EEVblog #974 - PCB Layout Walkthrough

[EEVblog]

Part 4 of the Nixie tube display project.
In this tutorial Dave walks you through a complete PCB design from begin to end, with a ton of hints and tips throughout that can be applied to any PCB layout package.

[RGB255_0_0]

74 minutes. Time to make some popcorn 

Nice vid, Dave. I ended up being trapped as a young player inbetween some traces. How do I get out?

[Smokey]

What a strange wonderful world.  I sat down with the intent of working on a layout, but ended up watching a video of someone else working on a layout.

[trophosphere]

I watched the video a quarter of the way through and then, while it was still playing, started working on laying out a PCB for my own project. Hurray for multiple screens. 

[mariush]

Interesting... watched it to the end.

I noticed you used LT1117 .. that's one of those regulators that needs some ESR on the output for stability, not sure that's satisfied with your ceramic capacitors. The datasheet recommends esr below 0.5 ohm .. the Linear datasheet datasheet doesn't say but other manufacturers mention at least 0.1 ohm esr

While you were routing those traces I was thinking ... you could just put those chips on a tiny vertical board with just their decoupling capacitors and basically create a SIP like module the width of the board (with a  right angle 0.1" spaced pins to connect it to the base board) . You'd get all the pins actually needed in a row nice and easy to route to the nixie tubes without going around chips, and you have plenty of vertical space anyway due to the height of the nixie tubes. Wouldn't add that much to the cost of making the board, you'd just put there an instruction to v-groove a portion of the pcb.

I was also thinking what if you placed all those chips at 45 degrees. Would have allowed for more routing room between the chips so maybe a bit nicer routing.  Yeah, would suck as you can't use straight "bus bar" style traces under all chips for the clock stuff but a couple of vias under each chip would be easy to add.

[Macbeth]

Dave, have you double checked that the IN-12 footprints you "borrowed" will work with your tubes mounted on the top side of the board?

I have to admit I have played with the same "borrowed" footprints and two different public STEP designs just getting to grips with CircuitStudio and am still kind of confused about the orientation.

[Zom-B]

Really... what's up with this forum... Thrice! I can't even post anymore?

"You already submitted this post! You might have accidentally double clicked or tried to refresh the page."

I just wanted to post this:

What's with this bloody forum?! Twice!!
"You already submitted this post! You might have accidentally double clicked or tried to refresh the page."

No it's not. Where is my post with good advice along with my complaint about another SMF bug? My actual post ended in something like this, but it's gone now:

What's with this forum bug? It complained that my image was >1Mb. Okay, fair, so I clicked back, compressed my image and tried again, then it complained that the last post from my IP was less than 60 seconds ago!

And there's my image, and because I hate typing stuff twice I'll let you figure out what It means. My conclusion and final advise was to swap the order of daisy-chaining (sending the last digit in first).

[dynorat]

great job looks really good you forgot the  bodge-wires lol nice video I watch them all thank you 

[Brumby]

Interesting video.  I watched it to the end.

It's been many years since I laid out my first PCB - and I did it by hand.  Fortunately, it wasn't too complicated.  I haven't had the need to do much of this for some time - but I understood all of the issues Dave mentioned and appreciated the limitations of the software.

One thing I would have liked to have seen is the result a full autorouting would have created - and have Dave go over a few of the most dastardly decisions it made.


Still ... it kinda makes me want to dip my toes into the water.............

[EEVblog]

What a strange wonderful world.  I sat down with the intent of working on a layout, but ended up watching a video of someone else working on a layout.

Isn't that how the worlds biggest Youtuber is a gamer?
People just watch him play instead of playing!

[EEVblog]

Dave, have you double checked that the IN-12 footprints you "borrowed" will work with your tubes mounted on the top side of the board?

Yes.

[cheetahkid]

I may have misheard it, about the high voltage PSU. I like it to see it on the same board rather than separated. But that up to you.

[Chupacabras]

Is it possible to render that board with better quality? That 3D model for nixies looks awsome, it would be nice to see your board rendered with that quality model. (If it is possible. I do not use Altium)

[HSPalm]

Unfortunately, a step-file does not know about transparency, reflections and/or materials. The rendering in the image was done with features from the CAD package and rendered in the image export. All those fancy extras are lost when exported to .step.

[Tabs]

Hi Dave,

Just watching this now. reached 12 mins into video ...

