Hi, it's time for part three in the Nixie Tube Display Driver project and we're onto the schematic now. But just a before we get into the schematic, we'll just go back and look at the drivers that we were going to use now. I was going to actually go with a UL N 2 double O 3 Darlington transistor driver with the Zener diode clamp as I mentioned in the previous video and then maybe some Sim 4 HC 5 9 5 s shift registers common as mud to drive those instead of the yup microchip solution like single chip type solution and interestingly, I was actually our part way through laying out that schematic when I went to the forum and somebody mentioned a chip that I'd actually done that back in the first video and I she actually shot a clip of it but I didn't and ultimately I didn't include it in the Edit because it was, you know? edit was already too long and everything but I had looked at this chip because I thought it was quite interesting but it didn't have the required voltage or so I thought. But somebody pointed out that this chip actually has internal clamping and it's suitable.

So I took another look at this thing and sure enough, so we're going to have a look at the 6 C 5 9 V series and these are a pitch shift registers and having 5 9 5 on the end Hey you may recognize that right? the 74 HC 595 the common is Mud very useful jellybean latched shift register which everyone seems to use and everyone I've been using them for decades and I was going to probably use it for this project as well I don't know if it's coincidence that they named it 5 9 5 but it works very similar. The front end and in terms of the shift register and the latched part of it is very similar to the semaphore hate C59 5. Anyway, as it turns out, um, this is a fairly jellybean part as well and that's what I liked about it last time is that it's available from TI S, T and n XP in various flavors and things like that various site packages but the standard one s O 16 one which will take get here now it's the TI one is called the T Pick Six C Five Nine five and the NX P one is called the N N Pick Six C Five Nine five but there pin-compatible basically our compatible logic between the two. It's got an eight stager shift register and an 8-bit storage register as well and a serial out which so we can cascade the things and it's got eight open drain outputs as well.

It's a quite a nice little part. it's aerated fans. got the Avalanche energy rated and everything are they assigned seven? Ohms typical all that sort of stuff. 250 ml amp current capability ESD Protection blah blah blah blah blah.

One thing I didn't notice in my first video. otherwise I would have chosen this chip straight away is that it has actually output clamps on it at 33 volts. and let's go down and take a look at this and all. I Saw when I first briefly looked at this thing was the maximum output voltage 33 volts.

but as I said, it's actually a Claire It's got a Zener diode clamps and we can actually go down here and have a look. Now it's logic level while supply voltage a standard 5-volt logic. Now it's high level input voltage. We'll come back to this.

that's going to be a bit troublesome. Null point 8 times VCC or 5 volts so that's going to cause us a bit of an issue, but we can solve that so we'll come back to that. Now if we have a look inside the thing, you'll notice this is a typical of all the drain outputs and you can see that it's got a N channel mosfet in there. Of course this diode is going to be the body diode inside that MOSFET but it's got Zener diode clamping as well, so look at that.

Absolutely brilliant! So we don't need external clamping devices and we've got everything all in the one chip so we can replace a 7, 4, HC 59.5 + au Ln - double O 3 into this one chip and it look it costs as little as 31 cents in 2500 volume. Okay you go down to one volume of one from Digi-key here 73 cents. but you know, hey, that's pretty decent. and they're available in quantity from three different manufacturers.

This is a part that you want to keep in your parts box to use. This should be like a standard jellybean part for any sort of like high-voltage interface and stuff like that. Very, very useful part. and the Mxp version, exactly.

It's basically exactly the same, although its output it's clamping is a little bit different. It doesn't have that extra Zener from the gate down there. Anyway, a slightly different part, but anyway, but I'm slightly leading you up a bit of a garden path here because this output clamping voltage 33 volts is not really going to do the business because unfortunately, if we take our 170 volt supply voltage and we subtract 33, that's going to give us a hundred and thirty seven volts. And if you remember the datasheet for the Ia in 12 B Nixie tube that we did in the part 1 of this video, then it's got an operational range of like 120 volts upwards.

So in theory, um, it's You know you might get some glow from the digits. so we need a higher clamping voltage, so there's probably closer to the 50 volts which I've mentioned before, because if you do 170 minus 50, it gives us that 120 volt datasheet value. But hey, in engineering that's too close. We liked it, like keep some sort of margin in there.

so if the datasheet says 120 volts are minimum that this thing that the Nixie tube will sustain a glow out if we're clamping at 50 volts with 170 volt supply. In theory, the often digits that are supposed to be off could have a faint glow to them. So hey, if we add some margin, assuming we can find a 50 volt clamping device, we could drop our power supply voltage doesn't have to be 170. We can drop it to 160.

