 and welcome to Lady Aida. Hey everybody, and welcome to my desk. It's me, Lady Aida, here at my desk. We went to the Lunar New Year Parade here in New York City, and we did some electronics. Let's talk about electronics. And there's actually a bunch of hardware designs this week. I'm still getting over this cold, but that's okay. This week what I worked on the most were some cowbells. I tend to go into little modes, and I'm like, I'm gonna design a bunch of BFFs. I'm gonna design a bunch of sensor breakouts. I'm gonna design a bunch of feathers or whatever, but that this week was cowbells, and this is our lovely bell, the cow bell logo. So let's go quickly to my computer, and I'll show off some cowbells so people can get reminded of what they are. So cowbells are boards that go with the Pico, or the Pico W, and they add a bunch of functionality. So like, you know, let's say you want to do data logging. So these boards are kind of thin because they fit basically right on top of the Raspberry Pi Pico. You know, this one has a micro SD card, an RTC coin cell and a stomach QT, and like a little reset button over here. And then, you know, I think in the guide, maybe we show, yeah, an assembly week, you can put the cowbell underneath, or you can put it on top. You do have to, you know, solder headers. This is like one example of like stacking headers on, and then you can have the board go into the piece, sort of a spread board, and then the Pico on top. So, you know, basically the Pico is very low cost. It's like $4 or $6 or something, but you know, there's other stuff you want to do with it, like add Canvas support, or maybe like, this is a DVI output feather that adds the ability, you know, the Pico can, using PIO, it can display graphics to a DVI monitor. So, there's a little demo for that. So, I designed like four, and then I had to take a break. I ended up doing a lot of more redesigns, but I did get started. You know, I got this prototyping one, which is like, you know, low cost, but the idea is that it's just like prototyping area. But then, you know, we had other ideas that I'd been kicking around. So, one thing is like, we've always had this wing shield, which is really popular, because it's a really easy way to connect wires to Arduino shield while, you know, you can stack another shield on top. And so, the first thing I designed was a Pico bell, hold on, I gotta find this. Okay, so, there's a proto. So, the terminal bell, and this is a rendering. So, I thought I, because I always think like, it's hard to see from the Eagle CAD, exactly what's up. We use 0.1 inch header. And so, this actually ends up fitting, you know, nicely on top of a Pico, and it has the same prototyping area, but I just sort of extended the board out and then put 0.1 inch terminal blocks. So, unlikely 0.5 inch terminal blocks, 0.1 inch terminal blocks don't like snap together. They do fit almost, but not quite 0.1 inch long. So, there's a little bit, like you can see here, there's a little bit of like a neep, neep, like this goes neep, and that one goes neep, like just like, you know, 10 mils, or whatever, either direction, to make room for either side. Cause they don't, like I said, unlike the 3.5 millimeter, the 2.54 millimeter, 0.1 inch terminal headers don't snap together. And if you're curious, 10 pen 2.5, 4, I think. Yes, this is the connector I'm using. So, you can see it's 10, they don't make them in 20, 10 is like the maximum. So, you just have to put one after the other. So, that's the first one I made. So, that's gonna come with the terminal blocks already on and stuff, and then like this rendering, and then you can use stacking headers or socket headers. But it's kinda nice because then you have like, support typing area, and then like you can wire up like anything you want, and this goes to each pen. So, it's like one to one, so it's nice. And then, let me see, I think the back, yeah, I have all the pins labeled on the back nicely too. So, you can quickly tell. What do you have to do? So, then I was like, okay, another thing I wanted to do is, you know, we have the Memento camera, and I've been doing a lot more camera projects. We added, you know, they have the OB-5640 camera breakout. These are a pain to wire to boards. So, like for example, if you're wiring this to, it's like a Pico camera, I think. If you're wiring this to like a Raspberry Pi Pico, it's just like, I'm like a nightmare to like wire. There's just so many pins, cause you need like eight data pins, and then v-sync, h-sync, p-clock, x-clock, power down, I don't know, whatever, there's like a bunch of pins. So, to make that a little simpler, and because the RP2040 has enough RAM to do like, you know, fairly enough pins, and it can do PIO, it can actually interface with these parallel interface camera