#488 – Sowing Discord

Chris Gammell: This is The Amp Hour Podcast. Released April 12th, 2020. Episode 488. Sponsored by Roden Schwartz. Sewing Discord.

Dave Jones: Welcome to the Amp Hour. I'm Dave Jones from the EEV blog.

Chris Gammell: And I'm Chris Gammell of Contextual Electronics.

Dave Jones: In lockdown. Yet again.

Chris Gammell: Yeah.

Dave Jones: Yeah, yeah.

Chris Gammell: It's a little disheartening. Yeah.

Dave Jones: But they haven't locked down my dumpster. I'm still dumpster diving.

Chris Gammell: I saw that, yeah. Yeah. Are you sanitizing everything as you pull it out?

Dave Jones: Well, once I get back, yeah. Get out the precious alcohol. Get out the precious IPA. Oh, yeah. Which was, you know, like, what, 15 bucks for like five liters? Like, two months ago. Now it's like, my precious. Yeah, it's like, because I got a 3D printer, one of these new LCD type ones, you know?

Chris Gammell: Uh-huh. Oh, yeah. Like the SLA type.

Dave Jones: And the SLA, which uses an LCD to expose each layer. And apparently, you've got to, like, clean these things with IPA or something. I don't know. I haven't actually tried it yet. And the company sent it to me, and it's like, they didn't send me any of the liquid and everyone, like, the, you know, the UV curable liquid.

Speaker ?: The goop, yeah.

Dave Jones: The goop stuff. And everyone was laughing at me in the comments saying, ah, yeah, sucked in because the goop costs more than the 3D printer is. And then.

Chris Gammell: It's a razor blade model.

Dave Jones: Right, yeah. It's the inkjet, right? They give you a free inkjet printer and, yeah.

Chris Gammell: Right. Pretty smart, actually.

Dave Jones: And then, on top of that, you've got the IPA, apparently. I don't know why, but you've got to, everyone's telling me you've got to use huge amounts of IPA to clean these prints up or something. Have you ever used one of these SLA printers?

Chris Gammell: I've never actually done the actual post-process. I mean, I've, you know, handled the parts before and I've had someone else do it, but no, I've never, I've never done it myself. Right. That's like, uh, Formlabs is like one of those as well, right? That's like the.

Dave Jones: Yeah, of course. That was one of the first sort of, uh, you know, affordable ones. Community ones, right?

Chris Gammell: Yeah, cool. I, yeah. So what is the, what is the IPA for? Is it like.

Dave Jones: I don't know. I haven't actually used it yet. It's for cleaning. Apparently you've got to clean the parts somehow and wash it all off and you use huge volumes of now, you know, liquid gold. Right. Which is IPA, yeah.

Chris Gammell: Liquid gold that just disappears if you leave it on your desk.

Dave Jones: Liquid gold. Texas tea. It's the new Beverly Hillbillies. Sorry. I guess so. You, you, you, you're, that's way beyond your. I used to watch it. Yeah. Really? You used to watch Beverly Hillbillies?

Chris Gammell: I mean, it wasn't like new episodes.

Dave Jones: No, right. Okay. Reruns.

Chris Gammell: Yeah.

Dave Jones: Oh God. Anyway. Yeah. So yes, I mean, uh, still dumpster diving stuff. Maybe like a lot of companies will go out of business. Who knows? And they'll have to.

Chris Gammell: So two weeks ago we talked and two weeks ago feels like three years ago. So what did we talk about three years ago? What did we talk about two weeks ago?

Dave Jones: You know me. I can't remember.

Chris Gammell: I guess I'll pull up the show notes. Uh, we talked about medical kits. Yeah. We talked about, you know, ventilators and similar things like that.

Dave Jones: Yeah. There's been a lot of, I keep getting daily emails about new ventilator projects. There's just so many of them.

Chris Gammell: It's great. It's great. It's great. People are working on it.

Dave Jones: Yeah.

Chris Gammell: Cause you made videos about the Medtronic files as well.

Dave Jones: Yeah. Had I made the second one since then?

Chris Gammell: I don't think so.

Dave Jones: Right. Okay. Yeah.

Chris Gammell: Yeah.

Dave Jones: It's good working on these products, but unfortunately it's like such a complicated and dangerous thing. Like people are going, oh yeah, let's just cobble something together to save somebody's life. Unfortunately, it's not, it's not that easy.

Chris Gammell: Yeah. Yeah. So Seth from, uh, the KiCad project is, is working and other people from the KiCad project as well are working on translating the files to KiCad. And then also, I think there's some other efforts to get the firmware.

Dave Jones: The Medtronic ones really?

Chris Gammell: Yeah. Yeah. Yeah. And, uh, it's got like an ST10 in there. I forget what the other things. There's another processor in there as well, but you know, it's medical electronics. Like, so like one of the first things, so there's like, there's a video stream you can watch where he's actually doing it too. And, uh, one of the first things he says is like, you know, this is, there's like a, there's like a Ram on there. I think a DRAM maybe, uh, I don't know. Maybe it was like North flash or something. I don't know. There was some memory component on board where it was like, you, you can't get it anymore. You know, it was like a, from 2006 because of when the thing was designed and then they had, you know, they have contracts in place to buy these parts, but it's just like some of them just aren't in the marketplace anymore. And so at that point you just have to replace it.

Dave Jones: So it's a very old design. It's like, it's like 12 years old plus or something like that. It uses some.

Chris Gammell: And you say 12 years, it doesn't sound that, it doesn't sound that old, but, but in the, if you have no one actually like maintaining it for 12 years, it's like, oh man, you think about the obsolete components. Like just the number of, a number of notices you'd get it. It's pretty extreme.

Dave Jones: Now it'd be remiss of me. Sorry for harping on for those who have already seen my videos, but I'm gonna, I'm gonna have to say this in that just because the key key key guys are converting this over to key key key key does not make it open source. So I don't know if you've watched my video or not, please. It's for those who think that, okay. The, the takeaway is, is that the license that comes with that Medtronics files, they are not free and open. The license is crippling. Okay.

Chris Gammell: I thought he has like an exploding license. Like once this is over, it's like, no, no, no, nevermind. You can't do this.

