Hi in a video on my Eevee blog 2 channel which I'll link in. uh, just about the background of the bench and everything here. I had a non-sequitur about my aircon unit on the wall here and I'm going to have to actually move this because now it's actually really difficult to reach over my 900 millimeter long bench and it's even further out from the wall. so like a meter out.

I've got to like reach over a meter to turn my aircon off and on all the time. But one of the problems with this damn thing is that I slowly over the last couple of years like I swear when I moved in like a decade ago this thing used to work. you press the on off button. It just worked and that's how it worked in my rented lab.

It had the exact same controller in it, but this one is a pain in the ass. It's been pissing me off for a long time so I'm going to finally do something about it. So let me show you what's actually happening here. When I press the on off button, it doesn't just turn off or on.

Now the only thing I do here is cool down this lab. I never ever heat it up, but it never gets that cold here in inside. I'm in the middle of one of these big high-rise you know, office, uh, tower kind of things and it'll get up to like uh, like 25 degrees in here or something. So I'm always cooling down but never drops below like 20 or 21 even in the middle of winter, it stays.

You know? So I've never, ever in a decade had to use the heating function of this. So I'm always using the cooling mode. So all I want to do is leave it on low fan speed so that you know you might be able to hear it in the background, but it's really hard. you'd really have to amp it up.

Generally when I shoot videos, I'm turning the aircon off just so there's no little aircon noise. uh, bleed. But generally I just have it continuous. low auto mode.

Cool. and that's it. I've got my temperature set to like 21 degrees. like.

there's got a timer thing so it's 22. It thinks it's 22 at the moment, hence why the aircon is running and that's the set temperature so I'll leave it set at that and I just turn it on and off. That's all I want to do. It's not asking much of an air con system, but watch this.

It'll probably make a fool of me. But I you can see it's like water. the silk screen's worn off that. but watch this right.

I pressed it. It went into heat mode. What the? This is an on off button. I swear over the years I've been slowly convincing myself that it's like how hard I press the button, how long I press it.

All sorts of, You know, my mind is coming up with lots of weird, convoluted explanations for what. Oh, there we go. It turned off. That's what I want it to do, right? But I obviously and I can turn it back on.

But there you go. It goes into heat mode. It goes into cool mode, but it's still like continuous and it just doesn't seem like it didn't turn off or on. If I hold it down and then release it, it'll turn off.

But it's not supposed. I don't believe it's supposed to work like that. So anyway, somebody in the previous videos um, said oh, They're pretty sure that these, uh, the keypad on this thing with all the buttons works as a like a ladder divider. basically a resistive divider and that might explain.

uh, you know it could be the contacts could be dodgy. It could be picking up noise from someone like, who knows. You know, there's various things that can go wrong with like, you know, high impedance ladder, uh, dividers like this. So I thought we'd actually take it off the wall because I want to move the damn thing anyway and have a tear down and then just investigate possible fix for this.

or I if I might want to put it back and then I could actually design a secondary. Possibly if I reverse engineer it, design a secondary button which then I could mount uh, somewhere else and wire it in parallel. I assume it's like some sort of I assume like there's a might little micro in there that that communicates via Rs 485, some differential thing. Uh, which goes back to the controller.

So I yeah, I assume that's it. Um, I probably don't want to go to the effort to reverse engineer the Rs23 Rx-485 protocol or whatever it is and do that. but I don't know. Maybe I can like bodge in some remote switch somehow or something.

Anyway, let's take it off the wall, do a tear down. I can't bloody well turn it off. Oh dude, did I swear I pressed it like five times before and it didn't turn. Ah, alright, so it's probably got some bracket thing and it's probably painted onto the wall when I had this paste, plain it and painted when I rented it out.

So usually you've got to break the seal around the paint job. Now it's not going to come off without a fight. I'll get back to you. Totally forgot to show.

Uh yeah, it does have a brand on it. It's an isom uh brand, but I believe the aircon I've got like is an Actron. but doll. It turns out that's a leesum that's an L with like air coming out of it.

