Hi Welcome to everyone's favorite segment mailbag. Let's get right into it. Sorry I did promise a couple of weeks back I do one every week. but yeah.

I've been sick and had various other issues. so I think you do it? Um, this one is from the heathen. It is addressed to the Haven Down Under Yes, I'm a haven. Well, no I'm not because I acknowledge the existence of the Flying Spaghetti Monster So that doesn't make me a heathen at all.

just because I don't think there's any validity whatever particular. God You happen to believe in one of the many thousands wide spaghetti monsters, the go, you talk like a pirate and everything. It's great. Anyway, let's see.

we're dumb. sorry Christine true true and sorry I can't pronounce that last night. that's too hot. Um, thank you very much Christine with a why it's not how you usually I like that oh oh yeah okay oh it's funny Author: it's pretty offer.

oh dear um it's it's it's a fairy tale. Excellent Christian Mythology for kids the secular families got. oh I Secular Oh Excellent. A secular families guide to modern Daf.

Thank you for supporting the creation of this book by helping spread the word. Please enjoy a copy of the finished product. Christine There you go, It's Christine Excellent. She's an enthusiastic atheist Ed, mother of two mindful and inquisitive boys.

Fantastic! Um Christian Mythology Book.com I'll link it down below because it's written by an atheist Beauty Aha I Remember this now. as it turns out, Christine is not a viewer, but her husband Dylan is and apparently my voice gives Christine the shivers, so go figure. anyway. I won't go into it, but suffice to say this was a Kickstarter They wanted 13,000 to print the book and it successful and they've sent me a copy.

so I know this is off topic so I'll spare you the details. but I just wanted to show you this. It's creepy. See anyone you know or think you might know that guy there's looking a bit dodgy.

Next up one from straw: Leah You've Ludie Beauty from nobody. It's just mailbag and it's a dollar. It's a dollar to post something now. Unbelievable.

But Australia Post hasn't been making money and all that sort of stuff because well, they don't know how to operate a proper business and they're slashing everything and moving into new. It's killed all our business. All that has I think is probably increase your business. Anyway, let's see what some person unknown has sent on the address flap on the inside.

Okay, we have a schematic. looks like it's done in Eagle and by Dave was always that kind of child and took apart old electronics. weren't we all? Ah, how about something? A stop there. we have a PCB let's check it out and we have a board from Daniel who's doing his master's in computer science.

Excellent army. He wanted to send in something from Alibag. Anyway, it's a new electronic dummy load that he's working on. tomorrow.

here it is. Yeah, we've had many dummy loads I think I really started something with my original dummy load video cuz the number of Eevblog forum threads for example, with people doing their own dummy loads is phenomenal. But anyway, it's something fantastic. And this looks like a decent looking board except for a problem which Daniel is having.

let's take a look. Um, it's to do. He's got two most MOSFETs on here, but one is dissipating more power than the other, so he's having issues balancing the MOSFETs here as he understands the problem. The RDS is different for the same VG due to manufacturing differences Yes, it is, and there's various other parameters involved as well.

and it usually involves a temperature differential. and also I was actually going to suggest the tracing on the board as well. So the first thing to look at with the offset problem and haha I can see it straight away. You gotta have an issue.

you're trying to match most MOSFETs I Believe these two must be the two MOSFET You can see the heatsink outlines here and here they're on separate heat sinks and Bingo! Therein lies your first problem when you try and parallel MOSFETs together. in theory, you know everything works great, uses parallel MOSFETs and they're supposed to be well behaved and all that sort of jazz. but if they're not tied to the same heatsink, you can get thermal definitely at thermal differences between them and you get an issue So that is the number one problem. Second one is, does he have current shearing resistors in the thing? to do that? we'll have to take a look at these schematic.

So the first thing we do is take a look at the schematic here. Sorry. I ripped it. Um, it looks very nice.

I Like how they're all separated into the separate subsections like that and are there actual word design notes on there as well? Anyway, it looks very good and take a look here. Where's my poker? I Don't know. Let's use this. Um, here's our MOSFETs And well, there's your problem.

