How low can the power consumption of the Cat Feeder Unreminder go? Parker and Stephen discuss leakage current on this episode of the podcast!
Stephen and Parker continue the discussion of the voltage measurement. Can you come up with a way to measure voltage without precision tools?
Is there a way to macgyver measuring a voltage without a multimeter? Is macgyvering even a word? Parker and Stephen discuss this for well too long.
Parker is an Electrical Engineer with backgrounds in Embedded System Design and Digital Signal Processing. He got his start in 2005 by hacking Nintendo consoles into portable gaming units. The following year he designed and produced an Atari 2600 video mod to allow the Atari to display a crisp, RF fuzz free picture on newer TVs. Over a thousand Atari video mods where produced by Parker from 2006 to 2011 and the mod is still made by other enthusiasts in the Atari community.
In 2006, Parker enrolled at The University of Texas at Austin as a Petroleum Engineer. After realizing electronics was his passion he switched majors in 2007 to Electrical and Computer Engineering. Following his previous background in making the Atari 2600 video mod, Parker decided to take more board layout classes and circuit design classes. Other areas of study include robotics, microcontroller theory and design, FPGA development with VHDL and Verilog, and image and signal processing with DSPs. In 2010, Parker won a Ti sponsored Launchpad programming and design contest that was held by the IEEE CS chapter at the University. Parker graduated with a BS in Electrical and Computer Engineering in the Spring of 2012.
In the Summer of 2012, Parker was hired on as an Electrical Engineer at Dynamic Perception to design and prototype new electronic products. Here, Parker learned about full product development cycles and honed his board layout skills. Seeing the difficulties in managing operations and FCC/CE compliance testing, Parker thought there had to be a better way for small electronic companies to get their product out in customer's hands.
Parker also runs the blog, longhornengineer.com, where he posts his personal projects, technical guides, and appnotes about board layout design and components.
Stephen Kraig began his electronics career by building musical oriented circuits in 2003. Stephen is an avid guitar player and, in his down time, manufactures audio electronics including guitar amplifiers, pedals, and pro audio gear. Stephen graduated with a BS in Electrical Engineering from Texas A&M University.
Special thanks to whixr over at Tymkrs for the intro and outro!
Hello, and welcome to the macro fab engineering podcast. We're your host, Spark abdomen and Steven Craig. This is episode 236. So the first topic I want to talk about today, lead forming, like, bending wires. Yes, on components, which is something that I think engineers don't really think about too often. Now, since most products have gone surface mounts, for more Georgia components, lead forming was really a big thing when you had like, you know, resistors and you had to lead form the leads at a 90 degree, so they fit in the holes correctly, or even more complex things where you had like power resistors, they have to sit a certain height off the board and things like that, or offset legs for like, to 220 packages, stuff like that.
So this is the interesting one is I've ordered, like, lead forming tools online, stuff like that for like, specific, like common offsets, you know, but we had a customer come to us that had a really weird use case for lead forming. And it was on a potentiometer. So like a normal through hole. potentiometer. Like a like a board mount potentiometer. Yeah, board mount potentiometer. That's got you know, solder lugs. Yeah, kind of like a borns series? Yeah, yeah. Yeah. That's got the plastic body. It's not like the the panel mount. Round one. Yeah, yeah.
And, but so they were using the solder lugs. But then the pins that go that's supposed to go into the board, they wanted those bent 90 out, and then put on SMT pads, and hand soldered? Why? I don't know exactly why. I haven't talked to their engineer yet for it for why it's designed that way. I mean, they're already having pins go through holes in a board. Yes, it already has the style potentiometer on it, that goes that have the whole set up that way, only thing I can think of is they have some components on maybe the backside of the board that you can't have through holes, they're sure, or something with the enclosure or like there's a battery there. I had no idea. I want to know more about why it's designed this way. But I was tasked to find or design a LEED forma for this really? Yeah. And and so that was the day actually, this morning, I was told I need to find a LEED forma for this. So I spent, I went to the normal resources to find like haco and what's the other 1x? XL extralight or what? Excellent. I think it's what it is. Yeah. There's a we have a lead former that I purchased it at work. No, it's xl to xl TA. Oh, yeah. eXe Elta Oh, okay.
