 and welcome to the show it's me JP and it's time for another episode of JP's product pick of the week here we are and it is Tuesday when we traditionally do this show thanks everyone for stopping by we've got some people over in the YouTube chat a lot of people over in the YouTube chat today hello John and Anthony Chad Chase Anthony Bill complex split John O. Gary T. Anthony banter tackle the world Dave Odessa Johnny Bergdahl Connor welcome everyone and I don't have to say these people's names because you can see them right here this is our discord chat so if you're over on Twitch or Periscope if that still exists or LinkedIn learning if it's still called that or any other places where we are broadcasting you're wondering where's all the chat going on it's right here right there that's at our discord and that's a to fruit dot i t slash discord go to the live broadcast chat channel and you can jump into the chat there so cool product here today let's let's dive in so before I say anything about this I'm gonna send you to the product page which is that URL right there and that QR code if you use that sort of thing hello Liz Liz just joined over in the chat and if you head to this page you will see the product pick of the week so that's gonna be early spoiler there spoiler alert but you'll also see that it is half off today so you can put this in your cart no coupon code needed when you buy it you get it for half price up to 10 maximum of 10 per person probably per address I don't know and do it during the show because pretty soon after the show it goes back to its full price so before I say any more however I will have lady Ada tell us about it from her new new new product video take it away lady Ada we've got the finally after many years the NA you 7802 strain gauge ADC it's a wheat break wheat stone bridge ADC very precise differential input that's designed for strain gauges but you could probably use it for other sensors as well this was a product that we actually started designing right before COVID and then COVID hit we kind of got busy designing ventilators and face shields and we went back to the design the chip wasn't available but we did get a shipment finally of these ships and so I wanted to get this STEM aqt board out because we sell strain gauges you'll want to read them and this is a great I squared C strain gauge reader it comes with the new Votan NA you 7802 this is a 24-bit ADC we only expose one of the ADC lines because most people using this with a strain gauge that you know you only need one ADC E minus and E plus are the two exciter sides of the wheat stone bridge so left you know E minus is ground E plus connects to the voltage output from the NA you it can generate a voltage between like 2.0 and 4.3 volts reason for that is I think it you know you can get a nice clean voltage reference there's seven qt port so you can just plug it into your micro controller or board or micro computer we've got Arduino code which I've got on the demo that I'll show the jelly also showed very kindly and there's also from Cedar Grove a great circuit Python slash Python library that you could use with a circuit Python board or like a Raspberry Pi or something so let me show you how it works so you connect the four points of the wheat stone bridge strain gauge in this case to the sensor I actually have the exciter and ADC pins backwards but it's okay because the wheat stone bridge is actually symmetric so it doesn't matter and then I have some Arduino code working on this feather that I just have plugged in and you'll see I have the gain up really high so you'll see like even even me touching this makes the number kind of grow up and down because I'm applying a little bit of strain just picking it up if I if I set it down it'll kind of stabilize a lot more and then of course you can add more filtering on top but then if I apply strain you can see I'm so strong and then the other way it makes a negative number because it's a differential reader so you know of course you can measure if you know positive or negative change in current through the resistive bridge that is attached to this chunk of metal this is a one kilogram strain gauge I haven't actually tried it with other wheat stone bridges but there's absolutely no reason it wouldn't work with others so if you have other projects that need a 24 bit ADC and you're okay with you know it's not gonna go that fast I'm running this at about 10 Hertz to get good precision out of it but I think it goes up to about 300 I think you probably use a couple bits lose a few bits of resolution at 300 that's the trade-off it's an inexpensive board that's designed for slow measurements of weight and I go yes that's right that is it let me show you it in my down shooter here this is my very own one actually have a couple of these and these are the little screw terminal blocks that come with it this is my product pick of the week it is the NAU 7802 24 bit ADC it's STEM a QT and it's used for strain gauges and load cells with the Wheatstone bridge arrangement in other words it's perfect for making scales so let me show you first a real simple demo and then a really cool more advanced one so I will jump into how about this view here and I'm gonna rearrange my camera a little bit so that you can see a couple things going on I'm gonna pull the terminal blocks out of there so here you can see I've got I've got the NAU 7802 plugged in over I squared C to a little feather an RF 52 840 no a little feather RP 2040 there and then you can see I'm using some crimp connectors connected up to