Dave Jones: And you can't do this anymore. So they've put fantastic work, putting all that work in and converting them to KECAD, but that does not give other people then it, it, it doesn't magically make them open source because you converted them to KECAD. Okay. It doesn't, it doesn't negate the license. So anyone who wants to then take those KECAD files and think, oh, these are free. I can make ventilators for the rest of my life. No. Medtronics can come and sue your ass. so just be aware that watch my video and read get your lawyer to read the license seriously like because it's a it's a trap it's a trap so um yeah like no it is a potential huge legal trap and you have to be aware of that and you can really come against it you could spend years of your life working on the world's best open source ventilator but if you used material that came from this or this medtronics uh design or some other uh design that you thought was open

Chris Gammell: source but it's not then uh yeah yeah how does that i don't think that we maybe you've talked to your brother-in-law about this but like like how does that work with like prior art though though too like so it's like out there right it's released to the public and then so if you don't copy it exactly but you're like oh it's like inspired by this thing and then you're using this concept well yeah it's it sounds i'm sure it's dicey no matter what but it is dicey no matter what only

Dave Jones: a judge can make that decision right right in a court of law so it's not like isn't that how the best things start dave right anyway i'm just saying be careful that's all yeah yeah um i i don't want people to get caught out by this that's my fear so yeah anyway anyhow yeah tons of projects and i went i showed this huge list of these and it wasn't even a complete list i don't even think half of them were on there a complete list of all these open source um ventilator projects and their current status somebody's maintaining this spreadsheet just absolutely awesome which has every well tries to have every project its status in like like five different categories or something like how open it is what their what their current uh you know is it uh does it meet these requirements in this in

Chris Gammell: all sorts of stuff and does it have like all these acronyms that i'm like i had never heard of before and it's like no but they're like very very critical to ventilator design and stuff like that now it's

Dave Jones: just like part of the nomenclature is like oh okay it's funny how everyone becomes an instant expert on ventilators you know it's like oh yeah yeah yeah okay i'm not one of them i know that yeah exactly yeah yeah anyway inductors can we talk about inductors sure where's inductors did you put this on here no oh but it comes from my tear down video that i just released this morning um sorry my my repair video that i just released this morning i was looking for an inductor right because it one of the spoiler alert uh and inductor blew in this laptop that i was repairing and so like a big surface mount you know a big like you know 18 20 jobby or something dc dc kind of thing that you're doing something like that no no no it was just the input choke it was just the input choke coming from the power connector right so you see you didn't really need to replace it right you could have just put a wire link in there and it would have been fine right it doesn't matter it's just like an emc kind of thing yeah right and uh so it it blew and i needed a replacement i've got these uh in inductor kits i've got three surface mount inductor kits do you think i could bloody well find one that fitted in three like i've got like like 80 different little tubes of a footprint problem not not like a value problem or anything like it was well it was both uh pretty much it was uh not only like i felt like in the end i just got one to fit but the three little tubs that i thought would have been the right size and potentially the right value they were empty it was like of course yeah that's how it always goes there's like like five there's like five or ten inductors in each one and clearly over the years i've i've used you know that that particular 10 micro henry you know size one and ah it's like those kind of kits

Chris Gammell: are like uh they're like inverse charts of how popular the thing is right so the more popular it is it's like it's like a heat map but like you know in reverse yeah i was doing this the other day i

Dave Jones: was going to discharge a whole bunch of batteries right because i'm doing my alkaline battery discharge test right so i wanted to discharge them all at once and i thought oh yeah i'll just use a 10 ohm resistor and then silly me realize that oh of like um it'd be too much uh power right so i can't use a quarter watt resistor right so i've got big stocks of quarter watt quarter watt resistors right i've got every value e96 and everything else but uh yeah but i don't have a big numbers of them and b not one watt ones right which is what i technically needed so i needed to make up multiple ones and it's like well i don't have that many freaking i needed like a hundred resistors or something it's like i don't have that in my general mixed value stock you know yeah i i might have a box of like 1k i might have like 3 000 1k resistors in a box somewhere right like you know how they come in those bandolier boxes yeah exactly the the axial ones the bandoliers right it's the boxes that eventually you're going to

Chris Gammell: throw away and you'd be like ah when am i ever going to need this and then the next day you're

Dave Jones: gonna 3 000 1k resistors but i needed like a hundred like 10 ohm resistors or something you know or 20 ohm

Chris Gammell: i was gonna say what you were trying to get to like into you so you were trying to have like 10 ohms for

Dave Jones: each battery is that the idea yeah for each battery to discharge each one individually with a 10 so in in the end no i didn't simply didn't have the number of resistors available and number and type of resistors available so i had to so i had to discharge them one by one in on my load my oh really yeah electronic load and took me like four days or something to four or five days to discharge them all anyway yeah so yeah so these uh these you know parts kits i mean how many how many different type parts kits have you got i mean you should have a a resistor kit at a minimum of course right do you have a

Chris Gammell: a capacitor kit i have uh i have some booklets of capacitors not like not like an extensive set i find that like the uh i i haven't updated my books in a while when you say booklet you mean like a

Dave Jones: little folder like a little folder with like little individual strips of each one that you can buy

Chris Gammell: those exactly yeah yeah yeah yeah yeah so not like not like a full full kit um and nothing like not power stuff like so like uh inductors nothing no power inductor stuff like that i have like one like uh like an rf i think it's branded with like an iot kind of thing so it's like you know low value like like capacitors and inductors for doing like for tuning tuning rf stuff yep it's been lightly used but it is useful for that kind of thing too where it's you know like you you know you don't want to go and like order from an online distributor it's like oh i need like a 0.7 picofarad capacitor or 1.3 picofarad you know like when you're like doing tuning stuff so it's nice for that kind of thing um yeah but that's pretty much all i have i think i think i think i used to have all you have yeah i think i used to have some like potentiometers too maybe or

Dave Jones: something yeah i've got yeah i've got uh pots i've got uh zenna's uh for example i bought you know a mix zenna kit so i've got every value of zenna but how much how much have you used that though i've used in a couple of videos i've used in i've used in a couple of videos okay yeah yeah i've i've used zenna's i haven't used them i don't think i've used them for projects i've used them for videos so um you know but i'm doing more videos and projects these days so that's not surprising you

Chris Gammell: know i think it's one of those things where it's like when you really need it it's like you know like it's one of those very very off rarely used things but then when you need it you like need it you

Dave Jones: know and uh yeah how how far do you go stocking you know having your own stock right you know

Chris Gammell: well and i'm space i'm space limited too right well you're dealing with moving right so like

Dave Jones: no i'm moving into a half size space yeah well and even just but even if you had the room like you

Chris Gammell: know you got to cart it from one place to the next and then you had to keep it maintained and i don't know like some people i think some people are working on projects where it's you know they they have the drawers and drawers of 74 series logic and it's just like always used and not just ben eater who's doing 74 series logic stuff we used to have that at work we had the metal

Dave Jones: cabinets with the with the pullout drawers you know like this was like you know 20 25 years ago circular tins of parts in there kind of thing or oh no no no full tubes so we would buy for and and but we would have we would have a uh lab guy right we would have a lab tech whose job was to maintain the lab right and and of course if he you know he'd periodically check the jaws or you'd tell him like oh sorry i i just used the last you know 7400 you know so we'd go out and buy another tube of 74800s and stock up the stock up the jaws these huge big flat pullout drawers and you had tubes of of almost every 74 series chip available you know it was fantastic it's like your own mini digi key

Chris Gammell: you know right that's uh that is uh quite a infrastructure investment it's pretty extreme you know it's yeah we had that at keithley we had we had the the localized part numbers you know they have like internal part numbers yeah of course so they kept those in like a drawer that's the little metal tins i was talking about so that was just like it was drawers but then like within the drawers there were like metal tins with like the the part names on them and stuff like that interesting okay yeah it's tough it's a tough uh who's it i was talking to elvro from uh river unnamed reverse engineering podcast and he has a freaking fantastic system i was telling him he has to make a video about it he keeps all of his stuff in parts box so i think we've maybe mentioned on the show before so so jan parts box parts box dot io um so parts box is like a self uh management system for for parts you know so basically if you say you kept buying you find yourself you're oh i'm always buying 0.1 microfarad capacitors because i don't know how many i have in a project kind of thing well you can actually like generate locations it's basically a maintenance system for your own stock so it'll give