They make a lot of hand lead forming tools. Yeah. So so the lead former we have at work is a pneumatic one that has little foot pedal, you stick components. And we use it mainly, we have a dye that is a particular thickness. And we use ours mainly for trimming lead for our selective solder machine such that everything is the particular length. But we have looked into getting
lead forming for some other applications. We have a customer that has some certain LEDs that need a particular height off the board. And we do spacers on every single LED. And we were thinking if we could just bend each one, then we could eliminate the spacers. And maybe we could have like a positive retention, like click where the LEDs go in. And kind of like grabbing to the legs are kind of like a snap in. Yeah, something like that. And maybe if we're doing something custom, maybe on the on the anode, we do one type of lead form and on the cathode, we do a different one. So you could tell you know, yeah, but But I I would not even know where to start with bleed forming potentiometer legs and like it for something this. I don't want to be mean to that. Whoever that customer is, but like something that's ridiculous. In a sense. Maybe it's not ridiculous. We don't know all Yeah, I don't know. We don't know maybe maybe there. It's a really brilliant thing. But like the the quantity better suit. You go in and doing all this research. Whether there are production customers? Sure, sure. Sure. So yes, the answer to that question is yes. Yeah, I do want to know why it the designs are because all I've seen is the assembly diagram. And I'm like okay, so I know how far I need to bend the leads that kind of stuff. So, but the normal people who make these kind of tools, they can custom make you a tool, but it takes like, eight weeks, and it's a lot of money to do it. And so I've built and printed lead formers before that do this for like, to 220 packages, stuff like that, that have like weird offsets that we've had customers have or like, they need one that's like, offset the off the board a bit. And it has a custom offset for heatsink. That kinds of so I was thinking about trying to apply that kind of mentality to the potentiometers. But what I want to talk about is the like, what should we look? What should engineer look out for when, like lead forming? Because that does cause I mean, you're bending metal. So it causes stress on the the component lead? And I was thinking mainly because I was looking at how other lead formers do this, it looked like they try to support like, you don't want to bend right at the package. No, no, absolutely not. And so it looks like a lot of them, they, they kind of support the package. And then like a part, I don't know what you would call it, but part of the leg that's near the package, they support that, and then you try to create a break, like a sheetmetal break to bend the leads, right? I guess that's the best way to do it. So are you trying to design like a hand tool? Or are you or is this like a enough quantity that you're going to try to make some kind of automated tool for it. It's gonna be a hand tool. There's, it's, you know, it's a couple of 1000 units. Okay. So yeah, it wouldn't be a automatic machine, but definitely trying to sit there by hand with a pair of needlenose pliers, or tweezers,
or pliers to bend three of these pins on each one accurately. Doesn't sound fun.
No, no. Well, and here's another question. Those particular pots, if I'm if I'm thinking of the right ones, they have three pot pins, and then they have the two mechanical pins on the on the left and right side of the pot. But those pins are not straight. They have they have a crooked angles, too. Yeah, they're snapping to snapping. Yeah. So does the customer want those parts to be flat? Or do they just want the legs to be bent upwards? Just the legs? So the board has the solder lugs there. Okay, so yeah, that's, that's even more confusing. Because like, the solder lugs there, why aren't the Why isn't the the pins? Why are they serve? So there's got to be a reason why. And maybe next week, I'll have that answer. If the customer will tell me, ya know, like, that's the part that's just like racking my brain. Why? Why is it worth going through all of this trouble, as opposed to go into the customer and being like Kenya put holes in the board? Well, it's clear that this, the answer is no. Right. The answer will be no. Yeah. Because they have that on, they have this footprint already designed. That's the through hole vert author hole because they use it everywhere. Right. Right. And this is the only one that's like this. It's very interesting. So wait, do they have multiple pots on the board? Yes. And they were all through hole. Okay, there's so there's one that's unique? Yes, one that's unique. And it's this one. And they it's the same part number two as the other ones, but they need to? They need to have they have surface mount pads there? Do they have like a multi board stack up where maybe the pins interfere with something that's underneath?
See? That's what I'm thinking? Because it is a multi board. stackup? Yeah, I haven't looked at the other diagrams yet. And but it clearly it doesn't interfere with the solder log portion of the pot, but we're just waiting legs, the mounting? Not the mounting the signal lines.
Right for the pot? Well, yeah, the Yeah. Okay. So the one of the things that I can think of that you're in luck with is the fact that the body of that potentiometer is square. So you can make like an anvil that, that you can support the pot on both sides. So even if it is like a mechanical thing. Yeah, it's at least easy enough to make it such that you can make a square cut out in something that the pot fits into. Yeah, that's
what I was thinking is that you basically have a little fixture that holds the pot correctly. Yeah. And then a apart on the on the fixture that slides and so that has a little thumb on a thumb holder, so you could slide that down and that is the die basically pushing the leads in the right spot. Yeah, but they want a nice clean 90 on those leads. Right? Yes. Yeah. You know, another good thing about that too, the fact that it the pots have the three signal legs hanging off of one side, it If you really can't put it in the jig back backwards, well, if you did screw everything up. Yeah. That's another thing is that the, if you're building a fixture like this, the component has to only fit one way. Right? Because that would be really bad that you send someone off to, you know, bend 1000 of these.
Because then you get the case, you can't bend them back without actually fatiguing that metal then.
Oh, for sure you get you get one shot on this. Yeah. So are they wanting them to be bent 90 degrees outward or inward? outwards? Okay, so they extend outside the body of the pot? Yeah. Outside the body, which also makes it easier? Sure. Sure. Yeah. Because I was thinking you could have, okay, you slide it in this jig? And there's, I don't know, I'm using the word anvil. It's probably wrong, like press plates that are that fit into it. And then those spread outward, like the reverse of a pliers, basically, and just bend it over. You know? I know I'm using the word just a lot there. Yeah.
At least that's what's coming to mind. Because there's, there's sort of not a good solution to it. Yeah, there isn't a, like the handheld for lead formers just don't work because the body of the potentiometer and the knob, like you just can't maneuver a tool in there. So yeah, it's gonna have to be something that this thing goes into and holds it. And then a anvil not able I die moves in. So I want to guess, and I don't know the answer this in lead for or in tooling. I want to guess the anvil is the part that can hold something right. The Anvil is what's pressed against. Right. And then the punch? I don't know I'm, I'm not talking right now. So forget it. But I am, that's I'm thinking through is the anvil is pretty sure that the anvil is what is pressed against. Yeah, so in this case, the anvil would be the thing that holds the potentiometer and the leads from from bending, and then the die. Bending does the bending. Yeah. Against the anvil. And electrical engineers trying to pretend like we're mechanical and yeah, no, actually, you know, it's funny because I recently purchased an anvil and a punch the other day foot just for we're doing some press fit. And three studs, or sorry, threads. We I found some I found some M three threads that just press into aluminum really well. And they just they're captive. And so I ended up buying that and the anvil is the part that is static effectively. And okay, the punch is the part that pushes. Okay. Yeah, so we're probably pretty close, I think. So. That's, that's really interesting. I would love to see it. You know, there is one other option that's coming up that comes to mind. If you look at the bottom of those potentiometers the plate that actually holds the world the plate that actually is the what's it called?
mechanical legs. It's like a plate that's that's pressed in and riveted in or somehow, like connected in, you could potentially just contact the the pot manufacturer and say, Hey, can you make this with straight legs as opposed to bent legs because they actually have to bend those legs down. You don't want them bent?
