk screen paint on top, and yet it still works. So it's not based on closing a contact. All right. So let's take a look now at this kind of upcoming project I've started working on. If you recall last week, I started showing how to design a switch plate for mechanical key switches. And the example that I was showing is this sort of big honking number pad sort of thing that I'm building. Interesting thing about this is that it is going to have non-1U spacing on it eventually. So let me look for some other props. Do I have a single, let me grab a thing off of my wall here. Where did you go? There it is. So this was from my product pick show. That is a 1U switch there.  This certainly says they need more chats open. Wow, a lot of chats. Thank you for moderating. We appreciate it. Let's see. I'll pop over a down shot camera there. Hey, why'd that get so small? One second. Wait a second. There we go. And you're okay. So we can unplug this in fact now. Lots of blue tack holding things on. So this is the spacing of a single key switch and key cap called 1U or one unit. And the generally accepted spacing for that is three quarters of an inch or 19.05 millimeters. That's the spacing you want from center to center for a 1U key or key cap. And so these here you can see these are 1U, one unit.  So there are or fractional multiples. So you'll find 1.25, 1.5, 1.75, 2.0, 2.25. I think this shift is maybe 2.25. This spacebar is like 6.25. So there's a lot of different sizes that these can be, which means we're not on a grid anymore, which is a little weird, a little scary. So one of the things I'm working on is a setup for building those layouts when they aren't 1U. And in fact this numpad I'm building is going to use some 2U. I believe these are 2U for the enter key, that big zero, and this plus key. So those ones are going to need different spacing. And then there's this one, which I think is 1.75, which is going to have to go down here. And it's not quite going to match up there. So I'm not sure if I'm going to do that or not. I realize that that's not an aesthetically pleasing spacing. So since we want to build things that are not on a grid, that's actually why Lady Aida built this snap apart ortho keypad. So this thing is, let me check my focus here real quick. Peel that blue tack off. That's bugging me. Let's go grab focus. That's better. So you can see that this has the connections between the keys that are necessary to do the diode matrix as well as the neopixel strand. So all of these are connected on traces that are running through. In fact, let me go to the big down cam here. Put me in the corner. So these, is that still not in focus? It's hard to tell when I'm focusing it. You know what? Hold on. That camera is at a low resolution. That's partly why. Hang on. Hang on. We have the technology necessary to fix this. Watch this. Zoom. High resolution. Yeah. So what we can do is snap these apart and lay them out pretty much in any spacing we want. So you could do something like a hugely ergonomic keyboard that's mounted inside of two halves of a couple of bowls and have like a crazy kinesis type of thing or a big weird tower or put them on your pants. I don't know. But I'm going to go a little simpler than that and eventually just snap a few off of one row so that I can do that 2U spacing on the end there and down here at the bottom where I need to. So first step of this is just using the thing as it is. So that's snapping apart without doing anything weird. So that's what I wanted to do today is take a look at how to just set this up and use it with a microcontroller. I'm going to use the Feather RP2040 which is lovely and available and we have enough GPIO pins to deal with the number of columns and rows that we have here. So I'm going to jump over to the Chrome browser again for a second and let's take a look in the learn guides. Just type in ortho in the learn guides and you'll see there's this ortho eight of root NeoKey five by six ortho snap apart guide by Catney. By the way I am still curious if there's like an engineering reason I should just ask Lady Aida why this is being called five by six because I always think of things as width height resolutions of graphic images with height. Your dresser is this many inches by this many inches in the depth. I'm sure there's a good reason actually as someone pointed out to me video you often talk about vertical scan line resolutions if you're just talking about 720p for example but when you talk about the actual thing I always think of width and height. Anyway we'll call it the five by six it's printed on there so Lady Aida wins right there or you can just do that turn it sideways. Now it's five by six. So this guide goes into how the ortho keypad is set up and actually I'll give you a brief aside ortho why is it called that. So let's look at a plonk keyboard. It's called PLANCK. So plonk keyboard where is here's OLKB. So these keyboards here's even a video what's a plonk keyboard. These keyboards are ortho linear they're called which means they don't have a staggered rows of a more typical keyboard. They instead are on a grid so when you're typing you just go straight up instead of off at diagonals and there's actually some pretty good research I've seen saying this is more effective more efficient easier to learn it's not too hard to relearn I don't have one I haven't used it but I'm going to build one and I believe there are claims that the staggered rows we use are just literally a holdover from how you have to fit the mechanical typewriter arms that all of those arms running off of the keys to their pivot to the strikers they can't be straight in a row so I don't know if that's true or not you probably make little bends but so an ortho or an ortho linear keyboard just means it's on a grid so you can you can look into that that's just one company who makes them there's a lot of people who make those out there and so this goes over the layout here if we look at this pinout page you'll see each of these squares on here mini PCBs on the one main PCB they have the kale sockets so that we can plop in a key switch so I'm just gonna try not to bend um wiggle wiggle there we go uh you couldn't see that sorry so I've got a key switch popped onto those two little key sockets that you see there and then they have this neopixel and these are south uh some of these sometimes these are made on the north but you can flip it around like that and use it that way if you want uh they have to be somewhere so those shine up through usually a little light pipe or hole in a key switch it's pretty standard to have have those in key switches uh so that's one string essentially of neopixels and you can see those are running through some traces in this zigzag pattern so if you were to just light them up one at a time like a typical neopixel row you're going to get that pattern that snake snake kind of pattern uh and then you can see here there are um redundant pins for the columns and then there are redundant pins for the rows so we can read a column and a row to determine which key is being pressed you can see here there are also uh in pins for the signal for the neopixel data line and then that's going to be tied to each consecutive one on the out now you don't have to wire uh any of those neopixel connections on here until you start snapping things apart and moving things over so by default those are um all wired to each other and we only need to put a single in data pin power and ground at the beginning of the chain and it'll from your microcontroller run all the way through uh but they're there in case you start breaking stuff apart that's how you re rewire that circuit uh there you can see the top and bottom uh pin rows the left side is the voltage in which will typically be three volts or five volts depending on the microcontroller more likely three volts these days uh and there's a couple ground pins there as well that are shared for neopixel and matrix then if we take a look at the next page on using this with circuit python you have a really nice diagram that catney made on uh if you're wiring up this whole board here's the connections you're going to make and i'm going to make at least some of these today just to see if we can get it working get it started so we have uh a i'm going to take a look at this large blow up here you can see this shows uh we're going to run three volts so three volt or volt in we're going to run ground to ground that's it for power connections and then we have a neopixel in pin uh which is which one are we using for that uh board d five to this snap in so you can see here board d five this green wire is running to the top middle pin there which is how we're going to um run the data line the beginning of the data line for neopixel and then the rest of it runs through uh and then every other connection you see here are sets of columns in row so pairs pairs of uh digital input pins on the microcontroller running to a column in a row column in a row column in a row column in a row column and so if we uh scroll around this image here actually let me go back to this page where it's a little smaller uh you can see we just fan out getting columns and rows all right uh so let's see beyond that uh when we want to code it we can use our uh keypad library which dan halbert wrote and this makes uh easy work of keypad matrix keypad shift register or straight gpio uh per pin switch per pin type of uh keyboards like the macro pad is but this one is way more this is uh 35 switches throughout my math rate 36 36 switches uh six times five right uh 30 30 switches not so good with a quick math uh so we have 30 of