 And welcome to my desk. I'm like disappearing. I'm so goth Welcome to My desk where I do electronics all day and all night and I got some of tracks in this weekend And I'm also trying to kind of get through a bunch of backlog things stuff. That's been Waiting the last few months to get done get fixed. So, you know, spinning a couple hours really analyzing like, you know Stuff that is working. Why isn't it working and then try to get it working so I can get to the shop So let's go to the overhead and I'll show off the first thing that I worked on this weekend. So these You know, I had this a weird mystery thing where We did a revision for These ink feather wings and you know, as you have watched I've been doing a lot of revisions I got a lot of TFTs get revised all the inks get revised So the way you can tell is, you know, for easily is I changed the silk screen to be Like a rastered silk screen instead of like a vectored. So this one is the new one You can tell because a nice silk screen and I moved on a couple parts There wasn't like one resistor that like for some weird reason like I put Like right next to the FPC and made it hard to open the FPC if you wanted to replace the ink so I moved then, you know, I had to do a couple of part replacements because like stuff was unavailable out of stock and We had this weird issue where This is the old one looks beautiful and the new one has like this kind of weird Speckly appearance afterwards unplugged. So I'll show you like this is the tester For this product when I run the test Just give a second because it has to Wipe the display Okay, so it looks like beautiful. It's lovely a crispy ink display and then when you unplug it Like six seconds later it does this like Thing and it starts to like getting speckly and this does happen, but it's not supposed to happen that quickly It's supposed to like take like a day for it to get like dim Like this one in contra, you know, when you compare them and this one looks much much better And I was like, oh like is it like the display it's not the display was it like I looked at the components All the component of them components will really change They were just moved around a little bit. I was like, was it the layout somehow or like what what could have happened? And then actually did eventually figure out what the issue was and this is when a part swap, you know Sometimes swaps are not swaps. So the dyads used for there's like a you know Buck converter and invert a buck converter to get a high voltage for bias and I think a negative voltage for bias There's like two DC converters and uses inductor the doctor did change and I was like maybe the inductor I get I picked a nice your inductor, but like maybe there was something about it that made the converter not work as well Actually the diode even though the diodes are the same part number NBR 05 4 0. I couldn't get the MCC NBR 05 4 0. So I got this other kind of like so-so brand and From from LCSE it actually turns out that even though the specs were on paper Equivalent there's something about this may be like reverse leakage or something that Ding-Ding that makes That converter like leak current or like the voltage droops once is connected and faster than supposed to and so When I soldered from the working one these NBR 05 40s on to This board this one's a pre Soldered fixed one It started working. So, you know again, it's like During part shortages like I couldn't get died. I can't get regulators like op-amps, you know, whatever transistors So I tried to find alternatives and the best choice is always to try to go with the same part number But in this case actually even the same part number was not equivalent So it does happen once in a while, but thankfully, you know, like I just swapped like I start swapping every part I was like, well, I like keep swapping and then when I swap the diodes, that's when it started working Okay, so it's just one of those like you have to spend a couple hours and just like You know, I swapped like one thing tried you did that help something. Thankfully I had a working Good version to like compare against I think would have been really frustrating if I was trying to do it They can go from scratch like a base design. So yeah, it turns out the diodes. I Thought shocky-dazzle shocky-dazzle turns out sometimes they're not And then another component thing you're that I did was I got this Prototype up and running. So this is oh, what is the part number again? Oh goodness, it's like the T USB 30 from TI it's a USB switch and so Kind of cool idea It takes a USB in so this is the host and then in you know, then it has two ports that I just Connected cables to but of course you can hardwire them and then this S pin determines which one is connected So, you know, you know, some ideas is You have, you know, two peripherals in one case and you want to swap them or You know, one is gadget mode and one isn't and so like you convert like I think it's just like