For example, with and with a 50 volt clamping voltage, we would get it down to a hundred and ten volts. That should give us a 10 volt margin. That should be nice. So where can we find this same chip with a 50 volt clamping voltage? Well I'm glad you asked.

And as it turns out, these are TP core in pig devices come in different series. We looked at the C series before. while you actually get the B-series you can take a look here. it's the B are the T pick B 5 9 5.

As it turns out, a little bit more expensive, dollar 48 one offers up Australia that's us prices dollar 48 So it's a bit more expensive and it's a 20 pin SOI C package. so a bit bigger than the 5 9 5 package. and if we go in here and have a look, it's actually an identical device. Pretty much it and but it has an output clamp bolt each of 50 volts.

It's 150 milliamps instead of 250 milliamps or whatever, but it's got lower RDS on. But you know it's practically an identical part in every way. Shape and form is just a little bit bigger, little bit more expensive, but that doesn't matter. a 50 volt clamping voltage, so we'll use that one in our solution.

But I think we need to do just one more bench test to see if these digits glow or not with 160 volt supply and 50 volt. Zener diode clamping. A very quick test here. I've got 850 volt Zener Diodes actually got 30 volts and 20 volts in series here, but it'll give a total 50 volt drop across here.

I've got those hooked up to the cathodes here and 170 volt supply. Let's switch it on 22 K source resistor and switch it on. No worries, there's no current draw whatsoever. these aren't It's not switching on whatever.

Go up to 180 and Bingo! We can see that they're just biased on 0.4 for our milliamps their total for all eight of those segments, so you know it just switches on. If we turn it back to 70, it's just still on, so there's a very faint glow there, but it certainly can't start up at that if we turn it to 160. Of course, it's not going to even remain on or switch on at 160 volts with 50 volt clamping on there. So a 50 volt clamping device 160.

volts looks, you know, pretty confident, gives the margin. We're outside of the datasheet value for the minimum operating voltage of the there will this particular display anyway. So, but your mileage may vary with different types of nixies. And just to prove that we can actually switch that on I've just got a shorting link here and I'll just switch on an individual segment.

There we go. switch on number Seven, Zero Eight, and by the way, if we do turn it back up to say, 180 volts there and we get that faint biased glow there and we actually switch a segment on. you can still see probably that we still have that glow inside these things. So, but we can switch them off and on.

and if you switch it to 160 volts there we go. So it proves they've been switched these segments off and on with 50 volt clamping and there's no residual glow in there, so that looks like it'll work a treat. All right. So we've chosen our driver and I know a lot of people will say I wouldn't use the microchip 100 I Do use a discrete transistor solution.

One look, it doesn't matter. Do whatever you want. they're all going to work the same I Just wanted to try out these nice little arty peak devices. Anyway, we've got the T Peak B 595.

Now let's have a look at the schematic here and this is basically pretty much it. Um, so let's check it out. Yes, I'm using out him designer here now of course. I Had to create a Nixie tube symbol here and it's very quick.

It only takes like a minute or two to create your own symbols. No worries. A nice little touch is that it's to embed an image like that just to show that it's an actual mixi. So I just stole that image from the website credit.

Do ever who took that? But you know, just a nice little touch like that to make it look nice, just embed the graphic in there and in Altium in that graphic file is not linked either. There's an option to actually embed that in the component itself so you don't ever lose the file or anything like that. So that's a nice touch. Yes, I've rotated it there and if we have a look at the total schematic here, zoom out.

I've got this on an A3 sheet here and you'll notice that we use precisely 11 of these chips here so we haven't wasted a single output. I Love that Now of course some to drive the mixi to bar display it. Can we can drive it directly? We got our 22 K dropper like we've done in the previous video and we just did the test. Then that's just fine.

but of course the decimal point that has a point 3 milli amp current limit on it. So because it's a physically smaller surface area on the digit decimal point itself, so it can only handle a smaller maximum current, so I've whacked another resistor in series with that I haven't actually measured that so I've just whacked in a value of 100k. I'll tweak that later. Doesn't matter, we're going to put a resistor in there and we've got 11 of these chips total and we didn't waste a single output.