Get it, Lease them anyway. um, Australian thing. And yeah, I found a manual for it. So yeah, but that doesn't help me get the damn thing off the wall.

I was able to get the there's a bottom uh like stick on deckle thing which hides the uh zone buttons there. I don't have multiple zones, but I I still cannot get this damn thing off the wall. I know there's clips and there seems to be clips on the bottom, but hang on. I think I got the bastard.

Heard a crack as I don't know if that was an injury from it or not. but uh, it's off. Bloody clips on the bottom. Oem Electronics Proprietary Limited Sydney Australia.

You can see all the hacks I had at it and that's like ah, that's crude as anyway, decent amount of cable ta-da so I'll disconnect that and bring it down to the bench. First of all, I'd better document what's connected to where because all but the black one is damn white. So yeah, I'll put some markers on those. First of all, let's measure the voltage on this thing.

Oh, one handed technique. seven and a half volts. Wow, that's that is surprising. All right.

So here it is. the lesson controls. That's I guess the part number is it interesting to find dips which are controls on here. This is inten interesting.

I like integral uh, Sns which would be sensor 1 here, which was actually connected. so I do. Actually there is a sensor elsewhere in the room, but I've never actually checked at all. if that actually works or whether or not it uses the internal sensor in here.

I don't know. It regulates the temperature, uh, fairly well within. Uh, plus minus half a degree. By the way, I've done temperature logging plots of this thing and it gives, you know, a sawtooth plus minus? You know, like half a degree.

I think we want no zones, so I don't know why zones are set. I'm pretty sure I've only got the one zone here, but anyway, it is set to uh, remote sense so I don't know why the sense one line is connected. That's interesting. I'd probably rather have the integral sense so I might experiment with that heat pump or cool.

um, a lick. I don't know what that is, but uh, yeah, we basically want cool elec. Um, does this thing even heat up at all? I I don't know. uh.

continuous fan or auto continuous fan? Definitely don't want continuous fan. so that's right. Um, a three speed fan it does have. It does seem to have three speeds because it goes through it on the display and it does seem to move a larger volume of air with a different speed.

So there you go anyway. Yeah, as I said, I was wrong about the Um differential pair Rs-485 We've got common power, which as you saw, 17.5 volts. so there's probably just like a 12-volt linear reg on here or something. and then there'll be a 5 volt linear reg for the micro because these things don't take much power so you don't need any of that switchy regulator rubbish.

Um, and the Ox line is obviously what's sending the back, So or is it a, uh, just a resistor ladder line from the power as the Youtube commenter suggested. But anyway, I've got some kind of cutouts in here for these electrolytic caps and a big whopping power resistor up there. That's because, well, they just couldn't fit in because the part of the case, yeah, it's curved down there, so I you know to get the nice curvy look, they've had to, uh, cut away the Pcb and then, um, yeah, none of that surface mount rubbish. So it's you know.

it's clearly an old design, you know, probably dates from like the 80s or something. Anyway, let's get this Pcb out. It just seems to claw. No, there's two screws there.

Ah, there we go, Got it. That's rather neat. I like that, uh, exposed pad fingers there? They've got the, uh, solder coat finish. let's flip it over.

and they just got the nuts. Oh, I've got to keep those square. I know they'd Actually, that's what the molding's for. It's pretty much what I expected.

a micro, few miscellaneous bits and bobs, and it looks like, uh, that a rechargeable battery down there because you wouldn't have a fixed, uh, Lithium in something like this, would you? I don't know. it could last forever. Anyway, that's for the real time clock because this thing does have a timer and you can see right up there. Geez, that's a weird layout, isn't it? I mean, you know you've got your real-time clock chip, that's your 32.768 Kilohertz crystal and up.

and your batteries all the way down there. So yeah, that wasn't good. Uh, planning on your Pcb layout point of view. There you go.