these we can't do 30 gpio pins on many microcontroller boards other than uh something like a grand central uh or a mega so we're we're definitely going to use the diode matrix capabilities here and the board actually has the diodes uh built on so it's a matrix with diodes to prevent ghost key switch um presses which is when you press one but it registers multiple uh so the code here imports board for pin definitions imports keypad so we can use all of that good easy uh helper code for for reading the the key matrix and then neopixel as well and you can see this is the key setup right here keys equals keypad dot key matrix and then all of the row pins are called out by name and all the column pins are called out by name then uh we define uh a key to pixel map so that you can do uh light up per neopixel per key if you want to you don't have to do it that way uh and then we uh let me go down to the main code here in the main loop here while true key event equals keys dot events dot get so it just checks for any key events happening on the diode matrix uh and then the um key number is returned and then we can use that to light up a neopixel or do whatever else we want uh so let's see let's start getting some of this setup so i'm gonna put this large screen up on my window so i can see it and then i'm gonna head over to the work bench and uh let's see what we can do so hold on i'm gonna make a screen i can see from over there i should have grabbed a laptop or an iPad but i didn't um and let's get started so hey that's more cameras than i meant to have viewing right now let me turn this one off here goodbye me there we go so i was thinking with this one um i have a couple of these uh boards i've left all of them over here so let me grab one and for testing and maybe for um the construction of the the final thing ultimately what i want to do is make it easy to test some stuff out and uh easy to change some of the wiring and change some of the uh the placement of things so what i'm thinking of doing is attaching some angled header pins where i need them uh under the board so for example i'm gonna break off a row three of these and if i need to use the uh v in column and uh neopixel in here i'll have those ready for some header sockets to plug in while i'm doing testing on breadboard so i'll take this type of uh i love these um sort of soft flexi silicone covered wires so if i place that right like that i'll be able to run that to my breadboard without soldering a wire directly to this um and which gives you fewer options later and if i want to make a carrier board or something like that later i can use a uh some kind of like angled headers to get back down to a pcb so this will be uh this will be interesting for i think for testing purposes and what i'm going to try to do is um at least make like a little mini uh one of these right now rather than solder everything onto there because i think we'd all get tired of that so let me see if i can control my computer over there with this uh yeah there we go that'll work so i've got trackpad over here that i'm using to change a monitor out so what i'll do is uh let me fire up a soldering iron here i've got one of these little pen ones that run off of usb-c they're really nice and uh i can probably just place a few of these to keep everything level even though i don't need these sets of three everywhere set a few in the corners and i'm just going to solder the one i need so something like that uh and then i'm going to try a very tricky maneuver here of flipping it over without making those fall out put some fingers on there flipping it over setting it on the edge of my workbench sliding it on and there we go make sure i put those facing out it's pretty good except for one that missed let me grab a little pick tool to flip that i could have used some tape or some rubber bands or some blue tack too uh but i did not okay that's good but now i lost this one so that's the one that matters let me try to get that back in place without i see you under there all right that's not a puzzle game that i'm going to win there we go whoo all right was it worth it i don't know sorry you couldn't see that fun game okay so i'm going to solder this uh little set right here and i don't have a fume extractor here but i do have a fan blowing from my hvac that is going to disperse those fumes pretty rapidly okay uh so let's see i will um i almost wonder about soldering in those corner ones now i'll leave them because when i start breaking stuff apart i i won't be as happy with those there okay so that one i need and now i'm gonna uh take a set of uh just two and what i one thing i like to do let me sorry let me zoom in here we can get a lot closer uh one thing i like to do with these if i'm doing um if i have a set of three holes there to work with and i only need two of them is rather than it's really terrible to try to solder individual ones sorry let me grab some needle nose pliers um but what you can do is if you have a reason uh to not include one if you're ever trying to um make sure you don't actually accidentally plug into something you don't need you can pull a pin uh right out from there and just end up with with two uh i'm trying to think this is yeah i can flip this over now i'm not worried about those that is an alternate in for um the neopixel data and i'm not going to use that so i think i will signal that to myself so i'm not wondering later hey what are you trying to plug into there so i just remove that pin just drag that right out of there and now we can solder in a pair uh now i think i'm going to end up i don't mind hanging these off the edges um i don't want to point them inward that'll become messy and you can see we've got this uh little space about i think it's like 10 millimeters spacing there's not 10 millimeter what is that for uh i've lost all rulers oh i i moved them that was bad idea uh so this this little border here let's call it five millimeters uh it doesn't exist on the sides but i'll probably add it when i do a case for this so i don't mind hanging these off the edges here so let me place that right there is that the limit yeah that's as close as i can get with this uh so let's go ahead and solder that in all right uh so now we've got uh that's ground up here is power and in fact i'll start connecting up some cables to these luckily i've got a lot of them so let's do power right here and we'll do ground over here my only uh desire for these um cables that we have is i wish they came in more colors because we just get four colors with these i could use eight easily especially for a project like this so now we're going to use um let's see this up above is going to be a row this uh this pin right here so we'll place a cable there and this is going to be a uh column and the neopixel so we'll do a column in yellow just so that the columns and rows are different colors uh and then for the neopixel i'll probably just go ahead with another yellow cable now just so i don't get confused later i'll go ahead and plug my neopixel cable into this pin d5 on the uh rp2040 feather so i think that's yeah that's what we're using there and then i can go ahead and plug power to 3.3 volts by the way this um feather rp2040 one difference between it and uh some of the other feathers is that it doesn't have a v reference voltage uh it just has two 3.3 volt next to each other there uh then i'm going to plug in ground to ground like so uh yeah we can go ahead and plug in the first column in room in fact we'll just do a couple of them and test and see if we can read four keys um i'm not sure if that'll work or not we'll find out so let's see this uh column is going to go over to pin 13 and this row is going to go to d4 okay so the next one we're going to do is just this single pin uh right here so uh for that i think i'll go ahead and i think i will solder in just the set of three it's going to be a pain to deal with singles i don't know making this up as i go along so hopefully we end up with a happy result if i put that in the right way yes and then i'm going to do a row and then i'll go over uh and we'll first of all i want to take a look at discord because i can't see it right now in case people are screaming that something horrible has happened to my audio i'd love to know uh but first let's do one more uh row here so and then like i said all of the traces exist running through these little mouse nibble ready snip off points uh there's actually some tiny perforations there to make those a little easier to snap apart uh if you snap them apart you'll then be bridging connections that currently exist uh okay so let's do one more column and row so i'm just going to use the same color scheme here uh so this is going to be the leftmost pin here and this will be the top most here and these ones go off to 12 and 12 for the column and the row goes to are you going to a three looks like i think i got that right all right so uh why don't we pop in some key switches sometimes you'll test you'll want to test things like this without any components added in case you've screwed up and bridged power and ground but uh key switches are pretty uh immune to problems the only thing i'd be likely to do is fry out uh neopixels if something was done horribly wrong these are some kale box black switches which are linear like a red but a little stronger a little stronger spring in there and so all right i'm gonna bring this over and i'll check the chat and see what's going on where did you go chat there you are hi chat uh is there any reason you could not attach the headers with the pins go under the board keep the square form out without having the