Beautiful! Now as for doing our schematics: I Also had to create my own symbol for the tea pic 6 CB 5, 9 5 Now actually did a symbol for the C version as well. and if you follow me on Eevblog to my second channel, I've already updated a quick video showing creating the symbol for this C version of this Tea Peak here and there's a reason why I've done the pin out exactly like this. So I actually recorded this clip I uploaded it like quite a few days ago and people have already seen that if you haven't subscribed Eevblog to, so I'll include that now and it just explains why. I've laid out some of the pins and it doesn't match the datasheet.

so roll the tape. Just one thing without making component symbols like this. because I had to do this I couldn't find it in the Allium Volt library. They've got everything but the one you want Murphy's Law of course, but it's trivial to create your own circuit symbol like this.

It takes you know a minute or two. it's you know, not hard at all. but just one thing. When you laying out the pins, let's have a look at the data sheet here.

Don't necessarily just follow this eye pin out in the datasheet because then it doesn't make for a nice flowing circuit diagram. So you'll notice how on the datasheet here like you know, half of the drains of in three to six on one side, half from the other. And if you're trying to draw a nice neat schematic and you know that is just a pain in the butt, you've got your Nixie tube on one side or your display or whatever you're driving it. so it makes sense to have all of the outputs on one side.

here. you'll notice that I've gone to the effort to put in the open collector output symbol here to show that there. Well, in this case they're open drain but you know the same thing. you convey the information and then here of course our VCC You want VCC up here so that you can put your symbol just there.

You want your ground down the bottom so you can put that there. Now the chip enable. Usually you're going to just you know for simple applications you're just going to tie it to ground. So why put it you know somewhere else like it pins seven down here and if your grounds over there then you put another ground symbol.

If you put it right next to your ground pin pin sixteen here then you can just tie it like that. Bingo real easy. and then VCC up the top of course then you can just put your VCC symbol there and of course your clear pin you often for simple applications. Again, you will just have that permanently tied high because it's an active low because I've put the knot symbol.

That's what that circuit is. It shows that it's an active low input. so you put it right next to the VCC pin that you most usually going to tie it to so you don't have to have all your you know wires on your schematic running everywhere and data in, data o'clock and then data out and that just makes a nice compact symbol like this that's going to flow really well because then I can put my Nixie tube right here next to it and all the wires will just pop straight out and it'll be ground. VCC they won't get in the way and then you can have your wires coming in and out for your clock, lines and everything else.

so it just makes for a nice flowing schematic. So put a little bit of thought into your circuit symbol there and really you'll may can make your life much easier and a much more presentable schematic so that equally applies to this zombie version as well. I've got all the outputs on one side here, including the art knock can the to not connect pins? You could have just left those out, but I like to include the not connect pins here and everything on the other side, the input and output pins the ground and VCC and you can see the advantage of having the clear pin which in most applications would like in a majority would likely be tied to VCC So having it there like that right next to it just makes it neat and tidy. Likewise for the three grounds and the enable which in majority of cases might be tied directly to the ground like this, so it just works out nice and neat because if you laid out this chip as per the actual data sheet, you would have had half the lines coming out here, half the lines coming out the bottom here and then going back around it would have been a mess you wouldn't have been able to.

Layout is schematic and nice. like eight digits like that and taking up a small amount of compact space on your schematic. This whole a three page probably would have been filled just with the lines going everywhere. Hickety Pickety all over the shoppers, so it's just much nicer.

And then we've got just got this bus running along here driving the data clock input you can see there. Yeah, the data clock and the register clock all common between all the chips. And then of course we just daisy chain them together. We've got our data out going here to the data out of the next one.

So this is our first chip here. We've got this from our microcontroller solution and then we have and then we just daisy chain them. Boom Like that chip to chip chip chip to chip until we get right to the end and we're not actually reading any data back. we're just shifting the data out now.

I mentioned before driving voltages and this is can be a real trap for young players. So let's take a look at this. We'll take a look at our microcontroller solution in a minute, but I mentioned before that we could come a gutter on the input threshold voltage. Let's go have a look at it here.

Here's our six: B Five Nine Five high level input voltage. Here it is and it's no Point Eight Five volts. No, sorry, not. Point Eight Five Times VCC which is VCC in this case, a four point five minimum.

Nominally five, So times 0.85 That's 4.25 volts minimum. So your input digital signal has to be at least four point Two Five volts for you to register a logic one on the input pin of that chip. And of course, that input pin includes the not only the data in pin here, but the D clock, data clock, and the register clock as well. So all those three pins must be must be 5 volt.

not only just 5 volt compatible logic, but they don't have a standard like an TT or input threshold. 4.25 volts input is a relatively high input voltage, so you really have to drive them hard with like a 5 volt signal. You can't drive them with 3.3 volt logic. So we're actually driving this thing with a we must say d1 many I'll talk about more than this more in a minute.