Well, they have to be bent. In that case, then we hit the bed and twice because they have to be bent down and then back out because they have to go down to the board and then out. Those legs aren't at PCB level. Oh, okay. Okay, so you don't yeah, you okay, I get what you're gonna? Well, that being said, you could contact the manufacturer and just have them do the, the bend for the second algebraically. And then you don't have to do any of this, this jazz. And that's probably much better. And if you're talking about you said a few 1000, you know, even 2000 I guarantee you somebody would do it for that much. I'm going to say the fact that I have samples in my hand from the customer, they probably already bought all of them. But that'd be good. They're consigning the parts. Yes. Okay, well, so I'm gonna guess that in the future, we could look at that. But that's up for this run. No. Well, okay, keep this in mind. And this is for anyone who's interested. There's a there's a company in Taiwan called Top Up industries. And when it comes to Jack's phone connectors, potentiometers slide pots, that kind of stuff. Top Up industries will work with you and get you anything you want. They're awesome. So anything I want anything you want. If you have a wacko thing where you like Hey, I went I went up through whole pot to not be through hold, they'll do it for you. Top up if you want to sponsor that macro engineering podcast, give me a call. We got light pipes made from them. They and they're fantastic. You know. And they're not a light pump company. Let's just put it that way. But they can do it. Interesting. Yeah. So last week you were talking about your seen see upgrades? Oh, yeah. Well, linear rails. Yeah. So, okay, it's kind of funny, because I ordered. I ordered some linear rail last week, or actually the week before, and I ordered a ball screw. And that ball screw was supposed to arrive last week on podcast eight, because I was going to play with it on podcast, it actually still has not arrived. And it's funny because it's shipped from a place in Texas. So it's two states away from me right now. But my linear rail ship from China, and it's here. So it's kind of funny that like, you can get something all the way across the world. And sometimes USPS is has trouble. You don't know. I actually have a story about that. What happened today with me is for my for home brewing, I ordered 50 pounds of lye to clean the curry 5050 pounds. That's a five gallon bucket. Yeah, I mean, that's a lot of lie, dude. And so but for its it lies, so sodium hydroxide. And that's a it's deemed a hazardous material, because it's very caustic. Because it is and because it's how it is right. So you have to sign for it when it arrives. And I guess that's so that a reasonable adult? Gets it and doesn't get stuck on your porch where someone else can get it? I
don't know. Anyways, I haven't signed for it. But it was supposed to arrive at my house last Thursday. It didn't show up and I got a notification saying, Hey, we missed you. No one was there to answer whatever. That happened four times.
And then I finally called them up and like you didn't like what did the door tag say? I'm like, Y'all were given me door tags. They didn't give me they, they delivery driver was trying to deliver this somewhere else and get someone else to sign for it for four days. And I actually had to go to because they couldn't drop it off at my local FedEx store. Yeah. Or if people remember, there used to be Kinkos. FedEx bought Kinkos. And they turn them all to FedEx stores anyways, couldn't be there because it was hazardous material. So I had to go to the actual like, FedEx depot, ground depot. Oh, wow. And like, go through security checkpoint, and get like my temperature read and like, answer all the questions that you don't have COVID all this stuff. And then finally, get my 50 gallon buck. 50 pound, five gallon bucket of lie. Truck. Like, that doesn't make you look suspicious at all. No. Especially when you walk in wearing a hat, sunglasses and a mask. And you're like, how do you buy sodium hydroxide? I need my hazardous chemicals. Yeah. But yeah, it's like, they tried delivering this to someone who probably had no idea what sodium hydroxide let alone 50 pounds of it was four. Yeah, these are these are weird times people are ordering all kinds of stuff.