you could totally do that uh cryorix uh so the the question is would you just put pins straight up into it definitely can i was actually just trying to keep a lower profile when you put a pin and then the cable into it you add a decent amount of space that i didn't want to do so i was trying to keep things level but absolutely that would work as far as this circuit goes um untitled lars game yikes okay good i don't see any panics happening in the chat right so uh let's take a look then at uh setup for this i'm gonna go to the circuit python setup part of this and let me put a little um down shoot view like that okay so what i'm gonna do is i'm gonna take this here feather rp 2040 and see if i can reach it with this usb c cable boy i love usb c just because i'm not constantly flipping it over three times to match polarity so uh what i'll do is uh i'm gonna hold down boot select and then press set i'm not um sharing windows of it i now see a rpi i Raspberry Pi rp 2 drive show up that's the feather and uh in my browser i'm gonna go to circuit python dot org downloads and if we do rp we get the feather rp 2040 uh i'm gonna actually double check the guide to see and catney i think is in the chat do we have a i'm going to use the circuit python 7 i think i think that's probably not a bad idea with this i don't know if you mention it explicitly but so let's get circuit python 7.0 point oh alpha five i'll download that uf 2 and it's downloaded now i'm gonna go ahead and drag that to the rpi drive it will um flash it and then restart uh and then i i think keypad might be baked into that let's find out this is kind of a fun uh fun way to find out without even heading over to uh to a web page to to look at it i'm instead gonna let's take a look at this view here uh i'm gonna go to chrome or uh atom rather and this one is probably that and let me open and see if there's any code on it that's not the right drive this is okay that was uh okay that was just a memory display stuff i did on that one great so what i'll do and just to prevent problems i'm gonna unplug i started using a macro pad as my camera switcher but i haven't uh done the shenanigans to prevent it from showing up as a drive thing yet uh so let's take a look in the repl here i'll do import board dirt board that's going to show me uh all the pins that are on the uh rp 2040 here that looks right right uh and then to check the libraries that are on it can i check that on the board now i can't remember uh does that have yeah you know what this is a i don't think it is okay this is a bit of a diversion i don't need to take but maybe i'll do that another time as a as a tip when i remember uh how to check which libraries are baked in so what i'll do is back in uh here i'll go to the top hit libraries i'll download the bundle version seven or i can use bundle fly why don't i do that so if we look at the uh code here in the guide circuit python usage this example here has download project bundle uh let's see that's a four by two okay we'll change that a little bit to just be two by two i think that should work so when i hit download project bundle we're going to get a zip file i'll unpack that and that'll include code and libraries so again you won't see this part but i'm going to go ahead and uh drag the contents of that code and library directory to my circuit pi drive here circuit pi drive paste two items dur that's right uh replace replace i'm just overwriting some stuff okay so let's jump back here and see if we run the code just reopen that in case i do anything wrong okay so i'm going to set two rows two columns uh the neopixels on d five yes okay the row pins this is a little different than what i was looking at for that full example so let's let's change those so uh column is d 13 and d 12 oh i have that okay uh row is d 4 a 3 oh it is right okay so i can just get rid of those two uh number neopixels should be four i don't know if there's anything else to change in there so i'm gonna hit save and let's see what happens hey so we've got key zero pressed released key one pressed released key two pressed released key three yay we have success i'm very excited about that uh so that is the uh the real time hey does this stuff really work if you just look at the guide in fact it does so hats off to dan halbert for this wonderful uh library that we're using and thank you so much catney for the very clear uh instructions in the guide there uh so now i think all that's uh that's going to remain is to either wire up more of this or i may stop um adding the pins until i do a little bit of my modification of the layout um so to get some of that two u keycap size spacing uh that i want to do for these you can see that that just doesn't work those those those don't fit like that and you can't just offset them like this so uh there's some pretty specific spacing that we'll have to do to get that to work and that means i'll be removing some keys and uh snippet them off and rewiring them so uh that's that's going to be oh does someone say the led mappings are off oh totally off whoops hey thanks for pointing that out uh jim neal let's fix that okay does anyone see the problem in the code i'm guessing someone did uh let's see uh someone tell me what what you see let's see uh where is the oh sure that makes sense actually right because one two three four one two three four yeah yeah okay so uh the full keyboard goes neopixel zero one two three four five so zero one two three like that so we need to do some remapping here uh unless i were to cut right there and and cut uh or rather re uh jumper that over to this side then we get one two three four um so i guess i won't deal with that in code we would just have to make like a little table that says the neopixels that we're lighting up are not um zero one two and three but would be zero one seven and eight right that's it so thank you good good catch there uh jim neal over in the youtube chat and uh sorry for anyone with um if i'm triggering your ocd with that right there where well that's kind of upsetting all right so i think that's gonna do uh let me know in the chats if you have any thoughts or questions about this i'm gonna go ahead and uh work on my layout stuff over in grasshopper uh and rhino so i can get the the spacings or parametrically so i don't have to just hand hand model that uh and then i'm gonna laser cut myself a nice key plate or three print one uh and then i'll be able to um essentially support the boards with the key switches and key plates from the top and then i'll probably do a bottom plate that screws in and nestles them in there so stay tuned that's what's coming up next i'm also still working on my macro pad for minecraft um and i'm gonna try to commit the code real soon and get the guide out there so that you can do minecraft shortcuts on your macro pad one other brief uh announcement i will point out that hey look macro pads came back in stock this morning and we have 40 left so if you were uh someone who did not get a um ate a box but you saw the ate a box unboxing last night and thought my gosh i'm really dying to get my hands on one of these now's your chance i believe you can get both this uh bare bones macro pad and you can also get the hardware add-on kit um um so those are those are available right now uh and there's a max of one per customer so they should we'd love for each person who wants one to get one and not uh not have people collecting too many all at once right now we'd be happy for you to do that in the future when we get uh more of them in stock but uh so i just wanted to mention that uh and i think that is it yeah so hey thanks again for stopping by i appreciate it and uh i will be seeing you next tuesday for my next product pick of the week and uh then probably continuation of this project next thursday as i build this out so that i can finally have the gigantic numpad of my dreams i still haven't asked my mom if it's okay that i kept these keycaps but i think she's okay with it maybe i'll check now after the show if not i'll be buying myself some dsa profile double shot keycaps because i love them all right uh thanks everyone for watching and i'm john park for eight of fruit industries this has been john park's workshop and i will see you next week goodbye