It's an Esp8266 X Wi-Fi module chipset because this design is going to be a Wi-Fi internet enabled 8 digit display and you'll find out why in a future video. But anyway, it's 5 volt powered the module, but its inputs and outputs its IO pins on here. Our only 3.3 volts has actually got a regulator built-in and this 3.3 volts is actually an output I Don't think we're using that before anything else on here. No, we're not.

So I didn't actually have to connect that at all but 3.3 volt output. so it's not enough to drive directly out. Six C Five Nine Five Chips We need a logic level translator in there. Now you can get a whole bunch of dedicated solutions for logic level translation TI and other manufacturers make a whole slew of logic level translator products.

But our requirements? very simple. Here, We only have to drive data ie. convert a 3.3 volt signal from our module here to drive 5 volt output so We don't need bi-directional down. If you get data back, don't have to do anything fancy like that.

So I just a simple jellybean. 7 for Hcto 4 will do the job, but there is a trap there of course. So let's take a look at the data sheet for the HC and the HC T version. you noticed I used specifically the HC T, and there's a reason for that.

So if we go down here and have a look, let's go down static, high-level input voltage. This is for the H C version, not the TTL compatible version. Now let's take a look here. So the minimum higher level input voltage here at a VCC I Find it rather annoying that they put like a standard 5 volts in there.

It's always just pretty annoying that they do that anyway. so you've got a sort of you know guess in between. But at 4.5 volts, supply voltage at 25 degrees are typical. The minimum is three point one, five volts.

so you know, like it's not ending at six volts is four point two. So really, we're inputting a 3.3 volt signal and that's it's. cutting it real fine. it may work.

it may not the hate Co4 version. So yeah, that's not the best. So let's go to the Hcto for down here and you'll notice the high level input voltage. Look at this.

it's a much better minimum. two volt for a VCC and it doesn't give individual voltages. it just gives a range for point five to five point five and minimum of 2 volts. Bingo! So we can easily drive the input to this inverter with our 3.3 volt logic.

guaranteed. Huge margin, no problems whatsoever. So you want the specific TTL compatible HC To4 So you could have come? A guts are there if you use the symbol for HC O for in your design. So you might have built this thing up prototype.

No worries. Worked in to HC o for and found it's not quite working or it might have worked some other time or it would be dependent varying with temperature or something like that. and to be intermittent and you're not quite sure what's going on, you really could have come a guts are there and troubleshooting that might have been a real pain in the butt. So without thinking of that upfront and choosing the correct HC t drive a chip.

yeah, we avoided a possible issue there. So to Sutton to watch out for. So our Hcto for will easily take our 3.3 volt input. And of course being a HC CMOS Technology driver chip, it'll output the five volts because we're powering it from the five volt.

VCC here. Just tie the unused inputs here. That's just nice practice. Just tie them high or low or whatever doesn't really matter.

And Bob's your uncle. That's pretty much our entire design. We've got our Wi-Fi module here. so which will program in a different video.

As for the power supply, I've just got a DC jack here on the thing which is a 12 volt input because of course we actually need 12 volts to power our pile. Oh Poo! Don't blame me for the name. that's the name of the website where that high voltage module we saw in the previous one comes from and we use a one point 1k resistor here to actually set our output voltage as we said to 160 volts instead of 170 because we want that extra margin on the Nixie tube bias and then I've just got a triple 1:7 could use the 7805 whatever here to give us our 5 volt output. No worries.

Power dissipation of course these are CMOS chips take bugger-all power. So the only major power on the 5 volt rail is the Wi-Fi module here and I've had a look at the specs for that and it's not a huge deal so we should only need you know, a pedal in kind of. Heatsink on this thing should do the business. so just a PCB heatsink will do the job.

So as I said, I want this to be an Internet enabled Internet of Things device Shock Aura Internet enabled counter module so that we can display a counter from a any sort of website. So there's many, many solutions here. and sorry if I haven't used your favorite little internet of things. Wi-Fi enabled widget I'm using the We Mas d one mini here from we Must dot CC nice little module I can buy this in stock in Australia on eBay for 10 bucks delivered.

you know it's like anyway, it's fantastic. It uses the esp8266 ES chipset this bugger all on it really. So it's got a little USB thing little point one in shot header with 0.9 inch spacing here. So yes, I had to do my own layout for that because of course we didn't have.