for cameras or like Some other devices where you might want to like maybe you want to access the internal mass storage through like an SD converter But then you also want to kick through the microcontroller. So just a switch that will let you do it so it's like designed for high-speed too so you can do USB 2.0 and As actually, you know, it was working This board is working just fine. You know, thankfully like where I got it going good I'm not gonna put this in because it actually takes down my USB hub which will like take down all this video stuff Which would be sad demo But the reason it was taking it down is because when I plug this in I tried to be like, well, you know, like you're switching the USB and maybe we should have plenty of power to like Avoid, you know avoid a brown out or whatever. So we put two 100 micro farad caps here So these are 1206 or 1210 100 micro farad caps. There's two of them in parallel on the V bus line Five volts. So that actually is more than most Hubs and ports want to deal with they don't like that high inrush current of a low ESR You know 200 micro and then another 10 years like almost like 220 micro farads of low ESR capacitance That's a huge surge of current and then, you know, my hub doesn't like it and then it basically resets. So the solution was Just swap them out for, you know, a couple to 10 micro farads and then this I changed from a 10 to a 1 micro farad So now it's from 220 to about 22 micro farads. That's well within Spec I will I will say it's something interesting. I remember really wants that The USB spec does not really want more than 10 or 20 micro farads of load when it first plugs in there is a Fuse that protects each port on a USB hub or like a computer. So, you know, it'll protect you from like, you know backpowering or overcurrent or whatever but You're too much surge current will will either cause the fuse to Flip or cause the power supply to dip because it's not expecting that much rush current But thankfully, you know, once I did that swap, I just soldered it in it worked great. So Those are two prototypes This prototype got sent out for manufacturer. So that's you'll get the PCBs manufactured get those in and then Another one that's just been pending for a very long time is I designed these really adorable TPS 61040 PCBs and this was also one of those like, you know a component swap was making it not work. This is the Working good one, you know, I had this working good one and They use this for just generating like a small 40 milliamp bias Voltage at 20 at 12 volts from the three to five volts And I did have to do a couple swaps. So like the inductor I couldn't quite get so I got a slightly different inductor And this was a solid state not a wire round inductor and then the shocky diode I did change this was an MBR 040 and I changed to an MBR 120 because I don't need 40 volts. So I was like, well it's 20 and But otherwise it was the same and it like wasn't like it wasn't generating 12 volts It wasn't like enabling and I was like did it I looked everything and then, you know, of course the thing that it turned out to be was This accidentally got pick in place with what should what should have been 860k 860 ohm resistors. So the resistor divider was way too Low and so it wasn't boosting. It was like it was like, oh, like your voltages There's no feedback voltage. So it's like you just shut off. So, you know, it's one of the side effects of using Ironically it's because I used 1% resistors and 1% resistors use the code on them Let's see if I can Zoom in. I don't know if it's gonna be able to see it But there's like a three-digit code like when you're using Larger resistors sometimes you get like, you know, three letters that'll be like one zero three And they'll tell you to get a 10k or one zero four. It's it's a 100k but this was like why three Q or something and like I should have looked up the code to verify but I didn't But, you know, I'll just get these, you know, what should we work them? We'll just remove this resistor and put in an 160k and hopefully they'll pop up a working 12 volts We'll get this back into the shop a little bit of rework, but then the next run I'll fix that, you know, I'll throw away them, you know batter sister put in the good one And we'll we'll get these fabric. Okay. So good. That's that's, you know And this is like by the way, I ordered these like a year ago Like they've been sitting on my desk for like a year like what does the wrong with these? Just spent like an hour today and just figured it out like it was it's a good holiday Brain cleanser. All right, let's go to the great search The great search for R2 about digikey and inter for thanks digikey every single week Lady to use the power of engineering help you yes, you find things that you want on digikey.com Lady to what are you looking for this week on digikey.com? Well, um, what I thought I would show off was actually Just 10 micro farad capacitors. So if you go back to