The Hamster That Chirps

Hello and welcome to the macro fab engineering podcast. We are your hosts, Steven Craig and Parker Dolman. This is episode 135.

So before we get started are like to announce that Katherine Scott and James Lewis will be judges for the Mac Web Design Contest blinking LEDs sponsored by Mouser. Catherine Scott's Twitter account is at K Scott's with a Z. And James Lewis Twitter account is bald engineer go check out their Twitter channels. And I think bald engineer chose out in our Slack channel as well. So go hang out with him. A lot

of people hang out in the Slack channel. It's like 140 people

now. Yeah.

For a while there it was, you know, on off conversation. But if you get on there, in the general channel, it's pretty much all day like non stop. There's there's something interesting going on. So

yeah, I think there's people that are chatting at like, four in the morning on Sunday.

I'm liking the little culture that's getting developed there. It's it's fun.

Everyone has, it's interesting, because everyone there is a these people who talk regularly they're like experts kind of in their field. And so they always have something to if you have a question, just asking it. Someone in there will know something about that subject.

Oh, absolutely. Oh, well, but at the same time, if nobody knows, like, I had an experience the other week where I posted a question up, and I just got a whole bunch of people researching it alongside of me. The question I asked was, if I had a copper wire, what would be the bend force? If I wanted to bend that wire? And, and it? No, there wasn't like a distinct answer. But there was a lot of people chiming in with, it's probably something like this, or, you know, posting links and all kinds of stuff. So it started to kind of lively conversation about that, that that kind of stuff happens all the time.

All the time. It's great when that community that we're building there has like that interest or curiosity to solve problems.

Oh, yeah. Yeah. Yeah. So I hope we sold it.

I hope so too. I really like that slack channel.

Yeah, both Parker and I were on there. So he, you know, if you want to come by and say hi. Come on. So Parker, you got some cool stuff for us this week?

Yeah. So I've been working, of course, on the wagon over the weekend, kind of working through electronics, kind of reverting stuff back to stock. And the big thing was the AC. So we've got the AC module sorted out. So the second thing I've been kind of working on is the interior stuff, like the chime module. So this is like the thing inside your car that when you leave your keys in and open the door, it goes blonde, blonde, Gong, Gong Gong. And also, like, makes noise when you leave your lights on that kind of stuff. Yeah, this being an older vehicle, all those kinds of electronics are in little plastic boxes that are plugged into places, instead of being incorporated into like a circuit board. Like behind your dash or whatever. Oh, so

it's like a bunch of different modules that serve as different things. Yeah. So

there's actually a thing called a chime module that say, of course, on the schematic, a black box that's got wires that go to it. So I pulled it out. And here it is, it is a bout two and a half by two and a half inch by one inch square blue box with

connectors on it. Okay, they look like relay tab connectors.

I was hoping something simple would be broken with it, like a blown diode or a blown capacitors or

whatnot. Like the like the other module that you pull.

Yeah. So I opened it up, and it has two ICS in it, which was a shock. The AC module went out of its way to design a transistor based op amp to not use integrated circuits. Right, right. This thing has two icees in it. One is a PECS inverter, okay, and the other one is a AND gate. So it's all just logic, no Boolean glue logic. Yeah. So the part numbers are MC 14 001 B, that's the end gate, and the other ones to MC 1406 Nine and that is the hex inverter. Also, what's interesting is I'm going to try to get the enclosure back apart. It's kind of

well you do that let's, I'll describe the enclosure. It's a blue box that has a handful of holes on it. And then on the bottom side are the the tabs that look like that's for the hamsters. Just to breathe, right? Yeah, yeah, the little Hanser that chirps wouldn't adore.

Before I've been trying to fix this, that's actually what it sound like. It would be like, Okay, seriously, that's it was it sounded like it was dying.

Go. That's, that's awful. So so the speaker is inside the module, right? Because that's why the holes are there. Yeah, so

the speaker is a metal speaker. It looks like a miniature walk with a metal can not soldered on top of it.

Hmm. You know, from from from here, it kind of looks like, you know, those coin cell battery solder on tabs where you slide a battery into it? Yes, it looks like one of those.

It's got a, I think it's a PICO actually inside of here. Because you can, when you have it on, you can feel it, like vibrate really quickly. And it's how it vibrates is different from a speaker I guess. Once vibrating, sure. So that yet so that's an interesting part. But that works. Because like it, this module makes noise now. So what what I did is I replaced the two electrical capacitors on it. One was like a one microfarad and one was a 22, micro farad. And I had just had this lying around. So you place them now makes noise but still doesn't work correctly. Okay, and so I was playing around with it. And basically you like touch different parts of the board and it would start working. Hmm. And then I bent bent the board like this. I'm like you flexed it, like really flexing it and it started working. So I think I was gonna re solder the board now. And it should work.