In case you didnt know -
use 3D mode and "Tools>3D Body Placement > Align Face with Board"

Pick the 3D body to align, then pick a face on the body to align with the board using the menus.
Switch to 2D to align centers.

[Windfall]

Entertaining and informative (especially all the Altium tricks, I currently use Diptrace, so I certainly make do with much less ...).

But I'm sorely missing an emphasis on consistency, which I find is the essential ingredient in designing nice PCBs, even one-offs. As far as I'm concerned, making a one-off is not a great excuse for (a term often used in the video) 'mucking about'. You might be doing a whole bunch of these next, and then you'd basically have to start over. In addition, a circuit like this practically dictates consistent routing, and I'm not seeing too much of that in the end result, really. Yes, yes, 'one-off' and 'mucking about'. I still don't like it. 

Just my two cents.

[johnmx]

Hi Dave,

A small hint. I notice you selected several segments (of the same track) one by one to delete them all (at minute 56:49). You can just select the first and press TAB to select the rest. If you press TAB again it will select the entire net.

[QuantumLogic]

I am a brand new learner of PCB design.  I've watched other videos about PCB design but still had questions like "But am I really doing this the right way?" in terms of some of things I end up doing in KiCad but don't see mentioned by the presenter.  I thought I might have been doing things the wrong way, the stupid/ass-backwards way, etc.  But Dave's video confirmed that many of the things that I end up doing with my extremely limited experience are the same things Dave does with his many years of experience and more mature PCB design software.

Some examples of what I mean:

1. Measurement standards: Dave mentioned that he constantly switches between imperial and metric.  I do too, but attributed it to being a noob. I use metric for board size, edge cuts, holes and trace widths but I use imperial for component spacing and pin alignment.  It was nice to see that Dave validated that switching between the two measuring standards is "normal."  For some reason I thought people would stick in only metric or imperial and I was weird for constantly switching around depending on what I was doing.

2. Vias: In my current 2-layer PCB design I have no additional vias, but everything is through-hole in my design so I am able to use the component holes as a via instead where needed.  I thought vias were considered to be a "last resort" type of thing and to be generally avoided due to the additional resistance each one adds to the circuit, but Dave uses them without too much concern in this particular design.  The sheer number of traces going between components also necessitates the use of vias in his case, but it is good to know that using vias is not really too much of a negative in basic DC/low current/low frequency PCB designs.  Obviously a high frequency design would need to be concerned about many more things than just vias.

3. Optimization:  It is clear that if Dave had more time to spend on the design, he would like to perform a lot of pin swapping in order to simplify the layout.  But a person only has a certain amount of time to dedicate to the task so compromises have to be made.  It was nice for me to see, as a complete noob to PCB design and layout, that even someone like Dave, who has many years of experience, reaches his limit of time and effort before coming up with a truly elegant layout.  And he's OK with that.  It is a one-off, after all. 

4. Tweaking:  While you could argue that this is similar to Optimization, above, I think it deserves its own discussion because I consider optimization to be more general in terms of overall layout and reduction in rats nest crossing before any traces are laid down while tweaking is the nitty gritty individual placement and slight movement of components, tracks and vias to "make it work."   Moving a track over to allow another one next to it, moving a via from down low to higher up the board in order to allow a cross trace go through, that kind of thing.   It was nice to see Dave doing those things which are similar to what I end up doing in my layouts.  I figured that with experience comes less fiddling around, but it seems that PCB design is really an art and every board needs individual attention to detail in a unique way.  My problem is that I am such a perfectionist that I will spend too much time on something rather than just "letting it go."  Good thing I don't get paid by the hour.

5.  Software features:  While watching the video, I could completely forget that Dave was using Altium Designer.  The overall basic functionality and features that Dave was using for this layout are available in the latest stable release of KiCad (4.0.5) so I could totally relate to everything Dave was doing and follow along as if Dave were using KiCad.  As a noob, I had no idea how much additional functionality would exist in a product like Altium but would have no equivalent in KiCad.  But at least for this particular non-demanding PCB design, I think everything Dave did in Altium could be done in KiCad in a similar way.  The new OpenGL push/shove trace router in KiCad seems to be very close in functionality to Altium's router which was nice to see.  I guess my point of this is that even open source software can give someone the power to create good designs - expensive design software is not required.  At least for the hobbyist, anyway.

Thanks, Dave, for making this video.  I thoroughly enjoyed watching all of it with great interest.