Yeah. But yeah, back to your your. Well, you know, and we've talked about this before, but it's always
like it brings. I'm always so happy when I see this. Where, where you get that? That lovely Shenzen stinky box, where it is made primarily of yellow tape. And like, it's the worst cardboard in the world. Oh, it's not, but it's like 20% cardboard and 80% tape. Yeah, it's it is totally one of those and it's always interesting is in for them. That has to be the most economical way to ship something. Because everything you get from that area is like that. It's the crappiest cardboard. Oh, yeah. Covered in tons of tape. And the tape is there to make sure it actually lives. Yeah, it makes it No, this isn't even a box. These are like random scraps of cardboard that they made into a box. Oh, no. Yeah. In fact, like the hardest part was I got the box and I was like, How do I open this? I mean, of course I can cut it but like Where's the place to cut and then I realized I just had to like hack it apart. And there is no seam because it's just so much change. But on the other spectrum you have Amazon. Oh, like barely puts enough tape What was the damn box? Right? And the cardboard is actually really nice cardboard for their boxes. So like, that's Amazon's most cost effective way. Yeah. But you get like, you get a thing that's the size of your thumb and they send you a box. That's, that's the size of your torso. And it's good. Those big old puffy packers in there. But it's like one of those big puffy air packs just like rattling around. But no, but it just amazes me that it's two completely different thoughts of like, what is economical? Yeah, for sure. Yeah. Because the Amazon boxes, everyone's got Amazon boxes just kicking around that you reuse for everything. No one reuses those tape boxes? Because you can't. Yeah, this is one time box. It's barely a one time use. Well, okay, so I ordered linear rail. And it shows up in this magical wonderful box that smells awesome. And it's like a tire factory. So linear rail is is intended to be like, a precision thing, right? It's meant to be to hold tight tolerances and, and scoot along smoothly, right? Well, first of all, the box shows up, I'm holding enough for Parker to see but there is no anything inside this box other than the linear rails and the trucks that go on it. Like there's no like packing foam or anything like that. They just threw linear rails in a box and put it put the trucks in there. So this was beaten to hell, as it came from China. And the whole purpose of this was less about like me actually wanting to use this. It's more about I wanted to see what is like bottom of the barrel linear rail, like what do you get when you when you search for something that says linear rail, and the only specification you get is like the width of the rail and the length of the rail. Like you don't get anything more than that it doesn't tell you the accuracy of the rail or anything like that. And it doesn't have a brand name. Like if you search enough, you you'll find I don't even know how to pronounce it, I think it's high win or hai wi N hit win or I don't know, whatever. That seems to be like the lower grade brand name where like you actually have a name to behind it. And this one the boxes for all the little blocks. They just say linear guideway, they have the same port number is as high when but I and all the same dimensions. But that's about all you get. So first of all these these linear rails are not polished, you can see the mill finish on them. So clearly, they just took you know they they just took a bit across this and just flattened it, but then didn't do any polishing whatsoever. And there's some what almost looks like corrosion maybe rust on it. So there it's not a cause of Milan Kyiv right they could it would stink a whole hell of a lot worse if it if it was because I've seen surfaces that it will look like Ross and it comes off with some brake clean. This I don't know this doesn't look like rust, but they're greasy. So they have they have machine oil on them. And the edges are
only in China. What machine oil caused something to rust. Yeah, for sure. So the edges are discolored and very uneven. It's clear that somebody took them to town with a with a bench grinder or like a like a sanding wheel. And just by hand just by hand. Oh yeah. Because like, I don't know, maybe Parker can see this. But the but the edge is is like heavily Oh yeah. Heavily poking over. It's
like, it's like they didn't cut through it all the way when they chopped it off. Right and then tried to fix it with a sander. So the biggest thing was I took one of these little linear trucks that goes on it, and I put that on one of these rails. And it sounds like there's sand in the bearings like, it sounds awful. In fact, I've got it on a rail right here. Let's see if I can make enough noise so people can hear this lovely linear rail
I can hear it. So it sounds a little bit like metal on metal. But, but in reality, like if you're standing right here, it sounds like sand in the bearings. And like as I move it across, like I could feel the truck jiggle across the rails like it it flows and everything. But I mean a linear truck should not stick if I hold the rail vertically and it totally does like I could get the truck to stand on a linear rail, and I think I'm holding the rail vertical right now and the truck is just stuck in place, I would think that a good linear rail would slide if it's held vertically. So all of this to be said, like this was kind of an experiment in having fun with it. And it's like, these are kind of garbage. And it's pretty obvious that these are kind of garbage.
So people build 3d printers with that kind of stuff. Well, and okay, so that's, that's the part that I want to I wanted to actually test with all of this was the concept of, or the idea that you can go to Amazon typing the word linear rail and get something good. You can, but keep an eye out, the guys who are good and actually selling good stuff will show the specifications on their page, and they will have a name tied to it, and you will get what you expect from it. But if it just says, like, linear guide rail, that is, you know, you get to choose the size and think this is a 15 millimeter, and, and the length is 300 millimeter, yeah, sure, you're gonna get something like that, but you're also gonna get sand in your bearings. So be really careful if you are watching a getting this up. Now, here's the thing, like, if I was building a 3d printer, and I wasn't super, like anal about accuracy, I would think he could use these for a home gamer thing. But like, if I want to have a CNC that has any kind of accuracy, I wouldn't use these at all. I'm wondering if you could clean that, that bury notes. Maybe, I mean, I haven't really played too much with these, I just got them out of the box, put it on the rail, I was like, Ooh, I need to talk about this on the podcast. So and the thing is, like, this particular 300 millimeters would be the z axis and on a CNC. And, you know, the Z axis is more about just like holding against gravity. Rather than like, you know, the X and Y, your verses are a whole hell of a lot more. So maybe I could use these on my Z. But I don't know, I might also just buy better ones. And buy name brand. And the funny thing was, like name brand that has, like its accuracy specs actually written out. And I'm not even talking about from Amazon I'm talking about from any buyer. They're not that much more than what I spent on these. So I was kind of thinking like, I want to do something with these rails, something fun, I want to do something that like I can actually control something. But it doesn't actually need to be super accurate. Automatic keyboard tray. That slides towards me, you know, actually, I'm realizing something else that is I just put two and two together with this. The holes on a on linear rails that have specifications, they define the edge of the linear rail to the first hole, and then they define the spacing between holes. This one clearly does not because if you hold them up next to each other, like the holes are super, super just drilled wherever, you know someone totally just like drill those with a drill press. Oh, for sure. Yeah, guaranteed, actually, like, I don't know. Yeah, these. So that's the big thing. I want to use my CNC at work to help design my XY carriage that would hold these things. And I would use that to punch holes that are very specific. Well, I wouldn't need these rails to line up with that. So I don't know these are garbage. So maybe I just need to come up with a reason or something cool to use for these rails could be a, like a fancy drawer or something. Yeah, yeah. I like something that an Arduino Oh, you know what the thing is? Eventually hopefully, I will get that ball screw that also is the same length as this. So something that is 300 millimeters worth of travel that doesn't need to be super accurate but is stable because these are you know, these hold some stable. Yeah, I hope
you hope Yeah. Okay, so what's up with the cat feeder on reminder? Okay, so last week, we talked about all the parts, right? I picked so if you go back to last week's episode, you can see all the components I picked.
