Hi. This is part two in the Macgyver project because nobody could come up with a better name for the project. So I'm gonna stick with the Macgyver project. Um, and I thought we'd actually, uh, power up this uh board the display board that we reverse engineered in part one, linkedin up here and down below if you haven't seen it.

Um, and there are a few questions regarding like actually driving this thing but I thought, like, does it actually work like so we don't want to go through the whole effort of actually designing a circuit to drive this thing, building it up, and then finding, oh, there's something wrong with this. Um, that would really ruin your day. So I thought we'd take the existing board out of here and just hook it up. I mean, we shouldn't need anything else.

I mean, presumably if we power it on, then we're going to get something on here. Um, shouldn't we Mr. Assistant say hi, Well, Mr. Assistant, you missed her assistant.

Hooray! Yay! Sagan's here with me. Hello there he is. Um, yeah. so we're going to power this thing up.

So let's have a look at this interface here. Sagan, let's have a look. What can you see there? What? Zero Volts? 24 24 volts And I don't have no. What am I am? I? uh, that would be.

Uh, that's the milliamp interface. That's the um, four to twenty milliamp current interface I think. And 485 is Rs 485. That's a really old serial protocol.

It's still used though. And 12 volts. I don't think 12 volts is going to be an input. I think that might be an output anyway.

So we've got the got the cable here from the casing and you can see that. Yeah, the 12 volts is this white wire here. But basically, yeah, we've got the Uh. 24 Volts.

Positive and negative. Yeah, so I think what a safe bet is just to connect up the 24 volts and see what happens. See what happens? See if the magic smoke escapes. What do you think? Sagan.

So um, up here is the So that's the interface board there. And uh yeah, we've got 0 24 volts and there's no 12 volts here. I don't see it. I'm not blind.

Am I saying there's no 12 volts there. There's the Uh 4 to 20 milliamp output. But so yeah, I reckon that 12 volts, it's an output. So that thing and that I reckon it's an output for something else, I don't know.

Go somewhere else internally. Maybe. Um, so let's hook up Zero and 24 volts and see what's what. So is our power supply turned off on Channel two? No, it's not there.

We go. Okay, I'm just going to step back because I don't want to get blown off. You're gonna step back. I don't want to get blown up.

You think the magic smoke's going to escape? Maybe Sagan's not confident. No, he's not confident. All right. Confidence is not high.

Ok, so 24 Volts. So we want to program that. So say again, can you program that for me? He's never used it before. He's never used the Roden Schwartz power supply jobby.

Okay, so well chan, there's a different channel so this is Channel two. so this rep. Yeah yeah yeah, it's Channel Two up there. so it is touchy feely screen.

so we wanna set the voltage to 24 volts. So click here. Yeah, there you go. 24 volts, not millivolts.

Oh oh, it did okay. It defaulted to volts. Okay, cool. So current wise I reckon this whole board is pretty.

You know, like I don't know. a couple hundred milliamps? it's already set to 2.25 amps, 250 milliamps. That sounds good. All right.

Have we got the probes around the right way? Red goes to positive. Blue is negative. That's a weird European thing if they use blue in Europe. For some reason I don't get it.

But anyway, um, all right, let's power it up and see and see if it does anything. Okay, please don't blow up. Well the good thing is is that we've current limited the power supply sagan so it won't block it. It's not going to do much.

There's not much power behind it there to actually do much. So let's I don't think there's any indicator Leds on there. Can you see any Sagan? Can you see any leads on that board? little surface mount leads or anything. I didn't see any.

I don't see any either. No, so you won't know if it's powered on or not. Well, no. we will know by the current drawer up here so you can read that out as we power it on.

Okay, uh. switch it on. You want to press the Channel Two button? Zero points. Yep.

Zero amps? Yeah, nothing. Zip. Yeah, it's not drawing any current at all. Um, okay.

Oh, maybe like it's got a fuse blown or something. Measure the fuse. Sagan, Let's see what we get. Yeah, that's intact.

No worries. Squeeze that sucker. There we go. 0.1 Ohms, right.

So our fuse is intact. So uh. all right, it's not that. why else would this not work.

Uh, maybe the Um connectors faulty? Maybe we didn't plug in properly? That's all I can think of. Yeah, did I? I can't remember when I tore this down. I put the board back in. Maybe I didn't connect it.

Something dumb like that screw turn. I remember they had screw terminals on the bottom. Okay, so what we want to do say again is we want to buzz out. So put it on continuity mode.