That's a bit of a surprise. We've got ourselves an St. Micro in here and I would have maybe expected an old school pick. or you know, like a Motorola part or something like that.

but an St, uh, 72c, 334 part of that uh series. So here's the data sheet for that. But uh yeah, it's just a general purpose eight bit, uh, micro design, fab, near so. Yeah, that's uh, well, and truly obsolete.

You can't really, uh, get that from any mainstream suppliers. Now you'd have to beg borrow. steal one of those from the gray market if you wanted to, uh, replace them. So you know they probably bought up, uh, all the stock they could.

You know, you buy like 10 000 of them. That'll do you for the next 20 years or whatever. But yeah, anyway, N is just an 8-bit uh, micro and looks like we have some, uh, we've got some lead drivers here. What are they? Oh, they're Uln 2003, Uh.

transistor arrays. old school. So uh. you no doubt saw on the video you probably would have seen the multiplexing of the lead.

So they're um, they're doing all of the visual. Uh, like the indicator Leds. Plus the seven segment displays are all part of the same uh, big ass matrix. There switches.

This micro. uh, like. this is obviously a switch array so it's all going into the mic. Well, I don't know.

I don't actually, until I trace it out. I don't know for sure, but I might trace out the sense line down to branches off there. thank you very much. Uh, but it goes down here.

It goes down here. Aha sense. There you go. That's the, um, that's a thermistor.

There's your temperature sensor. So yeah. I like. I suspect that the micro on here is not doing anything.

it's just an interface to, uh, you know, switches and the lead display and everything to tell the Aircon controller which will be up in my roof. Here that'll be the Actron Airtron Aircon controller. Yeah, so it might say oh, remote sense. But the remote sense might actually be on here.

so I don't think that the micro is actually sensing the temperature. Well, no, it does branch off, doesn't it? Maybe it does. Oh god, it goes under a switch. there.

Those two chippies down in there, which it seems to go down to. That one looks like it's a little uh, St Op amp and uh, this one is a you classic 393 dual comparator. So yeah, it looks like maybe it does go down to there somewhere. So maybe.

And as I suspected, that's a linear 5 volt regulator. But that's what the resistor's there for. It's just a dropper. It's just a dropper.

That's it from the 17.5 volt rail. Old school. Now that's switching rubbish. And what's that? Is that? Another five volt reg.

one for digital, one for the analog matrix? maybe? Anyway, Uh, first thing is the Uh switches. I thought like that might have been like a rubber membrane type thing, but it's not. That's a genuine tactile. So really, I wouldn't expect that to wear out.

It's not like this has had like a million operations or anything. I do have a genuine fault in that, like an intermittent contact in that tactile switch be. I was hoping that it would be that and that it would, uh, you know, I might be able to like re-silver the bottom of the contacts or uh, something like that on the rubber baby buggy bumper membrane. But no, it's a that's a real tactile switch.

It still seems to have its tactile feel, so I I'll measure that. though. I will actually get the meter on there and make sure it just goes zero. And it's not just dodgy.

Ohms. Okay, we've got 14.2 k there. That does indicate that, uh, it could be the resistor ladder, but let's just oh oh, I'm pressing that. Oh yeah yeah, it's a bit.

That's switch. Yeah, that's that's dodgy Brothers. Three Ohms. One arm.

Oh, when I move, I'm rotating that. pivoting that side to side. Oh yeah, that switch is dodgy. It's dodgy as wow.

A tactile switch 96. Ohms 75. Ohms for a tactile switch. Ah, who would have thought? There you go.

That's a repair right there. We know we're not chicken dinner. I think that's like a joystick. We've invented a joystick.

Um, yeah. the world's Uh yeah. The Clayton's joystick. Wow.

That right there is complete Dodgy Brothers. So uh yeah. I'm not sure I have. Or maybe I might have to look through my old boards.

This is why you keep like scrap boards and stuff. Maybe I might find something similar because the shaft length is going to matter. Um, because it's got to come through the button like this. and then it's got to push onto that.