And so why I spent the weekend doing was researching, choosing solar panels. That's another big key of this project. is, you know, how do you pick a solar panel? Because if you go to Digi key or mouser and type in solar panel, there's like 1000 Plus parks. Right? So how do you pick the right one? And I first started searching, like, how to choose solar panel for energy harvesting, how to choose solar panel for embedded system? There's nothing out there that's like, these are the steps, links, I couldn't find them released within the first like, That's surprising. Yeah, it is.
It's like, what specify is like, goes back to our picker idea, which we haven't done. So. So you want to say you want to solar panels, so you want a solar panel? So Well, I found out these are the specifications that are important, at least for doing a energy harvesting. Project is the first thing you need to know is the max power watt output of your solar panel. Okay? That's gonna be its peak power, it's going to be able to put out if like, if everything is perfect in the world, it's one meter from the sun, it'll be one meter from the sun can't melt. It's super chilled down. So it says best thermal efficiency, all that good stuff. Yeah. Okay, then the next thing we need to know is the current at peak power, because then you'll know how much actual current you'll have. And then you need that next big thing is the voltage at maximum power point, which means this is not the max voltage that it can output but the max at peak power. And that peak power is because how the relationship on a solar panel between its voltage and current and its power, is it's kind of funky. Okay? Because they're because they're diodes and other LEDs, light emitting diodes and reverse, right, so they're a diode effect. And so they act like current sources throughout their usable band of power. And so the trick is to keep the voltage or the power of your solar panel in that peak power area. And you do that by making sure that your load that you're pulling on the panel keeps that power inspect and spec, your transmission has to keep the gearing in the power band. Right. Yeah, that's exactly what it is basically, same thing. And then the also the other thing is, you also need to know what actually is the peak voltage, which you would call that the, it's called open circuit voltage. And so basically, if the solar panel is unconnected, and you have a high impedance load on it, like a multimeter, for example, what is the peak voltage? Do you is that something you get to pick? i It's been a long time since I've looked at,
you get, I mean, you, you pick it by picking the right solar panel?
And like, just in in terms of panels that you're looking at what kind of voltage ranges would you see open circuit? Like 1.8 to 2.2? volts? Okay. So use you'd use to in my application? Yeah. In series. So what does all these? What is all these numbers mean? Right? So in that case, it depends on your solar panel chip, and you really, really need a integrated circuit. That is what's that's able to do what's called V P, V MPP, which is basically keeping the maximum power point in check for your solar panel, is it just like a dynamic load or something like that? Yeah, that's what it is. It's basically doing a dynamic load. And then it's using a dc dc buckle boost converter to regulate the output of it. And so it's basically doing dynamic load on that solar panel to make sure that it's staying at the most efficient way. Efficient. Conversion not conversion is not the right word, but the most efficient power draw off the panel it can it can perform. So I'm using the ATM one Q nine for one solar panel chip. And so the big thing with this is the max voltage that it can accept is five volts. So your open your, your voltage at open circuits for your panel can't exceed five volts. Right. Basically, because at that point is you got to think of the situation where Okay, your your source, as aura is all charged up, right? So you don't have anywhere to put power And so now your buck boosters not doing anything and the voltage will climb through the roof on your your front end. So you want to make sure your, your voltage open circuit doesn't exceed five volts with this chip. Okay, which the solar panels I'm looking at, usually looking at, you know, the top ends, like 2.2 volts per cell, and you put them in series, so you got 4.4, you're good there. Now the next thing is you need to set is your maximum power point ratio. So what that is, is your, you have your voltage at open circuit, and then your voltage at max power is beneath that by a certain percentage. And so you need to look at what solar power you're picking, calculate that percentage ratio. And then you set that with this chip with some resistors. And some pull downs and stuff, and you set that ratio. So now you have that the chip knows, okay. From open circuit, if I, if I tried to maintain the voltage at x value off the cell, I know on that peak power. And so how it figures that out, though, is every this chip that the chips probably do differently. But what this chip does is every five seconds, it actually disconnects everything from the cell and puts a high impedance on it, and basically measures what the open circuit would be, oh, that's cool, I think goes okay, then takes the ratio that and then pulls a load on the cell to drop it to whatever that voltage would be at, for the
maximum power point. There's probably other things with solar panels that I didn't cover that is also super important. But
this is what I could figure out on my own by just reading like the icy data sheet and solar panel data sheets for what I'm using. Because really, there's not a lot of good articles out there about this. This this data sheet for this part is super colorful. Yes, it is. It's like everyone thinks that you need to know is like highlighter color bold colors. Yeah. And it's interesting, because sometimes you get those data sheets that are like, been photocopied at times since like, 1964. And then you have this one? Yeah, this is this is a modern data sheet for sure. Yeah. But it's gonna be interesting. It's a modern data sheet. Because like they're, they have like, a oscilloscope screenshots and stuff that are hand drawn. Yeah. Or like Excel charts or something like that. Yeah. But I think that's everything I need to know to get this rolling. If a solar panel expert is out there, come on the podcast. Yeah. Be a lot of fun. Tell us where we're energy harvesting and stuff like that. What? Where did you end up finding this chip? That chip, I Googled energy harvesting IC, and kept going through the links until I found a chip that looked cool. And I never heard of that company before. It's like, what's the company name? PS? Yeah, EPS or something like that. I'm sure that's probably peace. But um, yeah, I picked it because I'm like, I've never seen this chip before. And it looks interesting. It has, it has built in, you know, maximum power point tracking, it has LTO is built into it. And it handles charging or whatever your storage media is. So you can use supercaps. You can use lithium, you can use pretty much anything on the storage side, you know, a nice thing I'm looking at right now in the datasheet, you can actually use two super capacitors, or multiple super capacitors in series. And it has a balance control. So so it will make sure that they're equally charged, which that's super nice. Because a lot of times you find super capacitors in in the size you want, but they're like, Oh, this is 1.8 volts. And you need a little bit more. You know. That's cool.