Dave Jones: you like a a location of where it is in your stock pile it's you know row f you know yes three three down row f or something like that so you can have a huge wall of parts and things like that or we also at a company i used to work out we used to have these have you had those rotatable storage systems like like these motorized storage systems where they'd have all these carousel like like a big carousel and they're gigantic they're like the size of a room you know and and these big like huge carousels will go over and you once again you type it into the system and it'll rotate this whole big cabinet thing and out pops your um yeah so they had those at mhub because mhub used to be a

Chris Gammell: manufacturing facility so it's it was used for storage of like full reels and stuff like it wasn't like temperature controlled but it was used for storage of reels and stuff like that and you can get vertical storage really that's why it's really good instead of having like rows of of shelves you have vertical rows effectively and uh yeah no it's super fun you know it's on the tour right but it's it's it's actually pretty useful for storing a lot of crap you know yeah exactly

Dave Jones: yeah yeah but i've got so much old shit though i've i still got parts i've done a video on this i still got parts dating back from the 1970s when i was a kid yeah well and you you almost bought that collection of parts didn't you i remember you did a video oh my yeah i i got some of it and then i got a friend of mine who actually got it who who actually paid 400 bucks for the whole lot and he went there and took it all home and then he rented a storage his storage unit was filled with 80 document shipping you know there's cardboard document shipping oh yeah like legal boxes yeah the document boxes yeah he had like 80 or 100 of those stacked all through his storage unit and like six months later he was begging me to take them away for free it was like no dude no sorry no i mean this is what every

Chris Gammell: hackerspace deals with too right they get like donated parts and it's just like they just sit there you know like yeah it's tough i think you need to have a very certain mindset and it's always good to have like certain parts around like you know like having like some lm 7805 kind of things or something you know like something like that where it's just like yeah it's in every project you know yeah yeah

Dave Jones: of course i was actually going to sell a kit for this um david uh david too he did some work on this uh actually compiling like the most often used jellybean parts because uh i i still sell those micro sleeves which is the oh yeah sleeves that go into binders right you can still buy it on my store still got heaps of them and uh so i was actually going to sell like those actually pre-populated with all of the common parts but i'm not talking like i'm talking active parts i'm talking you know chips and and transistors and sure things like that so yeah all of your jellybean regulators all your jellybean op amps all your jellybean this and that and what happened oh it's a lot of work kind of you know we we we did get a list and it's like it's expensive right so if you had so this is

Chris Gammell: actually the idea behind so we've talked about this like two or three shows ago when it was you and i we did uh we talked about open parts list right we were talking about in the context of the shenzhen parts list that has somehow been kind of a different idea but the open parts list it's like 300 parts and it was this idea of like these really really often used parts same kind of thing right the problem is if you go and buy if you include the passives and the actives and then say you have 10 of each it gets pretty expensive you know like it's not cheap of course no it's you know a thousand bucks

Dave Jones: to stop up always stock up all your yeah right stuff probably i don't know it's like you know if you have a hundred different parts and you know you buy 10 bucks worth of each well it's still like the

Chris Gammell: uh the same problem is like okay so now you have yeah you got 1k 10k 100k resistors and maybe some 2.2s and you know like you have some r6 values but now what are you going to do when you need an r96 value you know and it's just like oh okay yep yeah you still you still need you need the other

Dave Jones: supplemental stuff so yeah i don't know i i think i might ultimately break it down into a more manageable thing like i'll just do one with voltage regulators i'll just do one with op amps like and it'll get and you know the actual kit will give you 10 different types of op amps you know something like that yeah right rather than oh here's the be all end all beginner kit just buy this and you're stocked

Chris Gammell: for life right right kind of thing yeah yeah it's it's a good idea i think i mean like you know you could do that kind of thing real quick back to parts box just because i want to talk about alvaro setup real quick because i'm going to send him this link after we record the show and force him to make a video about it he not only does all this stuff for his personal lab he wrote some python script that allows him to barcode scan all of the digi key bags he has ties it to a label printer and then he makes labels for all of the things he does like it sounds really cool so it sounds like a mental

Dave Jones: illness almost i'd say yes it sounds like yeah he's he's really into it but like yeah you know some

Chris Gammell: people what you really want to do is you want to like borrow alvaro's lab and be like oh you know i just needed like here's my parts list can i just go search through your stuff yeah

Dave Jones: no some people just some people that's their hobby they just love organizing their lab and that's fine there's nothing wrong with that you know i everyone wishes they could do that right it's just a matter of time investment really right sure i could do that and make a fantastic video but i've got to spend the next year or you know actually doing that to get this one fantastic video of this fantastic barcoded labeled system well and it's like if you're going to use it too right oh yeah of course

Chris Gammell: no because it's not just the one-time thing it's the maintenance the maintenance it's the maintenance

Dave Jones: of it you've got to keep it up yep yep i have a hard enough time that right i get you know i find these random bags that i've taken out of my kits oh they're still on the bench somewhere i didn't put them back because i was too lazy yep you know oh i'll just do that afterwards and there is no afterwards you know right you just never get back to it and then you find all these kits you know these bags missing out of your e12 resistor kit you know because yeah yeah boy anyway that's why you

Chris Gammell: need you need to hire a lab manager who is just like just a real hard ass that like you know like you need to like hire like a drill sergeant from the military yeah yeah private why didn't you put that that 0.1 microfair capacitor back

Dave Jones: uh yeah it's it's great when you have it and it works like that's why i loved like the company i worked at once when we had that lab with all every chip possible you know it was just fantastic you'd just go in there and you could almost guarantee that you know this op amp or this uh you know 74 or 4000 series cmos chip would be there it's great you know yeah but it's awesome oh yeah but these days you know you got so many you know there's so many different variations it's just ridiculous and then you've got well do you want through hole do you want surface mount what type of surface mount would you like sir yeah exactly which package sir right this uh this one this one uh dc to dc converter variant has six different types of packages so yeah good luck no i know it's just yeah it's painful yeah oh boy anyway so yeah i couldn't find a suitable inductor i've got three huge inductor kits that you know i still couldn't find one to do the job it's just yeah it's nuts because the problem is of course you can't it was like high current the problem is yeah i could have like i had the size inductor to put in there but it was 2.3 amps which is actually a lot right that's a lot of current for such a small yeah little surface mount uh package and of course when you go i mentioned this in the video when you go up in inductance it's not like oh yeah i've got okay every value from one one micro henry up to 100 micro henries right a couple hundred mics um but you can't just whack in the 100 micro henries because because the current drops basically the current drops proportionally with the um value so the current drops with as you increase the in inductance value it has to because you need a smaller gauge wire you've got to wind more of them on there to get your increased henries and uh the current current rating drops so yes the yes so the one micro henry the one that i had the one micro henry inductor in the same series all in the same series was rated at 1.8 amps but the 100 micro henry one was rated for like 100 milliamps so it's like at the same size you're saying at

Chris Gammell: exactly the same size yeah yeah exactly right right yeah unless you get like much much bigger