modules. And I thought, you know, to see what the Pico W, you could then do like internet camera text projects for cheap. And so this is a camera board version. So there's the camera module in the middle here. It plugs in, and it uses a very slim FPC connector. And you can see it just like, it just fits quite nicely. Turn off the button, so you can see it clear. And then this is a micro SD card, same as the Adalogger. And then they have a couple of components. There's a reset switch here, which I think won't be in the way of the camera. I think it'll be fine. And then there's a bunch of power supply stuff, cause these cameras use 2.8 and 1.5 volts. And then a little button, this is like actually not a recent button, this is a shutter button. I catch it to like pin 22. And so I think like, if you have a camera, you wanna have like a little button to like take a photo or whatever. And then a STEMMQT port. So I thought that'd be fun. Cause I got all these camera modules and I was like, oh, well we can make a cowbell so people can do camera projects with the Pico or Pico W. And then I was like, oh, to make it easier to like do some of this prototyping, we have the proto plate, but I thought it would be also good to do like what I call, look an under plate. And if you go the overhead real fast. So one of the things I use when I prototype feather stuff is I have these feather doublers and triplers and quad doublers where you can connect them side by side and they're wired through. So each socket is duplicated. They're all connected together. So you can have multiple, like of course, like the one thing I didn't like a feather. Okay, so I have like a feather wing, you know, here this like TFT feather wing and then like, you know, pretend that this has a header on it and then I can connect it's here and then like I connect two more feathers and as long as there are no pin, you know, conflicts that'll work. So I wanted to start with just a single. So can you go back to the computer? The reason that I'm having a single is because this is gonna use two by 20 like socket headers. And so if you have the Pico H or the Pico WH, which are like they have the headers pre-soldered in, this is like you can just plug it in directly. And so that can be kind of nice if you just wanna like, especially just want the reset and stomach UT port, you don't even care about the proto. It's like, boom, you don't even have to do any soldering and it's like nice and slim. So this has all the pins labeled for mounting holes, two by 20. And that means also when you plug it in, you'll have two more headers on the opposite of each side. So actually, can you go to the overhead again? Sorry, I forgot to show. So this is like, I use a similar setup on this, this brains board and you can see there's, you can kind of see there's like one row of header exposed because this is a double header. And I like the double header more than the single because I find that it's more mechanically stable. It's like wide enough. They do make one single row header, but I find it like bends, it kind of bends and breaks so easily. So I like the double and like bonus you get an extra row and it's not that much more expensive. It's about the same price. Okay, so let's go to the computer. We'll get through this, we'll wrap it up and we'll go to the great search. So this is the single and it was like, okay, so I just took the proto and then like I just like widened it, add the row of double headers. So this will be nice, just super great for quick debugging and prototyping. And then of course, if you have one, you're like, why want two? Cause I want to have maybe like the Pico and then like, you know, a bell. So I made a doubler. And this is the rendering of the doubler. So this is the same as the last one, right? You've got the reset button and the STEMI QT port. And then I like cloned it like clone tool, except not really, I think look at it, just like duplicated the work, but I don't want to have two reset switches and two STEMI QT ports. That doesn't make any sense. So I was like, oh, well, let's add an enable switch. So this connects to this enable pin here. And that'll shut off to the 3.3 volt buck converter. So that might be handy if you want to like turn something off. And the reason especially, I think that's extra useful is because it added a battery, lipo battery and charger circuit. So this is a 0402, it has to go kind of small. But this is, there's two LEDs, one for like charge done and one is like charge state. And then the MCP73831, some capacitors and then a pass transistor. And the pass transistor is basically doing, this diode actually already exists on the Pico. So what that diode is is like this plus this pull down. So like it's like this section here. And what that does is that when the USB is