Yep, there's our current sense resistor down there. there. It is tapping off there. no problems.

but there is no shearing current Sherin resistor in the source here. So that is one problem. and the other problem is that they're on separate heat sinks so they're not thermally matched. So therefore, yep, you're going to get an imbalance between.

Well, you can get an imbalance of those two. MOSFETs If you get two from exactly the same batch that came from the same way for and everything else, it can be more controlled. But yeah, it's not guaranteed. I Mean you're buying from Digi-key You know they might come in the same tube, but you know all the same art reel or whatever.

It doesn't mean they came from the same wafer so you know you can't guarantee that at all. So basically, you have to work around the maximum parameters on the datasheet and there's a whole lot of science between matching MOSFETs into it if you really want to get down to the nasty detail of you know the physics of the whole thing and everything else. But generally if you thermally match them on the same heatsink, close together and you put in some source resistor there, I won't go through the calculations of calculating a short a source current sharing resistor in there, but that should do the trick. And by the way, there's some debate whether or not you should actually separately drive each MOSFET with its own feedback loop and things like that.

And generally speaking, no, you don't have to do that, but you know, so you can get away easily with that. So doing those two things I think could solve the problem here. and he's put the performance envelope curve on there. Thank you very much.

And as Daniel mentioned on here before, the traces for the two MOSFETs can make a difference as well. so that's not the top. If we flip it over, we can have a look. What's happening here.

Here's the source. Okay, this is coming from out. There's our current shunt resistor there and you'll notice that yet short trace here to this MOSFET But then it's got to go through that. So the current for this MOSFET is actually coming through this trace for this MOSFET That's a no-no you should star that and preferably keep them equal length, but you probably had, don't But the fact that you know it's coming through there for the other? MOSFET Yep, that's a goof, so you want to fix that? You want that going straight across there like that.

But apart from that, he wants our feedback on the board and it. I Like it. I Like the little breakout tab here with the rotary encoder. Presumably that's done so that you can either use it on there or presumably you can break it off.

Just break off the tabs there, cut them out with a pair of side cutters, and mount that on the front panel, and he's kept that in the square of the thing. I Don't know, maybe this fits into a box or something, but that's a neat way just to get your extra board. You don't forget your extra board manufactured, it's all part of your panel. Very nice indeed.

And everything laid out. This is right near here. Oh yeah, yeah, your layouts good. Yep, there's no traces, you know Going from one side all the way to the other.

it looks neat. It looks neatly laid out. The good layer A good placement, good component placement is 90 percent of your layout work. trust me.

So you know if you whack this chip over here. for example, when you knew you had to connect it through to this Rs-232 or you say yeah, you had this Rs-232 driver here and you put it over here and then you have to run from your micro over to here and then back over there. Well that's poor layout and your design is going to be completely screwed on a double-sided board like this. but yeah, that's um, apart from that that looks so and so.

apart from the MOSFET I think that looks fairly decent good on your Daniel I'll link to it down below. it's all on github. it's all open source. all the usual business.

Next up another one from Australia Express post thank you very much Greg Poole and um he's from Okie in Queensland haven't been to Ooty I think I've sent some stuff to Ooty once but yeah having been there let's sell market feels kinda I'm like multimeter form-factor although it's a bit too heavy for a multimeter that's about 700 grams or something so which were had to come in to three kilo satchel east of the 500 gram satchel. they do have one kilo satchels now it just came out but only available in Express sorry little rant there. Um let's see what Gregor sent. So yeah, if you want to send over 500 grams, you've got a wide jump up.

You want to know why one that one of the reasons why I don't supply the multimeter, the multimeter, the manual. the printed manual with my BM 2:35 multimeter is because it actually puts it over 500 grams. which means for local postage, I've got to up it to the 3 kilo satchel and pay and charge a lot more for the postage just because the printed manual puts it over the 500 grams. So yep, so anyway, let's have a look pretty heavy.

It's like a power brick or something, Is it? No aha old school people complain about the weight of modern phones. It's the Telstra walkabout. Oh yeah, baby. that's more than a two minute teardown.

Retro Phone teardown. separate video? Awesome! Thanks Greg Wow Check it out, thank you very much! Gregg This is the Telstra walkabout. It is actually the Well. it's not manufactured by Telstra Telstra's like our national telecoms provider here in Australia It's actually manufactured by Mitsubishi and this was actually the first mobile phone in Australia.