a load cell looks a lot like this one except this one I have mounted to a little metal plate and I've added a little sort of place to set something that you're weighing so if you take a look at my there we go if you take a look at my little serial output there as I press on this little plate you'll see that the raw channel value is going up and up and up as I'm putting more and more pressure on it and then when I reduce it goes back to it's basically it's zero state this is a little higher than zero but I didn't didn't recalibrate this one so the way this is being read right now if you take a look at my code is simply with this read raw value command so NAU 7802 channel one there read raw value and that is giving us this raw 24 bit value here now the cool thing about this it has like I said a high resolution it's 24 bit there's a gain circuit on board which allows you to make really precise measurements of tiny little changes in the current of this this wheatstone bridge resistor arrangement that's built into the load cell there it runs over stem QT which makes it easy I squared C so you can plug it into a quick or stomach QT slot or any other I squared C pins that you have those pins are broken out by the way so we have not only the I squared C ports but also a little set of pins broken out at the bottom and there are Arduino and circuit Python libraries for it so this example I'm using here is using the circuit Python library right there that Cedar Grove made our very own Cedar Grove so thank him over in the chat thank you Cedar Grove Cedar Grove NAU 7802 import that and then we're able to address actually there are two channels on this chip we only have one broken out on here so in this case I'm just going to use a single channel to look at that now one of the things I'm really excited about is a much more elaborate example here so let me let me rearrange some things here I'm sorry that was a bit out of out of focus there wasn't it I moved the camera and forgot to focus all right so this this will take some setting up so I'm going to unplug power and I'm going to unplug my little stem a QT cable remember don't don't go unplugging I squared C stuff while there's power on and now I'm going to take a clue and plug that in again over the little stem a QT port there and I built this little scale arrangement for weighing coffee things so if you're if you're making coffee at a somewhat obsessive level then you probably want to be weighing your grounds before you make in my case espresso and you also want to weigh the shot rather than time it you can you can weigh how much is going into your cup which means you can use different size cups and you don't have to have graduated markings on them so this is going to actually become a based on code that that Jan mr. Cedar Grove made for us a more complete solution where I can weigh the grounds put them into the port a filter and then pour the shot and stop it when I get to the the volume I want based on this weight so let me plug this in and show you how this is working I'm gonna give this clue here some power and this can also run off of battery in the future so when this boots up it's going to do a bit of setup make it so you can see it pretty well that should work and then we get this really nice graphic that Cedar Grove made a little BMP with some text on there and some settings values you know futs with this until it's clear almost come on oh very nearly clear okay we'll go with that so now what I'll do is I will take a container that I want to pour my coffee beans into in this case and set that on the little tray that I bolted to the load cell and now I'm going to tear this scale I'm gonna hold the button there it's gonna remove the weight that it sees on there from the starting point so now we're at zero basically and now I can take some coffee beans I tend to grind one shot at a time so I weigh the beans rather than the grounds coming out of my grinder and so what I'm gonna go for for the double shot basket that I have on my port a filter they're gonna go for 18 grams of beans so I'll start pouring these in and you'll see that the weight is going up and up 18 I went a little over I'll pull some out of there you'll actually see let me put some in hand one at a time each bean weighs about point two grams so you can you can get close oh I nailed it okay watch this I'm gonna put one one bean in and you can see it's really precise measurement that went up to 18.1 from 18 the more complete version of the project also will beep when you reach certain weight levels so you can grind into it and just stop when you hear the beep pretty close same with pouring the shot and so the code for this is actually gonna be coming I believe there will be a guide there's also code up on cedar grove makers github which we can probably put over in the chat in fact let me bring up my chat window there so I can see if that's been posted not yet but I bet that's coming so to explain this a little more there's some questions over the YouTube chat this is the load cell and it has four wires coming from it it has two that are power and ground and two that are running through this arrangement that's called a wheat stone bridge and that's actually explained in the learn guide if you take a look here I'll bring that up so in the learn guide here for the new 7802 there's a link here says wheat stone bridge arrangement and then there's a Wikipedia article about how current is measured in these two sort of s-shaped arrangement of four resistors or two resistor pairs and so there's a differential between