 Every single week we do the great search for DigiKey where Aida Fruit shows you, specifically Lady Aida, how to find the things you're looking for on DigiKey. So this week, Lady Aida is 74 Series Logic, which I think should get a little bit more love because 74 Series Logic was invented in the 60s and 70s before many of us were born or doing electronics. But it's still really useful. It's like inexpensive, low power. It just works. You don't have to program it. There's no CPLD debugging or like FPGA hacking. It's just like it's 10 cents. You put it in. It does the job. It does it fast. It does it right. It's reliable. Love it. It comes in like all sorts of flavors, you know, like Bath and Rob. It's 5,000 flavors. So in this case, I'm looking for a three-input NOR gate, which will take these three inputs. And then, you know, when the buttons are held down and the reset signal is low, all three things are low. It'll turn the output to be high. And then that will turn on this transistor, pull down my boot zero pin, and that will put me into bootloader mode when we start up, I think. We'll build a prototype, but I'm pretty sure this will work. So here is, you know, a NOR gate. So, you know, there's a lot of good tutorials online if you don't know your NORs and your NANDs and your XORs, because you can get like every kind of logic you could possibly want, including counters. But once you know what it is, you're probably like, well, you know, what kinds of logic can I get? And like kind of there's dozens. What's interesting is there's actually like a logic to it. The logic is the logic in this Wikipedia article. Because I was wondering, like, is there any logic to the numbering and the naming? Because I kind of never thought there was. It turns out there is. You can use this table to see the different inputs. You can have quad two inputs. So you have like four gates, two inputs each. You can have triple three inputs. So three inputs with three gates. So you can do like more complicated combos with one chip. Schmidt trigger input versions, open collector versions. What's interesting is for the NOR gate. Remember, I said I wanted to have an open collector because I don't want it to. I wanted to be able to pull high and then like mess with the chip. You know, I wanted to be able to pull it down if I needed to while programming it in the factory. So the NOR gate triple input open collector doesn't seem to exist. Sorry. Yeah, the triple three input. Not every combination will exist, but there are all these different versions. Now, when I'm buying 74 logic, though, I will, I will not actually look at this table. I'll just kind of know how many gates I need. I'm like, oh, I need like five inverter gates. I need six buffers or eight, you know, switching bus transceiver, whatever. And then I'll actually just search on Digikey and find the part number just because I will not be able to memorize this table. And also I'm going to be looking at the package, not necessarily how many pins there are. Like there are sometimes when I will use a chip that has more logic gates than I need because the package is in a convenient shape and size that will that will work well. There's also different families. So there's the part number, right? Like how many gates and how many inputs and is it open collector and is it NAND or a nor what combo it is. And there's also the family of chips. So originally, the family of all these chips was bipolar logic, which was easy. It's simple to manufacture in large quantities in 60s and 70s. And they had, you know, I think I see 74 LS sometimes once in a while. But in general, you don't see people using the bipolar logic. It sometimes if you need like really high voltages, maybe you would use it. But I only see this in old equipment. People don't really use bipolar anymore. Why? Because CMOS is much faster and lower power. And with the really good ESD protection we have these days, you don't have to worry about like smashing your logic chips with a little bit of ESD. That's it pretty much doesn't happen anymore. Like we're, unless you're like one of those really staticky people, just take some reasonable care and you're probably good to go. So that said, I have seen like a real wide variety. So there are some cool ones like 74LV series. So these are five volt tolerant inputs. So I really like these as level shifting because you can have three or five volt input, but then the outputs are three volt logic. There's also, you know, low voltage ones. There's ones that go down to 1.6 volts, two volts. There's high speed, you know, different tolerances. There's ones that like are, you know, compatible logic level. I don't know. So I use like 74HC and 74HCT kind of the most. The T is kind of nice. It's transistor level logic, which means you can have very low logic levels and it will trigger. It doesn't trigger at halfway through the VCC point. It triggers like a volt or so, closer to bipolar logic, you know, gate threshold voltages. So which one