plugged in, it'll power from USB. And then when USB is not plugged in, it will charge, it'll connect the battery to the power input. And if you do it this way, it means that you don't end up like constantly charging and depleting your battery while on USB. Like the battery is completely disconnected from the load. It's only charged. So it's kind of nice. So it kind of ganged to that from the feather. And I even used the same like super, this super tiny PFET transistor, which has worked great, love it. So that's the doubler. And then I'm still working on the tripler because everyone's like, okay, like there's more. So you can see it's like in progress. Let me just pull it up real fast. So this is the tripler. No rendering yet. So you've got at the bottom, the reset and stomach UT still. And then the middle, the, oh, and then I forgot to mention on the back, there is like an adjustment for whether you want it to have high volt, high current. And also you can disconnect the charger. So if you want to like plug it in and power it from AA or AAA battery pack and you don't want to have the charging circuit, when you cut this jumper, it disconnects the charger from the battery. So there's, it's more advanced, but like I've actually started to try to do that a little bit more because sometimes people are like, oh, I don't want the charging circuit, but I do like the battery connector. And then let's see, this is tough. And then over here, I think I'm going to add an iSpike connector, although it might be like a real pain in the ass to route. So I'm not going to do it if it's a total nightmare, but I could add an iSpike connector. Some people can like, like displays really easily or like inks or whatever. And then I added a neopixel. Well, I don't know, we'll see. This is again, like still very, very much in progress. If this doesn't, obviously I have to remove these two pads, which is fine because I've got that broken out here and here, but like routing all these pins through might be kind of like, I mean, I think I can do it because I'm only using the bottom, but I don't know. Sometimes it doesn't work out in progress. Okay, so that is the hardware I'm working on. So let's move on to the great search. That's a great search brought to you by Digikey and Adafruit. Thank you, Digikey. Every single week, lady, I use the power of engineering to help you, yes, you find all the things you want to find on digikey.com. Take it away. Okay, and my hair is like Digikey red, right? Yeah. Okay, so this week I worked on this design, which is a underboard for, oops, sorry. An underboard for the Raspberry Pi, Pico, and I was saying like, oh, you know, I have a STEMQT connector and a reset button, so I squirt scene resets easy and then I have an enable switch. But I also wanted to add battery charging, because especially for the Pico W, it's wireless. Maybe you want to have like a IoT thing that runs on a battery with battery charging. And so I kind of borrowed a circuit that I use for the, let me get rid of the sidebar, it's so big, especially in 720p, it's very noticeable. Okay, sorry. Okay, I borrowed the circuit that I use for the feather boards, which uses an MCP73831, has two LEDs, one for charging red, one for green, which is like done. And then capacitors, you can set the charge rate with a resistor. And then there's like a pass transistor, but I realized I never actually covered LiPo chargers. And so even though I use this one, by the way, there are a lot of other options on DigiKey, but even this one has a lot of like, and especially during the part shortage, you got to really watch out, not all numbers are the same for this part. There's a lot of like dash XYZ, that's what I want to watch out for. So let's go to DigiKey and search for battery charger. So what we want is a battery charger that will charge 3.7 nominal, 4.2 volt max batteries from USB, because that's what we're getting, like five volts in. And I want something inexpensive that can also, it doesn't require I squared C to set up, it just is set by a resistor, because a lot of the really fancy chargers have like I squared C or that one Y or whatever. I don't want, you know, you can do all sorts of configuration and like also monitors the battery. I want something like cheap and easy. And again, resistor set. So you set the resistor and then here, I have my little guide that reminds me what you set it to in order to set the charge rate. And you know, I'll be honest, actually, this says one amp, this actually just charger actually can't do one amp, which we'll also talk about there are some other chargers that can. So let's go here and then we'll look for battery chargers. Okay, so there's like big battery chargers, there's battery management, but we want battery charging chips. So let's go here. So there's 