It's the MT, three nine, eight, and all those letters for those playing along at home and it came out in 1986. Absolute classic. Look at this now. this.

modern digital. GSM Rubbish, No siree. Bob But this thing's analog all the way with LBJ and love the antenna look at there. Obviously, it didn't look like this.

This is where the battery pack snapped in here. down, down like that. and there we go. That's a little whip on there that went inside the battery.

That's kinda sort of clever use of space there. But yeah, analog mobile phone. No coax up here. no coaxial I could see to hook into your iPhone Maybe they know they wouldn't have it as part of the battery solution.

so I don't know I'm a good couple? maybe I don't know. Anyway, it was, um, the first Australian analog mobile phone from 1986 and I found some classic photos on the web. Check them out you and there's one reference that said this cost $5,000 when it came out in I think there's another source that since 1987. so I think you know it probably came out somewhere else in 1986 Mitsubishi in some other country I Don't know.

But anyway, I'm around about that vintage so we're talking pretty close to 30 years old, but imagine if it did cost that much back in the day. Wow Now this mobile phone plan? rubbish. It's an Aussie bonanza. Well boom three in a row.

This one comes from person unknown, but it comes from North Sydney here in Sydney on the north side obviously. Um, no surprisingly, the Harbour Bridge does not link Australia to New Zealand which a lot of Americans think. believe it or not, Um, nope, it connects Sydney with North Sydney the Sydney Sea when you ignore Sydney Anyway, thank you very much unknown. certain majors will get a note inside so it's funny.

heavy rattle so let's it's got a funnel sticker on it I Doubt it's a final item though. We got oh wow. I had one of these ah, an old scale electric kit note for his old scale Ettrick it no. I have one of these Wow Wow that brings back memories.

Hang on. Oh I Can smell the memories back in the old garage with my old Hecho scale. umm Train Set is a trying. It's a trying train controller.

Fantastic! Oh thank you. very much in town already I Can remember tearing this down when I was like 7. Oh great. There's not much in it.

Ah, it's got that real electronic smell. Oh, this puppy brings back way too many memories like this built in. Australia Beautiful. trying in asks I Found the old same power in old scale electric kit but it's not for skate lettering.

it's Vera believe. Hobby Railways I mean trying. We're famous for it and if memory serves me correctly, that is an overload switch so it'll pop out if you overload the thing so you can just press it back in to reset it and forward and reverse voltage. that's it.

Is that a pot? No, that's not a pot under that? No, it's a one of these studs that has just fallen out. But yeah, Absolute Classic. We've got this: our controlled output: our 12 volts DC uncontrolled output you would typically use those for, you know, accessories points you know, lights and things like that and 15 volt AC output as well I don't ever recall using requiring the 15 volt AC output for anything. but anyway, that's obviously coming directly out of the transformer and this is coming out of the rectified DC side.

But as Ian says in here, the most interesting thing about inside is the rectifier. Yes! and we'll take a quick look at our Hitoshi V2 one - I Love that scope. The trace was nice and sharp. Beautiful little analog scope the Hitoshi one and they had like a 40 megahertz version and ah, beautiful.

Anyway, that was actually that was the first scope I used at my first job in 1989. I think it was. Yep, that's right. there you go anyway.

Love that little thing. Let's take a look inside and inside is just hilarious. We got ourselves our transformer here. We're getting our 15 volts AC out of here and none of this regulation rubbish.

No active circuitry in here. We simply got our rectifier which we'll take a closer look at and our nichrome presumably nichrome resistance wire and there's knob on the back side of that with the lever in there and that and goes either direction to switch the direction of the things. Rather clever, but yeah, no, there's no regulator inside this things and we have a rectifier a bit like there's no even output smoothing cap. so that's why you get that because it's it's rectified.

but yeah, you don't but it's not smooth at all. It's not even I like you wouldn't even call that 12 volts DC It's like you know, a hundred percent ripple. and here it is. For those who haven't seen one before, believe it or not, that is a diode.