That's weird. Okay, so is it one of those old boards where the solder mask is all like wavy now? It's all like puffed up and wavy? No, no, no. Okay. Yeah, it

looks fine. It's it's conformal coded to.

Oh, really. So they actually, that's so weird that they would put that much effort into a little beeper, as opposed to like you were saying earlier, making a transistor, you know, discreet level op amp. For the AC controller.

Yeah. Now, it does have a discrete level. It's got like a push pull transistor amplifier on it. Yeah, basically, the PISA driver. Yeah, the PISA drivers a push pull, at least I haven't, like drawn it out yet. But like looking at the traces, I'm like, Yeah, that's a typical poverty push pole. PISA driver. Yeah, yeah, I'm gonna bet you what it is, is the lead one of the electrolytics drives the frequency that that push pole transistor circuit flips that. And the other one does the seatbelt chime, which is a delay circuit as well. So like, if you don't have your seatbelt plugged in, it won't be continuously it will just let you know every so often that you're going to die.

That's great. So so the MC 14069, which is the hex inverter, it's got looks like it's got six elements in it. Is this is this thing, where one of those do they have it set up? Or one of those is an oscillator for the Pisa. And it just I don't know yet turns on? Oh, you haven't traced it out yet? Yeah.

I haven't traced out the board yet. I just got it apart today. Okay. Okay. So I am going to trace it apart. Even though I think I fixed it. I just have to re solder it. Gotcha. By I'm going to trace it out just so it's like being complete completionist in a video game, except it's a circuit. It's a hardware project.

I'm curious. Because if Yeah, if they just have hex inverters on there, then they probably have, you know, some hex inverters. If you tied the input to the output through some RC circuitry, you can control the the rate at which it oscillates. So they probably just have some of those hex inverters tied to each other for the tone, just through some RC circuits. So if the tone annoys you, I bet you could could you could change the RCS and kind of like make it a different pitch.

Well, you'd have to add more, so hopefully not using all of them.

What do you mean by add more?

You'd have to have more inverters to change the pitch. Yeah, more delay, right? Well, my thinking about that wrong. No one

that are like, Okay, if you if you put feedback on the output of the hex inverter through an RC time circuit, okay, yeah, then you can then using the the the R, you know, one divided by RC, you can control the frequency of the oscillation. So my electrolytic capacitors I replace, I'd have to go with a bigger value to lower the pitch. Ah, okay, that's probably the 22 micro farad. one micro farad. That's the one micro farad in the feedback. Okay. Yeah, the 22 I think is controlling because it's on the other side of the board. Yeah,

I think 22 is controlling the seat belt time, which is a slower delay to activate the chime. Ah, okay.

So So a while ago I built I built some pheromones using a 4069. And if you tie if you just do a straight tie from the output to the input on one of these things, you can Get it to oscillate, I believe at a megahertz. I think that's what, that's what I got. And then And then, you know, using some other fancy stuff, you can set up other oscillators, but but with a single 4069, you can get a whole Theramin out of that.

That's cool. Yeah. So my one question to the listeners is, it's got this conformal coating on it, which, when I replaced the capacitors, I just kind of scraped it off. And I was fine doing two parts, but now I got to re solder the whole board. What's gonna be the best way to remove this conformal coating? It's kind of like a lacquer because it's, yeah, it's yellow.

Mm hmm. It almost looks like a whole layer of solder resin. Yeah, actually, it's

got that that resin look to it, as well. Yeah. Yeah. Yeah. It's some kind of sprayed on lacquer or something. And this is circa 1990, which was actually probably built well before that, though. This was probably built in the late or not late, mid 80s. Probably.

A bit. You could spray some that aircraft paint remover on the back, probably eat right through.

Oh, yeah. Not remove it, but that might remove the solder masks to

eat through the board. That stuff is awesome.

It is made in Canada. Oh, interesting. Yeah. And the Katyn enclosures weird. It's a two piece enclosure, which is not a shock. But there's no fasteners, it goes together. And then they they hot welded. The bosses in. Oh, so you actually pried it apart? Oh, I know. I drilled the bosses out. Oh, okay. It's like it was like a rivet, plastic rivet? And they I just drilled out the rivet. Yeah, they

probably had on the assembly line somewhere. They probably had some mechanism that was like a, an arbor press that came down and just welded all four parts together. A panini press for enclosures. Yeah, panini press. Yeah, that's exactly. Making them beep and sandwiches.

And then. So I'm working on this. This should be done by you know, hopefully next couple days working again. So hopefully next week, I say it's done.

You really haven't fixed like everything on that leg. Every little tiny

thing? Yeah, ever. Yeah. Speaking of fixing power circuitry modules, the powered mirror circuit is also not working. Oh, yeah. No.