Dave Jones: yeah yeah so anyway i did i did squeeze one on i you know and it was one of those jobs where like the soldering iron's not actually touching the pad because the pad's actually under the under the lead oh yeah you know it's one of those like you put the soldering iron on the lead and then that heats up the pad kind of yeah yeah yep yep the old oversized uh component stuffed on the small pads yeah yep i've done that countless times i've done that one yep which which one do you which pad size do you use in the uh standard do you use the small medium or large in terms of uh if the the stand like the recommended ipc standards for footprints right say you've gotten and say you've got a 1206 they they come in three standard variants small medium and large

Chris Gammell: dave i'm going to be honest here i don't know much about the ipc standard i use uh yeah what do you

Dave Jones: use whatever's available well it depends if you're you if you're working on a high density design you're forced to use the small uh pad which means your fillet size changes and everything like your solder fillets on your on your components change and you know it's and and then you can't use the uh pads as test points or flying probe test points for example right right you don't have any like overhang yeah because that's one of the advantages of the larger pad size uh is that uh it extends out so far from the component that there's actually almost like a flat bit that your flying probe tester can come down your little needle probes can come down on and actually probe that particular pad yeah with the component on it so it doesn't have to try and probe the top of the component you know and then the probe slides off and ruins your day and uh yeah so it's so it's a trade-off there but if you've got the room available yeah and normally i would use the normal size ipc footprint uh one but yeah no if you're working on a high density one then you go for the go for the small size rarely will i use the large one you know unless i have some specific requirement and then i'll do custom ones of course so i think

Chris Gammell: usually at that point i'm like if i'm really getting tight on space i'll just size down unless i

Dave Jones: can't you know like that's right yeah of course all right so you would size down an individual

Chris Gammell: resistor or capacitor pad sure yeah oh no no i mean i would size down the actual resistor itself that's what i mean so if it was like a 1206 unless i had power requirements you know okay so you'll go from

Dave Jones: 0805 to an 0603 yeah exactly yeah gotcha yeah i think that i mean that's usually like uh

Chris Gammell: i don't know i kind of like eyeball it at the beginning of the design too and i'm like well this one's gonna be pretty tight this looks like an 0402 kind of design yeah right of course yeah you've got really there's like a there's probably like someone who's done like a spreadsheet or a calculator or something that's like well if you're gonna have 200 parts in this this board yeah you you can't use 0603 because of the size of the board it is you know like that kind of thing yeah that's called your brain i mean i'm sure that yes i i have that calculator as well i'm saying there must be an actual i'm sure someone's written like a script or a calculator that's done that kind

Dave Jones: of thing before uh i'd i'd actually be surprised if anyone would bother because the requirements are so like infinite number of variations that i don't think any such calculator would actually be useful i think i think you just have to rely on experience and and human judgment on that one yep i don't i don't think you can script that someone prove me wrong please by the end of by the next episode we want uh we want somebody to have written a script that comprehensively unfortunately you don't know until the end so it's not like at the end of the layout it's not like you can just like test it like you can't so that's a hard algorithm to tweak right because if you have to do like a couple of days to spin a board to test your new algorithm each time right like yeah that's pretty painful so that's why i suspect nobody's done that i'd be very surprised if such a thing actually exists so although um uh various packages have uh density things you can get maps you can get a density heat map oh these these things exist oh god when was the last time i used a a pcb density heat map oh wow it's a long long time ago in a galaxy far far away but yeah they you know all of your top end tools your altiums and all the rest of them they all have uh heat maps available and um you can see like the the component density and the layout density and everything else where you know where where things are getting tight and stuff like that yeah so that exists it's probably

Chris Gammell: not in key cad yet yeah and so would that give you like an idea of like i guess i guess one of the things that would like be really useful for me would be how many like supporting components are there because really that's when density starts to become a real problem right if it's like okay i need if i have like uh controlled impedance traces that are supposed to be close to a connector okay then that like is like a space limiting thing and then if that component is paired with another component that also has to be near that component that connector but both of them have a bunch of supporting components with them it's like it becomes this like bundley kind of thing and and that's when it really becomes a problem like i just finished a i just did a layout a couple weeks ago that was like that where it was like you know it's like bundled around usb but then there's also like you know there was all these uh so the usb had diodes you know for uh esd protection and like a bunch of but like the esd protection diodes had to be big for some reason you know so it was just like all of these things kind of piled up on top of each other so like one part of the design was really really dense and another part was like really wide open you know and it's just sometimes you can't you can't spread them out as much as you want to but that's not what

Dave Jones: heat map is oh that's god i've it's been 20 years since i've used a pcb heat map like it's not a i think it's literally been that long like layout has changed there is i believe oh god i'm stretching my i believe there are separate heat maps you can get for component density so you know if one component as you said one component is surrounded by like you know 10 other passive support components for example then that will show up as a like a red part of your heat map because there's a high density of components there rather than spread out the other one is a routing heat map like yeah because oh you've got 20 traces all flowing through they're all next to each other there's no more room to put any more so it'll show up as super red on your heat map right exactly or whatever so yeah and

Chris Gammell: sometimes like if you have like a i would think another thing would be if you had like a qfn or something like that you've got this big beefy um you know like center ground pad in the middle that you can't route through it's like oh okay well that kind of like just blocks off this whole area then you might be counting on otherwise exactly yeah so no no v is there no nothing yep oh layout

Dave Jones: isn't it fun no it's tough business and it's changed over the years like layout techniques have vastly changed you know from you know through hole to surface mount and then various types of surface mount and various technologies of pcb layout and things like that it's just a pcb manufacturer sorry yeah and it's just yeah it's nuts changes over these when i was a boy yep yep sorry had to get

Chris Gammell: one in yeah of course one per show we're focused on advertisers that help educate listeners of the amp hour today we're going to hear from james lewis also known online as the bald engineer not only does he have a great educational youtube channel about electronics called add ohms he's also product manager at rodent schwartz our sponsor for today's show here we're hearing him explain how

Chris Gammell: to use oscilloscopes a rule for test equipment is that when you add a probe you change the circuit to see how that works we're going to use the arduino's on board 16 megahertz oscillator and watch how it changes by adding a scope probe james is covering all types of scopes but is using

Chris Gammell: the rtm 3004 in this video a rodent schwartz 4 channel 10 bit oscilloscope with up to 1 gigahertz of analog bandwidth there are other variants in that product line as well james shows how the characteristics of oscilloscopes probes can alter the measurement you're ultimately trying to make

Chris Gammell: the uno uses a ceramic resonator for its clock which is this little ic stopping the scope i want to save a copy of the waveform so that i can compare it later now some scopes put a reference function inside of their math functions on the rtm 3000 there is a dedicated reference menu from here we can copy source 1 into r1 now if i run the scope again the live waveform is the yellow trace and the white waveform is the saved trace i have a second probe connected to channel 3 however i am not going to display channel 3 on the screen instead i'm going to take the probe tip and probe the same point that i'm already probing and then i'm going to say probe one more time as the second probe comes in contact notice how the signal changes the probes are loading down the