the overhead Um, you know just showing off a project why I replaced well this, you know I've got 10 micro farad capacitors here and here. This is a little buck at that boost converter to 12 volts I've got these two big caps here are 10 micro farads and then Over on this board, you know, I've got just, you know, all of these are 10 micro farads all these chonkers over here um This was a design where I had Two 100 micro farads turns out too big one big them back to 10 and I realized I haven't done a great search where I Talk about getting just jellybean 10 micro farad caps and we use a lot of 10 micro farad caps Obviously you pair them nicely Okay, like a like a cabernet with some lasagna You get your 10 micro farad your one micro farad and then a point one micro farad you put them together You've got a full decade, you know coverage for high frequency and like bulk capacitance And we you know we sometimes we use electrolytics And there's times to use electrolytics. So for example when you need High voltage a lot of bulk capacitance. This is 47 25 volt Um for the pricing you just go to electrolytic, but there's still A lot of 10 micro farads. Um Why 10 micro farad electrolyte? Uh ceramics? Um Ceramic caps capacitors are inexpensive easy to pick in place. They're small um They're very low esr. Which means that they'll perform fairly well at reducing high frequency noise But mostly they're just like really easy to pick in place and small. I mean like tantalum It's like a rare earth metal that a lot of people, you know It's complicated to make sure that you're getting it like ethically sourced and also they're much more expensive Uh, so I don't really use tantalum kind of at all. I don't think I like use it at all Um, I basically just use electrolytics when I need 47 and above and um For anything below I use ceramics and there's only one time I'll say that you should not use ceramics and there are some power supply chips that need Why esr for stability because they use that The series resistance of the capacitor to stabilize the feedback I think the mix 5 205 or like there's I don't remember exactly the part number but I remember seeing once Uh, you know, I tried making a power supply with a um, but get old older chip. It was a good old 1117 or something and I tried um Building on a pcv with ceramics. It actually wasn't stable. I saw like it was kind of oscillating When I put on um the same capacitance, but electrolytic it stabilized So, you know, it happens Um, okay, so let's go to the computer. I don't know if there's like some beta food stuff in this photo. That's kind of cool Um, okay, so your standard, uh 10 microfarad ceramic capacitor Is lovely and there's lots. Um, don't forget there's dark mode But I think it's easier to read the video in light mode. So I'm going to just continue in light mode So first off, we want only active 10 microfarad, of course and then, uh Let's just do, you know in stock and exclude marketplace just to look at what's in stock right now at digi key Um, and sold from digi so you get it like instantly Okay, so now we can actually start, you know, there's still a thousand options just for the 10 microfarad caps So the next thing I like to look at is tolerance. Um, and the tolerance is actually related to the um Actually, sorry, let's do surface mount Also, let's avoid through although there's many through hole ceramic capacitors, okay Um, so when you look at the tolerances Much like resistors capacitors have tolerance and that tolerance is going to be related to the temperature coefficient Which is also used as it's at the dielectric and sometimes you'll see this x5r x7r y5v so y5v is going to be like the cheapest one and that's the one that's Plus minus 20 but like these days you don't have to go with like it's I don't really use the y5v anymore because you get much better performance from Like x5r x7r x7r and x5r I think a slightly different temperature like one is industrial one's commercial So I look for like 10 20 percent Is kind of what I go with a reasonable price and also like doesn't it's not like too wobbly when it comes to the consistency Next up you're a voltage rating. So in general you would you want to use the lowest voltage rating For your situation. So if you're you know, it's a five volt power supply use 6.3 volt 9 volt power 8 volt power supply 10 volt 12 volt 16 You know, I always go a couple volts up and then that's your voltage rating however I don't want to stock like five different voltages for Um different use cases because a lot of my stuff is three volts or five volts So she gets 6.3. Well, you saw that little boost converter goes into 12 volts I don't want to have to pick like oh that one cap is a 16 and that one's So I pretty much always pick 16 to 25. I feel like that really covers a lot. Honestly, I tend to use 16 But like depending on your use cases, maybe you need that extra boost for for 25 go for it. Okay. And that actually cuts it down a lot. So it's like