these as we flex in one direction or another it's changing the resistance in a way that can be measured really really precisely there was also a question about could you measure something more flexible yeah I think you can you can do more traditional flex sensors with this if they are four wire type someone wanted to say could you measure something flexible like a fishing pole and see like how how heavy is this fish or how hard is it pulling before you get it up and out of the water I believe that's possible but these are the the ones that I've seen most frequently there was also a question about getting these these don't come with the the NAU 7802 but we have a few different ones available they're not expensive about four dollars you can get them in different weight ratings so the ones I'm using on the scale are the one kilogram we also have a five and a 10 and a 20 so depending on what you're you're trying to weigh you probably get these in other denominations elsewhere but these are the ones that we have here at Adafruit so not too expensive about four dollars per I think for any of those so let's see yeah Chad Lawson says I want to build a small scale for the dog's water bowl to fill with an ESP based device to send a signal to home assistant when I need to fill it this is perfect for that in fact if we take a look in the learn guide here for NAU 7802 you'll see there's two guides that come up one is the the guide for the product itself the other is a pet food scale that Liz Clark made with City DIY so here's a whole guide on doing something similar to what you've said here so using a in this case ESP32 S2 which gives you Wi-Fi potentially if you if you want to connect this up to Adafruit IO or another thing like home assistant and it uses the NAU 7802 and a strain gauge load cell to measure the weight of the of the pet food on top really great project very complete allows you to do things like calibrating and setting different modes using the buttons on front another thing I'll mention actually that I found interesting with these when I went to build actually let me show you show you the one here that I've built swap cameras again let's go back to here and here and you know what I'm gonna do let me let me unplug this and I'm gonna grab a driver for that I hope it's this one these are interesting because they use actually two different hole sizes that are tapped for essentially the base side and the weight side now this is somewhat arbitrary but if you're manufacturing things this is probably important I think it would work you could you could call one the sort of base of it that's that's non-moving in the other side the moving side but with the wiring coming out of here this is kind of convenient to consider the thing that's tied to your non-moving part your your bench or your plate of metal in this case this one's tapped for M5 these are two M5 screw holes this one is tapped for M4 they could have not done that but it's kind of kind of neat as long as you happen to have M5 in four screws which I did around the workshop and what you want to do is you want to give yourself a little distance from the base there right so it can still flex you'll see I've put it up on a couple of washers there it's not easy to show there you can see see that air you need to make sure you have enough air there for this thing to flex just a little bit doesn't flex much but flex enough without bumping into something so and this just happens to be one of our little helping hands trays that we have all right let's see anything else any other questions in the chat by Connor Connor had to run over over in the YouTube chat and over in our discord let's see oh I think there's some some good explanations come in our way over in the discord thank you yes you grover so this library is in the community bond bundles so you can use circup install see Grove no circuit Python a 7802 I think that'll install it yeah Todd mentioned there circup install cedar Grove underscore and a u7 802 and that'll install it nice and easy let's see Jenny screw asks if you can measure a spring with that I don't know I don't know if you can you would probably you could probably do that this my guess with with the proper arrangement of springs and and a rather with the resistors the pairs of resistors but I don't know that's a good question could be a good science project let's see if that is it then I think we'll wrap it up so let's let's jump back over to the product page there where'd you go there you are so that's product pick this week it is this na u7802 it's 24-bit ADC head to the product page you get it for $2.97 then pick up a load cell and you're good to go if you want to use two of these unfortunately there's only one I squared C address for this chip so you'll need to use an I squared C multiplexer we have one that would allow you to multiplex to I squared C devices that have the same address so you can't just run two of these on a single I squared C port or presumably you could use two I squared C ports if your microcontroller allows for that so that's another option all right well I think then it's time to wrap it up let me grab this one and where did I lose the cable I was going to use to hang it to here somewhere we'll grab this longer one all right bear with me plug it into itself okay that's my product pick of the week this week it is the na u7802 24-bit ADC for measuring strain gauges and load cells afraid of your industries I'm John Park this has been JP's product pick of the week thanks everyone for stopping by I will see you next time bye bye