That's a really interesting chip. I'm hoping that it works out. It looks very easy use doesn't have a lot of weird external components that you need.
Yeah, yeah. All packaged in one. That's cool. So hopefully next week, I have a board designed up unless I find something seriously flawed with my solar panel thinking which could happen. Well, and you said you've found a bunch of solar panels. Have you picked a particular one? No, I haven't picked one yet. Okay. I was just reading like the family data sheets for like the Panasonic, like BGS series, I think so what was the Battlestar Galactica series? Solar panels from Panasonic, and I was just reading, like, what specs do they provide? And then I was like, Okay, those are what you get from the solar panel. Which ones are important? Or why did they give you the specs? It's how I was looking at it. And then I looked at the IC chip IC and like, Okay, what specs do they care about? And then, yeah, but yeah, the big thing is, like, making sure you get enough power, figuring out how much luminosity your environment has, so that you like, make sure what your solar panel can provide enough wattage that you need. Are you gonna get by a meter and figure all that out?
No, I'm just using like, what is the average indoor luminosity for home? Just use an average and stuff. There's no reason to actually measure that. Oh,
come on, you got to figure out your environment man. design that in.
Got feeders got to work anywhere. Set that night. So the supercaps that's what the super capsulated there for? Yeah. It's gonna be fun. Cool. But yeah, so if you are a,
a solar panel designer, or use solar panels in your designs, you should definitely hit us up and come on the podcasts and, and teach us some more about these? Because it's definitely, it's really weird, because usually, engineers think of power sources as like, you get 3.3 volts at this match current, and you don't really have to worry about it as a net. And it's like, no, solar panels are weird. Hence the whole, you gotta have integrated boost and buck converters, and like big storage media and things like that. Yeah. So cool. So recently, I've been working a bit at work, but also at home on I'm hoping you're working at work. I wouldn't your boss say, hey, hey, he listened to on occasion. Yes, I work a lot. No, and I deserve a raise. Yeah, please. So I've been working on on read designing our voltage references. So we have some stock voltage references that we use in our designs. And I've actually been needing them on some things that I've been doing it at home. In fact, Parker may remember this board, I'm holding it up to the camera right now. Yes, it's called the 16. In 16. Out, it's one of the first boards I made at macro fab. And it was it's basically it's two maximum chips. One is a 16 bit DAC and one is a 16 bit ADC. And surprisingly, so I only have one. But surprisingly, like I have used this thing so many times. It's a really nice little dev board that has headers on it, but I can just plug into my breadboard. And it's basically a 16 bit DAC and a 16 bit ADC. That's it. So it's just really nice to be able to prove ideas that I have, where I don't want to design an entire board for and I can just plug an Arduino into this and control and read voltages with it. But anyone who's even spent a few seconds with ADC or or a DAC, you know, you need to have a voltage reference with it. And a lot of the circuits that we deal with at work rely really heavily on stable voltage references, stable and accurate voltage references.