to use? I mean, sometimes you don't have a choice. Like I'll show you for this particular chip, there was really only one family, but then you might want to look up the family to verify that this is good. You have the logic level you need and the speeds you need. For the most part, you know, you don't, you know, unless you really need something that's a specifically low voltage or specifically, you know, high voltage or specific speed, you can kind of go with almost anything. But when you need something specific, you know, go here and check it out. Also, these are kind of cool. There's the high output current ones. These are kind of cool because you can like drive LEDs directly from them. All right. And there was a whole segment for logic gates. But like I said, when I was looking for this Norgate, I didn't like figure out the part number. Like I didn't look in the panel and say like, oh, it's a 74 blah, blah, blah, 125. I just like typed in what I was looking for. And then I used the search boxes to narrow down what I was looking for. So in this case, I just looked for Norgate, which is super great. And then there's a couple of like kits. And of course, there was, you know, gates and inverters multifunctional configurable. So it's like a CPLD or sometimes there's like little mini logic chips that you can configure. Those are going to be more expensive and complicated. We're going to go with just the plain gates and inverters. Let's go with active ones and normally stocking just so we can look at what's normal. So yeah, you can see there's this like 74 LS, HCT, AUP, AXP, HCU, LCX, VHC, who knows, tons. But let's just go for what I want to do, which is a three input Norgate. So I want one circuit, although I might do two just because like sometimes you can get them in like dual and it's cheaper or easier to get that package. I want three inputs on the Norgate. And you see there's only 13 available. Like when you're looking for a very specific thing like that, there's not going to be hundreds and hundreds of options. So then mostly it's about the package. And what I really like about 74 Logic is they have this. And this is why, by the way, I never type in like 74 HCT 125 or whatever. Even if I kind of know the number, if you want to type in like 74 and then, you know, 127, like you want, like there's no way to put in a star to match any of the families. And there are so many families and that one might be in stock that is close enough to what you need that you can use it because again, some might be a little bit faster, maybe have a wider voltage input. But for your use case, they could be compatible. So when you're searching just like unless you really need just the HCT, then put that in. Otherwise I would go here and then find the one that matches what you need and then look at the family. Like what's your what's your power supply range, for example. So, right. So let's look at package case. So I don't want, I kind of want like a SOP323 or maybe an SC74 or SOP236. I don't want an XDF and these are like really tiny chips. I want something easy to pick in place. All right. So that gets rid of like half of them. And then you can look and you can see that there's actually they're all kind of named the same thing. Like I said, 74LVC, 1G27. The 1G, I think stands for like one gate. It's like you get a chip with one gate in it. And like honestly, oftentimes you just need one gate. Sometimes, you know, I'll have a buffer chip. And just I need one pin to be buffered because it's supposed to be tri-state. It's not, you can make it into a tri-state with like a selectable buffer. So in this case, these are all going to be pretty much the same because they're all the 74 logic. And they've got like 27 is the part number. This is the only one out. This onSemi uses a different, I don't know why they call it something different. But what's nice is that they're all, these are all generic and there's lots of them in stock. So you can kind of pick any of them. I think in the end I went with the next period one. And it's just a TSOP, you know, SOIC, sorry, not SOIC, SOT 236 shaped basically. And they're like 10 cents. And like this could really solve my problem. Very, very simple. And then you can see the series over here. You can see in this case, you can only get LVC for this chip. And LVC, let's go here. LVC is low voltage and 5 volt tolerant inputs. I mean, that's perfectly great. I'm using everything at 3 volt logic. If it's tolerant, good, goodie for you, right? But I don't, I don't really care. And it's plenty fast. And it's small and easy to place in my design. So here is the chip right here. Nice, small. And this is the SOIC 323 package I picked up. And it's very simple. It's got six pins, three inputs, one output, power and ground. And that's the story. Very easy. So we're going to try this out. I'm going to see if this hack works. I hope so because I really want to avoid putting a button onto this PCB design. All right. That's a great search this week.