So again, it's kind of a true question because it depends on you know, which way are we applying a force to the material, right on which axis and Let's see Selena says plywood because the wood fibers go in different ways Yeah, so that's correct The pine plywood if we were just to try to karate chop it the pine plywood would be superior Okay, and that's because we have The different directions of the grains going cross laminate and we're making a composite That's going to be stronger in all different directions rather than the solid pine board where it's uni directional All right, and this is why you know If if you're familiar with baseball with baseball bats, right baseball bats professional baseball bats are made out of wood All right solid piece of wood and the the wood has a certain direction of the grain and Usually on these bats there's like maybe a little dot that indicates which way you're supposed to be swinging the bat because if you swing it The wrong way and the ball hits along a certain Direction of the grain it can it's more prone to breaking all right So that's what we call an isotropic material or the pine plywood is taking care of this problem It's making more isotropic. We're changing the direction of the grain making layers. So it's like a composite Yeah, so like I said, it's it's a bit of a trick question, but okay, and so let's move on And then I have a lot of slides so I'm going to kind of quickly go through this right So we take elemental properties the properties of elements their atomic arrangement. We can change that then through processing We can change their microstructure different microstructures can also give us different unique properties Here's an image of titanium oxide nanotubes And then so these will give us the material properties that we can use through our designing and manufacturing For certain applications devices So we have an example of a Computer chip here and inside the computer computer chip. There are billions of semiconductor Transistors silicon dope silicon transistors billions of them inside and that's what makes our computers do or their calculations We have lithium-ion batteries orthopedics for implants like Titanium metal implants and so there's certain properties you have to consider like the the biocompatibility of the material You don't want to put a material in that's going to make a sick That's going to leech into our body or maybe corrode due to our body and leech into us And you also want a material that has a compatible Young's modulus if you have a strong gradient of young's modulus between your bone and the the implant that's going to lead to a Problems as well. And then also like for example steel structural engineering Dr. Brush on Monday's class mentioned the historical ages, right stone age iron or bronze age iron age And I think another one that's very important is the steel age, right? So when we take iron and we add carbon to make it stronger It allows us to do things that we haven't done before like build skyscrapers There's a there's a great example also during I believe maybe the 1700s or so There was a I think it was Beethoven, but it might be Bach I forget the details of the story but one of these composers makes the song for piano or harpsichord or some instrument some stringed instrument and The song is so intense that it can never be completely played through because the the piano wires keep breaking Okay, and it's not until a certain Advancement in the technology of making these steel wires that allows you to that finally this song could be played completely without the steel piano wires breaking So it's kind of a interesting and antidote What is the bottom? Tetrahedron probably yeah, let's see performance properties processing and structure So microstructure is here what I say, right structure can play an important role, right? Like in this example here. I have titanium oxide and they're they're made as nanotubes All right, you could also have titanium oxide made as spherical particles and they're going to for this application was for I believe a Electrolysis of water so using light UV energy to to break water down And so the advantage of having nanotubes they have a high surface area allowing the more water to break down. Oh I skipped ahead. So here's another example of Taking a single element. All right in this case. It's carbon and there's two different types of carbon and you guys can help me I kind of gave it away. What are the two different types of carbon this single element can can exist as Okay, thank you Gregory. So graphite and diamond and that's given by their crystal structures And dr. Brush had mentioned this and we'll we'll go over it more in detail next week in these lectures the crystal structure a crystal is the repeating Symmetry of how the atoms are arranged. All right So carbon can be arranged in two different crystal structures one is in these planar units where you have these sheets of carbon and Then they're hexagonally coordinated in a plane and then you also have it Coordinated in tetrahedrons like this and so these make two distinct different Materials and yes, Sophia and Gregory's mentioned it graphite and diamond So one is graphite and one is diamond and just by changing the arrangement just by changing the atomic arrangement of the same atom You drastically change the properties of the material right graphite Obviously, we have optical properties graphite is opaque. It's black. It's shiny Maybe slightly reflective diamond on the other hand is transparent. Okay, and so what are Next question what are Some different applications of these different materials of carbon of these different forms of carbon, so let's start with graphite Who can tell me one or two? different applications of Graphite good pencils is one Can we get another one cooling and cooling because maybe it has high thermal connectivity? Lubricant perfect.  Yeah, so my examples are pencil lead and lithium-ion battery anode. All right, let's start with the pencil lead and Someone mentioned lubricant and that's exactly why we use it as a pencil lead All right, so I believe the lead itself is a composite of graphite and some other clay like material That can change the hardness of the pencil But graphite because it's made out of these layers of carbon these sheets called graphene The sheets are not very well bonded together. I believe it's the Vanderwalls bonds that keep them together So the bonding is very weak between the sheets that allows the sheets to be to be peeled off very easily And that's why it's used as a lubricant In fact in many mechanical processes graphite is added as a lubricant to reduce wear between You know rubbing services and for the same reason in pencil lead when you put it across a piece of paper The graphene sheets are flaking off and they're they remain on the paper for lithium-ion batteries for the anode first off, it's a it's a common misconception that lithium-ion batteries like your phone battery or yourself your Your computer battery your laptop battery that it's a misconception that they contain lithium metal None of these batteries none of the commercial batteries for your like your car or whatever Electronic devices contain lithium metal. That is a misconception. It'd be way too dangerous to have a rechargeable battery There's too much liability to have Lithium metal now primary batteries those that do not recharge you can buy those at the like the store Primary batteries do contain lithium metal, but those are not for recharging But in place of lithium metal the anode is graphite and they use graphite because graphite has this nice Interplanar spacing that lithium can get into or ions different ions can get into in between Yeah, lithium ions are the ones that occasionally explode and and that can be because of Quick cycling or charging there could be different defects but over time the batteries will wear down sometimes lithium metal does form deposits on the surface of the graphite and if the Over many many cycles that lithium metal can grow and these are called dendrites And if they reach the other side of the battery then it's short circuits and that creates a lot of heat but Commercial lithium-ion batteries for electronic applications do not contain lithium metal. So how about diamond? What are a couple? What are a couple? Applications of diamond a different form of carbon Good saw edges tools. Why would we use? Why would we use it for tools like saws a hardness because diamond is the hardest material We know of so we use it for things that need to cut things, right? So here we have someone also mentioned jewelry All right, so but diamond coated saw blades right or different cutting tools. It's very hard. So it's going to cut other materials, right? If diamond is the hardest material How do we polish diamond into these different shapes? Okay, Justin says with diamond. It looks like Liam said lasers. I'm not too sure perhaps with lasers as well But yeah, so Diamonds are polished with other diamonds the very very small like diamond grit, you know We can still crush diamond diamond is a ceramic material. It doesn't have a very high toughness Right if you apply a lot of force to it You can still break it but it's still very hard hardness and toughness not necessarily the same thing Okay And also we use diamond as jewelry because it's it has nice optical properties It has a very high index of refraction so the light can bend a lot whenever it reflects inside also large You know diamond itself is not Too scarce of material, but you know large diamonds are are more rare But mostly the cost is controlled by the industry anyways, how do they Lab grown so I'm not sure about jewelry for lab grown diamonds But I do know that you there are lab grown diamonds, and I'm not sure how what impact it has on the economy but to make a lab grown diamond they have these these machines and basically their big metal components and They you need to apply a large amount of pressure right diamond only forms at a high pressure and temperature And so to to create such a high pressure. I believe what they do is they they take these metal You know blocks and they heat them up and when a material gets heat heated up when it increases its temperature It expands so if you have two metal blocks and then inside is your carbon and you heat them both up They're going to expand against each other and that creates an enormous amount of pressure enough to you know Make diamond which diamond remember you probably know this diamond at room temperature and atmospheric pressure is not stable right the most stable phase of Carbon is graphite. So the to make diamond you have to reach that that equilibrium environment, which is high pressure and high temperature All right, you guys are there's too much chat. I can't keep up So if you have something important to say you're gonna have to say it out loud. Let's move on So today we talked about electron configuration and we have a couple problems dealing with that right and so Dr. Brush probably showed