So it's not like I have a stock of tactile buttons. I have to look through old projects and stuff like that. And therein lies the uh, the the dilemma. Do you store your parts based on project? Which I do a lot of the time? Well, I've probably got half half half my stafford.

You know, switches like this. I would have like a project box containing just parts for a specific project that I was working on. You know, because if you want to pick up the project again, then all the parts are there. Or your stuff or your boards or your development.

Whatever for it. Uh, is all there in in that one box? ready to go, ready to get back into it. If you don't ever want to work on those projects anymore, you can say, well, it's you're better off putting those into like a generic opponent bin um, labeled Smd switches. But you know how often do I need a to get an Smd switch? Not very often.

All right. So what I've done now is, uh, hooked up the probes to the common terminal and ground it's supposed to go to. There you go. let's try another button.

13.1 13.3 13.6 You seen a pattern nine. I had like eight. Ah, these contacts are dodgy down here. by the way.

get the idea that yeah, this seems to be Youtube commented It was right that this is some sort of divider array, but you mentioned voltages go down to zero. But pressing these buttons does affect the Ox line, so that's in it. So it shows that that Aux line is not like you know, some sort of digital output coming from the micro or anything like that. It's analogy to do with the buttons, which is really interesting.

Unfortunately, here's where Murphy gets you every time you try and trace this out. This comes across to this via here. goes down, drops under there, which then goes under a damn switch so it doesn't go there. I guess I could trace that that resistor there with the Ox line.

Yeah, that's right there you go. This is how we start tracing this out, but I I'm not going to do a full reverse engineer of this. Jeez, it does seem that's connected through a 10k resistor. Well, there's two 10k resistors here, but I believe they go over to.

yeah, this pin the micro over here. So the Ox line is. is that like? I don't think that's a pull up. Now the other side of that is not a pull-up I'm just using a bipod.

that would almost certainly be the bypass cap for the chip down there. so it's not pulling up to the micro rail. So yeah, there you go. So they got that pin through a 10k to the Ox over here.

But where else is it going? Um, okay. I did find out that uh, one of these 10ks does go down to ground here. So the Ox line is actually 10k to ground. and you can.

I can show you that over here. There you go. 10k to ground and then the other side of that. Um, Well, exactly.

Well, there you go. It's exactly that. 14.2 which is varied by the buttons there. So that's the five volt rail.

that's between Ox and Five Volt rail there. So hmm. it does have a built-in Adc. So uh, yeah.

I guess there. I presume that they're not doing a switching matrix here, but they're um, yeah, reading the analog voltage from there and that would make sense if this is giving you a dicky contact. Uh, then you would expect that you know the voltage would be all edge up and all over the place and it could be sensing incorrect things And that's what I'm actually experiencing. I've been experiencing over the years.

Is this thing just? you know, just mucking around not being consistent at all? And of course, uh, if this was just your regular switch matrix then the really? the dicky contact on this wouldn't really matter Because it'd be. You know it doesn't matter whether it's a couple of hundred ohms or zero or one ohm five ohms. Whatever it is doesn't really matter. It should read, it should either register or not on your key matrix.

Um, so yeah, obviously they're doing this as like an analog uh sense thing. So I don't think that the analog sense is going directly to the ox. Let's say it's going into the micro And anyway, I think what we need to do is hook this thing back up and actually put a scope on the ox pin and see what's happening. Now before you go probing anything like this, you don't want to assume that the ground wire on there that black one is a mains earth referenced.

If you do and it's not, then you can come a gutsy because I've done a video how to not to blow up your oscilloscope about ground earth referencing and stuff like that. So before you do that, you can either just use your we'll talk about this in a minute, high voltage differential probe like this which it makes it safe or you can actually check it so I'm just going to check that now to see what's what. So I'm just going to. I know this is Mains Earth Reference to down here and that's the measurement thing we're using.

or you could use like your portable scope or whatever. But anyway, let's let's have a squares put your tongue at the right angle. Yep, that's Mains Earth Reference. So it's got Zero.