Just like everything is wrong with

that gets on the power power and mirrored circuit, it's actually a just a switch, okay, is what what it is. But the thing about the switch, it's it was only made for this one specific vehicle, the grand wagon years, from like, 86 to 91. And they only made like 17 to 18,000 of these vehicles in that time period. And they didn't make any extra parts for the switch. And it's like, so there's only like, 18,000 of these that existed and most of them broke. So what exists people want like gold money for like they want like 300 400 bucks for the switch for a switch for the switch. And the crazy thing about the switch is sorts of four way joystick on it. And then there's a switch to go from left to right. Okay, but the switch from left to right isn't an electrical switch. It's actually a mechanical switch switch that cogs the entire back of the joystick to another set of contacts.

Oh, really?

Yeah. It's crazy. I really wish I had it. Because I've seen pictures of it how it works. I'm like, That is amazing. It would be awesome. Just to have that thing because that will the mechanical toggle switch thing worked.

That sounds so over engineered. Yeah. No, because

especially when nowadays, we would just do it with like a microcontroller and attack switch.

Of Yeah, exactly. Actually, yeah. No, the little rocker that controls all the all the directions would just be four or Yeah, no, it would just be for tech switches that yeah, rockers on Yeah.

And so too, I can't get the switch, I'm not going to spend 400 bucks on it. I will spend like $400 in my own time to design something that will fix it though, right?

On the low end,

yeah, on the low end. So I want to use a I want to switch the toggle switch and then the four way to just two four way switches. Okay. And then use two motor controllers per side. So want to motor controls do one does up, down, left, right, and the other to do the other side, the right side. And that way I don't actually have to have a microcontroller in it. The basically the the four way directional switch will control the motor controllers directly. Apps or apps and maybe it's Apps has a really cool like directional switch that looks really beefy that we use. That's like our our KJXT one f4 2001 And that's a really cool switch. cuz it's a four way directional with a push button, which I won't use, and it has an encoder, which I won't use. But it is really cool. Wow.

How much is that?

I think like six to eight bucks. Wow, that's really cool. Yeah. And I'm actually using it because they make cheaper just regular directional tack switches, but they don't look Skookum. And this is going to need to be Skookum because it's gonna be living in a door in a door.

Yeah. Mouser has it right now for $6.26. Yeah, that and then the

motor controllers are going to use it's a BTM 7752 G, which is by an Finneran, I think. And that's way overkill, because I like measured how much current the motors in the mirrors pole. And it's like, they pull like maybe 300 milliamps at 12 volts. And those motor controllers are like six amps. And I already have it designed and confirmed.

Oh, you've used them before? Yeah,

I've used these before. And I saw I already have like bass, I went into my like Eagle library and just search going to I found motor controllers. I'm like, Ah, that one works. I don't have to design the only thing I need to design is the footprint for the switch. And that's, you know, slap the board together this so for next week, I had that board order. This thing

looks vaguely familiar from a project we both worked on at macro fab. I am almost 100% Sure certain that we've seen these come through on some motor boards.

Probably because I actually recommend that series A motor controllers to our customers a lot. Okay, yeah. Okay, cool. They're they're not the cheapest, but they're fairly inexpensive. And they just have crazy stats. You can pump a lot of amperage to that, that that part?

Yeah, you can also hit them with 45 volts. Yeah, so the you got a really wide operating range. Mm hmm. Nice.

So I hopefully I have that board designed by next week as well and ordered. And yeah, should be pretty cool. Awesome.

I'm really interested to see how that switch. Turns out, it's an encoder, a switch and a HDMI two and a button push button. Well, it's a it's a one on sorry, it's a four way thing with, it's almost, it's almost like a, like a modern game controller with an encoder rotation added in.

So what I'm gonna do with that is I'm actually, when I install it, I'm actually going to superglue the encoders. So the knob doesn't rotate. Cool, because I want my for my application, I don't need them. And it'd be kind of weird. If you rotated a knob on I mean, I know it's it's my vehicle. So I know it won't do anything, but just in case someone else needs to drive it.

Oh, yeah. You know, I was it's funny little side tangent. But on control surfaces. I was I was joking around with a guy at work the other day. We were talking about a linear rotary potentiometer. Which, let me let me describe this real quick. Think think of a, a slide potentiometer. So you know, it's just like, up, down or left, right, something like that. But think of also if the potential ometer itself could slide but you could also rotate knob the the shaft in the knob in there. So how cool would it be if you had a graphic equalizer? That was horizontal? And you could slide to whatever frequency and then you could turn it to like boost or cut at that frequency?

Oh, so once your ones your frequency and and once the DB amplitude. Yeah, yeah. And then and then of course, of course, you had like the scientific term for it, or engineering term. amplitude, not dB. Uptown, not? Not

there's loud. Yeah, yeah. Well, and of course, you'd have to somehow go three dimensional with this control surface, and have it be like you could pull it in or out or something like that to represent the cue of the filter notch or something. Make it just like Minority Report equalizer. Like you move your hands on.