It's a rectifier. And also, believe it or not, it actually works. Not too dissimilar to you know the regular silicon diode you used to because it's called a metal plate rectifier or a Selenium rectifier or a plate rectifier whatever you want to call it. And the plates in there a coated with either of us, Selenium hence the name Selenium rectifier or a copper oxide.

and both of those are actually a semiconductor. So this essentially is a semiconductor diode. It just uses these big metal plates in there, but they're horribly inefficient. I Mean these things date back to the you know, the 30s and 40s and things like that.

So why it's still used in a trying power supply like this? But that was a when I was a kid in the 70s. This was not uncommon to get battery charges with these things in them for example, and when I first actually opened this I had no idea what this was because you know I was growing up in the 70s I started my electronics hobby stuff in the 70s and you know silicon diodes. I could buy it at my local Tandy store or you know dick Smith store. So it like these things were just a complete mystery to me because we didn't you know I couldn't find any information on didn't have any information you might are in my data books and archives and magazines and things like that.

and I just had no idea you it was sums. It had to be some sort of rectifier, but it didn't actually know how it worked or what was in it cuz we didn't have access to the internet like we did these days. But yeah, fascinating old things. These plate rectifiers.

But they're horrible things. Absolutely horrible. so that is certain. One crappy, inefficient power supply.

It's probably the worst 12 volt DC power supply you could possibly get. But hey, you know these things worked for preparing your trains and your points and everything else. These things worked just fine back in the day. So yeah, oh yes.

my old Hecho train layout I had a 16 B 8, 16 by 8 train hecho scale. won't train lay out in the garage. Beauty. And if you're wondering why they actually contain multiple plates down in here is because each they're actually multiple ones in series.

It's the reason is because they had very poor like as in a couple of volts. reverse breakdown voltage. Nonetheless, you know, 50 hundred volts or a thousand volts you used to with regular silicon diodes. No siree.

Bob a couple of volts so you had to string them in series to get adequate reverse voltage. Unbelievable. These things were just awful. Alright, just for kicks.

I've put a 2200 M 10 watt resistor on the controlled output and we've got it off at the moment. 2 volts per division here and if we switch it on BAM it is 2/4 That's what we're getting. Quite a high output voltage that's incredible. Actually, that's like that's barely on.

so that's off and that's on the average Here we get in about five point three volts. Remember, this is into a 22 own load and we turn it up, turn it up and we're looking at 12 volts our peak now and seven point one average. But if we turn it up here, we go all the way. and yet there we go.

About 13 volts average there. so you know a bit. look at it. I mean it's direct current? Yeah, it's not going negative.

there's our ground point. But jeez, it's not very good is it? And if I Center it here, that's what we had before I'm now on five volts per division and if we go the other direction, there we go. you can see it go in the negative direction as well. just a bit of a bit of noise on you can see the yeah, that's just the crusty old pot.

I Got one from Switzerland Hi to all my Swiss viewers I Love Sweets Wood! Went to Switzerland for lunch one day as you do when you're in Europe So I unfortunately haven't seen much of Switzerland I've seen Geneva that's about it. So thank you very much your jog jog sorry um it's Schneider Thank you very much from Bo Bean something like that. Anyway, let's have a look. I Noticed while watching some of the tear downs that using a screwdriver from PB Swiss Tools? Yes I Do somebody set them into my mailbag? Thank you very much I forgive you sent them in.

That's his favorite brand. a friend of Mine manufacture, friend of mine manufacturer assembling an imprint in Tools by Pepys Whistles Oh okay. cool. so let's have a look.

Spoiler: Oh yeah baby. I don't even have to look at that. Oh, it's personalized that bloody. Ripper Eevblog Oh oh oh no.

gasm Nerdgasm? Oh yeah, baby. Yes. Beautiful! Swiss Toolset that's got the one with all the all the shots. Jeez, they're long too, so if you're really needed.

