 and welcome to This Lady Eight-O. Hey everybody, and welcome to my desk. It's a great week. We had a lot of people visiting from out of town because of hope, but we're back at our desk ready to do engineering and electronics. Do you have any updates, Mr. Lady Eight-O? Yeah, I mean, for super fans who follow the site and our shows and everything, if it all works out, Adam Savage will be on our show until Wednesday at 7.30, so yeah, I'm just like dropping in higher. Yeah, so we're going to be talking about Silicon, which is an event out of California and Makerverse. So if it all works out, it's always hard to time these things, but we'll let everyone know. But if you're around and you want to see Adam talk about this cool event, it's the coolest thing to like a Maker Faire. Lots of familiar faces are going to be there and more. And out in Silicon Valley, great. If you're in the California or West Coast area. All right, so check it out. And other things going on and more, but that's the kind of highlight of the week. Okay. So what is going on at the desk way to this week? All right, let's kick it. Okay, first up, let's talk about revisions. Okay, so let's go to the overhead and I'll show off a board that I'm revising. And why? Let's set up. Okay, so the Metro Mini is one of my favorite boards. I actually use this all the time, mostly because I find it easiest to write drivers for the Arduino Uno first and then to other platforms. Partially because the compiler and uploading for the Mega328 is kind of like the fastest. And because it has a separate USB serial, I can press reset and I don't have to worry about the serial port disappearing and reappearing and the enumeration. So it's kind of nice for debugging. It doesn't have a lot of memory, but also it's like the standard Arduino. This is a breadboard friendly version of the Metro, so it has all of the pins that you would expect for using an Arduino compatible. Let me zoom in this to lock. And it's got the Mega328, LED, RXTX, CP 2104, your serial USB, serial converter, micro USB three volt and five volt regulators. I mean, it can't give you two amps like the Arduino Uno peak out of the five volts, but you can do a lot of breadboarding and you can see here, I have this often wired up to a STEMI QT board as I'm working on it. So good news, I love this board. And we actually have quite a few in stock. We did get at Mega328s and CP 2104s and we were able to keep these in stock. But the CP 2104, as we've mentioned many times on this show is slowly being discontinued and being replaced with the CP 2102N, which requires a resistor divider. So I've been slowly going through all of our designs and making it so you basically can use the CP 2104 or 2102N or the CH 9102, that WCH USB to serial chip. Although I do, I still like the CP series the most. So that's all good. So this board wasn't in a rush to get designed, but it does need to get designed and one of the things that I was actually, you know, I'm working on some drivers this weekend and I was getting kind of annoyed of having to like plug in a STEMI QT cable like this to do my, you know, my very common STEMI QT drivers. I really wanted a QT port at the end and I was like, oh, you know, if I'm gonna do that and I'm just gonna have to redesign anyways, I might as well do like a gut renovation and kind of like tear everything out and start over. And so I designed a new version, the V2 of this board, which looks like this. And I'll show the difference. So, you know, it's the same size, same pinout mounting hole, same location, GPIO in the same location, but a couple of things moved around. Someone I moved to USB-C because that's kind of standard. People are expecting and trying to make it so any new boards unless there's a really good reason I go with USB-C. And a lot of 0805 parts got shrunk into 0603 and, you know, these LEDs are 0603 now. So you can see they got shifted over to the left. The regulators are the same. You know, I have the resistors for the USB-C and the resistor divider for the CP 2102N. So again, I can swap between the two parts. That this main shift looks smaller and it looks smaller because it actually is smaller. This is the 32 QFN version of the 328P, which is, you know, our standard bread and butter at Mega 328 chip. But because of the chip shortage, I, all those, all those at Mega 328QFNs have been allocated. Like they're, we're, we've used them in production. And so in order to get this design out, I actually was able to find, you know, Microchip actually had a couple thousand of the 28 QFN version of this chip available. And the 28 QFN doesn't have the extra A6 and A7. You know, there's two extra analog pins and, you know, there's the, there's just like one less ground pin. I mean, there's still ground, but it's just