[PeterL]

Dave, maybe I missed it in the video, but have you checked if you have the nixie's right side up? I ask, because on the datasheet at 2:00 they have pin 12 upwards, whereas you have pin12 downwards. 

Also if you really want to avoid via's as much as possible you could swap pin's around. That would be at the cost of a messy schematic though..

[Unixon]

Dave, do you use grid alignment during component placement? I find it much easier to work on layout and routing when components are [next to] perfectly aligned. Personally prefer 50-mil to 25-mil grid for coarse alignment all over the board, 5 mil grid for fine alignment of neighbor components (passives to IC etc).

[22swg]

Thumbs up indeed, Dave , not seen PCB layout vid before, quite an education   

[DrChiron]

Dave: This is redundant to 2 comments I left under the you-tube video.
The Russian Nixie datasheet shows the bottom view pinout for the display. I noticed that you chose to capture the clock PCB Nixie part drawing from the rear of the CLOCK board (the pinout there matches the datasheet). When you created the Part Spec for the Nixie Tube I noticed that the upper left-hand part label indicated TOP SURFACE, although you had just pasted the captured bottom view image there. I think you may have all 8 of your Nixie pinouts upside down!  Dr Chiron

[EEVblog]

Dave: This is redundant to 2 comments I left under the you-tube video.
The Russian Nixie datasheet shows the bottom view pinout for the display. I noticed that you chose to capture the clock PCB Nixie part drawing from the rear of the CLOCK board (the pinout there matches the datasheet). When you created the Part Spec for the Nixie Tube I noticed that the upper left-hand part label indicated TOP SURFACE, although you had just pasted the captured bottom view image there. I think you may have all 8 of your Nixie pinouts upside down!  Dr Chiron

The datasheet I have has the pinout as a bottom view, so it is correct that I flipped it. I have checked this with the actual tube.
I didn't copy the component from the bottom side, it was just the bottom side view. PCB's are viewed "through the board".

[EEVblog]

Dave, do you use grid alignment during component placement? I find it much easier to work on layout and routing when components are [next to] perfectly aligned. Personally prefer 50-mil to 25-mil grid for coarse alignment all over the board, 5 mil grid for fine alignment of neighbor components (passives to IC etc).

Yes, I thought I showed that? I used 1mm placement grid.

[EEVblog]

Dave, maybe I missed it in the video, but have you checked if you have the nixie's right side up? I ask, because on the datasheet at 2:00 they have pin 12 upwards, whereas you have pin12 downwards. 

Yes, I checked.
That datasheet is different to the actual one I had, I just didn't have it scanned.

Also if you really want to avoid via's as much as possible you could swap pin's around. That would be at the cost of a messy schematic though..

I mentioned that.

[tautech]

Much enjoyed, once started couldn't stop watching. <rubbing eyes now> Nice to see some of the AD features being used to great effect. 

[mrpackethead]

Hi Dave,

I saw you struggling to get the 3d objects placed in the right orientation.. Theres a simple thing to do.
Tools -- 3D body Placement -- Align face with board.
in 3d mode you just click on teh face you want aligned with the board and it sorts out the orientaiton and standoff for you. :-)  Easy peasy.

Also Since you had so much repeatativeness in the circuit, you coudl have used some hyricheal sheet design.. these would end up being 'rooms' in the pcb, and then you only need to route out one, and copy the format from room to room.  On things that have so much repititon this can save hours!

[mash107]

Dave-- far be it for me to second guess you, but those resistors seem undersized for 160V (not Pd, as they are 22k in value, but dielectric withstanding).
You'll need a 1206 or larger I think: http://www.vishay.com/docs/20035/dcrcwe3.pdf

[EEVblog]

Dave-- far be it for me to second guess you, but those resistors seem undersized for 160V (not Pd, as they are 22k in value, but dielectric withstanding).
You'll need a 1206 or larger I think: http://www.vishay.com/docs/20035/dcrcwe3.pdf

They will never see 160V. You will always have the supply minus either the zener clamping voltage or filament voltage.

[EEVblog]

Also Since you had so much repeatativeness in the circuit, you coudl have used some hyricheal sheet design.. these would end up being 'rooms' in the pcb, and then you only need to route out one, and copy the format from room to room.  On things that have so much repititon this can save hours!

Not when you share chips between displays.

[DutchGert]

Nice video but I though you would put in a bit more 'pride' and nit picking into the layout and make it a bit nicer/teach the young ones some tricks.