Yeah, Okay, yeah. Fantastic. Beautiful. Oh Chocolate Leather AK Leather ik chocolate anyway Swiss Chocolate.

look at that. What a Bobby Dazzler Thank you very much Joerg I am sure I'm pronouncing your name incorrectly because I'm totally incapable of pronouncing names, but this is just fantastic. We've got talks. We've got large Phillips large flats.

we've even got up pretty sharp that sharp point there bloody Ripper and we've got a couple of smaller ones here. Excellent. They're just they're great for like our treatment and stuff like that you've got to have the spin top on I'm fantastic. So that you get in there and go, there's the money shot for those playing along at home.

Beautiful! Swiss Made! thank you very much and these are supposed to be ESD George says that from one Meg to one gig I Would have expected static dissipative, but anyway, let's try measure it I would actually expect nothing with the meter and yep, sure enough, dig you're in and zippity-doo-dah Yes, because they're not conductive, they're static dissipative. Let's get something a little bit better. I've got the key site you 1461 a meter but we haven't seen this here. I Don't think I've actually done a teardown on this I'm headed to a teardown.

So Ip67 rated and it's got a mega building. 50 volt range up to a thousand volts and that 50 volt range is actually very handy having such a low voltage range. specific applications: When I was working in the seismic industry, we had a and testing I our seismic underwater cables which would have hydrophones on them and they were actually limited to 50 volts. You put any higher than that on your risk actually blowing the hydrophones on things.

I'm gonna have to test the lines and it was. Actually, it wasn't easy to get a mega with a 50 volt range back there. and this was, you know, like a decade ago, you know you might be able to get one with a hundred volts minimum or something, but getting, yeah, having a low voltage can be handy Anyway, let's give this a go and and see, we've got our Whoa! I'm seeing flicker I'm seeing flicker on the display here. But so let's give this a burl here.

Oh I Just bring this better into Shot for you and let's proud this no touchy with these Megas even 50 volts near, you know shouldn't be touching it. Anyway, let's go and you've got to hold it down. 66 gig. but wait for it.

Trap young players gonna charge up there. We go about 23 gig or there abouts at 50 volts. Beauty. All right, let's up that to a thousand volts and give it a bell.

There we go. 15 gig at 17 gig at a thousand volts. So so much for their I claim. Ear surface resistance of the dissipative plastic is 1 Meg to 1 gig.

It's much higher than that, but it doesn't matter. as long as it's dissipative, that's fine. And what I'm going to do is actually the internal black plastic. I Mean this was the outer rubber.

So let's go back to 50 volts just for interest sake. And there we go: 130 Meg's so that's right for the plastic. So they are talking about the plastic inside, not necessarily the outer rubber type coding here. And a thousand volts.

What? Come on, you can do it. There we go. Point Three Three Meg point Two mega mm. Well, it's actually dropped right down to 250.

You saw it there. Could you just couldn't deliver enough current And this tiny little set that snaps out double-ended oh, that's just beautiful brings a tear to the eye. Thank you very much Jog and your friend for a write producing this Fantastic. This one's going straight to the pool room next up.

I Got one from Italy Hide all my Italian viewers. this one's from my Gabriela leggy, lousy thank you very much Gabrielle That stuff have a look. It's relatively light, but it's a bit big trying to get through the bigger ones on here. so I'll see what happens.

Yes, cutting towards myself because I'm a professional. All right here we go. and it's in one of these nothing else. Some old newspapers Italian newspapers.

some of these frustration-free like Amazon Like frustration-free packaging. let's have a look. It looks totally legit from our G Tronics dotnet. I'm pretty sure Gabriella's um, sent stuff in before Monday give this kid to Sagan but probably even if he's used to deal with scopes and all kind of, you'll still be too young.

Obama Okay, it's a kid spoiler file here. we go. All right. we're in.

Lakeland It's not instructions. it's a proto shield front. We know. And gin we know.

gin, we know. genuine, aren't we? no? I don't think so. Um, Anyway, it's A.m. it's a bread board.

II Typekit Awesome! Thank you. Everyall take a look, we've got ourselves another. Bobby Dazzler here. Check this thing out.

Isn't it beautiful? It's a breadboard interface. Or a breadboard with all sorts of Arduino interfaces here. Look at this. We've got an Arduino which plugs on the bottom.

