 Hi, I'm MPI. Hi, I'm MPI, brought to you by Digikey and Adafruit. This week it is PIC. PIC. Switching the smart way. What is IMPI this week? OK, this week. This is a new company we're featuring, PIC. It's a German company. And they make read relay switches and sensors and more. And we're going to be talking about their read sensor chains, which I was like, what is that? And when I actually got the board, I ordered one. And it's kind of a cool idea. And it's designed for liquid level sensing, but it could be used for other stuff as well. So the one cool thing I want to show off first is they've got great graphics treatment. I mean, look at this amazing logo that they've got on the front of their catalog. There's a head and a light bulb. And inside is a read switch. So cool. But they also do hall effect sensors and magnets and other magnetic sensors. So their main product is read switches. So this is what a read switch looks like if you've never seen one. It doesn't literally have a read in it, but the metal inside looks like a read, the kind that you'd have in a woodwind instrument. It's a thin, flat sheet of metal. And when you put a magnet nearby, the two reads touch together and close the switch. And it's encased in this glass bubble with the two metal contacts. These are extremely common. They're used in everything for detecting when something is touching something or a float sensor. We have these door switch sensors that detect when a window or a door is opened. Those have a read sensor inside of a plastic casing for protection. So if you watch out for the glass bubble, you don't want it to crack. They have a very long lifetime. They're very inexpensive and they're very reliable. And one of the nice things about them which we'll talk later is they can work at very high voltages and fairly high currents. So fluid level sensing is a common engineering challenge for automation or industrial usage. You have a bucket or a vat of some fluid. And you need to know when you're about to run out of fluid or when the fluid maybe gets too high and you have to vent it out or stop the process, refill it. Very, very common. So there's a couple of different ways to do that. I'll just talk about a couple of ways and why this read chain is different. So one is using one of these e-tapes sensors at WeStock. And for this sensor, it's got a conductive fluid in it. And as the water, you put the sensor inside the fluid and as it rises, it squeezes on the envelope and it changes the resistivity. And you can measure that resistivity and it's continuous, which is quite nice. You can measure how high the fluid is, whereas most fluid sensors just tell you like when it's hit a certain point or not. Like it's a single point sensor. This is a continuous sensor, but it has to be inside the vat. And of course, the e-tapes have to come at a certain length. If they don't come in the length you want, you can't increase the size and you can't cut them down. But most importantly, it has to sit in the fluid. Another option is you can use like sonar sensors at your bouncing sound waves over it, but then this is exposed to whatever the fluid is. It could be hard to sterilize. It could get really dirty because it could possibly come in contact with splashes of fluid. And so sonar is used for a lot of things, but maybe that's also not a perfect usage. Also, there's a cone and you have to make sure that the cone of the sonar doesn't hit the side of the vat. Another one is a time of flight sensor that's also fairly common, a more recent type. Doesn't have as much depth. I think these go up to like maybe four meters. Maybe that's long enough. You have to have the light be visible. They can be a little bit flaky, reflections, and light dispersal on the liquid can affect it. And if the material is caustic, you have to protect this. And you have to get the I-squared C data out and it's a little more complicated. And so having level sensors using read switches, it's like an ancient, it's reliable and it's known and it's well understood. You have, you see in the center there a single read and then the magnet goes around it and everything can be coated in whenever material you want. It can be totally hermetically sealed because as long as it's not metal, the magnetic field can reach through the plastic material. So this is like, from a video that they have of a single read that just, it's a single point. It just tells you is the water above or below and this cup of water as it fills in, the magnet rises or lowers and as it gets close to the center of the read switch, it closes and then you just detect the closure of the read switch. When you have a single read though, you don't know whether the, you don't know what the level is. You just know whether it hit a certain point. So it could be above or below, it's a little bit risky. If you happen to somehow miss the rises or lowers, you won't get another notification. You know, like the switches either closes or opens, it only closes when that magnet is right next to it. So to solve this, and also if you want to have continuous measurement, they're like, well, why have one read when you can have multiple? So this is a read chain and that's the board that we're talking about. And basically it's dozens of these read switches, side by side diagonal, so it's nice and slim and each one connects, you can kind of see it the bottom. I'll show in the overhead in a bit. There is a 1K resistor and as each one closes, it's going to short the chain against that resistor. So if the water's at the very bottom, you're gonna read zero ohms. If it's the next, you know, the first read is open and the second