Yeah, there we go. Yep, buzzer. Make sure that make sure it buzzes. There we go.

It buzzes all right. Uh, we want to probe. Oh, take one and you take the other. I want to turn in contact.

Uh yeah. we're measuring continuity to the black wire down here. Yep, Yep. Positive.

Uh. the red one do the same for the red one Yeah, you probably have to get to this side. They're pesky. Those connectors.

Oh, there we go. All right. So we're getting 24 volt. We will definitely be getting 24 volts on our board.

So turn the power supply back on. We do like output. Daddy's so dumb. I'm sorry we didn't click out output.

Press the output button please. Okay, hey, look, look look here it is. It showed all lights. it shot I think you captured that on camera.

It showed all eights and then it showed all decimal and turned off and on again saying yeah, it shows all eights. geez, that's pretty bright and 40db. 40db? Um, Four Zero dot Db? Yeah, 40db. I assume 40 db is the like power setting for the measurement of the ultrasonic sensor.

Um, they've got it in Db. I don't know why else you'd have Db and we've got a flashy Led there, but that's pretty bright. That display is pretty bright. so they're running those segments at a uh, you know, fairly juicy current.

And by the way, um, in the previous video, we came to the conclusion that they're probably multiplex in this and they're probably multiplexing each individual segment because you can see turn it off and on again. Sagan. Hang on. Uh, okay, yeah.

Go. You can see that's a consistent brightness between having all lights on and not having all of them on. So it looks like I reckon that they're actually multiplexing every single segment. so not just an individual display.

So they're uh, multiplexing, you know? So then you would have a set amount of current in each segment. but then you've got a multiplex. Um, you know, 40 different segments. Which is a lot.

Um, but that's how they. That's how they're doing it. And as we said, they didn't have a dropper resistor. But meh.

you know. Um, So there there you go. So it works. It's basically sending the same signal strength across each one of the segments.

Yes, from the one energy source, the same current split, then puts it into each segment. Yep, Well, it multiplexes. Yep. So it turns on one segment at a time.

But it's doing it so fast. It's doing it so fast that you can't see it. But each one of those segments is turning on. um, at least 40 times per second.

At least. Let's just probe some stuff for fun. Uh, let me find a ground point. There we go.

That's a ground point. It's very convenient so I'll hook that up to there and we can probe around because you don't want to hook uh, your crocodile clip up to the pin headers because you can short out the other pins trap for young players. Okay, so we've got our pin out here and uh, let's have a look at the clock. and well, the clock.

Let's have a look how fast that's going. One, two, three, four. and let's have a look here. Sagan, What do we have here? We've got five packets here.

Why do you think we've got five packets? Because there's um, five digits and each and each line going up and down would mean that one digit's turning on and off Correct. And then of course, there'd be different, even smaller segments inside those lines. Yeah, which would be each one of the little, um, count, how many how many pulses we got in one of those one of those packets. Just maybe.

the bottom one's easy. One two three four, five, six, seven, eight, eight eight. What a convenience. Um, what a coincidence.

How many digits have we got in each? Oh, how many segments have we got in each digit? That's exactly what we expect to see and you can see. Um, they don't update this often. So whoa. Hang on.

Well, there we go. Every two divisions, we're at 10 milliseconds per division. So how much time between each one? Say again, 10 milliseconds Sorry. 20 minutes.

20 milliseconds total. So 20 milliseconds they turn on. Um, they update. Um, or they clock the information into the Led display there.

No workers and these, uh yeah, we just got ringing on the bottom. The reason we got horrible ringing down there is because of my, uh, in inductive um, lead here. It's not great, so yeah, it's a bit how you're doing, but you can see the signal so no worries. So that's our clock.

And then our data is the pin next to it and it's more randomy. Oh, hang on. is the trigger level that's all over the shop? Isn't it? That's everywhere? Yeah, Wow. So they're really so we can single shot capture that? if we just single shot capture it a couple of times.

Oh, hang on. I've got to put it back in the middle. There we go. There we go.

It changes. It'll change a few times because we've got different displays. So depending on which one we actually, um, just happen to trigger off, it displays that. So there you have it, that that is random.

Wow. Okay, so our data's going in every 100 microseconds because we're 50 microseconds per division. So every 100 microseconds we're getting data. What did we say before on the clock? Uh, 10, 10, 20 milliseconds? Was it every 20? It was Millie or Micro? It was Milly.

It was Milly, wasn't it? Yeah. So our data is updating like way more frequently. 20 times, 100 times as fast. Wow.