There's the Juninho Oh, that's their version of the Arduino but it plugs in the bottom there. and look, you could actually have still got the headers on the top where you can plug your shields into. We've got LCD and we've got switches and we've got the Arduino Nano. Look at this.

the Arduino microwave. the Arduino mini can plug in all different types of Arduino is into this thing and then a break in of course break out all the I/o onto and I got a whole bunch of these and maybe I'm. sure these are coming with the standard kit and we've got other stuff up the top. We've got some output leads.

We've got more interface. Unfortunately, there is no power supply circuitry on board, but you can plug in a DC jack here, but yet there is no circuitry on there to actually produce those separate power supply so that's a shame. But look at the bottom of this thing. Look, they've got all the push-button all the info you need on the back of this.

This is just brilliant. If you're working with Arduino Ah man, you've got to have one of these Here you go. Here's the LCD I Squared C interface external USB to serial interface and we've got some em. some prototyping error and stuff like that.

The push buttons and look all the pin outs have labeled them all and you can just of course a plug and unplug your Arduino from the bottom. There it's just in this the LCD configuration. it's it's got everything. more stuff the Polk acro probe at and it looks like I've got a starter kit of LEDs and resistors and some trainees in there and all sorts of stuff.

Oh Fun for the whole family and let's have a look. Thanks for the entertaining blog thank you very much and he wanted to give this kit to Sagan but yeah, he's probably is a bit too young to play with red boards. they don't want to start him on that yet. I don't think anyway as prototyping shell for Arduino it's a little bigger and usable than a little standard produce shield.

No kidding, it's called the proto Shield Plus is used to quickly test ideas, key features, artworks if I'd we know and all sorts of versions of Arduino um LCD ready IO Expander on board it's a PCF 85-74 expander and all sorts of stuff. It is absolutely brilliant. I will link this in down below and I Have got the manual for the thing and the manual looks really good. Check it out this user manual version 3 this beautiful or color code are beautiful photos.

It's very professionally done I Like it using the proto Shield using all sorts of different things. the USB serial signals, it's all there. Winner winner chicken dinner! Huge thumbs up for this! Nice! So the entire starter kit that you see here at 69 euros. that and that includes the Arduino on the bottom and everything.

and the kit and the wires and the LCD and everything. you can get like a stripped-down version of this cheaper without the LCD if you just sort of want. and if you've got your own, Arduino is bare-bones a little bit cheaper. but yeah, that is a bargain so that's got to be the most comprehensive, inflexible.

Arduino Prototyping platform I've seen. Very nice suit. I Assume it doesn't have any extra power supply stuff that would have been nice on there, but you know you're powering through the Arduino and and you've got access to the yeah, three Point three and the five volts. But yeah, I don't know, it's just when you're working on breadboard.

just would have been nicer to have that potat. You can supply them from external power supply, no worries, but that is incredibly flexible and it's very well done. A lot of effort has gone into designing that. A lot of thought that would have taken a while.

Awesome From Switzerland to Sweden. In the height of all my Swedish viewers, this one comes from: I I Won't mention the company because that might kind of be a bit of a spoiler. I Still don't know what it is, but sounds interesting. The name of the company sounds interesting anyway.

so let's oh sorry. this is like this is a weird one. Some weirdo thing happening here. couple of boxes note: hi Dave doing these in line with email discussion.

Oh right. Returned multimeters. Oh yes. I Remember what? Yes because he ordered two microcurrents and accidentally sent two multimeters.

Oh so sorry about that. That's not really interesting. My Oh bag is it back in the stuff? So sorry. Lord What an excellent Swedish name Thord Oh Sweetie Shop won't be called forward.

So thanks to everyone who sends something into today's mailbag. sorry if yours are still on the Shelf and getting around to it. I Had I've got like over 30 items on the shelf I had before I started this so I'm slowly getting around to it anyway. If you like my Oh bag, please give it a big thumbs up.

Catch you next time You are not gonna believe what this puppy is. It is a little pocket open-source counter and this is one of the coolest things I've ever gotten in the mailbag. Check this out! Tada! Wow look and yes, you did hear a vibration motor there. It's a little a Geiger counter slash digital art dosimeter.

It's called the ultra micron and isn't it cute? It's just absolutely tiny. This is the size of it compared to an Australian 50-cent piece.