Why is it absolute zero? A little bit interesting that it had absolute Zero there. so I'm gonna see if I can measure any voltage on that. No, there's no Ac voltage that is genuinely connected. Yep, there we go.

And I double checked, uh, that with my Bm235 and sure enough, yep, it's zero point. You know this one has an extra Uh digit. This is the new Bmr 786, hopefully to be say available very shortly 0.04 but maybe there's like a little bit of residual voltage on there due to like the ground going from the air con unit uh, through to the Uh scope here and that's maybe just causing it to offset a little bit. That's sort of to be expected when you start introducing uh, and even very minute voltages into a um, a pretty precision measurement thing like the Ohms range on a multimeter sprint so we could hook our scope probe straight up.

Oh, that's a bit of a bummer because I wanted to use um, the new mix Egg and Dp1 triple Or7 and this is a new model which uh, they designed at my request because I wanted a times 10 at times 101. They've got others in this Dp 10000 series that have a different divider ratios, but I wanted one to match my Hvp-70 Pro: a potentially lower cost option. Uh, for that, have I got to fully test this one But everyone says you know it's a pretty decent performer and it's lower cost than the Hvp 70. so I might eventually carry this on the Eev blog store.

That's the plan. but yeah, um, they specifically made this to my Uh request. like took them like six or nine months and they eventually um said yep. we can do a times 10 times 100 design so you should see the Uh specs of this match almost precisely the Hvp70 except it's made.

it's a little bit wider bandwidth but otherwise very similar specs all round. Anyway, I'm probing the Ox line there and aha if we single shot capture that, look at that so that's you know it's got some ripply doodah on there and periodically, is that going to be a 50 Hertz thing? Oh no. 515 Hertz. There you go.

That's interesting. Like it's doing some sort of periodic scanning or something like that. Perhaps I can't get a consistent trigger on that. So aha, at a longer ah, it's packet based.

There you go. It's packet based trap for young when. Basically, if you see and otherwise periodics, you know if you're zoomed in like this. If you see like, what what you think, you know.

You do single shot capture like that and this looks periodic if you zoom out like this. This is just a how to use a scope thing. and it appears periodic like that. But you've got your trigger level set to where you think it should trigger from.

And if you actually put your scope into run mode and it doesn't trigger like that at the trigger level you thought it does either above or below like that, then obviously it's got. it's not completely periodic. So then you know to zoom out. and aha, of course it's a packet based thing.

At there you go. 2.7 odd Hertz, something like that. And there's a tool. There's a packet on there, whether or not it's like an actual packet, Whether it's supposed to do that or whether or not.

that's just I don't know. some noise pick up on the line. I like have no idea the aircon is not actually working at the moment. So anyway, let me switch it on and see if you can see a difference.

Okay here we go. Big Power button. No. did you see anything in that? Let me press it again.

It's gone. That's not analog level. It's so yeah. It seems to be doing some packety-based thing there I like.

Yeah, I don't. You know. it's kind of not what you expect, is it? I don't know if anyone's got any details about this. You know if you're into this, uh, Aircon control, Aircon market, Aircon controllers, and stuff like that.

So the youtube commenter uh, Stephen G, um, I'm not sure where he's getting his voltages uh, from. But yeah, here's his uh post where he says yeah, like the voltages, uh when you press the buttons and that, uh, makes sense from a point of view of that uh, it was possibly confusing my on off button because it's down. it's supposed to be like zero volts. but where's he actually measuring that from? I don't know.

I'd have to do more. It's it's certainly not on the Ox line that's for sure because this is the Ox line here. So yeah, um, but it does make sense in that uh, it could be confusing the on off button with a because it's You know you saw the dodgy resistance there, causing a problem, a conflict with the next one up the threshold level, which was the uh, heat cool thing. So that's why it was sort of like jumping into heat or cool mode randomly when I tried to turn the offer on.

So that makes sense. Okay, so the way we can trigger on this is our pet looks like every uh, 500 milliseconds. So I'm going to change my told off time here to uh oh. it's all over the shop.