this He showed this slide I know but So if we look at the the periodic table of elements right it and I know dr. Brush and mentioned this that the The orbitals of these materials will fill based on the you know the order of the periodic table Right, so we start with the s orbitals and we work our way to the second principle number 2s And then that has sub orbitals P and so on Okay, so the way these orbitals fill up is Goes by what's called the poly exclusion principle and that's for each sub orbital You can only only two electrons are allowed to occupy that shell the sub orbital Okay, so for s we have only one sub orbital orbital for P. We have three for D We have five for F. We have seven and so on and the way we We add the electrons to these orbitals goes by what's called the off-bowl rule Wait, okay We start at we always fill it in at the lowest energy, right? The electrons always want to take the lowest energy available, right? If we're talking about for example, like potential energy, we want the lowest negative potential energy Okay, so that's the order that they fill these shells They always go to the lowest energy now what's important about the off-bowl rule is that it doesn't necessarily go Spd once you get to 3p you want to go fill start filling the 4s rather than the 3d even though 3d has a lower principle number than the 4s And that's because the 4s when you occupy the 4s it has a lower energy in the 3d That's partially occupied, but we'll see this sort of breaks down a little bit later when we talk about ionization And then also we Dr. Brush mentioned the Bohr model, right? And so this is a kind of a way we can illustrate how to fill these different shells however You really have to forget about the Bohr model because that's not a good representation of what these these orbitals these electron orbitals look like, right? So these electron orbitals or electron clouds look more like these shapes, okay? And so this is an example of the probability of finding an electron in these electron orbitals for like 1s 2s and 3s So s is very easy because it's it's Spherical and it's very easy to calculate because it's symmetric but when you get to p and d and f then they they get more complex and The way to calculate these probabilities of finding the electron in these different shells is like Dr. Brush had mentioned through the hydrogen that through the wave function And the easiest to calculate is hydrogen wave function because it only has one electron You do not need to know Any of this but you should know that the electron orbitals do take up different shapes at least to the you know The the p shapes those are you should should know and then I think further on if you get into more advanced Classes you should you should know about the d's as well I deal a lot of electrochemistry deals with the d orbitals and the d orbitals for Transition metals can help determine the shape of these crystals and the shape of these molecules that we use in our materials Okay, and then the quantum numbers It's kind of like a barcode or a serial number for each electron that exists in an atom It has a specific quantum number associated with it and this is something you should know If and we'll have an example problem that you should be able to identify the quantum number for a given electron Okay, so and it starts off very easily easy with principal number, right? That's just the different the principal level, right one two and three and so on Okay, and this is an example for sodium So the sodium was an example before right and this is the electron configuration of sodium if we look on the periodic table Okay, well this one doesn't give it but sodium would be so we have hydrogen lithium sodium is this one right here So if we were to fill it up, we would say hydrogen has 1s then healing has 2s and then so on Excuse me 1s 2 and then 2s 2 2p 6 and then sodium is right here the valence electron of sodium would be 3s 1 right so this is how you would write that out and so the question is if we want to take this one electron here the valence electron What is the quantum number? That is used to identify that one valence electron Okay, so this is the example I have so it's 3s 1 or remember so the principal number is 3 Orbital angular momentum that relates with you know the whether it's s or p So in this case, it's zero s is always zero Okay, p would be one for example, so it's zero magnetic The quantum number, okay, that also refers to the symmetry of these sub orbitals for s The it doesn't have any unique symmetry like p does it's always going to be zero and then spin is arbitrary up or down or Positive one half or negative one half so you can assign it positive one half for exist this example But there will be another problem after this So here's our first a problem, and I want you guys to take a Good 30 seconds. It shouldn't take too long, but we'll go over it together But I won't give you some time to do it yourself, and then we can come together as a class To solve it. So this is just looking at the electron Configuration for oxygen and iron and I want you to find oxygen and ion o2 minus and also iron 2 plus so the ferrous ion But my recommendation is if you're not too familiar with this and we'll do this together start with the neutral atom Okay, don't worry about the ion yet Just find the electron configuration of the neutral atom, and then we can worry about that ionization later So I'll give you a good minute or so try to write this down and we can we can talk about it together Okay, how does the quiz work is it just lecture or actual canvas quiz? So right now I have we haven't done this before so in my mind It's going to be a canvas quiz that we will Locate time during lecture for or during quiz section for and it will only be available during that time Maybe some so there might be some grace period before and after but Well, I think that's going to be how it is. We'll try it out see how it works Okay, so let's go over this problem. Let's start with oxygen and let's start with Oxygen the neutral atom of oxygen so not the ion And if we'll go through this but if if something does not make sense to you Please shout out and we can we can go over it again a little bit more slowly but Who who can give me the electron configuration of oxygen the neutral atom of oxygen 1s to 2s to 2p 4 yes, that's correct So I'll put it up here. So here's the neutral Adam of oxygen 1s to 2s to 2p4 Here it is written out So, you know if this was on a test or homework I think this was this is going to be the expected answer I just to write this this long list of letters and numbers But I also drew out the you know The filling of these orbitals and the filling of these orbitals, you know We use these up half arrows and down half arrows to represent each electron that gets filled And remember because of the poly exclusion principle each suborbital can only Occupied have two electrons occupied at once and when you get to a spot such as the top orbitals here where we start occupying on Do the off-bowl principle We're going to try to minimize the energy of these electrons so the best way to fill it up is to first fill up one in each and Then we'll pair them up because it takes additional energy to pair up Two electrons together that the analogy I like to use is you know if you're getting on a bus You know you always when people get on the bus that you always try to go for an empty seat And then when the bus gets filled then you start doubling up, right? That's the analogy So how about oh in the up arrow represents up spin and down arrows down spin or positive one half and negative one half For the quantum number. How about now? Let's look at the anion All right anion means we're giving the molecule or the we're giving the atom more electrons, all right Oxygen if we look at the periodic table Oxygen would like to receive two electrons. They always want to fill up this what we call the noble gases, right? If that makes it a complete Octet or completely filled orbitals if it receives those two electrons So what would the the configuration be for oxygen two minus? That's right two p six. So we're adding two electrons They're just gonna fill in those those vacant half spots of the p groups, right? So that's oxygen anion How about iron? Let's start with just the neutral atom for iron who can who can give me a a a electron configuration All right, so we have 1s to 2s to 2p 6 3s to 3p 6 4s to 3d 6. Yeah, that's correct now According remember according to the off-bow rule, right? We would fill the 4s first and then fill the 3d Just like you wrote out you have the 3d 6 after 4s 2. However In the in the in Callister your textbook and also I think this is the correct way to do it I would put the four the higher principal numbers After even though they're the ones that you don't necessarily fill up First and the reason is and you'll see the reason is because you want to ask yourself which which electrons have the highest energy Is it the 3d electrons or is it the 4s electrons? Okay now Even we'll see that when we when we ionize this ion so let's go to the iron 2 plus What is the configuration for iron 2 plus and I I guess I gave away a really big hint So it's gonna be obvious But who can and you can just give me give me the 3d's and 4s is what was that look like? If you don't want to write up the whole thing 3d 4 4s 2. Okay. I'm glad you brought that up. So that is not Going to be the correct answer the correct answer would be to remove the 4s electrons Before touching the 3d electrons and I actually now now you've made me a little bit nervous because I want to make sure I'm pretty sure that's correct, but