And you'd be surprised even a lot of the analog stuff that we do, in fact, virtually every analog potentiometer if it's not acting as an attenuator, in some way, we have at reference to either a positive or a negative or both positive and negative voltage references, because we want every unit, you know, unit to unit in a batch to respond the same way across the entire sweep of a potentiometer. And we don't want it such that if you turn the unit maximum on this unit, it it responds in a completely different way to another unit. So having good voltage references is kind of critical. And a lot of the if you look at a lot of hobby projects, you'll see like ADCs and DACs that are referenced to the 3.3 volt rail. And that totally does work. There's nothing necessarily wrong with that. But typically your bulk power supply is not is both not stable and it's not accurate. So if you're if you're really wanting to actually measure specific voltages or you want something to be consistent across two units, you really got to look for a voltage reference. And so I've been designing or redesigning our voltage reference our kind of like stock circuits that we have at work to be a little bit better because we've noticed that over temperature, the ones that we have are not fantastic. And we have some op amps in our circuits that have enough offset to be noticeable. It because It's funny, because in the whole, like legacy of our designs at work, we've had a good chunk of products that work fine in the analog domain, and have worked fine. But we're really starting to push the boundaries on a lot of analog stuff, to the point that the offsets in in op amps are becoming apparent where we're needing to get sub offset voltages and things like that. So we're having to pick a lot better op amps, having to pick a lot better references, and a lot better, you know, pay attention to temperature coefficients and things like that. Which is funny because, you know, it's like musical instruments, who, who cares most of the time, but it's, we're starting to get to that point, let's just put it that way. So, one of the one of the references I wanted to point out, because I did a big study on a bunch of different resit references, and I found one that's, that's for what I can tell from the datasheet. It's fantastic. And it's not terribly priced. In quantity, for sure. It's the MCP 1501. It's a microchip voltage reference that has a 0.1 initial 0.1% initial accuracy. So like, if you pick a three volt reference, you're gonna be between 2.1997 and 3.003. At room temperature, which is, which is pretty damn good. You know, you can't really can't really beat that. It's got low noise, worst case, temperature coefficient is 50 PPM across the entire range of negative 40 to plus 125 C. And typical is 10 PPM on that. Here's the big thing that's really nice for at least my circuits is it's capable of syncing and sourcing 20 milliamps by itself. So it acts as its own op amp effectively. And it only takes one op amp, you know, inversion stage, and you can get a positive negative voltage reference. So just use point 1% resistors on a good op amp, and you can get a plus minus three volt reference out of just this package, or via a really expensive lto. Well, that only sources 20 milli Amps, right? Yeah, does a terrible one. But in terms of actually getting like accurate readings from a ADC or DAC, like, it doesn't matter how many bits you choose, if your reference is garbage, right? Yeah, like you could take a 24 bit ADC and plug it into your power rails, and it's, you've thrown away three quarters of those bits, right? Like it's garbage, who cares. So you got to have a good reference. And for an all around like, good specs, and generally cheap price like this, this MCP 1501 is pretty fantastic. And really the one that the part of it that stands out to me is that temperature coefficient or its temperature, performance is really good. And that's, that's the thing that's kind of been killing our our units as they drift over temperature. And that's not like, that's not necessarily an analog thing. It's just like, everything shifts a little bit.
Electrons just get excited differently. Yeah, they just don't, they either want to flow more, or they don't want to flow, right. That's how it works. So at the same time, we, you know, I like using this guy, but I kind of I wanted to have a voltage reference at home, and I didn't want to buy a or design a board just to have a voltage reference with one of these little chips. So I went to Amazon and I typed in voltage reference, and I found a little board that's available that This cost me 15 bucks shipped. And it has a one of those older, I don't know, maybe this date need here, but one of those older can transistor guys like the big silver can that has a circular pattern to the leads. Yeah, you don't really see these that much anymore. But it's this is one of those types. It's the 8584 which comes in a bunch of different flavors. Like if you look at the data sheet, there's all kinds of stuff but Sherry, strawberry, vanilla. So the version I have has a point 3% initial accuracy, which isn't obviously as good as that other microchip thing. But for for home gamer stuff that I'm just like testing ideas out with or with in conjunction with my 16 and 16 out little board. This is actually really fantastic. It's a point 3% initial accuracy for the J version. There's a K version of this thing that is point one. But if you go to Mauser and look at the K versions, they're like, they're between 20 and $60 for just just the reference, but you get 10 millivolt accuracy on 10 volts. So that's that's pretty good. That's pretty awesome. You know? So yeah, I put up a an Amazon link on that if you You want to check this out? I fired it up.
It's funny because so this thing with a point three initial accuracy, or point 3%, on 10 volts, you would expect 30 millivolts. Right? So I fired this guy up and I put my meter to it. And I've read 30 millivolts off on this. So I don't know if this is binned because it's 30 millivolts off. Or I don't know if it's my meter because it's a Harbor Freight wonder, you know, like, so. It's always like, which one is more accurate? I don't know. Like, I kind of want this ice to be more accurate, but it couldn't be the Harbor Freight meter. wants you to use your oscilloscope. Cuz it wasn't plugged in.
Because I was leaving scopes going to have a party better. Resolution. Yeah, yeah. I just hadn't tried it yet. And then I liked that term, though. Harbor Freight wonder. Oh, yeah. HF W Egypt. Yeah.
I like that a lot. Honestly, I can't remember how much I paid for that. meter. I think it was like 30 bucks. It's great. For
Oh, i i So because we're electrical engineers. And everyone's like, Oh, yeah, electrical engineers had the best tools. Whatever. No electronics. I use the worst three. I use the free harbor freight. HW.
Little red rectangle. Yeah. Because what I have taught I have $15 leads for it.