You could actually they make those 3d mouse's? Yeah, yeah, yeah, you should turn like just can you map because those are fairly pricey. Think about like an entire wall for your synthesizer.

Oh, have you ever used one of those?

I've looked at them and I guess use them in terms of like, I put my hand on it and like move like the cursor around in 3d space. And I'm like, That's not for me.

We used to have a guy who worked at macro fab. His name was Jared. He was a he was a fun individual. And he after he left McAfee he got a job as sort of like engineering tech support for some some high level software. Where, and he started using a 3d mouse and I went over to his apartment. And he was like, check this out. I put my hand on it. I was just like, Nope, no. No, I'm not doing this. Sorry.

I wonder if any of our listeners use 1d mouse's

1d? Isn't a slide pot, a 1d mouse?

Sure. Yeah, actually, yeah. I just said mouse's

Oh, mess. Mice. Yep.

So if you use a 1d mouse, let us know in Slack.

Or not, if you're one of those cool, guys. Nobody's isn't Monday. All right.

So Steven, what have you been up to?

Ah, I've been up to completing things. Which that's not a unlike me. That's not a statement that's uttered very often on the Mac. No, this is no, it's not. This is momentous, in a way, because we have actually, we, you know, me, but we because extension to the Feb, have actually completed yet another project. And I want to say completed with a caveat. The reason why is because I don't have the knobs on my device yet. So it's not truly completed until the knobs are on it. Ah, you said you were going to do that this morning. Yeah, will that I was, but the knobs didn't actually work. So I need to find other. Ah, so I completed my micro tracer, the you tracer, my tube tester. So everything is up and running, all the code is working. I've already taken about 20 or 30 tubes worth of data on it. So I'm super, super happy with how this turned out. Because I had this idea to make this about five or six years ago. And in fact, I used this tube tester the entire time, I was running Craig amplification. And I always wanted it in a better case, and I wanted it to operate better. But just, you know, never really had the time. And, and so like, I'm super happy that this is finally like complete. And the thing about it is, you know, above and beyond it just being what it actually is, in terms of what it actually does, it does a better job than how it was in the old enclosure. Because in the old enclosure, I had flying wires that connected all the signals to the tube sockets, those potentially, not potentially that you could you could visualize it on the screen, when you're taking data off of this thing. It actually had oscillations, it had some crosstalk there were some some other issues with it. But now that I've integrated all of the signals onto the PCB, I could, you know, I had a much better way of routing all the signals such that they didn't interfere with each other. And it reflects very much in the data, like the data is a lot cleaner, the lines are a lot sharper. There was a lot of times in the past when I was testing a tube where I had to just, you know, look at it and be like, Okay, I know what it's trying to do. But it's not actually doing it because, you know, oscillations or whatnot. But now it's it's much, much better. And I've got ferrite beads on any wires that I have going into the end of the board now. So even if there is some extra high frequency garbage on there, those will probably not probably the intent of those is to kind of like clean that up a little bit. But

yeah, so So what

how do ferret by beads work? Their beads basically act as a magnetic core that wraps around a wire. So you can either have them have a wire pass through the ferrite core, or you can have the wire actually loop around a ferrite core. And for high frequency signals, it actually acts as a large impedance. So effectively just squelches high frequency noise, or the chance for high frequency oscillation, which tubes have a notorious issue with because they don't really reject high frequency stuff, they'll just let it go right through. So I'm actually squelching a lot of the high frequency noise right at the source, which works really well. And I was able to on the PCB, I was able to observe a lot of specific requirements like tray spacing for high voltage stuff, because I've got multiple 400 volt signals. I also have some signals that can go negative 40 volts. So really, if you have negative 40 and 400, you have 440 volt separation between traces, you kind of have to pay attention to that on your board and crosstalk between all of those. So I paid a lot of attention to parallel traces. If I ever had to cross traces. I traced the cross at a 90 degree angle, things like that. And it all turned out really well. I'm super super happy with it.

Yeah, the i It's when We were last week after last week's podcast. And we were working on the code and the fact that, like, the moment we wrapped up all the code like it worked, yep.

Yep. Yeah, that's a that's that's a good feeling. I love when that happens. So yeah, I basically the fact that all your hardware was solid, yeah, yeah, yeah, that you know, the basis behind everything that goes into this box, there's not a lot of like, mysticism or like crazy complex circuitry, it's a lot of step and repeat. You know, there's a lot of like, duplicate circuitry and stuff in here. So nothing like super special. But it is really nice. When you design a circuit, you drop it in, you fire it up. And it just works. And that happened. In this case. Yeah, especially with

all the other pre work, you had to do like the enclosure, like you've finished the enclosure. Well, before you even knew your circuit board would work.