if you guys find otherwise you shout out. I'm pretty sure this is correct Because it's the the lowest energy state if we were to you know Say we did did it your way and say we left two electrons in here and then We take two away from the D instead of the 4s Then we don't have a it's lower energy to have this partial half filled and partially filled d orbitals than to have You know the 4s with Unfilled on half filled 3d. That's just the way it is for energy-wise It's always trying to have the lowest energy state and in this case it'd be to take away the 4s first So this is this is where it gets a little bit complicated So, you know, if we look at let's not go to the transition metals yet Let's just look at potassium and calcium for example All right, so if we get to argon argon has a full Was a 3p 3p6 and now we get to potassium. What are we going to fill first? again, it is it You're going to be a lower energy to partially fill The 4s or is it lower energy to partially fill the 3d and in this case for potassium It'd be lower energy to first fill half fill the 4s and then let you see that it's more evident in calcium If you have a Completely filled orbital that's usually more stable less fill less energy than if you have a unfilled Like d orbital. Yeah, half filled would be more stable Oh, okay. Yeah, so you you do bring up a good point So if it would be 3d 4s one would be to have filled So in this case, I think you should double-check me on that, but I'm pretty sure I'm correct But I could be wrong pretty sure I'm corrected to remove the 4s, but you know, anyways, so that's the ferrous ion ferrous iron, which is iron 2 plus And also you can replace a lot of this with the noble metal or excuse me not the noble the noble gas Configuration because the noble gas configuration is going to represent if you just put this in brackets It's going to represent all the way up to 3p6 and then you can continue after that Okay, let's move on. Okay. How about the quantum number? For iron, so let's say given the quantum number give the quantum number for iron Of the electron removed from iron 2 plus during its oxidation. So first off when you know what oxidation means Oxidation means we're taking electrons away from the ion or element Okay, so if we take an electron away from iron 2 plus it becomes what? Iron 3 plus. Yeah, so if we take a negative charge away from the iron 2 plus it oxidizes It becomes more positively charged. It becomes iron 3 plus Okay, and now the question is which electron are we from this diagram? Are we taking away because we want we want to find the quantum number of that specific electron So which electron are we talking about in this energy diagram? In other words, which electron has the higher energy Yeah, the negative spin in the 3d Okay So I've highlighted here. This is the electron. We're talking about it's part of the d orbitals Okay, in this case, we're calling it a negative spin And it's part of the principal number is three because it's part of this three energy level energy state All right, so oil rig oxidation is loss and reduction is gain. That's yeah I always use that as well. Let's say oxidation or reduction is gain and it sticks Okay, now how about L the the orbital? angular Momentum quantum number remember L Corresponds to like spd and f So we say three we say two Okay, so two is correct because remember L is always going to be it can be any number from zero to one minus n Okay, so it can't be three and if we look at principal number three The orbitals that are allowed to be in principal number three are s orbitals p orbitals and d orbitals So that would correspond to zero one and two. So in this case L would be two because we're talking about the d orbitals if we're just talking about this one electron to now what about the this is the magnetic quantum number and Okay, so this one's a bit arbitrary because we don't know which orbital this corresponds to The magnetic number will correspond to these different symmetries these different sub orbitals, right of the d Orbitals, okay, and remember the number is available for the magnetic quantum number are Negative negative L So it could be negative two all the way integer values all the way to positive L a positive two So just arbitrarily we're going to say it's this first one this first symmetry which would be negative two All right, so that represents this symmetry You don't need for you know, whatever exam you don't need to know these symmetries But you do need to know, you know, you can assign these numbers And then how about the magnetic spin? Quantum number Yeah, so again, this is a bit arbitrary but since since our arrow is pointing down. I like to give it a negative one half Okay, so you should that's what you should know what to do is find the The electron configuration of different atoms I think you know, like I said, it gets a little bit more complicated and as we saw for the transition Metals, but before the transition metals you should know It should be pretty clear how to come up with these numbers and then also the finding the quantum number of an electron Okay, so you that's what you should know Um, so we're going to talk a little bit more about bonding. I think I'm going to skip over this a little bit You don't need to necessarily know This part, but I think later in this course you will be talking about band theory Or like these electron energy bands and these what's what's important about these energy bands and how different elements Uh And this is we're talking about a bulk material now We went from a single atom and now we're talking about a bulk material and the electron energies of a bulk material and they fill up what we call bands and the bands are important because it will tell you What type of material? You're dealing with electronically that speaking. So whether it's uh, I have some examples here. Well, we have magnesium silicon Here's an example of sp hybridization. So here we in silicon and other like, uh, covalent materials like carbon They'll the s orbitals and p orbitals will combine to make an sp hybrid So for example graphene remember carbon is bonded to three different other carbons that'd be sp2 hybridization carbon and diamond or silicon is uh, the diamond Crystal structure has sp3 hybridization and then they can also so on this is called molecular orbital theory But you don't need to know that for this class But eventually I think when we start talking about electronic properties You will need to know a bit about the the band structure And so like I said, the different band structures can tell you information on its electronic properties Whether it's an unfilled band or it has a band overlap. Those are different Conductors like metals will have that type of band structure insulators and semiconductors have what's called a band gap and then this is very important for different semiconductor devices like uh Solar cells for example solar cells the the voltage That generated by a solar cell is related to the band gap or for example the led If you have an light emitting diode the color of the wavelength of the light or the color of the light Corresponds to the band gap of that material. Okay. Anyways, so but we'll we will talk a bit about bonding Today so there's different type of bonding covalent bonding as you you probably know, this is pretty standard stuff You should already know a covalent bonding is the sharing of electrons between atoms Ionic bonding is the stealing or giving of electrons Between different atoms. So we get what we call ions So a lot of ceramic materials are made out of these Ionic bonded materials covalently and ionic bonded materials are typically insulators or semi conducting materials and then metallic bonding uh, so you'll have electrons that are that are Part of bonding that and then you have electrons that are part of conduction and we call that the valence electrons sea of valence electrons um Okay, and of course a lot of the conduction and like thermal conductivity and electrical conductivity Are our functions of temperature right as we increase the temperature that can change the conductivities It can change the number of electrons in the sea of electrons or it can change the number of electrons that Maybe are not part of bonding and covalent materials like silicon And so temperature has a big effect on those properties as well so You know, it's easy to to make this diagram and in kind of categorize materials as being either covalent or ionic But in reality There's very few materials that are purely covalent or purely ionic and in reality there there's a bit of mixed character Uh, if you if you combine different elements in the molecules There's a bit of mixed character and we call that the percent ionic character um, so for example like some some I guess you could consider silicon Like uh and carbon diamond as purely covalent. All right, but um other you know In general if you mix a a metal or transition metal with a non-metal and you get a a Ionic compound so some examples are like lithium oxide titanium oxide iron oxide aluminum oxide or alumina Sodium chloride, which is very common uh salt table salt um, and then covalent compounds are typically uh more similar compounds So like the oxygen molecule or nitrogen molecule or a diamond So um, uh, let's think Well, here's some examples examples hydrogen so hydrogen is one that gets stuck over here as well hydrogen fluoride gallium arsenide CO2 gas or silicon semi-metal are considered mostly covalent so but We can calculate the percent ionic character using this equation So the next problem is to calculate the percent ionic character of si-02 Where x a is going to