you don't have like three grounds. You have like two ground pins or something. So it's otherwise pretty much it's the equivalent chip. It's just a 28 QFN instead of a 32 QFN. So a lot of people don't use this package. They use this one. So this one I think was available. It's one of those like weird things where the, the package was available, you know, the different package was available. So I snagged them and I'm going to release this with the 28 QFN and, you know, until I get through the 8,000 pieces. And then, you know, I can always revise it. I make sure that there's space. I can make it fit this big chip, bigger chip. And then you can see with the space I saved, I've got a STEMI QT port at the end there. Yay. And at the STEMI QT port, the design decision I made to drop my oscilloscope probe is, you know, because I was chatting with Mr. Lady and I about this, we have to make design decisions. So STEMI QT boards all have level shifters in them. So you can use them with three volt or five volt logic. And they're all can work with either, but quick boards only work with three volt logic. So the only thing is that needs to be done is I didn't really have space for a logic level shifter. And also I didn't want to put pull-ups on the ice, the ice board sea lines, because there's also analog pins. So on the bottom, the silk screens actually, I forgot to have the silk screen, but you have to change the logic level from five to three in order to use the STEMI QT with three volt only. But I think it's not a big deal. I do it all the time. I think this board has, you know, it'll say, yeah, has the VIO silk screen. So you can see it's default five volt, but you can set to three volts and then you could run this whole thing at three volt logic and power. So, pardon me. So this is a new board and I'm using this and it's super fun because I can just, you know, plug in a sensor and I can start coding for it. So this is a UV sensor that I'm gonna work on a driver for. So that's cool. So that's one board that I finished and I ordered the PCBs. So you'll see that in the shop in a couple of weeks. It'll be a new product ID because I do think that there's some people who, you know, they do want to have the, you know, the button did move and, you know, we still have a bunch of these in stock. So I think people can choose which one they want. I think there's, there's reason to carry both for a bit because it's a pretty big redesign. So that's that. Any questions for a move on? No, there was a CP2102N for new version. I don't know if that's a question or if it was just a word. Yes, we're using the CP21. Well, either CP2102 or 2104. All right. Okay. So the next thing. Are you gone? Yes. So next thing I've been working on, which he has one of those things where, like I kind of made a joke. I was working on like a different tester and like, you know how you're just like, oh, all I have to do is update, you know, a version of like Rasmian on tester. And then before you know it, you're installing like WSL V2 and like messing with your BIOS. So I'm playing with this sensor which I dropped, hold on. It's a very weird, oh, oh, I lost it. What? Hold on. Oh yeah. I made a little under attack. I dropped my sensor underneath. Do you need a flashlight? No, but it's like, it's stuck in the worst place. No. Well, how about I get it in? Why don't you? Okay. Got it. It not only did it fall underneath, it fell underneath like that. Stay tuned for Under the Desk of Lady Rita, a new series that will be started. Under the Desk leg and it was like kind of there. We'll start that series then. So this is kind of an interesting sensor. This is called the AGS02MA. And it's by the same company that makes the DHT22, which is why it looks like a DHT22, but it's actually a gas, volatile organic compound sensor. Which is interesting, like look, it's cheap, right? It's a cheap gas sensor. It definitely like works, but it's not what I would call like a high precision sensor. So I've got it hooked up here. And then it does have, it does require external pull-ups. So let me wire this up like so. And then I had this hooked up to, hold on, man, there's a lot of, there's a disaster everywhere. Okay. Got my sensor. I was hooking it up to my Arduino, my Metro mini. And the thing that's interesting about this is that, you know, it does work. You can read the gas resistance. Inside is actually a little microcontroller. It's like a little, like eight bit micro. And it reads from an analog gas sensor and converts it to I squared C. The thing that's really annoying about the sensors requires a 20 kilohertz I squared C clock, which is really low. Most things are a hundred kilohertz. And when you set the clock for most chips, they expect you to go only higher than a hundred. Like you go up to like 