I finished the enclosure before I ordered the PCB. But that's because I spent a ton of time on CAD. And I did a whole lot of double checking that all the lines, all the holes would line up and everything and that all worked. And I did a ton of stackup drawings to make sure that you know, if I've got this board with this spacer that goes to another spacer goes to another board with a to 220 and a heatsink on it. Will it fit within the height of this box, you know, like there was a lot of that that went into it. And the box I chose is a little bit goofy because it's like, it's one of the more cosmetic I'm saying that in quotes, boxes you can buy on Mouser because it's a steel box with wooden ends on it. Because it because it just makes it look like a piece of tube test gear you can see it

actually does why your signals are so clean.

Oh yeah.

Your signals are routed. What was the term by actually aligned to the woodgrain?

Oh, yeah, yeah. Well by actually aligned but also organically aligned at the same time. You know, there's an organic aspect to this that goes along with it. The walnut helps direct the magnetic flux lines, right. Yes, exactly. Of course. The only one that does that, but Right, right, right. No, Pyne would be terrible. He would never choose that. No, it's terrible. So yeah, no. So yeah, everything's everything's up and running. I did have two issues with with the thing and whenever, you know, the thing is, like with these kind of like one off projects, you don't get a chance to really prototype you like it's just it is what it is you just deal with it. So so two issues that I ran into one was easy to fix. One was a little bit more of a pain in the ass to fix. The first one was I just selected the wrong part for one of the parts on the board. So luckily, it was just you know, I still accidentally selected a low voltage version of a part I think I've discussed this in a previous podcast, so it was just a matter of ordering the other part and that was to drive the relays Correct. All the relays and all the seven segment displays it basically it's just a Darlington transistor array, like a you all n whatever a it's a UL in 2003 but I think I got the UL in 2003 V or L or whatever it is. LV low voltage. Yeah, and it wasn't a painful version so didn't work. So that's that's no problem. The other thing and I absolutely hate when this happens and I pulled a really dumb mistake, but I drew my

USB connector upside down. So my the pads for my USB connector because I chose a USB. What is it? A? A is the one that's the big box B that's b I can never remember which one is the printer one yeah the printer one I chose the printer one because I like those two beefy they're good for stuff like that and and the datasheet for it the the layout for it showed it showed a bottom view through that top view so my signals my ground my power my d plus my Deep Mind is were flipped so the this I hate having to do this but I drilled a hole through my piece all the traces and I ran signals from the bottom of the board to the top never told me that flying wires yeah

I thought you I thought I thought this would be a good venue. Oh my god that's brutal. I hate that because it like everything was flawless but now I've got a hole in my PCB with flying wires with the USB and and they're the high the like the highest speed signals on my whole board. And they're the ones I have to like free wire that way I hate that uh,

you know, shame on that company though doing a bottom view.

It is what it is, you know, get on the slack and and I'd love to hear if that's ever happened to you before because I've known multiple people

who've that's happened to me for for as well. I had to solder an SMT part upside down rotated. Oh, you had to like flip a dead bug. Yeah, flip. Flip the part over it was a Q fn flipped over and rotated it.

Right? Yeah, yeah. So, you know, excuse me sucks. But it's, but it works. So whatever and it's all enclosed. No one will ever see it if I if I ever wanted to go and like make this an actual product, which I never would because it's too damn expensive. But it's got like

$8,000 worth of really.

It's got. It's got 56 relays, it's. But I would obviously fix all those things. But whatever it, it works. I think if I built that product, or built that board, the first thing I would do was just toggle all the relays in sequence. Just repeat and just listen. Oh, yeah, well, the first time I turned the board on, because my microcontroller wasn't working right. Or it didn't have any code. It actually fired all the relays. And the whole board was like cut chunk, and brown out. No, actually, you know what's really great about that, all the relays fired, and that little switch mode power supply that I purchased for this, we talked about that in a previous podcast, it's a little switch mode, power supply. That's only a three legged little thing that can handle 12 volts one amp handled it like a champ didn't even get hot, and it was pulling 800 milliamps. Oh, that's cool. Yeah, I'm super happy with that. That little switch mode guy cuz it was $2.50. And it means that I didn't have to design switch boat vouch but

yeah, that's the one that's supposed to basically replicate a 7805 or seven 812. I think in your case,

it Yeah, that's right. It has a

point one inch pitch. It's basically a 90 degree angle header on the on the end, and it has the same pinout as a 7812. The cool thing is though, this thing can also produce negative 12. If you just flip switch the ground and the and the output, it'll actually rearrange itself give you negative 12. So if you purchase two of them, you can get a positive and a negative 12. That's cool. Yeah, it's kind of nice. So it's a pretty, pretty good happy with it.