be the larger And excuse me. I forgot to mention that this is the Electronegativities. All right. Electronegativity is it's you know, it's ability Or it's willingness to accept electrons, right? So we talked about oxygen oxygen forms the anion o2 minus to complete its orbital And so it's it's more willing to To receive electrons than give away where the transition metals and other metals are or more willing to give away Their electrons so they have lower Electronegativities so x a is always going to be the element with the higher Electronegativity xb will be the element with the lower electron activity So from this chart of electronegativities find silicon and oxygen and calculate the percent ionic character. So I'll give you A few seconds for that All right, uh, who who has an answer? Who would like to share an answer for ionic character of silicon oxide? So silicon is a semi-metal Oxygen is a non-metal. So if you think it's uh, probably kind of covalent Yeah, so we have 51 percent since we square the value doesn't matter, which is uh, there's Yeah, I guess it doesn't matter does it Because if you take the difference, it'll be negative if it's negative you square it becomes positive. Yeah, I guess it doesn't matter Um, yeah, 51 percent is is what I also got Yeah, so x a 3.5 for silicon for or excuse me for oxygen 3.5 for silicon 1.8 and then uh, 51.4 percent so you know silicon Isn't necessarily silicon oxide. That is not necessarily entirely covalently bonded. It also has a bit of ionicity as well now let's talk about interatomic distance or essentially the distance between Ions or atoms in a solid now for ionic materials if we consider the material To be a point charge, right? So this one's a positive plus one charge. This is negative minus one charge There will be a coulombic interaction between those ions, right? So you'll have a an attractive force between them because one's positive when it's negative and the positive and negative attract to each other But also remember that there's still an electron cloud of negative charge surrounding the the ion This still has that cloud. So if they get too close together those electron clouds would interact and then That will create a coulombic repulsion force. So you have two competing forces You have an attractive coulombic force and a repulsive coulombic force So we have this diagram here. We're in the blue We have the attractive force in the I believe it's green is repulsive force And then the sum of them the two is this red line here All right. And so the question is, you know, what's the equilibrium distance that these ions will want to be at You know, that's the bonding distance. All right, so that's when the force the attractive force in the repulsive force is net zero Okay, so there's no no attraction and no net repulsion And we can look at it more On an energy scale for potential energy where energy is just the integral of the force versus distance And so now we have a repulsive energy And an attractive energy. Okay. And so again at the equilibrium distance are not Between the two ions The potential energy will be a minimum Okay, the lowest potential energy is where it's more the most comfortable at right So the net energy is the sum of the attractive energy Which is the negative of a constant a and these constants depend on, you know, the system and Perhaps the coordination as well and then r is the distance That these ions are apart from each other So it's the attractive energy and the repulsive potential energy another constant and then r to a power of n And typically n is around eight and I have a problem later on where we can do some calculations But first here's a problem Just conceptually if we take a look at these these different energy wells for energy potential energy versus atomic spacing of the two different material atoms We have some questions we can consider So we have two different materials material a material b material a as a oops Excuse me is a bit more steep of a well and material b is more shallow and spread out First question is which material has a higher melting temperature Okay, so when you think about what what is melting temperature mean? And which one of these would be considering having the higher melting temperature And you can say yes for material a and no for material b if we if we don't get some answers here Okay, yeah, so many of you are seeing a you might have seen the answer that already had And now let's consider why does material a yeah the answer is a Why does material a have a higher Would be have a higher melting temperature than material b does anyone want to Speak up or write and chat impossible Is it because a can absorb the energy wells deeper so a can take in more energy before it breaks apart Right. Yeah, so it's taking more energy before the atomic spacing and like you said breaks apart that breaks its crystal Structure so so the melted the definition of melting temperature is basically, you know Well, of course, it's going from a solid to a liquid But also, you know, you think of this we have this crystalline structure where the atoms are arranged in a certain way And then they gain enough energy where that it goes from crystalline to amorphous Like in a liquid, right and they lose that they lose that Coordination with their neighbors so having a steeper well would Have a higher melting temperature now. How about thermal expansion coefficient? So if you're not familiar with this term, it's basically how much does the material expand when we heat the material up in general materials In general materials will expand when they get hotter So which one of these materials will have the higher thermal expansion coefficient? Okay, so he Looks like a lot of you are seeing B. Maybe not too sure if someone has an idea Go ahead and speak up or write in the chat. Why was would material be in the answer? I have his material be why would material be Have a higher thermal expansion coefficient or in other words, but I'll let you guys go go ahead So we're not let's say we're not reaching the melting temperature. We're below the melting temperature We're still a solid and we just increase the temperature and as we increase the temperature the solid will we'll get a little bit bigger Why why might that be? It takes less energy to influence the bonds between the molecules Yeah, perfect. And we can tell that by the diagram because it's more it's more spread out So so essentially, you know, if we think of the atoms in a solid We it's easy to think of them as frozen in space But that's not necessarily true atoms and solid are have a lot of energy at room temperature and they're vibrating around All right, so we see this and it's only at this this lowest point At zero kelvin at zero kelvin. There's no thermal energy, right? It's the coldest temperature you can be at At zero kelvin, you're just going to be at this stuck at this one position But at room temperature you're going to have a bit of energy a bit of thermal energy, right? So you might be higher up on this graph where the you know, the atoms can be the The atom can be a little bit closer at times to its neighbor or a little bit further away at times its neighbor And if you look at this this dashed line the dashed line should represent the average between You know the one side and the other side Okay. Yeah, just a quick question about that. Yeah, the graph we're shown is like a probability distribution of the spacing, right? The graph we're showing is like the range of the spacing possible at an actual the graph we're showing is the energy Um, it will be the attractive minus the repulsive energy um Yeah, I guess you could think of it as distribution Yeah, just trying to understand so let's say like on material B on a single horizontal line Is that the range of the intertonic spacing at a given energy level? Yes. Yes. Yes. Okay. You can do that Yeah, so as we're increasing the temperature, it's going to be more You know some more of the atoms are going to be you know closer or further apart But you see that the average is shifting to the right the average is shifting to higher Intertonic spacing and that's why these material looks expand In general they expand as we heat them up because on average they're going to be further away from each other All right, we're on this more shadow this steeper curve The average is not is not as significant as this one at a given given temperature Okay Yeah, so it just is important to realize that atoms are they're always constantly moving around You know only at absolute zero Kelvin do they they stay still, right? So at room temperature, they're they have a bit of energy Okay, and how about the higher elastic modulus? so If you don't know yet elastic modulus is essentially the stiffness of a material or Basically, how much force you need to apply on a material to give it a little bit of strain And we're in the elastic region, which means That there's not going to be any permanent deformation All right, so again check mark for a and x mark for b so some Yeah, so i'll explain the elastic modulus again Elastic modulus is essentially the stiffness of material. Okay, and that's that's basically, you know, how much force is required to To pull the material apart But while we're still in the elastic region, right? For example, like a rubber band you can you can stretch the rubber band apart and then if you let go it returns to its original shape There's no permanent deformation the same thing if you take a metal Like a aluminum bar and you put a force on it You're going to be changing the dimension of the material Depending on how much force you put on it now for metals that have very