Chris Gammell: signal this is a bit hard to see in audio but the sine wave that represents the 16 megahertz signal coming off the oscillator is a lower amplitude this is because of the quote loading that james is discussing is actually the probe capacitance adding a second probe effectively doubles the capacitance the signal experiences which reduces the signal amplitude at 16 megahertz check out more of james's videos to see other oscilloscopes and general electronics projects and if you're interested in learning more about rodent schwartz and some of the value instruments helping engineers every day check out askanengineer.us you can see other reviews from people like james or from shariar who we heard from last time that's askanengineer.us and now we're back to the show

Dave Jones: all right what else we got on today's amp hour well let me tell you what we got here dave

Chris Gammell: so this was in the last episode you and i recorded and i cut it out of it and uh there was this interchange that dave and i had right at the end of the show where we thanked our patrons and then dave goes you don't really do much for the patrons do we i was like oh shit no we don't and so i was like well you know we should start doing that and so in the meantime i have i've i've set some stuff up so we now have a community discord so our patrons you sign up you get access to the discord i've sourced some questions for them we also are able to leave voice messages there so that's going to lead into how we do the uh call-in shows eventually oh i didn't know you could leave voice messages on

Dave Jones: basically i don't use discord i've dabbled but i don't it's not a discord person you know so you can leave people can leave like little audio snippets can they that's right yeah exactly

Chris Gammell: and so uh i have another thing about that in a second too because there's another discord thing that came up this is also you know this kind of relates back to like hey i am hungry for human connection and covet is not helping with this at all so so basically patreon is tied right into discord so like you sign up on patreon you automatically get access so it's pretty cool uh we also give discounts on merch so uh if you want to get a t-shirt all that kind of stuff there's different discounts for different people and of course we are super appreciative for we're looking for other reasons to come up with stuff for to send to our patrons as well so if you have other ideas things that you think would be you know like group chat with me and dave or something like that we'll we'll figure it out i was thinking maybe we'll try and get the uh guests to go and do like a q a on there or something too so sweet we're brainstorming but uh yeah there is a discord and patrons get access that is uh that's a new thing excellent we also so you know that i do uh hardware

Dave Jones: meetups yes you do you keep yapping on about it not anymore uh because the world is shut down so some

Chris Gammell: of the other hardware meetups that are out there uh we all kind of all got together and started talking about like what what can we do and so scott shawcroft who's been on the show before him and eric moyer run the seattle one and they so basically scott shut it set up another discord and now we have a global hardware happy hour which is kind of weird because it's like you're not meeting at a restaurant or a bar but it's a kind of place to do it so it's joined all of them around the world has it that's right yeah so there's there's different like rooms you can join in for chicago or san francisco or you know uh seattle or austin or all these different places where there are actual ones but then there's also just generic anyone can join there so oh if you want you can join there as well and uh we are they've done one hangout so far but we're actually going to try uh chicago's going to do a

Dave Jones: hangout as well this is a discord hangout or a google hangout it's a discord hangout so this is

Chris Gammell: what's interesting about it so i was thinking like is this a video hangout it's not it's audio only right

Dave Jones: now we're gonna we're gonna try different things out does discord do video i don't know it does uh you

Chris Gammell: can do video like uh up to 10 people but you have to like you can't do it through the rooms you have to do it like you have to like set up chats and it's so it's not not 100 there yet all right one of the things that i was thinking about is like we didn't want to just do one big thing like one of the things i hate about like virtual conferences and all these other you know like all these things it's always one to many right so like even right now it's like you and i are talking to each other but it's also broadcasting to many many people the thing is if you if all of our listening audience was in a room together it would just it wouldn't work right it would be like one person talking then another person talking another you know it's just like so you have to basically shrink the size down so what we're going to do is we're going to try and do like a bunch of small like tables like at a uh like at a meetup and we'll see if that actually helps people to right with one another

Dave Jones: so well that's like if you go to if people don't know when you go to these uh meetups like usually like once you have more than like three or four people like standing together like talking it it becomes too many like it's not like you can have one person talking and 10 people listening right unless there's like a demo demo is a different unless a demo is a different you would have to specifically go guys look sure listen up i'm going to do a demo for the next 10 minutes and then everyone stands crowds around watching right kind of it's got to be controlled you know it can't be like a free-for-all if you've got 10 people all standing in a circle and chatting it doesn't doesn't

Chris Gammell: work right yep yep so we're going to try that and see how it goes and uh you know and you know we're all nerds too and so like some people don't want to turn their video on no problem it's just chat if you need to share something you send a link and you're good to go so and do you have to chat can

Dave Jones: you just like sit there and type can you just be a keyboard warrior

Chris Gammell: you could be a keyboard warrior any day of the week yeah so it's always it's always there you know you can always be there but we're gonna have like a actual time to get together uh next week so next tuesday so if you're listening to this on tuesday it may be too late but it's uh so the show goes out sunday night it'll be two days later so early birds get the worm but there will be other meetups for other cities and stuff too so uh cool yeah good way to keep in touch with folks we'll see see how it goes excellent i miss people dave i'm glad you and i get to talk i think i've

Dave Jones: seen a total of two people in the past week right i haven't seen well i get to see my dhl driver you

Chris Gammell: know my dhl yeah right right well it's like family members and then uh you know yeah it's yep yep it's

Dave Jones: it's the wife and kids the dhl guy or the fedex guy turned up the other day and uh the post office

Chris Gammell: yeah right you're like stopping over somewhere right yeah yep that's that's my entire life

Dave Jones: yep yep it's my entire human interaction hey yep 2020 i don't mind just leave me alone solitary nerd you know it's it's like self-isolation for a nerd is not a is not a problem really it's like yeah leave me alone yeah i was making a joke with my friends the other day that

Chris Gammell: like uh so we were like doing like a zoom call with like some old buddies and i was like the only real excuse you have anymore is like i'm sick right now and i i can literally cannot make it to the call or i have another call like those are the only two valid excuses anymore

Dave Jones: what you can't be busy working on a project i mean well no and that's there's other there's

Chris Gammell: many other valid excuses like uh you know you're taking care of your kids or yeah you got other stuff going on uh but like if it's like past bedtimes and you know like i was like my buddies don't have any they don't have any uh any excuses all right can we talk about the myth of three capacitor values yeah what was this i didn't i saw you post this right yeah because i've i've done a

Dave Jones: video um specifically on this i've done several bypass capacitor videos actually i haven't looked yet

Chris Gammell: is this going to be about voltage dependence of capacitors or something else no it's well it's from

Dave Jones: um eric hoggerton who we've had we've had eric on the show haven't we that's right yep yep yes yes we've had eric larry smith sorry i don't know who larry smith is and steve sandler sorry i don't know who they are but i know eric hoggerton of course anyway it's this article on this in the signal integrity journal it's on brand for eric yeah yeah yeah right okay and uh basically there's this uh common there's this you know myth that you should put three bypass capacitors in value and they should be a decade apart so you'll put a 10n 100n and a one mic right all in parallel and basically they're saying that anytime you see that it means that didn't know what they're doing that the designer has no idea what they're doing it's like yeah and because this comes from and i cover this in my video it comes from the response curve the the esr impedance response curve of a capacitor right so it's like if you can visualize it's it it's not a bell curve but it's like a slope that goes down and it peaks so at one particular frequency the esr of capacitor is it's absolute lowest right and then and then either side of that frequency above or below it goes higher in impedance right