Yeah, so I can't remember the part number for that thing offhand. But we'll put it in the show notes again.

Yeah, yeah, for sure. So, on the show notes, you ask a quick question like, what what would I do different? If I could do you know, there's only one thing so far that I would do different. And I don't really care too much about it. But it's just gone through my head a couple times. Seven segment displays are great. But you can't display everything on a seven segment display. So if I were to redo this, I would actually do them as a 14 segment display, and have them be able to, or 16. Yeah, and have them do the whole gamut such that, like, I could actually display the letter K, you know, or something of that sort. Because right now I can't, and technically in tube speak, the cathode is spelled with a K. But I have to display it as a C right now, or, you know, grid, you know, have a capital G or something like that. So you're

gonna find that one person that's like, that's a deal breaker for me with this book. Yeah. So, so So actually,

what's been what's been really nice about this is, for gosh, for a few years, I, I've been having a handful of six B, C, eight, I think that's the number that yes, six BC eight tubes lying around, that have actually been part of a compressor, a tube compressor project that I've had for a while, I've actually built three of these compressors. But I'm finally getting around to building one for myself, the other two I built for friends. But I've had 10 of these tubes lying around, and I need four of them. And I wanted to pick the best for the or the best matched for so last night actually fired up the tube tester and I got like, gosh, a couple 1000 data points from all of the all of the tubes. So now I'm going to dump them all into Excel. And I can do a comparison. So which ones are the closest together? Which ones are the closest, so you want to match the the output resistance of the tube, you want to match the transconductance of the tube, and the overall gain of the tube. So I can pick the best ones which will result in the lowest noise

transconductance sounds like a sci fi term that doesn't actually mean anything.

I really I love transconductance I love it because it's such a great noise.

I really talked about this on a podcast a long time ago. Yeah.

It's it's it's a really, it's a it's a it's a hard thing to like, understand fully, but it's really easy to like explain. It's like if I put in a volt, how many milliamps do I have control over? Basically, for every volt how many milliamps does it control? That's that's all it does. But if you try to like visualize it and use it in equations, it just gets confusing really, really fast. But overall, basically, it's just a measure of how much control your device actually has. And transconductance isn't just, just tubes, like, all transistors have a transconductance value also. So it's it's worthwhile mode, knowing what it is. But it's, it can be confusing. But it's also it's not easy to it's not like something where you can just like ask a transistor, what's your transconductance you actually have to, like, measure it across a whole range of values. So it's, it's an ever changing value.

I think if you could ask a transistor, what its values were, that'd be really weird.

Well, it's not as easy as like, you know, like a lot of like, even crappy multimeters have a beta tester tester. And so you can't you can basically ask a transistor, what's your gain or a BJT? At least? What's you know, funny? I always thought that was interesting that a lot of DMMs had a beta tester on it. Because for the most part, nobody does that.

Yeah. Who's gonna use a $2 Harbor Freight multimeter to test the transistor, right? Yeah, no,

if you're the cut, now, I

bet you someone's going to email in and be like,

I did that.

But besides you one yet,

but that brings up a good point. If you're the kind of person that actually cares about the beta on a transistor, or has a circuit where that's actually required, you're probably gonna have a better piece of test equipment than a Harbor Freight multimeter. Oh, like

that little test that you had? Yeah. Uh huh. Yeah, that thing was great. I remember one time at the fab you like went through like 400 to end with a 390? Fours? transistors?

Yes. They were 3904. Yeah.

Yeah. Because you bought like, it looked like 1000 of them, because they came in a big Mauser box, on the tubes.

You know, I've been I've been a whole bunch of 3904 is based off of their VBE, which is the base to emitter voltage, and on their Beta value. And the reason why I did that is because I was trying to get a hand matched pair for a noise gate pedal that I had built. And if you don't have a matched pair inside there, then you get a whole bunch of extra noise, and it doesn't open and close the noise gate smoothly. As soon as you put a match pair in there, then it works just as well as you, you know, expect, however, you know, like doing it by hand, the way I was doing, it was just more fun for me, I guess, because you can buy a matched pair transistor on Mouser for like, six cents, you know, and, and and it'd be better than matching it by hand. I think also I was doing that for some synthesizer. VCOs.

Yep. Yep. And you're using them also for that op amp, like eight pin op amp thing you built.

That's right, the diode compression op amp. I actually, you know, I relayed out those boards last week, and I bought stuff for that. Because at at WMD. In fact, this is, I guess, the first time anyone's announcing this, it's not really a big deal or anything like that. But we hold DIY classes every once in a while at WMD. And our next DIY class is actually going to be a guitar pedal that I designed. It's based off of a tube screamer pedal. And so people can sign up for that you come in, you learn how to solder and you solder up a pedal and you leave with a pedal. That's really cool. Yeah, one of the things I redesign that diode compression op amp, because I wanted to plug that in also and have that available. That's

really cool. Yeah. Yay. I wish I was there in Colorado take that class. I probably would learn a lot. Yeah, we.