3000, there's quite a few. And you know, they come from anything like DFN and SOCT to like they can get a lot of pans and very complicated. You know, they come in BGA also. So let's just try to pare down this massive number. We're only gonna look for the active items and we're only gonna look for ones that can handle one cell because there's some that do two or more. And then I'll also get, I'll pick up the dash as well. And then let's just, well, we only want surface mount. And let's just say we only want in stock. So it's available to purchase now. Chips shortage is kind of over. So basically if it's in stock, that means it's gonna, you know, if it's not in stock, it means it's probably like not available. And no marketplace just because I don't wanna have the double entries for externally sold parts. Okay, next up, so the battery I'm using is a lithium ion slash polymer battery. And there are other chemistries available, but pretty much, you know, I'm gonna pick up the dash just because who knows. Lithium ion and polymer, lithium iron phosphate, I think it's something different, multi-chemistry. I actually don't want any of the multi-chemistry ones because those are always gonna be more expensive than just a dedicated charger. And then I want to also set the voltage of the, I actually don't know if we can set the voltage. Well, let me do this. Let's filter on the chemistry. Okay, good. So that's much, much chiller. Okay, so next up, charge current max. Well, I really feel like if I'm gonna charge these batteries, it needs to be at least 200 milliamps. And, you know, I can go higher, but honestly, like no charger that's gonna be affordable is gonna be over like three amps. And then the battery pack voltage, I want it to be for these batteries that we're using. So these are lipoly batteries. You know, if you're using other batteries, you know, go to town, but the ones I'm using, I think I actually call them lithium polymer, but, oops, sorry. Great. These are 3.7 volt nominal 4.2 volt max. And so watch out, because even though it says 3.7 volts on the battery, you don't actually want 3.7 volts. You want like 4.2. So I'm gonna pick also the ones that can do, you know, whatever, but I definitely don't want the ones that do higher voltages. This is all I want, 4.2. And then interface, I actually don't want I-squared C or USB. I want something that is, again, a very simple interface. So just GPIO programmable. And this will reduce the number quite a bit. Yeah, now we're only getting like, okay, there's one or two or three cells. Okay, now I think we're good. I mean, the voltage, you know, I don't care as long as there were five, all of them are over five. Current max, I think is okay. So let's look at some of the options. So we've got the MCP738 standard option. And, you know, they have a ton in stock. There's also the 832, and they have them also in DFN. But there are other families. I'll say the VQ series from TI, they're quite good. These are, you know, they also have a charge LED. You can set the current with a resistor. Some of them have like termination timers, like how long you wait before you time out or whatever. They also have a power of good output. So, you know, the more pins you get, the more options you're gonna get. And this also has a temperature reading, which I'll say, you know, if you're charging at a higher, if you are going to have people with batteries that are charging at a very high rate, like one C or above, it's not a bad idea to have a temperature monitor, especially in like a production product. For this board I'm making, it's very simple. It's like low cost. And the charge rate is already kind of set quite low. So I'm not worried about it. But a built-in thermistor battery pack is never a bad idea. So, one thing I'll mention is the battery charger I use on that board, that design, does not have a thermistor built in. It's a good idea, especially if it's gonna be used outdoors because at very low and very high temperatures, you do have to change the charge rate. There's also ST has, you know, a nice low cost battery charger. One thing that is nice about this one is it does up to 800 milliamps, which again, the charger I'm gonna show does not do 800. And it's very simple. It just has like LED program power in battery. It's like, there's something quite nice about it. And I like that it has a little bit higher input supply voltage max up to 10 volts. Not that you should use 10 volts, but like sometimes I've seen people like they plug in like some random off the shelf USB power adapter and it like kind of floats a little bit above five volts. And sometimes it can actually get popped, kind of where, but it does happen. One thing that I'll say that I've never seen is a battery charger chip that is reverse battery protected. Which