Chris Gammell: it's like the inverse of a resonance peak it's the inverse of a resonance thing it's it's an upside

Dave Jones: down resonance thing anyway so the theory is is that okay you want for a bypass capacity you want as lower esr as possible over as wide a frequency range as possible and if you've only got one capacitor then you're obviously only going to get that lowest esr at one particular frequency so that's why like the rule of thumb for the last like 50 years has been you put multiple capacitors in parallel and then they each have their own different dips and then when you combine when you overlay those graphs right then you have like basically a lower esr over a wider frequency range you have multiple

Chris Gammell: low esr that's the uh that's the initial thought and it works right it's it's a real like

Dave Jones: there is truth behind this right it is a real thing but the devil's in the detail when you actually take into account real capacitors and their package size and the and their lead inductance if they've got leads but then even that even then you've got end cap inductance you've got so you've got your pads you've got your vias going to your ground plane and i it's just like there's an infinite number of variables involved in the effectiveness of a capacitor and there's another school of thought that says that you should only have one that one bypass capacitor and should be as big as possible it should be 10 microfarads or it should be 100 microfarads and it should be you know that's it because there's a lot of people that say and once again this theory that can back this up evidence that can back this up that it's only the bulk capacitance value that matters right so but it's but it all depends on the intricacies of your design the specific requirements of your design etc etc so there is no one thing is better than the other right and what they're saying is that uh basically anyone who whacks these capacitors in has not done any modeling whatsoever they just have no clue what they're doing they haven't done any modeling and well that's great in theory but the flip side of that is well okay you're working on your design right you're laying out your board you've got 50 chips on there each one needs its own bypass capacitor are you going to go and seriously individually model the bypass capacitors for each chip which is going to vary for each for each different chip for each each chip has its own unique bypass requirements right um especially based on layout and functionality yeah well like switching speeds and stuff like that all sorts of stuff yeah right yeah depends where you know if it's an fpga that draws massive gulps of current when it first powers on you know you might need a lot of bulk capacitance if it's some you know high frequency thing you're going to need some like some like lower values to uh have lower esr at higher frequencies and start like more effective or whatever you might need different types of bypass capacitors you might need ah it's just endless so you can't possibly model each one so there's a reason why no you could just most people won't the cost of doing so is if you're sending a probe to pluto you might do that right well or if you're making a if

Chris Gammell: you're making a front end for like uh you know if you're if you're going to make something that shariar is going to pull apart at some point you're probably modeling everything if it's some exactly

Dave Jones: some hundred gigahertz thing yeah of course you're going to start modeling your stuff right yeah but

Chris Gammell: you're making something that's like 10 megahertz and below yeah you probably you're probably cool

Dave Jones: you know and and that's the thing so they're they're lamenting the fact that nobody does modeling of their bypass capacitors well it's bloody not easy you know you can't just like you can spend weeks just modeling one bypass capacity and capacitor and measuring it properly seriously you could spend

Chris Gammell: weeks just doing that one thing for that one chip so i got a really good uh education and all this stuff from mr mightyome he was like helping me when i was starting to learn rf stuff and like he was really really doing a good job well my learning was not was very slow but like he was very adamant and this is jeff kaiser people don't know who mightyome is past guest of the show and uh past co-host of the show but he always tries to like talk about how important it is that like capacitors inductors have like all these other characteristics like you're talking about but i think the thing is i wasn't up until the point where i was starting to dip a toe into the rf world like it just it mattered of course it mattered and it probably had like failures i probably had like intermittent type of problems and circuits that i designed poorly but there's a younger engineer kind of thing that maybe i just didn't catch or that you know it surely matters yeah but it's just it really starts to matter at a certain point especially when like if you had eric boca talking about it and it has signal integrity somewhere in the title it's like oh okay you're probably up at higher speeds you're you know you're really needing to worry about all of your all of that what seems like corner case stuff becomes a much much bigger piece of the pie and so if i was going to go back and tell six months ago chris i'd say first off invest in masks you know you can help people yep but after that or you know sell all your stocks that'd be the other thing uh but after that i'd be like uh understanding like how all of these other things like jeff was talking about it's important but it's only important when not only important it's it's it's increasingly important as your speeds move up in time and don't stress about it too much until you really are moving up in speeds and i think that threshold you know you could say it's 100 megahertz you could say it's a gigahertz you know it's somewhere in there right it's maybe even lower than that but like if i went back and told 20 euros ago chris i'd say buy some stocks and then i also say maybe don't worry about this stuff so much you know like no yeah of course right and

Dave Jones: well see the thing is right you you go to the experts at you know xilinx and altera and those sort of companies right who like if you've ever seen there's probably no more bypassing on any chip in existence than an fpga than a modern high density fpga right if you look right and they they have

Chris Gammell: like an intel intel processors underneath you know like they they've started to put them in the chip

Dave Jones: the package yeah of course oh yeah no it's all high-end processors right so you know fpga's or high-end processors and things they have like 100 page application notes dedicated to power supplies and bypassing of their chips that's how important and complicated it is right and even in there they they just go oh use a 10 mic use a one mic use 100n right so it's because it is so ridiculously complex to actually test and model this sort of bypass stuff yes you can do it as an academic thing or if you have very specific requirements to do it but even the experts tell you yeah just whack a 10 you know even like xilinx right you're whacking 100 mic because they have as i said those huge gulps of current when you first power them on right it massive gulps of current because all the s rams have to be set up or whatever you know um and uh and then you've got you know like a one mic and then a hundred and then a 10n and so that's why and then they've got 20 power pins on the chip right so then you end up with a hundred capac a hundred bypass capacitors under a modern high-end fpga right it's crazy but that's the recommendation from the experts right so yeah but then you've got experts on top of experts like eric boggerton right who take their well and he is i mean he is an expert

Chris Gammell: yeah of course of course right and um he does the does he do the rules of thumb is that oh is that his

Dave Jones: his category i thought he does those yeah he does rules of thumb yeah so yeah those guys who who spend all their you know their their hobby is actually getting out their vna and measuring the uh measuring the impedance of bypass caps under various scenarios and they design different boards and how much impact the via has and you know like and which is great you know it's you know it's fantastic academic research that has lots of practical implementations but unfortunately at the end of the day engineering is about getting a job done on on time under budget and with a good enough margin and good enough design margin that you've often got no choice but to just whack you know two or three bypass caps in parallel and cross your fingers yeah just get it out the door yeah but then like there's lots of traps as i mentioned in my videos traps alone plays the more actually technically the more caps you put in parallel the more chance you have of actually hitting some obscure bypass resonance and like especially if you've got like if you're trying to bypass like a phase lock loop chip or something like that if you have the right combination of bypass capacitance tracking uh impedance track inductance and things like that you can actually cause more problems you're better off with no bypass capacitor than putting a bypass capacitor of the wrong value on there so because yeah it can hit a resonance and um yeah lc resonance oh i have to find it i don't know i've done a couple done a couple of videos on this so um yep let me i'll share the link after the show and i will uh give you yeah but it's a real thing because you've got a capacitor you've got an inductor which is all your traces and your ground planes and everything else right hello lc resonance like that's actually a thing right so especially and the other thing is is if you've got if you're trying to bypass like fast rising edges of course right everything's switching like that eventually right if you've got an infinitely fast edge then you have an infinite number of frequencies effectively that you're generating fourier says as much yes fourier right fourier says this right it's a real thing and yeah so the odds of you actually finding one of those resonant peaks that matches up with your bypass capacitance and your trace inductance oh you can really come a gutter and that can really cause big overshoots and things like that it can resonate slightly and actually cause more overshoot and undershoot than you're trying to actually then your bypass capacitors are trying to minimize right because the whole idea is you're trying to stop ringing on fast changing signals right with bypass caps right trying to keep everything nice and tight but yeah you get it wrong and um it can be a real problem so but thankfully it's pretty obscure but it does happen just be aware of that so yeah yep so yes big complicated messy subject the myth of the three capacitor values so you have your uh purists like eric eric who's saying ah you don't know what you're doing if you're just whacking all three in parallel and he certainly has a point on the flip side that's often the only way you can get engineering done you know yeah so well he uh