So this would this likely be the second class that we that we're doing the first class, some people came in, and they learned how to solder and they left with a synthesizer module. So we're going to kind of like mix it up and do some stuff, some guitar stuff and all over the place. So eventually, we're hoping to open it up and have a more advanced class where instead of learning how to solder through hole stuff, we're actually going to sit you down and teach you how to solder surface mount stuff. And then you leave. Oh, that'd be cool. Yeah, then you can do like the more advanced stuff. And that's really fun. Yeah, now there's a bunch of a bunch of cool people at work that are really into this kind of stuff. So and they want to they want to share the information. In fact, last Friday, I actually opened up a class and I had six or seven people come and we did a whole like two hours worth of learning dip trace. Because there's a handful of people at work that are all you know, they they have ideas for these great projects, but they have no idea how to turn it into a schematic turn it into a board. So we got everyone's feet wet. With that, and there's already people creating their own little projects there. So Oh, that's awesome. Yeah, it'll be a bunch of fun.

So we talked about, like, what you would do different? Yeah. What is something that you learned from this project?

A little bit harder? It will, it is harder. It's not that, of course, I learned something. You know, even though I kind of knew how to do this already, I had to learn a whole brand new mill, in order to mill this enclosure. So I spent some time learning that and, you know, got the enclosure, all milled up. I did a UV print on the top for all the artwork on there. I'd never used a digital UV printer before. So it's difficult, but it's also not that difficult. You know?

No, no, I think using those two machines. That's perfectly valid.

Yeah, yeah. So learn how to do both of those. You know, I think most of the electronics I've done before. Oh, you know what, no, duh. Of course, I've never, I've never actually coded for an STM chip. So I did. I did all of that from scratch. So and that's surprisingly easier than I thought it was going to be. Well, especially because Parker helped me.

But I didn't have to do anything besides, like, tell you how to like, architect the switches?

Yeah, right. Right. And in fact, have you have you put that video

up? Not yet. I was meant to do that last week. And then I never I finished editing it. And it's all done. I just had to sit down and listen to it. Because we did a after hours podcast stream last week on Tuesday night. And it sounds great. The quality's not perfect, because I was just like recording the the Hangouts video. So it's like, you know, whenever Steven like, loses connection, and he goes all like eight bit pixels, and stuff like that, but I wasn't down to listen to it to make sure like, because we because it's a secret. But like, during the podcast, we always have a beer, and an ad of the podcast. Yeah. We might have another might have had like three more beers each. So by the end, I was actually a little drunk. So I want to make sure everything sounds because it's gonna go up on like the macro fab YouTube channel. So that makes sure it's like, okay, this is an accurate representation of what we want to show.

Well, and the whole reason why I even asked if the video was up is just because that was something that we just tried out kind of off the cuff. It was something where I was like, hey, Parker, we helped me with the coat. And he's like, Sure, I'm gonna string it was one of those things, it actually turned out to be a lot of fun. And we had at one point, we had five other people watching. And and it was something that we kind of discussed that maybe we want to do things like that in the future, where maybe we you know, stream and discuss some one of us laying out a board or maybe even other people, I don't know. So if you're interested in that, jump on our Slack channel in and hit us up. And

then I'm also would like to finally move to like video podcasts. So we're still have the audio podcast, but then the video podcasts would just be like recording the Hangout session. So the quality wouldn't be as good as the audio version. But hey, you can actually see us talk our heads move around.

Well, and and and when Yeah, when we show off our little projects and stuff, you can actually see it without having to go to the show notes. Exactly. So yeah, so yeah, if you're interested in in watching us do you know, stuff like that? It was it was actually a lot more fun than I expected. And I'd love to do more than more of that kind of stuff. Especially because I'd like to get better at coding and Parker's He's pretty good at helping me step through it.

I assume the RFO even though we kind of already did that already. Um, Craig, this is not you Craig different Craig with a see asks, cost comparison between two layer and four layer boards are two layer much cheaper, would a four layer board allow a smaller board area verse to layer to make up for the cost? So I he asked us on Twitter, and I said the pens.