You put you put some nice leads on a piece of crap. I use my old old leads I had on one of my meters. Yeah. And I'm like, oh, yeah, I'll just buy some new leads. I'll put these old leads on this box. I guess what though, it works great. I can just throw it you can throw it that HF w around. And that's fine. You know, and the thing is, like I have I have NIST calibrated Fluke meters at work, that, you know, if I really needed to, I could go in and test something at work at home. 99% of the time, I'm testing stuff that the accuracy doesn't matter. Like, I'm getting ballpark numbers at home, and I'm happy enough most of the time. And yeah, I can use my scope. My scope has a built in DMM. And it's actually pretty accurate. Well, and now I have a voltage reference that I can actually test if it is accurate or not. I can check it and I suppose calibrated. It will be funny if it's been in, given that. What's the price difference between them? Because one is $20. What's the other one? Like? 10? Okay, I'm gonna bet you at that price point there probably bend. I think so. I think it's been so binned means effectively that if it says it's plus minus 30, it probably is close to plus minus 30. Yeah, yeah. Well, it's somewhere in between plus minus point one. Yeah, it's in between point one and point three is where it's at. It's not going to be better than point one at all, because those would be classified as case. Right. Exactly, exactly. But I'm thinking worst case scenario. It's probably when actually it might not even be binned. They might be they pick the center of the die, as those are the ones that gonna be case, because there's gonna be better than the ones on the outside of the die. Perhaps, I don't know, I might, I'm gonna use wafer, the wafer. Yeah, the die is after it's cut. Yeah. So they're the outside the the peripheral of the wafer is probably going to be the Jays, because you're farther away from the light source. Yep. Sure. So I don't know, check it out. This is a little cool little board to have at home. If you if you have something like, you know, if you breadboarding with ADCs, and DACs. And stuff, I've got a pretty cool little thing I'm working out right now where basically, what I'm doing is I'm doing a mapping of some vacuum tubes, where I'm looking at their output, effectively, basically, what I want to do is, is just inject a voltage and read read a voltage on the output back and then make a map from the input to the output. So instead of trying to calculate like the weird nonlinearities of a vacuum tube, I just want to measure it and create an input to output map of, isn't that what your tube testers for my tube tester doesn't, doesn't take them to distortion levels. So I want to take them to full distortion levels. And say, like, I know that if I put x voltage in I get y voltage out such that I can make an array and I can access that array and study the distortion a little bit more. In other words, I know there are three sections to the vacuum tube, there's the linear portion, and then there is the positive voltage person and the negative voltage portion. The linear portion is like okay, x is equal to some constant times y. It's easy, right? The positive voltage portion is going to be some nonlinear function that maybe I can do a threshold piecewise linear equation and define like what it looks like if it's in the positive, and then the negative is going to be a different one. So if I do a three piece piecewise equation, maybe I can better define the characteristics of a vacuum tube. So my thought was get a voltage reference, plug it into my 16 and 16 out, and then measure that. Because Because what I want to do is I want to actually take a signal, plug it into a tube, and then make a circuit that can emulate that and see if I can make them basically exactly the same on an oscilloscope. Just for fun. Cool, cool. So when are you going to do the testing of those tubes? And actually, so I want to ask you, you're gonna put your ref your, because you're gonna use the reference on the ADC DAC, so that you have a good reference point for your voltage. Yep, I'm gonna guess those, the DAC is gonna go through an amplifier into the tube, right? You know, maybe not, because this reference actually has a hell, okay, so as for reference, voltage out that as to 2.5 volts, five volts, 7.5 and 10. And the tubes that I'm working with their range is usually within five volts on the input. So I think I might just be able to use the five volts on this. And so that's even better know how much voltage you had to pump into a tube to go overdrive? You know, it's funny. Yeah, so tubes start to distort, okay, so tubes are the particular ones that I use are typically from zero to negative four volts, or negative five, something like that, that's their, their effective input range. And it's not actually negative, but like, the way you configure it, you can pretend like it's negative, so
that, you know, they don't. So it's like pretending electrons go from positive negative, because it makes your brain processes easier. Well,
it's more about the fact that the tube is biased at a positive voltage. So you are referencing to a positive voltage, so you get a negative voltage. Okay? It's like, if you look at the tube datasheet, the numbers are in reference to the cathode, and the cathode is typically positive. So okay, so you gotta flip it in your mind. So it's gonna, but but but effectively, you know, if your, if your cathode is say, at three volts, and you put three volts into a tube, you're at zero volts effectively. So, tubes start to draw a lot of input current at when you when the grid the cathode voltage is zero. So that they start to draw a think of like a, think of like a MOSFET, if they respond, similar to a MOSFET. But as soon as you get to a certain threshold, they stopped acting like a MOSFET. And they act like a really power hungry BJT. So okay, so base current starts to flow pretty heavily. At a certain point, well, if you have any impedance in line with the base of a BJT, well, then you'll get a drop in voltage, well, if you get a drop in voltage, you get some kind of distortion, right? So it's really linear up to a point where current begins to flow, and then it starts to flow in an exponential format that isn't really well defined. And I want to start Do you want change that I want, I want to like figure that out. And this is my initial way of looking at it. I'm, I want to know how I do too. So hopefully, I'll have some, I mean, like, the best part about this is like, I was thinking, I could design an entire board to do all of this stuff. Or I could take my two dev boards in an Arduino and just make an Excel chart. And that's why I love having these little dev boards around. And now I've got a little nice voltage reference that has well defined specifications, such that I can do these little tests without having to wait weeks and then have to design a board.
And then you got to take the linear rail, linear rail plugs in the tubes, the same insertion force every single time you're going a little far now 300 millimeter throats for just like controlling something that's like two millimeters long. Yeah. I think it's going to wrap up this episode this week. I think so we are 15 seconds away from one hour. So that was the macro vibe engineering podcast. We were your host Stephen, Greg. And Park, Gerd Dolman. Take it easy. Later, every one there one hour.
Stephen and Parker continue the discussion of the voltage measurement. Can you come up with a way to measure voltage without precision tools?
How low can the power consumption of the Cat Feeder Unreminder go? Parker and Stephen discuss leakage current on this episode of the podcast!
Is there a way to macgyver measuring a voltage without a multimeter? Is macgyvering even a word? Parker and Stephen discuss this for well too long.