 The great search brought to you by did you key and a fruit. Thank you. Did you key every single week lady? Do you use a power of engineering help you? Yes, you find the things that you want on did you key calm lady data? What are you looking for this week? Okay, so let's go to the overheads. I'll show what I'm going to chat about so on the desk of lady Ada this week I took apart this adorable chicken McNugget themed Tetris toy Game we kind of looked at what's going on inside The one thing I noticed is that to make its BB blops it uses a piezo disk buzzer element and we've talked about and Search for buzzer elements before on the great search. So let me go to the blog and Great search Yeah, go computer. Sorry Don't forget you can always see all the previous Great searches Look at the blog so Yes, many years ago November 12th 24th 2020. Oh, what a time piezo and magnetic buzzers so for a lot of our Boards like the circuit playground and like the the clue and the mag tag and basically the time or the macro pad Whenever we have something that needs to make a little little tones Not very loud tones like a little quiet, you know, just alerts. I like to use Magnetic buzzers and since it's a magnetic buzzer And they have lots of stock which is great. So this is kind of the magnetic buzzers. I might go to seven millimeters by seven millimeters square and you give it about 3.6 volts Way forms and you know, it can make a slightly better sounding than beeps. I mean that the trade-off is It's not a piezo element a piezo element is like two discs Separated by this piezo crystal and when voltage goes across the AC voltage goes across it vibrates Whereas inside here is actually a floating Magnetic disc Look at like a diaphragm and then there's a coil. It's like a 16 ohm coil or 32 ohm coil and when the coil has AC voltage going through it or current going through it it lifts and raises the magnet just like a normal speaker So it's like a little miniature speaker speaker like with the magnetic. So you need fairly a good amount of current Going through but the trade-off is first off. These are picking placeable. Whereas piezos are not picking placeable You need to have wire solder to them. So you if you saw If you go back to the overhead Real fast. I'll show This you know, sometimes there's a spring, but oftentimes there's wire soldered into One part and the other part of the piezo disc and then in between there is the crystal So this is the flat disc, which is what ends up vibrating And then there's the thin crystal and then a conductive layer put on top Which is what these two wires are soldered to and then again in between is a Dielectric of piezo material. So this is not it is a capacitor whereas The magnetic buzzer is an inductor. So it changes how you drive it with a capacitive drive You're going to want to have you know differential drive that can handle high capacitance with the Magnetic buzzer you're going to want something that's you know I use a very small class D amplifier But you want like a true class a or class AB amplifier that pushes DC current through not AC Okay, so and doesn't and doesn't have a bias across it. Which is this of course, you know, you can have a bias It's fine. All right, just go back to the computer. Okay, so this is a magnetic buzzer again You know, I use them, but the trade-off is they're not particularly loud You know, they do Make a fair bit of noise and you can pick in place some which is what I like but they're also going to be more expensive than a Piezo transducer, so let's look at piezos and it's not surprising that this Toy company that made the Tetris toy They made like a half million of these and every penny counts like you want to be as inexpensive as possible And you don't have to have very good resolution But you do want to have it be kind of loud so you can hear it whereas our little buzzers are not very loud So don't forget that piezos can be used both as Voltage to like AC voltage to sound, but they could also detect vibration In and turn it into a voltage for sensing so vibration sensors are also piezos But you want the kind that are like these large discs, which looks just like the thing that We were just checking out Okay, so it's also looking only look at active ones to start Um, they're sometimes called piezo benders because again, they they bend and flex as the voltage goes across them And yeah, there's these start to look pretty good. So we're not going to look for the exact one What we want is actually just the least expensive One available. So let's let's say we're you know, we're gonna look at at least 5,000 pieces Let's look for ones that are normally stocking and not marketplace Okay, so, you know, as you can see they get pretty expensive 15 cents It's a lot cheaper than the 80 cents for the magnetic buzzer Marana makes a lot of these looks like Ola Wolf is another company This one that's kind of interesting little. Oh, it looks like there's a feedback So you can you can read the feedback which can help you adjust The frequency the resident frequency of your piezo But most of them look just like this, you know, very simple element, you know, you can see they usually don't even have data sheets because They're like, hi, it's just a piezo. There's usually a resident frequency And that's like where they're going to be the loudest and that's based on the size and the thickness of the material And with these, you know, they they have a impedance and the max input voltage But again, we're running it off of a couple of AA batteries. So we don't have to worry about hitting the maximum The frequency the other frequency it's gonna be, you know, it's not like they don't make noise at other frequencies But that you're gonna hear like a louder squeak at You know this eight kilohertz or 3.6 kilohertz You know, again, it's meant for like your multimeter, you know, it beeps when you do conductivity testing or you're some a simple alarm clock Not meant for really making very musical tones for this Tetris toy. It works out. Okay, because you're kind of like deep, deep, deep, deep, deep, deep It's not a very symphonic sound. You're looking for just a very basic beep when it you press the buttons Feedback element So the next thing is is that, you know, we want wire terminals One thing is, you know, springs are kind of interesting Let's just look at the springs There are ones that, you know, it's a disc and on your PCB I've seen this actually on multimeters you take them apart and instead of wires because they want, you know, they have a different Manufacturability they to make it inexpensive sort of soldering wires the piezo they have springs that come out of the PCB And I think the springs are pickin placeable and then the springs touch the piezo and the two contact points and that's how they they make contact I think the so far when I've taken a multimeter apart. That's how that works But we want with wire leads, so let's check it out So wire leads, you know, none of these are going to be and we want the standard style. You don't really care for feedback It's a little less expensive that way. Different diameters are available Looks like a couple ones are available. These marata ones look good PUI audio. I mean, they're going to be very generic and yeah, they're going to be, you know, 40 cents With water leads, that's nice. You get to skip one step. You can just solder these in or use terminal blocks and you're good to go So I think this one's not in stock. So let's go with this one, you know, in quantity 40 cents Got the wire leads. Oh, they're even tinned. So like even one less step you have to do Easy to integrate. You will want to have something holding up the desk. So usually you can't of course glue the whole thing Because you have to let it resonate within the cavity. So if you go to the overhead again The way this tends to be done is if you look here, this is a plastic. It's a soft, you know, ABS plastic enclosure And then these are little heat steaks There's little parts that are molded in and there's a little like a like a hot stamp that comes down You place the piezo in and there were these little fingers and then the three pronged heat presser Majig came down and heated up the plastic and then molded it in place that this this has nothing underneath it But it's held in place by these three fingers. So you'll want to do something like that Or you'll have a, you know, cavity with like a little ridge on it so that this can freely vibrate Within your enclosure. So this is my pick. We can go back to the computer, the Morata ZB7Z Sorry, the Morata 7BB series comes in a bunch of different diameters I picked the larger it is, the louder it's going to be basically This little one is going to make a good amount of sound And then don't forget you'll need something to drive it. You'll need a good AC driver for that impedance 300 ohms is, you know, you'll need something not a microcontroller pin if you want to get the good amount of sound And then differential drive like an H bridge drive will also get you the best audio output So it's like pick if you want to add some beeps and boops Search