Something like that. That's it's. almost constant. The data is almost constant, but the clock is not the clock.

If you feed in the data, it's not going to do anything unless you clock it through. Here It is down here. you can feed in all the data you want until the cows come home. But if you don't clock it through, then it doesn't go through, the shift register to drive the display.

Exactly what I said. So that's interesting. You can put as much data in as you want, but you won't get out and until you clock it until you clock it. that is interesting.

Why are they bothering to update the information like that? So there is the clock. and there is your data. there. It is there.

So wow. Big difference. They're just wasting their time. Like literally.

Okay, so again, I'm gonna probe this sucker. Ah, there's our data. There's our clock I need you to press. Oh, hang on.

Whoa. Single. uh. it's run.

Stop. Yep. Go. We captured it.

There we go. So we now have a time correlated signal between there. There you go. So they're feeding in.

They're doing the data thing there. So there you go. down the bottom of the clock, data's down, the bottom, clocks up the top. You can tell it's clocked because it's all periodic.

There you go and you can see that they're feeding in. Uh well, we can. Actually we can actually have a look here. So now let's try and decode these displays.

Sagan One of the displays here only has looks like one of the bits turned on. Is that correct? One of the I know, hang on one other one. It's only got one of the segments turned on. Which display has one of the segments turned on? Surprise.

surprise that one. So that maps over to there Like that. Sagan's probably not following this because he hasn't watched my previous video. Well, actually, I was going to this morning because I do check his subscribers.

You do. Oh, he's one. You're one of my subscribers, one of my valued subscribers. Thank you.

But you're not on the forum though. No, no, because I've got a school laptop and like they don't allow that, right? Yeah, yeah. Anyway, I have to talk to him about that. Okay, let's see if we can correlate this.

You remember in the previous video how data shifted in over here on this chip here. Okay, so that would actually so it's got to shift in first. but it is basically the last to come out. this one with our single digit there.

We just so happen to capture it when that uh, little flashing, uh, decimal point is turned on. Okay, so that one is actually where out controlled by this chip, which is where our data is first shifted in. So what happens is is the first one to shift in over here has to be the last digit over here. Okay, so so the first data that goes in here has to be shifted all the way over to here.

So that data there ends up in this chip here. It's even correlated u1, u2, u3, u4, u5, and u2 U3. It directly maps over like that. And here, have we got two segments turned on? Or is It more? It depends on you'd have to go in here? No.

So a second one. It looks like we've got one, two, three, four digits on. So our second display has got four digits. one, two, three.

That's digits. I keep getting the terminology confused. segments, segments. It's got four segments turned on and that correlates perfectly with that over there.

Doesn't it say again? Yeah, surprise, surprise. What a cleansing sentence. Engineering's always amazing coincidences like that. Wow.

Well done, dude. All right. I've now learned nothing is a coincidence. Nothing is a coincidence in engineering.

That's right. everything happens for a reason. Call it faith, Call it lock. Call it karma.

I believe that everything happens for a reason. Look, there's just data going in, data going in willy-nilly and there's a dead period here. Then they've got a little flurry of data here. What? why? I mean, this data is useless to even generate it if you're not clocking it through.

So that's I don't know. Um, that's just an artifact of the state machine that they're using inside. I'm sure it's the actual uh, pld here that makes would it be? I don't know. They have to trace it out Actually, whether or not I assume it's coming from the Xilinx Cpld here.

Um, that was. I think most people's theory was that it was that and not the microcontroller. So can you come up with any other reason? Sagan? Any theory why they're bothering to clock the data in here? Other than that, I just think it's a just artifact of the state machine. It just keeps doing its thing.

And I don't know. Think of any other reason. No, I've only got two sides. Okay, two sides.

what. Side one: The technical technical side of my brain says i've got absolutely no idea. Yeah, Side two: Told my brain says it's data running free. Oh, data run.

it's just free running data. Free range data. Yeah, okay, it's free range data. That's that's A.

Yep, Yep. Free range data. There you go. It's probably organic.

I think it's organic. Free range data. We'll call that. Yeah.

Okay, there you go Security. New terminology invented by Sagan. Uh, free range data. So there you go.

the segment current. I'm not going to tap in there and try and generally get the oh no, no yeah. we didn't even have a series resistor. did we So like I'd have to like Bodge in a series resistor somewhere if we wanted to actually see the current consumption.