200 kilohertz, 400 kilohertz or even one megahertz for I squared C clock. It's not very common for microcontrollers to set their clock rate to below a hundred. And so, for example, as I was doing this, it's like, oh, I just wanna like read the sensor. Before you know it, it's like, oh, it turns out the Arduino core doesn't, you know, it doesn't do the pre-scaler right. So you can't use the low clock rate. And then I was like, okay, I'll like do the PR for that. And then, you know, like two hours past. But I did get this sensor going. So let me hold on. I have to get the right port. Maybe I'm gonna have to re-upload the code. Okay. So, oh, can you get it to the computer? So this is the, there's a little bit of I squared C debugging, but you can see the gas resistance and the total of all volatile organic compounds. It's about 400 parts per billion. And then, you know, if I take my handy dandy rubbing alcohol, I support alcohol used for cleaning off floppy drives. And I just kind of waft the cap over it. You'll see in a few seconds, the total volatile organic compounds spike up to, you know, 12,000 or 50,000 parts per billion. So it is reactive. I wouldn't like, I would definitely not use this for anything more than just overall trends rather than trying to actually, you know, use this as a calibrated source. It's definitely a scientific source for organic compounds, but it gives you a rough idea. Like if there is alcohol, gases in the area, it will, you know, methane or ethylene or whatever, it'll probably detect them and give you like a sense that it's gone up or down. But I did have to do a bit of work to get the set clock function working. We also have a circuit python library. And then it turns out that some chips actually, it's very challenging to get them to clock at lower than 30 kilohertz. But luckily, ESP32 and AVR8 bit did work out after a little bit of tweaking. So that's good. And so I'm gonna shut that library tonight and then we'll have these sensors in the shop so that people can use them. And I think it's, you know, I can't help it. I love little ice cream sensors that even if they're cheap, they're great for students. You know, I can definitely see a lot of kids in school that are like, I want to make a basic, you know, how does the breathalyzer work or whatever? Or how does, you know, a gas alert sensor work, you could protect it for a couple of bucks because gas sensors can be kind of pricey. All right, you want to do the great search? Okay, just said, yeah, if there's any other questions. Otherwise, let's go to the great search. The great search brought to you by Edford and Digikey. Thank you, Digikey. This is the weekly segment where a lady to use their power of engineering to help you. Yes, you find the things you're looking at and for on digikey.com. Lady Aida, what are you looking for this week in the great search? You would never guess it, but this one has to do with a part that I can't get anymore. I bet it has something to do with parts. Oh, good guess. It does. So this week, we are, you know, what's interesting is half the time you can tell I do a part shortage because I'm like, hey, I'm designing anything and I got to spec a part. And the other half is I'm told by the fabrication team that Edford, they're like, hey, like we can't get this. And the production team says, this part went end of line, we can't get anymore. We need your help to find an alternative so we can keep production going. So this week, the part that I was told is no longer available. Because again, not only is it hard to get some parts, but parts that are available are going end of line much faster, end of life and are, you know, no non-cancellable, non-returnable, which means they're kind of nearing the end of their functionality life. And so, you know, finding a good alternative for this part, the fan, five, three, three, three, even though there's a last time buy, I even learned my lesson. It used to be last time buy, meant you could actually last time buy does not mean that anymore. It means like, it's over, good luck. Maybe we'll send you to some in two years. So this week we're going to, let's go to the computer and I'll show the part that I am getting. So the part that we're going to get is the fan five, three, three, three, B. And I love this part, to be honest. It was a high current, 1.5 amp internal switch fast, 1.5 megahertz switching frequency, super small and expensive, SOP 23.5 boost converter for LEDs. And what's cool about this is that it was a constant current LED driver, which means that, you know, if you're dealing with back lights, so oftentimes you get a TFT, anything that's kind of big like this, like anything that's over like three inch TFTs, the back lights are often in parallel. So let's look at the backlight