Oh geez, that's a that's jumping around. Oh anyway, let's set it to like. You know, I don't know. 400 milliseconds or something like that.

There you go. We should be able to trigger off that fairly reliably. Where's my trigger point? Yep, there you go. So I'm sure I've done videos on this.

So what happens is after the trigger, it waits another 400 milliseconds before it arms the triggering system again. so that, yeah, it'll arm within that dead period. It'll re-arm about there something like that, and then it'll capture the next packet. So that's how we can reliably trigger on that.

So there you go. Okay, now watch that. I am going to turn the on off button. Oh oh, is that changed? Oh way hello.

Press it again. No. So it's changing. It's certainly changing you can see.

Is it back on? Oh god. I can't see it because it's back to panels back to front. Ah okay, that's all that's our aircon on. That's aircon completely off.

So that's completely off. So we've got all pulses there. so air con and now it's on auto cooling. So what I'm going to guess here is that maybe it just continuously sends out the last button that was pressed.

Perhaps. and then the different combinations are what you see here. I, I don't know. Leave it in the comments down below.

if you've got a better idea of what's going on here, but that that seems to be the case because this is just repeating repeating, i'm not Touching These buttons This is just like this code just changes and stays changed every time you press a button. So let me go off again and hopefully we'll get all of them back again. Okay, yep, it's off. And yep, we get all of them back.

so that seems consistent. So I think we're on to something there. so it seems to be just transmitting. yeah, it over and over again.

The last key that was pressed and then the controller that it's going to the aircon controller knows. Well, you know, I'm not going to do that again because you've already pressed that button. But oh okay right now. So the micro right? because the on off button is the same for both on and off.

so it needs to know that you've pressed it again. So when you turn it on, it switches to another mode. so it's not outputting what key. it's outputting the last key and mode something like that.

It's a bit how you're doing. It's not what I was, uh, expecting, so it doesn't look like it'd be something easy to sort of like. build another controller to do it. You have to spend a bit of time reverse engineering this and figure it all out.

It's there. It's certainly not that uh, voltage level, uh system that uh, Stephen on the comments was uh, alluding to, but that that might be like internal. but that certainly pointed to the switch. So yeah, that uh switch array they probably are using like an Adc internal to the micro to detect the switch.

and that's we're just getting that dodgy switch. So anyway, I think that's enough around with the waveforms there. I think I'll just, uh, go in there and see if I can find a replacement switch and then just get this back up and running at the very least. And if we power it from an external Uh lab supply here, it does actually well.

it powers up, but it just ends up flashing, does a little power on cycle, and then flashes a zone one here. So, and of course, the uh. the power button does absolutely nothing. Um, as you'd expect, because it's got nothing to do with the power of this Uh unit.

It's designed to talk with the Uh with the main controller. so um, unfortunately, I've uh, I've probed the Aux line here and we just get enough All so it's not doing anything. Yeah, it's doing okay. So after it's power on sequence, it, uh, yeah, it's up.

But it's well. no, it's periodically doing something. Is it I need to trigger off that? No, I can't, uh, trigger off anything there. really? Um, on the positive side or on the lower side either.

So getting diddly squat so it's not, it's not doing anything. Yeah, is that uh can signal being actually uh provided by it must be provided by the controller I would assume. And then the Lmr 339 that we saw on here, the dual comparator. That's exactly what you'd need to decode this.

So you just decode it at uh, you know, two different threshold levels that turn it into a digital uh signal. which this thing which the micro can then decode very easily. So yeah, it looks like um, this thing is just a passive slave. It doesn't do anything without the signal being generated uh, by the master controller.

so it seems to just sit at mid-rail there as you saw and then just, uh, pulses up and down. So yeah, it doesn't do us anything. Completely forgot. Oh well, not completely.

because I did eventually remember that I do actually unlabeled. Uh, I really have to label. I do have, um, a thing full of switches, but uh, unfortunately, these are no. hang on.