I mean, the entire board, if you're interested, is taking 100 milliamps at 24 volts fair amount, you know, 2.4 watts. Geez, that's you know. But uh yeah, we don't care about the segment current. So yeah, we do know that they're uh, shifting in the data like that.

Although we, uh, no, we haven't uh correlated the blanking line as well. Oh, we've got a ah, we need three hands to probe this thing to get the blanket in line. Should we go to the efforts again, Probe? What is it? Probe's already up. Oh, you have to close that.

Okay, so all we've got really is the lead. Um, drive like that. So let's probe that, see if we can see anything. I'm gonna have to do this.

Three hands? Okay, there's a clock There you go. I can do this so I can do this and pin eight. Yeah, okay. Press stop.

Okay, so what we've got here is all this stuff in here is just noise. It's just, uh, because we're not probing. You know, it's just picking up. Um, just rubbish from here.

So we ignore that. But it is. You can see that it's uh, it's grounded down here. So this is the display period.

So it's on. So it's on during this period. And then when it goes high like this, this is, uh, 500 millivolts per division. There you go.

And then during this period, it's actually blanking. So let's go to a wider. We're gonna have to re do this. Sagan.

Let's go out like that and hold the tongue at the right angle and go. There we go. Okay, now. hopefully we've got enough memory depth to see that there.

Yep, Okay, so yeah, only Durant. So it blanks it. It blanks it during the period that it's updating the display. Otherwise, you'd see all the data turning off and on.

Well, real quick. You probably wouldn't see it, but you get flicker on the display, so they're effectively turning that off there. So it stays on for 20 milliseconds. So it updates the display almost every 20 milliseconds.

I think it's a smidge over 21 milliseconds rounded to 20 milliseconds. Um, which it keeps the information on and then updates it. So it just updates the display every 20 milliseconds. No.

If they're leaving it on all the time, then they're not multiplexing the individual segments. That would mean that they're not doing that. Which just changes the whole perspective of this. It does.

Doesn't it say Again, It changes. It changes everything. Um, multiplex. Because yeah, so that, um, common collector output is low.

Which means that you know if you're getting the one, the onesie data out here. If you're getting the ones out of your chip which turns the segment on, then it's going to switch those on. So they're not actually multiplexing this thing. It's just nuts.

And of course they're They're shift registers, so once you've shifted, that data in, the data is going to stay on the output here. If you feed out the ones to this out out of this chip, then they're going to stay on. And as long as that common collector's low, then it's going to source current through all of those. So it looks like they're not multiplexing this thing at at all.

They're not doing individual segments, they're actually turning on all of the displays. But we didn't really see any brightness change. Did we say again? Although the eye is incredibly good at compensating, um, for brightness changes, it's the eye is one of the most amazing high dynamic range things in the world. The eye is amazing.

You can kind of stare at the sun, kind of. sorta not really. But and then you can see right down in the dark and it gains things up. and it's It's really amazing.

So yeah, um, the eye is very adaptive. I think it's got 10 orders or something of dynamic, right? And it's got massive a massive dynamic range. It's got more than 40 db. The I has more than 40 db of dynamic range.

I can tell you that for nothing. Um, so yeah. I it doesn't look like it's multiplexing that. So there you have it, Sagan.

But guess what? what? I'm multiplexing it from a certain point from a certain point of view. Sagan's always thrown in Star Wars references. so what they're doing is uh, yeah. like I don't recommend you drive your displays like this.

So what they're relying on is the Rds on of the Hc-161 driver in here because there's no dropper resistors at all. so well there is effectively inside the chip the Rds on of the output mosfet. They're reliant on that to drop the current for each segment here. so I think they have to be driving this at a really low voltage.

So let's actually have a squeeze at the Uh at the voltage. So looking at pin Two here, it's got to be low. Um, so Well, actually one Ri Tx that? that's one of the Vcc inputs. What's pin One? That's 12 volts? Okay, they're definitely not.

The Hc only goes up to six, so it's definitely got to be 3.3 or under be my guess. Wha? 1.95 Um, uh. Technically, that's actually under the minimum spec, isn't it? For a 74 Hc, it'll go down to 2 volts. It's actually 1.95 Oh my goodness, It's just.

oh. the pause. The poor thing. Let's actually disconnect the display, right? So it's drawing.

No. So it's drawing no current and see what that voltage rail goes to. Oh, see if it's actually a solid two volts or whether or not it's just dropped? Yeah, there it is. They're supplying a solid two volts.