Chris Gammell: he is the one who does the rules of thumb and i i like i like that article series i'll link that but i guess this would not be one of them

Dave Jones: this is like a yeah rule of thumb what not to do you know but the thing is uh today yeah you know there's he shows like an impedance um curve of course if you just put like a single 10 microfarad capacity bypass cap right that is more effective over a wider frequency range than a single 0.1 microfarad and that's great right saying that is fantastic well why don't you whack in 100 mic well size cost right actual capacitance which varies you know once you if you want an 0603 100 mic capacitor yeah you can buy it but it's not much of a capacitor right it's dielectric it's awful it's one of those awful dielectrics which changes with voltage and it's just there right terrible y5u dielectric right awful hideous stuff right it's not x7r right yeah it's hideous and and they're expensive like you can't afford to populate your board with you know 10 microfarad caps everywhere jeez that that's actually going to add up if you've got a big board and you've got a hundred 10 microfarad 0603 ceramic caps on there that's a big cost so you know yeah yeah so yeah there's no magic bullet there i'm afraid ah engineering it's wonderful trade-off so yeah anyway go and read the article it's fascinating yeah

Chris Gammell: yeah um okay so i'm gonna i'm gonna pull a uh so i had asked on the uh the discord earlier today about uh what people wanted us to talk about here are some potential topics that were recommended trade-offs between simulation versus experimenting which i think we kind of just covered there which is kind of interesting uh another one was uh staying motivated when you don't have people around i think we kind of talked about that earlier so these are all kind of good uh lance asked about uh comparing spice programs i was trying to think if we've talked about spice in the past have we

Dave Jones: talked about spice oh but various times over the years i mean uh what's a name is free um they've just released micro cap you remember micro cap right it's a i don't know it dates back no you haven't no you haven't used it anyway it's a famous um circuit simulation package that dates back oh to the 80s or something i i i used to use it in the early 90s probably i used micro cap 3 i think now it's up to micro cap 12 anyway the designer of that it's written by one guy so i i forget his name sorry but he's finally retired and said i don't want to do this anymore here it's free so he's released micro cap 12 it's completely free it used to be like a paid package he he used to sell like a pro version now he's just giving it away for free um and yeah you can get it's pretty good micro cap um once again pros and cons for each package some people swear by it other people go oh no i don't like it you know it's one of those things you know some people like lt spice others hate it you know it's yeah yeah yep so anyway so that's free there's a big uh forum topic on the ev blog forum about that and free and uh i was probably going to try and maybe get in contact with him and uh see if he wants to come on the show or something like that yeah that'd be great yeah talking about you know simulators and yep whatnot but anyway there's lots of free simulators these days so which is really good so choose and and there's even web web-based ones are pretty good you know these

Chris Gammell: yeah i mean they're all using like the the open source engines that are out there like the berkeley

Dave Jones: well they're all using a spice engine right it yeah exactly it all comes from the original engine yeah yeah i i believe almost every one of them please correct me if i'm wrong almost every one of them

Chris Gammell: comes has you're wrong wrong comes from the berkeley spice engine no it's because uh mike talked about it when he was on the show so mike anklehart was on the show we'll link that in uh but he talked about how lt spice is not was not the berkeley because he like had all these criticisms about it and i had no idea what he was talking about i thought he used some of it i think well i think yeah i think it's all based on it but it's not it's not as i remember him saying specifically it's not

Dave Jones: yeah yeah yeah that's what i'm saying sure sure it started it's based on some of the it started for every simulator is almost but i think you know has some but i think that some of the web ones that are

Chris Gammell: out there are like actually still using the berkeley like engine underneath right whereas some of the

Dave Jones: other stuff has diverged and take another oh of course yeah yeah no if you work on it long enough evolutionary tree it's going to eventually evolve into something that's not it's right i'm just saying

Chris Gammell: that some of the cheapo web engines the web it's like a nice web front end unlike uh you know something that's just open source and kind of out there and so they didn't really think as much about the about the stuff underneath but for what a lot of people need it yes you know it's kind of like the same thing with the capacitors it's like for people that are just getting started and like need to just want to like have a visualization or something like that like i think yeah of course it's fine

Dave Jones: yeah you know oh there's tons of them out there now it's great oh yeah yeah and i think the ones

Chris Gammell: that actually do have nice visualizations are like like uh falstad does that um the falstad circuit simulator thing um and there was another one that was out there that was like that too i really liked how it showed it like visualized like ac waveforms and stuff like that talking about capacitors again like seeing like how things like that kind of you know getting like a mental model for that is just so

Dave Jones: important so it'd be nice to do like a shootout video or something like that but unfortunately they're everyone's requirements are yeah exactly you know it's like it's you can't say which one's best it's like yeah this one might have nice you know like uh visuals and things like that it shows the current flow and you know these animated nice animated colors and everything else and you know fantastic but for other people that's you know useless so is is there a list i'm sure there's a big there's a big there should be a big list of uh simulators out there yeah someone's done it guarantee it

Chris Gammell: um other questions from the the i would keep on to say subreddit but it's actually uh the for the chat i don't know what it's good for the discord is listing of hobbies that are electronics adjacent that are not just building electronics what do you mean yeah examples so examples given were like like rc planes or you know like rc is a hobby you know you're like working electronics but the end goal is usually to build a thing instead of just building a circuit or like ham radio it's usually to communicate with someone over vast distances but you know you have to have electronics in there

Dave Jones: i wasn't sure other ones maybe like oh there's countless examples yeah i'm sure do you have any off offhand i don't know anything anything in life can be dave you're on the spot uh like anything that involves electronics and stuff like that you know you could yeah i don't know it's been kind of like

Chris Gammell: like um it's come up again with like thinking about the the ventilator thing and like in terms of you know it's much more a systems problem right there are electronics in a lot of these things you know some of the things i've some of the solutions i've seen out there for example you know music like

Dave Jones: a lot of people you know might design their own effects pedal or something like that you know they might design their own audio amp because they like you know the sound of tubes you know so they'll

Chris Gammell: design their own tube amp yeah that's a good example you know yeah okay and there's other ones like