would be kind of cool because I do one of the things, and ending in this small package at a reasonable price. They do see a lot of customers, they end up, we warn people like eight billion times do not buy batteries from Amazon that are the opposite polarity. And then people are like, I plugged in this battery that I bought from Amazon. And then I realized it's reverse polarity. Did I damage it? And I'm like, yeah, it's dead. Like it's like, but then I unplugged it within like a minute. And I'm like, it's done within like 10 microseconds. You can't unplug it fast enough. That'd be cool. If anyone knows of a battery that does that, you know, or a battery charger that does that, let me know. But this one is nice because it does 800 milliamps. But the one I tend to use is this, let me get the part number quick, 73831, which is available in, it's kind of the one they have the most of. And there's a couple of different ones in this family. Or first off, they have a DFN version if you want smaller. But there's a 31 and the 32. And then also there's like these letters afterwards. And you do have to watch out for these letters. So one, there's the difference between the 831 and the 832. Is the 831 has a status pin that can, yeah, so this is the difference. The 831 has a push pull output on the status. Whereas the 832 only has a open drain pull down. Why does that matter? Because in this case, on this board, not every board that I use some feathers, I don't use two LEDs. You can on the 831 only have two LEDs. One for charging and one for completed charging. And then it floats in the middle when there's like no battery detected. Whereas the 832, it only does in charging. Like there's only the orange light. There is no green completed light. I don't like that you can have both. So I tend to use the 831 because I like to have the two LED option and I only want to stock one part. Next, if we go down to the product identification, there's a lot of options that you'll see. So you'll see MCP7-831-2CI, 2AD, 2DC. You'll have to watch out because they're not the same. One, the regulation voltage. The T is just a taping wheel versus a tube, I think. But the regulation voltage is that first digit. So if you get the 73831-3 or 4-5, that's gonna have a battery pack voltage that's higher than 4.2 volts. Why would you ever get that? There are some batteries that have anodes that are a little bit higher. They're not low cost, a little bit more expensive, but you see them in some automotive projects and I've seen them in skateboards and stuff. They have a slightly higher voltage due to the anode cathode chemistry. So they have a little bit more power you get out of them to a wattage, but you have to have, you cannot have the regulated voltage here be higher than the battery pack where you could damage it. You can't charge a 4.2 with 4.4. You can't charge a 4.4 or 4.2, but you won't get all the power possible out of it. And second, there is the termination voltage versus the regulated voltage. And this has to do with when you first, if you have a dead battery or very, very low battery, you sort of triple charge it until it gets up to 3.2, 3.3 volts. So there's a little bit of how much current versus the maximum current and then like how long do you do it for whatever? That's not as important. So I've sometimes used the AD instead of the AC because it's like so closely related, but do check which one. And then there's two packages. There's the DFN and the OT. That said, the one I use the most, again, it's like kind of the standard, standard issue. It's like, again, I like the 31 and two AC means 4.2 volts. AC is kind of like default termination current, triple current, and it's in stock in DigiKeys. So let's just put on dark mode. Yeah, it's in stock. And it's like, you know, pretty cheap, like 60 cents per. Some people are like, why don't you use like the really cheap, inexpensive, like 20 cent chips that are available that are like, you know, from like random asked companies? And the answer is you really don't want to like go cheap on your battery charger. I always use the genuine microchip parts because like I know that they have good engineers. The really inexpensive parts, it's just too risky. It's like, if you don't charge your battery right, it's very bad for the battery and you know, it can be bad for the person handling the battery. So I recommend getting like a genuine part from DigiKeys. So MCP73831T to ACI, that's our pick of the week. Pick of the week. Thanks so much everybody. We'll see you throughout the week. We have 3D Hangouts, JP's Workshop. We've got show and tell. We've got Ask an Engineer. A lot of products. We've got Dive with Scott or Tim. With Scott this weekend. Tune in all week long. We've got new products and more. We'll see you next week. Bye everybody.