Why not:
-use (almost) the same fanout on each tube
-set up proper design rules/classes for the high voltage stuff. Everything 8/8 but the HV stuff 15/15 for example.
-tidy up the schematic
-tidy up the silkscreen
-use proper 3D footprints for the IC's (Altium IPC wizards even generates those) and the module
-'direct connect' and don't use thermal relieves on via's and tent those while you are at it

I mean, it is a functional board but why not teach the new kids something more than just maken a functional board.

Like you said, pcb design is an art and it's ok to put a bit of effort and pride into it .

edit: I know it's a one off board but this video will be watch by >100000 people.

[Windfall]

Like you said, pcb design is an art and it's ok to put a bit of effort and pride into it .

This is what I am sorely missing too. This is hardly a demonstration of 'art', even if it doesn't really pretend to be (which it should).

[EEVblog]

Nice video but I though you would put in a bit more 'pride' and nit picking into the layout and make it a bit nicer/teach the young ones some tricks.
Why not:
-use (almost) the same fanout on each tube
-set up proper design rules/classes for the high voltage stuff. Everything 8/8 but the HV stuff 15/15 for example.
-tidy up the schematic
-tidy up the silkscreen
-use proper 3D footprints for the IC's (Altium IPC wizards even generates those) and the module
-'direct connect' and don't use thermal relieves on via's and tent those while you are at it

I mean, it is a functional board but why not teach the new kids something more than just make a functional board.
As for the nixie fanout, I mentioned that I addressed that in a previous comment.
As for tented ground vias, you don't always want those, as they can be handy for ground test points. yeah I know, put in ground test points too. The tweaks can go on forever...
Like you said, pcb design is an art and it's ok to put a bit of effort and pride into it .
edit: I know it's a one off board but this video will be watch by >100000 people.

It was never intended to be a tutorial, it was just supposed to be me screen capturing the layout and adding a few comments.
By the time I realised it was turning more into a tutorial kinda it was too late to go back and do many things more stringently as I'd do for a production board. It was alos getting very long.
I could add a dozen things to your list I could have done and talked about, you have to stop somewhere.

[casinada]

Did I miss the 0.1 uf  decoupling capacitor on each integrated circuit?

[rrinker]

 My only question is, wouldn't it be better to put the power jack on the back side as well, so that the only real thing projecting above the front would be the nixie tubes themselves? Seems that would make the mounting in a front panel be that much more flexible. Or is it that it just doesn't matter in this application, as we will see in a future video?

[Philfreeze]

If you want to make a 3d component with transparent parts in it you have to split the model.
Go into your CAD software of choice, open the step file and split it ito two step models, one with all the transparent stuff in it and one with the solid stuff.

I did exactly that already for you.
You will find a parts library with the two step parts already in them.
Alternatively you can place them by yourself. Just set the transparency of the bulb in Altium to 50% or so.
Additionally the part is oriented correctly to make the placement easier.
The only thing you will probably have to correct is the standoff height.

https://www.dropbox.com/sh/of6hdoe2dau3p5q/AACtShcnasLTcCttIhHl390Wa?dl=0

[Deridex]

Nice video but I though you would put in a bit more 'pride' and nit picking into the layout and make it a bit nicer/teach the young ones some tricks.
Why not:
-use (almost) the same fanout on each tube
-set up proper design rules/classes for the high voltage stuff. Everything 8/8 but the HV stuff 15/15 for example.
-tidy up the schematic
-tidy up the silkscreen
-use proper 3D footprints for the IC's (Altium IPC wizards even generates those) and the module
-'direct connect' and don't use thermal relieves on via's and tent those while you are at it

I mean, it is a functional board but why not teach the new kids something more than just make a functional board.
As for the nixie fanout, I mentioned that I addressed that in a previous comment.
As for tented ground vias, you don't always want those, as they can be handy for ground test points. yeah I know, put in ground test points too. The tweaks can go on forever...
Like you said, pcb design is an art and it's ok to put a bit of effort and pride into it .
edit: I know it's a one off board but this video will be watch by >100000 people.

It was never intended to be a tutorial, it was just supposed to be me screen capturing the layout and adding a few comments.
By the time I realised it was turning more into a tutorial kinda it was too late to go back and do many things more stringently as I'd do for a production board. It was alos getting very long.
I could add a dozen things to your list I could have done and talked about, you have to stop somewhere.

Your video is closer to a tutorial than quite a few "tutorials" i have seen so far.
It was quite interresting, even though i routed already quite a few boards already.