diagram. Okay, so this is the display and there's the pinout. And then when you look at the backlight, it's like, bam, you have six or seven LEDs in a row. You want to drive the 20 milliamps, but you have to, the V forward for the LEDs is 22 volts. And this is not uncommon. Most largest displays require a boost converter to drive the LED backlight. And the V forward of course is dependent on, you know, if you have like one LED, you know, you can use a resistor. You don't have to do constant current because it's like, ah, it's three, it's 3.4. It's, you know, somewhere around three-ish volts. But when you have a bunch in a row and there's variations in the backlight design and variations in temperature and, you know, whatever, how bright you want to run it, that VF is, it says 21.7, but that's not guaranteed. It can really vary from 20 to 24. So having something that's constant current, you said it, look, I just want 20 milliamps and you boost it as high as possible to get to that voltage. That's what you want a constant current driver for. And that's what the FAN 5333B did wonderfully. I loved it. So up to 30 volts, again, did, you know, 1.5 amps because let's say you had, you know, 24 volts output divided by 3.3 volts input. So it's a seven, seven and a half times multiply. And then let's say you had a 0.5, sorry, 0.05 amp output so you need at least, you know, 400 milliamps, 0.4 amp current switch. But honestly, I would really double it. You really want, you know, at least 750 milliamp internal switch current so you don't overload it and also, you know, if you need a little bit more like 75 milliamps, you can do it. So this was a really great driver, which is why it's so tragic that it's not available. So let's look at what it used to be. Here we go, last time by, this is it, end of line. So let's find an alternative. And I will say it's a little challenging to find a perfect alternative, but I'll do the best I can. And one thing, another thing is the price was really nice. These are about 60 cents a piece, which is like really sweet. So you do need an inductor, you need a diode and these also needed a protection diode. They would actually, they needed a diode to avoid going over voltage, but, you know, those were cheap, those were 10 cents. So not bad. So let's find something similar again from three to five volt input, 20, 24 volts output, switch current of at least a half an amp, but, you know, as much as possible, high speed, PWM volt and ideally the same size and pinout, wouldn't that be nice? So let's find something. It's a DC-DC regulator. It's a step up with internal switch and one output. I'm not gonna set the voltage input min max because of course it can always be a wider range, but also I'm a little flexible on it. Voltage output again, I don't need up to 30. I just need around like 20. Current output, I'll just see what's available. I do want surface mount and I don't pick the package case because remember there's Saat 23.5 and there's T-Saat 23.5 and both will work. So I don't set this and I set this on the next page. So, all right, here we are. So let's look for only active items because again, we don't wanna find things we've already found. Next up, we do want to set the package. So I'm gonna go down here and I'm going to select Saat 23, thin or T-Saat. Which is also the same as SC74A. I'm like pretty sure that was the one. It's not the same as 70. Yeah, 70-5 is the smaller version. 74A is the same as T-Saat 23.5. I will say by the way, because obviously I do these earlier because I get it all ready to make sure I can actually find something. There is a lot more options if I'm willing to go to the T-Saat 6. So I will say, if there might be some situation where I'm like, oh, if I have to update the design, there might be better, there'll be more and better options if I'm willing to go to a six pin Saat 23.6. But again, I'm looking for something that could swap into my current designs to just let me stretch out the PCBs I have now. So let's look here and this is already only 35 options. So I'm also gonna look for stuff that's in stock right now. I will say that there's a couple options that are not in stock but if it's not in stock, a lot of them aren't coming into stock until 2023. And then the voltage output, I will say, I didn't wanna limit this because some of them, they were like voltage output that can actually go a little bit higher than 20 or 21 volts. Also the current output, because some of these are switch current and some of these are non-switch, I was like, you know what, let me, I'll just look at the data sheet for each and see what's up. Next step, search by price because I wanna kinda get something close. So the first thing I'm gonna look at is this, like ZXLD with boost converters, you really do have to