high elastic modulus It's going to take more force to change the the dimension Uh, and this is before permanent deformation. Yeah, if you put too much force Then you'll you'll you know permanently change the shape and this is not that does not include the elastic region elastic modulus Yeah, higher modulus means it will stretch Nope, not quite not quite a higher the modulus does not That's yeah, the modulus and when it will break not related um Higher modulus means that it takes more force to elastically deform So elastically means it's not going to break or permanent. It does not permanently deform Uh, it just takes more force to to strain it a little bit. All right, so it looks like overwhelmingly more people are saying Yes for a does anyone want to have a x shout out explanation of why a would be The material with higher elastic modulus I think it would be a Because on the underneath the slope This is a bit ahead I guess but the area underneath the slope is the Energy absorbed so if you have a deeper well, it would take more energy absorbed before you get into plastic deformations Yeah, that's that's a great explanation. I believe that's also uh in the textbook It should should say that as well. Yeah, so we're taking it takes more energy, right is the area uh under the slope to Change the atomic spacing a little bit, right? So that's where we want to change the atomic spacing by applying force Which is force times distance is energy, right? So the steeper the curve. It takes more energy to change the atomic distance It will take more force Yeah, I guess you can also say though the average slope here is less steep Or more steep Should be more steep. Yeah, all right. Let's move on So here's a problem still dealing with the energy in atomic spacing And this problem wants you to calculate the equilibrium bonding energy. You know, it's uh I think we'll go through this together because it's it's it's just more of a proof than a calculation Um, so as we said if we're looking at potential energy versus in atomic spacing We have a repulsive energy and an attractive energy And the sum of the two is the net energy. Okay, and of course the equilibrium distance are not Is going to be at the point of minimum potential energy. So the question is, you know, how can we uh Here's the question determine e not the equilibrium energy bonding essentially bonding energy Determine the bonding energy In terms of a b and n. So we we want to remove r from the equation basically So the question is how how can we go about doing that? And I think the big hint here is that remember The equilibrium Distance and energy is going to be at the minimum point. So that should be a big hint And another hint is that we're going to have to use some some a little bit of calculus, but not too much So those two things together that should that should light off a light in your head when we're talking about minimum and calculus What do we want to do? We're going to start we're starting with this equation here. Yeah, so we're going to take the derivative of this equation And uh, why remember? Yeah set the derivative equal to zero, right? So we're taking the derivative of this curve here the red curve And when the the the curve The derivative of the curve is zero that will be the minimum point And then we're going to try to solve for r not at that minimum So we're going to take this equation Differentiate the equation respect the r. Okay, so we have a constant negative constant over r and a positive constant over r to a a power of n All right, does anyone uh want to give uh an answer for the derivative of each of these? So we can start with this this first term here. What's the derivative of this term? With respect to r. So basically this is one over r, right? That's right. So I gave away the next one, but oh well Yeah, so the first term is uh, it will become a over r squared The second one is uh, you take the exponent out becomes a negative as well So negative uh n b and R n comes r n plus one And then as we said before we're going to set the derivative We're going to set this derivative equal to zero and that will be the minimum of the energy curve Okay, and then we can then we can solve for r and that will be r or not Okay, so we set equal to zero we solve for r or not Okay, and we can separate these terms to get r not on one side Okay, and so now we have a value of r not which is the equilibrium atomic spacing And it's a given in terms of the constants a b and n which are constants that are usually given um in a problem okay, so Then what you would do is go back to the original equation substitute the r for the r not that we just found And then that gives you your final equation where you can Find the energy the the bonding energy Given these constant values, which again like I said would in a problem would be given to you as values Um, I don't I there might be a homework problem Similar to this but I'm not I'm not sure I haven't seen the homework yet Um, but the next one will be oh you guys it's 210. Is it not 210? Is that the end of class? I believe it's 210 Yes, okay. So in that case, uh, this that's and that's the end of class, right? um I will Yeah, I will post these slides online, but there's only a few more. There's only one more problem basically uh, calculating the The r not value For lithium chloride given some constants. Uh, so pretty straightforward I'll post it on canvas also later this week. I think I'll post Maybe a survey or something to see what time will work for office hours Also, Sid the other ta will also have office hours. So we'll find the time that works for everyone And of course you guys are welcome to email me At any time if you have a question. So go ahead Quizzes occur on canvas not this week this week will not have a quiz The first quiz will be wednesday next wednesday And like I said, I I will send out enough information Maybe a day in advance. So Yeah, next quiz and homework will be due wednesday Um, and like dr. Brush said that should be figured out by tomorrow. All right. Have a good weekend guys


The top 5 best security companies in the UAE. Hi guys, welcome back to my channel. It's Meks from the Meks creation. Consider subscribing. By the way, don't forget to press that bell icon. Neurores, be notified when I upload a new video. In today's video, let us look at the top best 5 security companies in the UAE. What we need to know is that the UAE security companies operate under two security regulations. We have the private security business department known as the PSBD and the department of the protective system that is the DPS. The UAE government implemented a new security regulation in 2001. Why? This was to brand the security service providers more responsible for keeping the community safe at that time. Remember, the security companies operate in Dubai, they require a license from DPC and the companies operating other states except Dubai must have a license from the PSBD. Only the companies which have an operating license from both departments can provide security services in all over the UAE. Remember, security companies, security companies funding in the UAE, there are hundreds of security companies with more than 30,000 security officers are protecting the people private properties and the government entities. Something still you need to note, the security companies provide different types of services except the man-guarding such as the general building protection, cash transit, cash center, security, hotel, hospital, bank, event and what we call critical infrastructure security services in the UAE. Remember, when we talk about the best security companies, there are lot of things that we put into consideration or the indicators of things that we talk about. Remember, security officers in the UAE are paid more money compared to other nationals in the GCC countries and had what you call the higher salary compared to our counterparts in the Gulf region. Even though some companies pay their employers according to PSBD or DPC regulations, but when it comes to the overtime pay, it remains different and depends on what you call particular company policies. So, working with an excellent security company nearby, you should not worry about your salary over time, accommodation, vacation, leave health insurance and other compensations that you need to get as by the rules and regulations of the government. Why are some larger companies are not mentioned or not included in the list? There's a lot of considerations or a lot of indicators that we are considered or a lot of things that we are considered as we are trying to look at these companies and we look at your leave salary, we look at your accommodation, we look at your health insurance, those are some of the factors that we are considered as we are trying to give an indicator. This survey was taken for the individual guard that have worked in this company for some good time like 2 to 3 years, they will probably tell you exactly how much it is and how this ratio will be. To some extent, you may find some small companies with 500 security guards that have been included in such kind of list because of services that you do give to their guards, what is being promised in the contract that is being given to their guards and they have a very good welfare. Let's get into the video and we look at these companies as they appear from 1 to number 10. Watch the video. By the way, don't forget to put a comment in the subsection below if you really feel the video is very useful. Share, comment and always be more than happy to get back to you. Let's get into the video and see these companies from number 1 until number 5.