Dave Jones: where where you'll design like a little gadget to help out or something like that like you might be into astronomy for example but you need like a custom motorized drive for your telescope yeah yeah just as a random example so you build like a little custom motorized drive and mount and things like that so you've got a you know you've got design circuits you've got to maybe 3d print all sorts of stuff you might have to machine stuff you might have to do all sorts of things you might have to there's a mill i guarantee there's a million examples if we ask people yeah yeah i mean sure there are but yeah i don't know we're just too dumb to think of them right

Chris Gammell: i well i just i was just asking for questions on the on the discourse i just asked questions i

Dave Jones: didn't have to think about answers that was for us to discuss here so the so the op wanted um

Chris Gammell: other examples did he yeah exactly yeah yeah exactly okay and there were some other examples in there i didn't want to give them away though come on i've got the answer key in front of me dave like home automation was also in there 3d printing was an example oh the 3d printing is kind of like a uh fundamental type of thing as well right so like the the goal might be to make figurines and 3d printing is like a enable of that that hobby of that but there's like all the like people are

Dave Jones: into fashion these days everyone wants their you know their dress to light up right so they're going to make a custom thing all the wearables stuff you know yeah so so people that are into who would think have no association with our world at all and now you know using little and lord knows that

Chris Gammell: we don't have any association with anything that's fashionable so no one's ever accused me of having a good fashion sense that's for sure right uh maybe someday maybe someday when i combine my knowledge of electronics with clothing you'll you'll make it big huh no i won't i won't know all right all right uh there was one other thing on the list what was it so someone had written in from a large company and they heard john day who was on the show he was from microchip and so another an engineer another company was inspired by that and wanted to know was basically asking for other app notes that would be useful to listeners the empire audience i mean yeah it's like a super broad thing right

Dave Jones: super broad i mean app notes oh god there's just i've i've got one i've literally got one open in front of me right now which is the uh ti an 11 this is app note of the week um this is uh this is the texas instruments an 1148 linear regulators theory of operation and compensation of linear regulators so if you want to know about your poll what's the number again it is an 11 dash 1148 1148 so that shows there are a lot out there yeah like and and this goes into your polls and your zeros and your phase margins and your bode plots and your you know different types of ldo regulators and you know your phase shifts and all your all your sort of stuff about you know stay if you want to design your own power supply for example all sorts of stuff to do with like stabilizing the loop stabilizing your power supply and all that sort of jets you know right op amp compensation and things like that so yep and that's you know how many pages long i don't know uh actually this one's not that long this one's not that long it's short so it's easy bedtime reading okay oh sorry it's not an application note it's an application report so maybe yeah okay yeah i i don't know why i have this i i had it open for some reason i've i've got lots of tabs i'm a tab you know hoarder right right right yep and i had it open for some reason and uh like maybe i was like you know stealing a stealing an image from it or something for a video as i often do so uh yeah so it's not you know it's not the most comprehensive one out there but it might give you a nice overview of how you know phase margin works in power supply design for example so there you go

Chris Gammell: yeah i mean that's the thing like there are so many like narrow narrow topics that you could ask someone to do but this was an offer from someone at a large uh chip company like no strings attached they wanted to know some so if you got suggestions we'll link there there's a subreddit and i'm just going to send the subreddit back to this person when they're i'm surprised you have not mentioned the ultimate which is the keithley low power guidebook oh the uh yeah the low level management low or low low low power or sorry low level measurement handbook low level measurement

Dave Jones: handbook that's it it's like the bible in the industry of low level measurement that's what they

Chris Gammell: were on when i was there it was the sixth edition it might be up to seventh now is there actually a

Dave Jones: printed version of that i have one yeah oh hey you did okay all right yeah yeah it's good it's uh it's

Chris Gammell: it's short and like it's it's probably it's hundreds of pages isn't it no it's only like low measurement handbook no let me double check i it's on it's on seventh edition now and it's by tektronics not keithley of course uh yeah let's see it's oh wow okay never mind it's 244 pages

Dave Jones: uh-huh thank you very much seventh edition yep maybe i maybe the printed book was like uh

Chris Gammell: right they're like yeah just take this it's like the first chapter right yep here i am it's it's

Dave Jones: still keithley branded keithley a tektronics company well on google it's not that's what yeah yeah oh well i the one i just downloaded the seventh edition it's got big tektronics in there but it's also got keithley low measurement handbook yep it's a couple hundred pages long so yeah it's a good one

Chris Gammell: that's a good one yep yep it's that was a good investment in education on their part for sure yeah i know it's kind of like you know there's lots of app notes that are out there app notes and also like you know white papers and you know sometimes um but it's usually you can tell pretty quickly how high quality the content is oh yeah so people who listen to the episode with john day you could tell like there was some time that went into the stuff he was working on and you know like

Dave Jones: that kind of thing there's one i keep going back to because i just did another recent video on how to convert an lcd into an e-paper display oh cool and uh i keep going back to the microchip app note of how lcds work i can't remember the exact if you search a microchip uh lcd app notes it'll probably pop up it's an658 an658 that's the second app note of the week and it's from microchip and it's

Chris Gammell: um yeah and if you want to do this we could just be like an658 the app note of the week

Dave Jones: and 657 app note of the week and it's great it's just like how how lcds work how to drive them it's yeah it's fan it's got fantastic diagrams in it which i stole um of course because they're fantastic and put them in my videos and it's just yeah yeah it's it's really great so yeah if you're driving lcds if you've got a product this is the app note that you want so yeah someone's put a lot of work into that mary tamar tan roger ricky jason layton from microchip technology there you go three three offers fantastic yeah yep yeah it's a great app note so yeah there are some classics like that and actually dates back to 1997 by the looks of it wow wow and it's been updated but yeah it's just an absolute classic it's got tons of stuff in it it's terrific abno could have a beer at this point

Chris Gammell: yep love app notes all right well we should uh cut it off here but as people may have noticed uh we have a discord now and uh that is brought to you by uh and this show is brought to you by uh in in part by our patrons who we are patrons who we are very grateful to so thank you to them if you want to join in it's as little as a dollar per month and so you can do that oh no it's per episode isn't it we do per episode but you can if if you only want to do a dollar you you can do a dollar it's a dollar you basically say hey i want to do a dollar per episode that's the minimum you can do and then uh and then you say the max i want to do per month is a dollar and so basically you only get charged for

Dave Jones: the first episode of the month oh i didn't know patreon had that capability i thought you had to choose

Chris Gammell: either per episode or per month well we do as the creators but as people like sponsoring so like they sponsor an episode oh i sponsor an episode they say like i i will i will pay a dollar per episode but cap i want to cap it at some you know so if we put out like 100 episodes in a month they might say well i only want to sponsor the first up to ten dollars worth right so it's like a got a cost saving

Dave Jones: cost got it yes of course yep yes yeah because and that that is the risk if you back somebody on uh patreon and then they spew out a hundred videos in a month yeah exactly then you can

Chris Gammell: get charged a lot of money you know exactly yeah so anyways as little as a dollar a month uh to be part of the community and uh support the empire so we appreciate everyone who does awesome thank you very much that's it all right man we're well over stay safe stay healthy wash your hands we'll talk you soon catch you next time you