Maybe maybe I can find one? Oh, that's a bit shorty. Oh, that's super long shaft. Look at that. Oh, that one might do it.

I can always, uh, cut the shaft to length and uh yeah, it might be through-hole but I can fix that. there. Goes successfully chopped off and converted to surface mount. No wackers.

I trim those lead. They're a bit long, but uh yeah. just trim the leads and we're good to go. There you go like I bought one.

from brown to black. no worries. And oh, it's got a nice snappy feel to it. Okay, let's just re-verify that Dodgy Brothers resistance there.

Need the old third hand? Oh yeah. 190 Ohms 170 Ohms. Wow. Can I get it right down? I'm pushing really hard on that.

Oh three. Ohms Two. Ohms. Oh yeah.

Dodgy. Now let's put in our new switch. 14.2 K. Press it and Zero.

Thank you very much. I don't think we're gonna have any more issues that looks pretty darn repeatable to me and give it a little wiggle wiggle wiggle Yeah down the bottom? No, that's all good. All right. let's see if this sucker works Here we go.

One push. Oh nice, clicky, nice clicky and oh beautiful. First go. gotta do it a couple of times.

Where are my poor aircon? Oh, it's flashing. Uh, run. I don't know why flashes run, but yep. Yep.

fixed and there we go. Auto Heat. Cool. Yep.

winner, winner chicken dinner that is fixed. So it was like a switch. I thought maybe it might be like a membrane type thing. Turned out to be a tactile switch.

Usually it's pretty rare that those tactile switches are fail like that. Have seen it before, but it's not something. It's not my initial conclusion that I'd uh, jump to for something like this. And as I said, if this was a range, this was designed as a uh switch matrix in the micro.

As you'd normally do it, you know you'd have a bunch of uh, digital lines for the common, don't bunch of digital lines for the uh rows and then you, uh, multiplex them and you scan you continuously scan the keyboard. It really, it doesn't matter whether or not that switch is a couple hundred ohms, it'd still work. and it wouldn't confuse it with other buttons on there, but that's not how they implement that. So they've implemented obviously using some sort of resistor divider thing.

I don't know we could like reverse engineer this. If anyone actually does have a reverse engineered or a schematic for this thing, please leave it in the comments down below. But yeah, obviously it is what um, Stephen said in the comments, they're obviously trying to do some sort of resistor dividery, uh, type keypad arrangement. I, you know, and trying to read that value.

So that's a dicky design decision that, um, it can come back to bite me. Basically, it's been bugging me for years. I can't believe I put up with it. Um, I think I did actually try to take the thing off the wall before and I just couldn't get the damn thing off.

So I'll bugger it, you know. And so I finally it took a lot of effort to get that off the wall, but yeah, it, was like somehow painted on. It's been on there for like 15 years. It's never been taken off ever since.

Uh, this building was built. probably you know, 17 18 years or something like that. And yet that switch finally come a guts uh and was causing it to like put it into heating and cooling mode and doing also these weird modes like you'd come up with all these convoluted theories. Oh like if I hold it on for a bit longer if I press it twice in a row quickly, it'll do this and that.

But no, it was just there was no method and sometimes you might think oh, it might repeat it a couple of times so you might think you've found something and something else is playing up with it. No, it was just a dodgy switch contact with a a dodgy ass implementation of a keypad matrix. uh, you know, or a keypad. um, input design, sense design and that was just causing different modes.

That's A. That was a real interesting repair. So I'm going to call that a repair video. Actually, it was going to be like a maybe a reverse engineering video.

But anyway, if you've got details about that command system, yeah, please leave it in the comments down below. Got any other info? Please let me know Anyway, hope you found that interesting. If you did, please give it a big well a thumb. There it is foreground thumb.

because I'm zoomed in a lot. Give it a big a thumbs up. And as always you can discuss in the comments down below: Ev blog forum, alternative platforms, all that sort of stuff you know, the deal, ring the subscribe bell and all that Youtubers stuff we say. hope you liked it.

Catch you next time you.