just look at the design. So the only thing is that this is actually kinda weird. It is a backlight driver, but it's actually like a cell. It's for a photo cell, photovoltaic cell input to an LED. So it's a funky, useful thing, but it's not what I want. It's not the kind of boost converter I'm looking for. Next step is the NCP 507, also a pretty good price, but the same. Looking at this, okay, so this looks promising because you can tell it's actually a boost converter and it's meant for a string of LEDs. It can do up to 22 volt output, which is a little bit low, but I think it might work fine for most of my designs because it said about 20, 22 volt output. Let's look at the current. It can do 1.0 watts, which is, if you divide by 22 volts, about 45 milliamps. So yeah, not too bad. The only thing is I looked at this one and I looked at this and you see it's a switch ground feedback and this one is feedback ground. And so it's not the same package, but it's not the same pinout. So that doesn't mean I'm gonna say no to it because I could reroute some traces. I could still use the same pick and place program, the same stencil, but I'm not loving this one so far. All right, next up is the CAT 4139. This one, looking at, so switch ground feedback and this one does switch ground feedback, shut down VA. And so this has the right pinout, which is good. It has the right package, which is good. It also says can drive lines up to 22 volts. But when I looked, yeah, I'd like to have 22 volts, but it was actually willing to do a little bit above, I think I remember I saw it was like, oh, you know, you could go to, there's an old overvoltage detection at 23 or 24. So depending on the displays, it might actually be okay. And then the switch current is 750 milliamps. Remember, you've got like, that's the multiplied current from the input. So that would mean, let's see, 22 volts divided by 3.3, which is like seven times. So 750 divided by seven. So max 100 milliamp output, but really I'd say 50 milliamps is probably good. That means two parallel strands, which for that 4.3 inch display, it only had one strand, but the seven inch displays we have, have two strands in a row. So that's good to know. And it has some open LED detection and it has PWM control. So, the only thing that was a little odd is it wanted a little bit of like, it had a resistor here to protect the feedback pin, but it wasn't clear if you actually needed it. The feedback resistance is a little different. So this uses a 0.3 volts feedback and I believe this one uses, oh no, it also has about 0.3 volts. So that's good. The feedback resistor is the same. And you can, PWM, the input, no more than two kilohertz, but it is PWM mode, which is what I would do for our design. So I would use that for the, that's how you PWM the LEDs. You actually just like turn on and off the boost converter really, really fast. So will this work? I mean, it doesn't go as high. It's not 30 volts, it's 22 volts. That said, I think given the small number of items in stock, like after this, the price gets really high and like this boost converter is only 350 milliamp switch. And then it's like, okay, now the pricing gets quite high. One chip that did look like it was a very good option if the cat4139 doesn't work is the MCP1664. This goes up to 36 volts and a 1.8 amp switch. So it's a really good output. And I think, I think the, yeah, switch ground feedback, switch ground feedback. So this is also pin compatible. The only thing is it's twice the price, but it will definitely do the job. It does that voltage or higher. It does that much current or higher. So it's kind of an upgrade. So we've got two options. I'm probably going to try this one for some of the smaller displays, like again, the ones that only have one strand. But if I need two strand or three strand, something that really wants to push a lot of current for high voltage across the display, I can always go to the MCP1664. So two options, but I'm going to probably start with this one, the cat. We'll go back here, the cat4139. And there's a couple of thousand stocks that can pick these up and then, you know, see how they do in the design. And of course, you know, I'll know immediately if it's not lighting up the backlight or if there's any issues. So I'll probably pick some up, hot air them onto the backlight controller for some of my displays and just like, do they light up bright enough? If so, we'll be able to use that. I'll just check each display one after the other. If it doesn't work with this one, I'll try the MCP as well. All right, that's a great search. Okay, it's a desk of Lady Aida tonight. That's what I got. And we'll see everybody throughout the week. Thanks so much for joining us on this Sunday Eve. We shall see you next week. Bye everybody.