[ion]

Dave, you mentioned the possibility of swapping the software defined pins - that's a reason I prefer to mimic the physical chip when I make my own components.
I know you gave a reason for not doing that in a previous video, but sometimes you can see potential layout headaches while still working on the schematic.

[thm_w]

2. Vias: In my current 2-layer PCB design I have no additional vias, but everything is through-hole in my design so I am able to use the component holes as a via instead where needed.  I thought vias were considered to be a "last resort" type of thing and to be generally avoided due to the additional resistance each one adds to the circuit, but Dave uses them without too much concern in this particular design.  The sheer number of traces going between components also necessitates the use of vias in his case, but it is good to know that using vias is not really too much of a negative in basic DC/low current/low frequency PCB designs.  Obviously a high frequency design would need to be concerned about many more things than just vias.

Anyone saying to minimize vias in general is either an old-timer, or basing the suggestion off if you are lazy at layout you will often end up with an excess of vias. ie autorouting the board.
The resistance is minimal, but be sure to calculate if using them for high current traces: http://circuitcalculator.com/wordpress/2006/03/12/pcb-via-calculator/

Did I miss the 0.1 uf  decoupling capacitor on each integrated circuit?

Frequency is low enough it doesn't really matter, and he isnt trying to pass EMC.

[casinada]

I don't want to argue but it is recommended practice to add the 0.1uf decoupling capacitors on each chip. They're probably a penny each and don't take much real estate. There are lots of chips changing states all the time and the capacitors make sure that the supplied voltage at each chip stays as constant as possible.

[mrpackethead]

Dave, what was the logic behind not having decoupling caps?

[HSPalm]

Where do you find a manufacturer that has 8/8 mil track width/clearance? I think most, if not all, on PCB shopper is 6/6. And when they say they can handle it, is there any reason you should not trust it? I got the feeling that even though you set DRC to 8/8 you tried to avoid putting the tracks next to each other.

[DutchGert]

If you want to make a 3d component with transparent parts in it you have to split the model.
Go into your CAD software of choice, open the step file and split it ito two step models, one with all the transparent stuff in it and one with the solid stuff.

I did exactly that already for you.
You will find a parts library with the two step parts already in them.
Alternatively you can place them by yourself. Just set the transparency of the bulb in Altium to 50% or so.
Additionally the part is oriented correctly to make the placement easier.
The only thing you will probably have to correct is the standoff height.

https://www.dropbox.com/sh/of6hdoe2dau3p5q/AACtShcnasLTcCttIhHl390Wa?dl=0

Very nice trick and thx for the Lib, will use this in the future

[GekkePrutser]

Great video! I watched it all the way as I was just about to start on a project of my own (in Circuitmaker after I heard about it in one of your earlier videos - love the 3D thing). I could also have learned Eagle but I like your tutorials.

I was just wondering: Where did you get the WeMos D1 Mini footprint from? I am using the same module and I could really use it. I know I can make one myself but I'm afraid I'd mess it up It's already happened once that I measured something wrong and got a 3D print (bezel) produced and it didn't fit the screen At least I have my own 3D printer now so I can prototype.

PS: Yes I just signed up here to ask this but I'm a regular viewer of your video channel Just never got around to registering here.

[AF6LJ]

Thanks Dave, this was great...
Please do show the next steps, for those of us who do have long attention spans...

I've laid out a few boards the old fashioned way and here soon will attempt to do one the new fangled way.

[Macbeth]

It would be great if the final design is published on the free Altium CircuitMaker cloud open source thingy.

I mean that must be nice and easy to export Altium Designer files to, right?

[AlphaRomeo]

It would be great if the final design is published on the free Altium CircuitMaker cloud open source thingy.

I mean that must be nice and easy to export Altium Designer files to, right?

Altium Designer is the software used  for this video?

[thm_w]

Altium Designer is the software used  for this video?

Yes, Altium Designer 17, shows at the top.

[Nobody2]

While watching I was thinking how i might try lay out the board and make it nice looking.

1. Take a look at the nixi tube and make a layout with all traces in order
  b)  find a nice looking layout with all traces in parallel
2. if b change the pin order of the schematic model to avoid a messy schematic
3. make a layout for the shift registers to get all outputs in parallel and in order
After that connecting everything should be easy.

Btw, I was surprised how the hard the autorouter failed, especially when restricted to only a few connections.