You know, it's funny, in the dip fridge class that I that I was doing last Friday, I got this exact same question where people are like, well, when does it make sense to go two to four layers? And if you if it just makes sense to go for layers, why not always go for layers? And the exact same answer came up where it's like well, depends, you know,

depends. So in the prototype world, there is a cost difference. Yes, between two and four layer and it's, it's about double. When you when you look at a two layer board. I like to think about it as layers. So you actually have a top layer which is copper, middle, which is preg pegboard, prepreg prepreg are then another layer copper. So you have three layers. And you essentially have three operations of copper being squished down and glued, and all that good stuff. Whereas a four layer, you have top prepreg, layer, again, prepreg layer again, prepreg. So you have six, which turns out to be double of so 2436. And it actually works out in the low volume, which is, it's actually pretty close to double the costs. That's right. So in low volume, it's about double the cost. Now in medium volume boards. So this is like 100 to 1000. It only costs a little bit more to do for layer, right, per units. But when you start doing the mass production, which is like 10,000, plus, that little bit extra adds up. So it really depends on what you're trying to design. And what the ideal market would be if you really need to hammer down the PCB cost. Like the, the pin HEC controller is a six layer board, because a four layer board only costs like $2 less. And the quantities were running

well and your design really kind of demand six layers, we could easily do it in four. But but your performance comes from a lot from having six layers.

Yes, exactly. But we could do four layer just fine without increasing the board size. So we reduce it by two bucks. But at two bucks over, you know, a pinball run a 300 units is only $600. It's gonna take me longer to route. It's much harder to make that design work on four layer.

Yeah, right? Well, and here's the thing, when when we say that a four layer board, for prototypes is roughly double a two layer board, that's just board cost, the assembly cost should be identical. The only thing that that might make it, you know, above and beyond the board cost being different is the fact that four layer boards can take longer to make. So you might have a little bit of cost associated with that. At the same time. Oh, like lead time? Yeah, you're right, right. Cuz, you know, sometimes two layer boards are like, you know, two to three day turnaround, whereas for boards are like four to six day turnaround. Okay, I see that. So So yeah, the doubling is purely for the raw PCB, not correct parts or labor for assembly.

So how I start designing stuff is basically it's like, how many power lead planes are you doing? And how many traces you're doing, I don't think I've ever actually built a board that was like, I need more than two signal layers, like the pin hack board is to signal layers, and everything else is ground and power inside. So I think if you had a really dense design that you had to have multiple, like more than two signal layers, then yeah, you need to go for or, actually, at that point, if you have, if you have a board that needs three signal layers, you should be looking at six layer. Yeah, because with four layer, your advantage with four layer is you use the internal tools for power, power and ground. And I'll put this way, just once I started moving to four layer boards, it makes routing fun again, because you don't have to worry about power ground.

So I've only ever had one board that has ever required more than two signal layers. And it actually required four signal layers. Fancy, because we had a 512 pin BGA on one board. And the only way you can get all the signals out which we use almost all of the signals was eight layers. And so we had multiple power layers, multiple ground layers, and multiple signal layers. So that makes a lot of sense. That's actually a pretty good, you know, compass, if you want to use that for how many signal layers you need to use is what what is the single most pin dense component on your board? And does that require more than two signal layers that will drive? How many layers you have for most cases?

That's a good way to put it. Cool. So hopefully we answered that question for you, Craig. Comment in Slack channel or on Twitter.

We're pushing the Slack channel hard. Oh, yeah, exactly. Yeah. What's a lot of fun in there. Yeah, it is. It is.

I mean, I chat in there all the time. So yeah,

I am in it right now. So a little a little side note on the on the micro chaser thing. I am going to have a blog Post coming up here soon on, potentially a new blog. So we'll we'll kind of flag that and you can see some more pictures of the guts and the outset where you want to call the blog. I don't know yet. I got to figure I got to figure all that out. So hopefully by next podcast, I'll have all that figured out. Well, and the blog posts written Craig's cool blog. Okay, great example of what I'm not gonna

tweet us at macro crab or macro ninja near or Longhorn engineer. If you have a name for Stephens blog. Yeah, that's it. Hey,

or get on the Slack channel and tell me directly. Yeah, if you have any ideas for what I should call my and new engineering blog, which hopefully this will be the first of multiple projects get posted up there.

Oh, we should compete. See who can keep it updated the most.

Hey, didn't you tell me a while ago that you are going to update once a week?

I've missed two weeks. It's been a lot better than it's been

now. So yeah, it has it is.

So that is the thing is I've been taking pictures of everything I've been doing. Yeah, I just haven't put them online which is it was for a long time or averaged them and taking pictures and stuff I was building right so now I've got all the evidence. I just have to upload.

Yeah. Okay, cool. I guess with that, that was the macro fab engineering podcast. We were your host, Stephen Craig

and Parker Dolman.

Take it easy.

Later everyone. Thank you. Yes, you our listener for downloading our show. If you have a cool idea project topic or name for Stephens blog. Tweet us at Matt crab or emails at podcasts at Mack fab.com. Also, check out that slack channel. Stevens give me a thumbs up. If you have not subscribed to the podcast yet. Click that subscribe button. That way you get the latest map episode right when it releases and please review us wherever you listen as it helps the show. stay visible. helps new listeners. Join our Slack channel. Ooh, ooh, ah Ooh.