one is closed, you'll get 1K all the way up to n times 1K resistors. You read that resistance and now you know exactly where the float value is and you know the height of the liquid. And here's just a diagram showing there's a, you know, there's a few different variations of this. One, I think it's slightly different spacing. So depending on, you know, you're gonna pay a little bit more for more densely spaced because you need more read relays, read switches. And then another nice thing about these is you can extend them, because that was kind of a cool hack. So if you go to the overhead, I'll show this off because this is I think a good visual demo. Okay, so the way this PCB is made is it's like a thick PCB. It's like a two millimeter thick PCB and you can see here, it's grooved out a little bit. It's machined out so that all of these can, let's see, I don't feel like I said, I'll zoom in. Zoom, zoom, zoom, zoom, zoom. Okay, so you see each read is here and they're all connected to one common, you know, ground or high voltage, whatever. And then they're each individually connected to this chain of resistors. This becomes like an R and R ladder, right? It's like as, you know, as the shorts, you can determine between the two contexts what the resistance is. And then if you want, and then there's like one extra resistance, I guess so it's not, if it's at the very bottom, you'll read one K, not zero because there's one extra resistor. You can, these are symmetric. And so you can, you know, chain them, literally, even more. You can have another one on the other end here and you just solder mechanically and you maybe glue it. And then you can have, you know, as long as you want, this one is like, you know, about a foot. You want 10 feet, you get 10 of these, you sort them together and now it's 10 feet long and you just, now you're measuring between, you know, this is maybe, you know, 50 resistors. This is up to zero to 50 K. And then if you have 10 of them, now it's 500 K, all within reason to be able to measure with an op amp or resistor divider. Okay, so a constant current source. Yeah, so go there. Okay, sorry, that's the mechanical variations. And then this is how you can combine them. We just talked about that, you can extend them. So one of the nice things about, you know, there's a lot of different ways to read, you know, tank, water tank levels. One of the things that's kind of nice about this is, you know, you don't need any software, you don't need any special, you know, firmware configuration of my controller. It's a while resistance in. And because it's not powered externally, it's just a switch and, you know, the magnet is the thing that closes the switch. You can pass fairly high voltages through and you can pass, you know, some reasonable amount of current as well. So you could use this like other than the resistor that's involved, you can use this with higher voltages if you desire. You don't have to use three to five volts. If you want to power this from, you know, 48 volts or 24 volts, you don't have to worry about doing any conversion. And then you can use an op amp to just like, you know, get the voltage out and the resistance out and convert that to any voltage you desire. So depending on your control circuitry, you may not need to have a mic control. You can have a fully solid state feedback loop. So I thought that was kind of neat. And I'm sure there's a lot of situations where this might come in handy. You'll also need, of course, the float. They do sell magnetic floats that are covered in polypropylene and a couple of other materials. You know, one thing that they definitely say is if you have food safe or, you know, caustic materials, this is going to work great. You don't have to worry about caustic gases. You don't have to worry about the difficulty of sterilizing your sensors because it can be sterilized along with the, you know, the stainless steel or plastic vat that you're using. Because again, it's fully mechanically and electrically isolated from everything. They also have a couple other things, you know, while I was looking around, they sell SMT relays, which I thought was reeds. I keep saying relay, I'm used to saying reed relay. They sell SMT reed switches that are stocked at DigiKey and they also have kind of a cool little like interactive reed switch demo where you can like drag it around and you can like try different types and you're like latching type and shielded types and like there's a little magnet you can drag around and you can determine how the reed, you simulate the reed switch and how it'll act. So that is just kind of neat as well. All right, available on DigiKey and, you know, in this post part shortage world when we show things. It's great, so I can't show you. Yeah, they're usually in stock. It says stock. So check it out. There's configurations as well. I thought it was neat. Oh, and I want to mention one more thing. It's designed, you know, it's designed for float leveling, but I thought another thing is I've had situations where I want to measure whether something has moved back and forth on a railing and like you could, there's sensors you could use that are fairly complicated, but you just want to measure like, hey, where is something on an X, Y or like an X position, not just a Z position? The magnet could be the slider and you could detect where it is. Potentiometer would break. You could use like a belt driven system with a wheel ring coder, but then you don't have absolute positioning. This could give you absolute positioning in any orientation. It does not have to be just Z axis. Okay, and that is this week's IonMPI. IonMPI.