 All right, it's time for Digikey plus Adafruit present This week, it's Lufius. Yes, they make little fuses, but they also Recently acquired US sensors. They have a bunch of sensors as well They've a bunch of other electronics as well, but nice cute logo I like the little like wave in the middle to know and it's you know, there's some Signal going through. Yeah, maybe they're saying that they stopped these signals It could be okay. So this week's MPI is the PPG one XXX series of little RTD sensors. These are so small These are small chunks of platinum bonded onto the back of a ceramic Material to give them strength and then there's two little leads that you plug into a circuit You measure the resistance and you know the temperature and last week when I asked Phil What do you what should I do for next week's MPI this week's? You said well, can you do like some sort of turkey theme and so it's like okay like a turkey theme? Well, this is a turkey This is some cool photos. I found on Flickr that were public domain. Thanks for all those cool photos. This is a beautiful beautiful turkey Yeah, how it started how it's going. Okay, so when you're making a turkey You know, it's important to make sure that first of you got to defrost it if you got a frozen turkey And then you have to cook it all the way through like Raw turkey is really gross and overcooked turkeys and so great either so you want to get it to like exactly 165 degrees Fahrenheit and to do that you've got this like thermometer here, right? It's got a little plug-in thermometer But how could we engineer be electrical engineers? How can we make an electrical engineering version of this thermometers? We can monitor our turkey Maybe we would have it even like, you know The temperature sense would be in the oven and it would like SMSS when it's time to get the turkey because it's like in there for four or five Hours, okay, so here's a couple options So the simplest way you can make a temperature sensor and temperature sensors are so common for engineers to add Whether it's making a turkey monitor or you have a thermal system that you want to monitor Like you want to make sure your your processor isn't getting too hot for example Or maybe you want to have a little bit of heating in your circuit, but not too much Or maybe you have to compensate or de-rate something due to temperature, you know Your electronics or your amplifier may not work the same at high versus low temperatures or you know I'm working with the ink displays need to know the temperature because they act differently at different temperatures So the easiest way to measure temperature the cheapest is just use a diode You put a constant current through it you measure the voltage across it and if you remember your Diode equation you might remember this, but you definitely remember that vt equals kt Over q which is like the standard, you know temperature constant voltage equation and you can Basically, you know diodes work differently different temperatures But you can use that to kind of reverse solve for the temperature because everything else here's a constant if you have The temperature is a constant and you know what like the voltage is you can measure it over different Temperatures so you can see that the differential So this is a diode equation. So this works quite well, but it's not very precise There's ways to improve it you can use a silicon band gap temperature sensors There's actually basically two diodes and you're measuring the difference, you know that the the ratio between the two and You can do that and you also basically solve this kt over q you solve for the t you get the temperature and actually this is used In a lot of sensors is the most common sensor you're going to see in an embedded Like a microcontroller or a sensor. Here's the the Analog design for it. It's just basically you basically get rid of this common mode error because you have Two transistors that are fabricated on the same Substrate and then you get the output and this is you know, whenever you buy like a silicon Temperature sensor like not silicon which you're like silicon isn't it's integrated circuitry Like this, you know one wire temperature sensor is very common And these work quite well, but they top out right there. They're pretty precise You can get like easily point one percent precision out of them and accuracy But they top out at like a hundred and twenty five Degrees see which is you know hotter than you want your turkey to be But it's not as hot as your oven can get because your oven now I have to do that conversion between Fahrenheit and Celsius Sure wrote down Right so inside of an oven it could be 450 degrees Fahrenheit, which is 230 C Which is twice as high as what your circuitry might want And so you don't want the risk of your your sensor getting damaged because it's exposed to the high heat in the oven And so you know, okay What do you do when you have to measure something high? Temperature like a high-range low-range those silicon diode style ones are great for high-temperature ranges You'll want to go with something like a thermocouple classic. This is like an ancient technology you take some, you know alimony take some other metals and you bond them together and You know the output of there just a micro voltage difference with temperature and these go up to like massive ranges You do need to have a little amplifier driver So here we see, you know, I have a circuit driver that you plug the thermocouple into and then does the amplification for you converting that micro voltage level into a higher voltage and then does the Analogical conversion and then you can convert that into temperature What's nice about thermocouples as you can see here. They're they're happy to go up to five hundred one thousand degrees See easily right that the common ones are type K But type J are also quite popular and these these go up to You know fifteen hundred well at least a thousand degrees C So these are quite common, you know, actually a lot of times when you get oven thermometers You'll see them have a thermocouple But there's one thing that's not so great about thermocouples is that they have air they have quite a bit of air in them They're not as accurate or precise as we might want if we want to get to you know Point one percent or better or less than one percent You're gonna have about like a couple degree offsets with thermocouples And so when you need to have Higher precision that's when you would go to an RTD So, you know, you need low accuracy low voltage range diodes are great You want high temperature range, but somewhat lower accuracy Thermocouples are great But if you want both you want the best of both worlds because you want the stuffing and the cranberry sauce You want to go with an RTD? And these are little chunks of platinum and they come in different resistance ohms at zero degree C, you know So it's like a freezing so they're easy to calibrate because you can use ice water baths to calibrate, you know to make sure You get hundred five hundred or one thousand ohms And the resistance change for these is like almost totally linear, which is really wonderful And you're just measuring the resistance So you don't need you want to have like a high precision circuit But it's not you're not dealing with microvolts here You're dealing with a couple ohms, which is a lot easier to deal with than these noisy Microvolts that might be affected by you know your your local environment For these you know, you still do want to have some sort of amplification circuit some op amp you need a constant current source But that's a lot not too hard there's built-in all-in-one drivers and we have a driver here that can handle RTDs quite easily and This is great because now you can measure your turkey in your oven at high temperatures high precision and this the sensor I'll show it Let me let's show the demo now, and then we'll go is this a demo. No, that's turkey Okay, so So this is actually the sensor it's so small it's meant to go into like you know pretty much any device You maybe well, I don't want to zoom too much because I need to keep this yeah, this number visible Yeah, okay, so this is just my you know pocket multimeter. It's it's not the you know, it's not the best Way of measuring this resistance, but it does a good enough job. Okay. Sorry. This is getting loose Okay, so, you know the resistance right now is about like 1.1 K This is a 1k RTD and then when I put my finger on it, you can see the temperature is going up And if I'm like really gross and I put it on my tongue Yeah, mm-hmm warm Not quite turkey warm, but warm and when I blow on it You can see the number goes down So it's cooling off so it's nice as you can see that even a couple degree change all you know The the ohms if it's a one kilo and then they take even a couple ohms. It'll start move quick It's very fast very responsive And it's it's quite easy to measure that change so you can get you know, I think There's 0.06 percent Accurate RTDs and these are like a couple dollars So these are kind of starting to replace thermocouples in a lot of places and again, they're much smaller They're these really tiny little things and they're it's going to be a lot smaller and easier to integrate into an existing Circuit than a thermocouple. So You can get these I picked this one. This is the PT 100 0.06 Radial sensor, but they have a couple different in the family. There's the 500 and the 1000 as well There's tons of app notes online on how to convert these into Other assistance is into the exact temperature if you want to you can you can do Algorithmically or you can use a table if you want better accuracy They're not too expensive and they're really small. So if you have a small high accuracy high precision And why temperature range sensing need this will be what I would recommend. All right, and it's available on digikey the Her number is 18 PPT 101ja and d or you can just go to short URL digikey.com forward slash short forward slash z v 7 5 2 3 and that's this week's I on double double