Once there we go, it just did my own symbol there. It took like a minute. It's like bugger all I sort of. You know it got almost close to the right dimensions I sort of guesstimate it.

a couple of things because it didn't have a dimension from here to here I Don't physically have one in hand, but it's going to be good enough from photos and other info. Got that it was point nine inches across here at nine hundred thousand Me? no worries whatsoever. So we've got our PCB footprint for that. and once again, creating this sort of stuff is not a problem.

like a schematic symbol takes a minute or two. PCB symbol takes a minute or two I Didn't do anything fancy with importing the 3d you know, some sort of 3d step model and stuff like that which you can do if I was doing a serious board for production and for all for a client or you know a company I work for a professional sort of board, then you go to a lot more trouble that and make sure it's exactly right and include the models. but this is just a one-off thing. I Don't plan to take this thing into production at all so you know you just slap it down and Bob's your uncle so you might be wondering why did I choose this? We must ID one many I could have used any other solution out there sort of Arduino solutions or and by the way, this we mas d one Mini actually is compatible with the Arduino environment.

Now they've got like a some sort of wrapper layer that allows you to do it with the Arduino Chris and absolutely anything on the market. a It's cheap, readily available, but mainly because somebody has already produced a library and everything for a pretty much what I want to. you know a very similar application of what I want to do. so I I don't want to reinvent the code wheel here and I I suck at sort of web program you know MoMA I'm finding like in just regular embedded C programming.

That's no problem for me, but all this web enabled crap, you know I'm nice. Want the thing to work I don't want to spend any more time and reinvent the wheel. So it turns out that sixteen year old Joey Babcock here has on his website has created but is put all this information here step by step of how to use the way Mas D1 Mini to do. very similar to what I would.

So brilliant I'll just use that code so that's one of the reasons I chose the We Mas D1 Mini chip said why not? you know. So a search for your if you've got an application like this and you want to spend the list and you want to get it up and running as quickly as possible. of course you're going to use a solution that already had that's already out there for you that's close to your application. so I just need to download that code.

Don't need to know any of the nuts and bolts about all the web programming and the api's and all that sort of stuff. I Use copy the code in and then start modifying it and that's by far the easiest way to get up and running. I should be up and running in you know, tens of minutes with this thing. hopefully.

so that's the plan. so that's why I chose that. we must do one mineable, see if it works. Now you might think that we're actually done here and we are, but there's one more step which is called an electrical rules check and I actually was going to put that in this video but I decided people might want to know about this separately.

So I've just branched that out into a separate video which should be uploaded at the same time as this one. So check that out. If you want to know about electrical rules, check in in schematics. Basically, we're passed a DRC as I said.

like the hidden pin thing before, you'll notice that there's no ground of VCC inside these things. but I could like go in here and then just show what show all pins even if hidden and you'll notice that there are actually some hidden pins in there. So that's it. That's our schematic and hopefully that works and hopefully if you found that interest.

and I what does this been like? half an hour of waffle or something like that, but you know we've covered Laiia done ERC and component layout. nice schematic design and you know stuff like that and it looks like you know a nice layout. I Haven't done anything fancy on here like you know, engineering notes and stuff like that. I'm a big fan of adding like notes like of how to drive I might you know? add notes down here, maybe some info for driving pins or you know, something like that.

whatever. but this one doesn't really our warrant that sort of thing. I'll show you a good one that I've done in the previous video. An example of that I've done in a previous video as my micro supply old micro supply project for example.

look I categorize things in nice neat groups and then I add little engineering calculations and notes all in there and little formulas and things like that for calculating and resistor values and stuff like that. So I could have done that here. For example: I could have added a little engineering note saying hey, how did I calculate that one K one resistor there and well without knowing you'd have no clue why I picked that Is it important If you're just looking at the schematic I don't know. Can I work at 1k in there? Well, no, you can't.

You'd have to go look at the data sheet for the high voltage supply, the pileup. ooh supply and it's actually quite a little complex. Our formula in there to calculate the one point 1k to give you your hundred and sixty volts. It's a fairly critical value.

It's not quite precise, but it's a you know, near enough. So something like that might warrant an engineering note. But now you know this is just a one-off not too fast so we're ready to go. so I'm sure in a follow-up video I'll be doing the PCB for this thing and then we'll order it.

Then we'll assemble it and then we'll program it and we'll see the final application. So I hope you enjoyed that and you found it interesting. If you did, please give it a big thumbs up and or as always, discuss in the comments or links to the Eevblog forum or blog. follow me on Twitter or another.

Now all that sort of stuff and hi to all my Patreon! Thank you to all my Patreon supporters as well. Catch you next time you.