So they're They're as well. You know? So yeah, I think they've They've deliberately tried to set it for two volts, which is the absolute minimum required for the Uh 74 Hc series logic to work. So they get that's how they're getting away with this without dropper resistors and the high brightness. So, and I know there's people in the comments, it'll go.

Oh yeah, that's pretty clever. Um, okay, yeah. Maybe if you would like if you really couldn't afford those dropper resistors and you had to have a high brightness display and you were light and so you'd rely on the Um Rds on of the Hc output driver the upper mosfet in there driving it. Yeah, nah, but they're getting away with it and that's how they're doing it.

They're driving it at a fixed 2 volt. so there's got to be a 2 volt rail on here somewhere. So yeah, for this sort of like high certification environment where this thing's being used like in potentially explosive atmospheres and stuff, they go to all the effort to like engineer cases with these O-rings and everything and the extra penetration depth on the case and everything when they join together to stop the explosions coming out and igniting the atmosphere and all that and all the regulations that goes involved that's involved in getting that and they drive the displays like that. Um, yeah.

okay, just why can't you just put the dropper resistors in? I mean, if I was like, like analyzing this design for certification, I don't know if it's like part of the standard. Maybe they're just not looking at that sort of thing. but I'd go. how are you limiting your current in your leads? Oh, you've got no current limiter.

Fail there. You go Right on the chip. Yeah. 1.5 1.95 Right on the chip.

So that's how they're doing it. Technically, that's under spec. So there you go. That was, certainly, uh, unexpected.

I expected to see a individual segment multiplex display, but I guess they've done I'd something better that allows them to have a more, uh, you know, a better clearer display because that is pretty bright. You know, I don't know the actual output of that. I got no real easy way to measure that, but it is. You know, pretty bright even with my lab lights on here.

Um, so yeah, I'm sure that is. you know, reasonably outdoor readable, which is what you need this thing because it's using an outdoor environment and that's how they're doing it. And that's how of course we can do this. Uh, to drive this board.

we can simply have a two-volt rail as well. Um, why not let's duplicate what they do. Although everyone will complain. Ah, Dave is showing bad design practice.

Well, you know it's not me just copying banshee. So yeah, we have uh, two options. There One is to do exactly the same as what they're doing is just like shifting the data. Uh, like, uh, normal.

and uh, you know, just like have it displayed on. Just update it periodically like they're updating every 20 milliseconds with it. Like you don't even have to update the display that quickly. You can just leave it on all the time.

You can update it once per second or whatever. And and the free range data of course, new industry term there it is free range data. That's for when you send in data that can't possibly be used. Um, because you're not clocking it so it's just free range.

Or yep, we could, uh, just enjoy the sucker at two Volts and it's terrible. Muriel. But you know, I can't say I haven't done it when I was a kid. You know.

Geez, come on, put your dropper resistors in. But anyway, yeah, we can certainly drive this sucker at two volts. But then, if you want to drive it from other logic, yeah, you might need like a level translator or something like that, depending on what you're doing. Oh, and I just realized that, uh yeah.

one volt per division? The data is only two volts. I didn't actually notice that before. So whatever chip on this board is driving that. um, it's also running at two volts as well.

Or is there a like a level translator on there? Now I have to inspect the board a bit more. This is just like. this has nothing to do with the actual project. So sorry for taking you know, another 30 minutes.

But uh yeah, this is just interesting. So that's the actual segment voltage that we're dropping 1.65 I assume it's going to be like, you know, they're going to be all reasonably matched. You know, kind of. Sort of.

So there you have it. That's a rather interesting part too, so I think we'll leave it at that. Uh yeah, we can just, um, drive this thing. We don't have to go because it's more complicated to drive this thing.

like multiplex each individual segment. It's much easier. like, from a software point of view to actually just drive this thing the way they did it there. Um, that's much simpler and then just, yeah, um, supply two volts and bob's your uncle.

Um, and it looks like you can get away with it and that's what they're doing here and we could get away with that as well. Anyway, well, it depends. Um, because you know we want this thing to be battery powered. So yeah, well, that's the thing.

I don't know. I maybe in another video I'm going to have to measure how much power consumption this all takes and I won't do it in this video. measure individual segment currents and stuff like that. So yeah, if we do want to reuse this, um, it's not the best thing because uh, yeah, it may just draw too much, uh, battery power.

If you want to like, have the display on all the time and power from an internal battery, that might be troublesome. So anyway, hope you enjoyed the video. Found it interesting if you did give it a big thumbs up. As always comments and suggestions down below for the Macgyver project here and I'll catch you next time you.