now 350 options So next is the package case. So You know without going into like, you know, like a 30 minute Discussion, there's a lot of videos about it The bigger the package the more So the bigger the package and the coefficient Depending on the coefficient, you're going to have less dc bias loss of your bulk capacitance What do I mean? so electrolytic capacitors are actually Kind of nice in that when you put 16 volts across them 47 microfarad, you're going to actually get 47 microfarad of capacitance That's not true of ceramics The dc voltage across them actually greatly reduces like easily 50 percent or more The capacitance rating. So you buy a 10 microfarad capacitor. You put six volts across or five volts across it Now it's at 4.7 Which is fine. You just add, you know, that's why I put lots of them on there They're only like a penny or two a piece But it's something to think about just if you're like, I mean, I wouldn't design these into filters I think if you're doing filters, you're going to use smaller capacitors and you'll use cog C0g, which is um A uh dielectric that doesn't lose the bulk capacitance But let's just look at the data sheet Here, I don't know if it's in the data sheet. It might be in the spec sheet Yeah, okay That that that that that that that that voltage do rating So there's temperature do rating as they get hotter. They also lose up to 60 percent So watch for that but the one that is Voltage Hold on It might not be in this Do rating. Okay. This is only temperature do rating applied voltage It doesn't have the graph. Okay. Hold on one second if you go to the product page because I saw this earlier Characteristics Uh, so this has fairly good temperature characteristics. That's good But the dc bias characteristics you can see here as we go from zero To like five you've lost 50 and you go higher you lose even more And that is a 0805 if you go to Hold on got mixed up if you go to like a 1206 or whatever So let's look at this uh 1206 capacitor and look at this specifications Hopefully it's in this document. I probably should have I pulled it. I probably should pull these up. Ah, here you go Um Day rating DC bias, okay. Um, no, sorry. This is still the X5r. This is not the specific one one moment. Did I click on the spec? Hold on let me find one that has I may not be able to find it but basically the larger it is Maybe maybe tdk has characteristic Okay, so for this one the 1206 instead of the 0805 You'll notice at the 5 volt you lose 15 percent or do you remember on the 0805 we lost 50 percent So the bigger that the the physically larger the capacitor in general check the spec sheet like and you see sometimes you have to like look around It's going to de-rate but the de-rating will vary and the de-rating also varies by the electric um And the um, so it's like y5 x5r x7r C0g of small obviously for like if you're getting you're like 22 pico farad capacitors Those are not going to be De-rating as much because you're going to get ones that are that have a high quality dielectric um, but when you're talking with the bulk capacitance, it does matter so You just put like twice as many on I don't know. They're like a penny or two apiece Um, so let's go back I will I tend to use 0805s to be honest Um, so let's look at 0805 and It's about 100 options And there's a couple of different ones again different Voltages what you're going to be paying for. I mean you're like, what's the difference all these y's are 100 Um, so they different heights and sizes Uh, some are different temperature gradings And some are just different tape and reel sizes. So like there you know, there's the um This one like I think is you know, I don't know the g maybe it's like the reel is bigger When you get it, there's like a 3000. Yeah, this is like a 2000 tape reel 3000 4000 10 000 That's another thing if you're getting These caps by the reel, um Because you're in a picking place the 10 k piece reels are awesome because you load them once you forget them But your feeder has to support that size reel something which I learned once when accident was like Oh, I'll just buy the 10 000 and then we got this like 13 inch reel and I realized it wouldn't Go out on the pick in place machine, but if you're just Buying these generically this one is super cool the cl 21a 106 uh Co-q q and any I don't 10 micro farads samsung generic cap. I use these by like the bazillion. We literally sell like a million a year Uh through all of our components that go to our products. So that's my pick for the great search. That's a great search And that's our show for sunday. Thank you so much everybody. We'll see everybody throughout the week. Um, just a little bit of reminder Uh, limited number of data boxes are going out. We'll be contacting folks soon. We've got, um gift certificates and the next couple weeks We'll still be around doing stuff making open source hardware shipping and sharing knowledge getting it out there. We'll see everybody Next week