Feedback wanted on my first Eagle Schematic and PCB design

Thread Starter

bignobody

Joined Jan 21, 2020
80
Hi Everyone!

After building a bunch of circuits on prototype board last year I decided it was time to try PCB design.

After getting a few different recommendations last year, I finally decided to make an Autodesk account and learn the Free version of Eagle two weeks ago.

I skipped through some Webinars for the good bits and googled some other questions I had about how to use this clunky beast, and I've come up with my first schematic and PCB design.


The purpose of the circuit is to be the electronics part of a light and sound sculpture. 3 tunable audio oscillators to make chords or droning sounds with each oscillator also driving the Red, Green or Blue channel of a 10mm common cathode RGB LED.

It has 5 general sections:
- Power/voltage regulation

- 3 Audio Oscillators

- RGB LED buffers and output

- Audio buffers, Mixer with switch between 2 amplification stages

- Amplifier + Speaker (with Monojack bypass output)

I've attached a .zip file of what I hope is all the necessary files for it to be loaded by Eagle, but here are some screenshots for convenience:

1611278166164.png
1611278182386.png


I'm hoping for some feedback on absolutely any aspect of it, especially since I may have missed something important about the process given my self-directed crash-course.

A few random Eagle questions to finish:

I used US capacitors for standard and EU capacitors for polarized because the EU versions show polarized in the schematic. But it seems like they both show as standard capacitors on the PCB board view. How do I get polarized capacitors to show oriented footprints on the board?

There didn't seem to be a LM7809 device in the library, which is what I am intending to use. I've gone with a LM7812 which was there and the footprint is the same, so I think that will be ok.

Thanks for looking!

Edit: Updated with a corrected version after I figured out some error checks in Eagle (Pin 2 of the LM386-4 wasn't grounded).
 

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Ylli

Joined Nov 13, 2015
1,051
Never used Eagle. Do the traces shown on the board layout actually indicate trace width? If so, I'd say your traces widths are too narrow. Try something like 0.025"
 

Thread Starter

bignobody

Joined Jan 21, 2020
80
To be honest, I just used the defaults in the hopes they would be reasonable. The numbers in the tutorials I saw didn't seem to match up with what I was seeing, but that might be a difference between Imperial and Metric?

1611373595752.png


Anyway, thanks for looking and commenting. People like seeing schematics posted here along with questions, but I also recognize that asking a very general question like this is still a big thing to ask. I appreciate your time.
 

Thread Starter

bignobody

Joined Jan 21, 2020
80
Also, regarding capacitor polarity, I've ended up just adding + and - notations on the silkscreen as a reasonable solution.
 

jpanhalt

Joined Jan 18, 2008
11,088
Your traces are 6 mil wide and drills for vias are a little less than 14 mil (.35 mm). Those may push the limits of some board houses. There is no need for the traces to be that narrow.

What is did the DRC (design rules check) show?

As for your specific questions:
I used US capacitors for standard and EU capacitors for polarized because the EU versions show polarized in the schematic. But it seems like they both show as standard capacitors on the PCB board view. How do I get polarized capacitors to show oriented footprints on the board?
Both American and Euro style capacitors show polarity. I add polarity to the foot print if it is not included. You can also modify the footprint to include whatever, including polarity, you want. Go into the component library, "package" and change it.

There didn't seem to be a LM7809 device in the library, which is what I am intending to use. I've gone with a LM7812 which was there and the footprint is the same, so I think that will be ok.
Yes. Be sure to change the value on the schematic to LM7809.
 

Thread Starter

bignobody

Joined Jan 21, 2020
80
Thanks, @jpanhalt !

I'll update my design with wider traces. The vias are pretty much all from through-hole component footprints, so I didn't think I would need to adjust those.


DRC only gives a warning about one airwire that it thinks should be there (but shouldn't be, these pads are bridged by the on/off switch).
1611412083250.png


ERC has some warnings (and coming from a programming background I've learned to at least read the warnings!) but I've looked at them and based on my experience working with these particular ICs, I think they're ok.
1611412198102.png

Thanks for your other answers, too. I've got a bunch more Eagle functionality to learn still, but I'm happy to have made it this far.
 

jpanhalt

Joined Jan 18, 2008
11,088
Yes, those warnings are Eagle's way to nag you. They can be important, particularly if your circuit has different grounds. On grounds, I try to be consistent as they may affect a ground pour. That is, a GND pour may not connect to a VSS, unless intentionally connected*. In your case, it is VSS connected to ground, so a GND pour will probably be OK. The VDD to VCC warning is one I also ignore.

*When I do that with my earlier version, I get a pop-up asking whether I want to connect VSS to GND. And of course, I affirm it.
 

Thread Starter

bignobody

Joined Jan 21, 2020
80
Updated with 24 mm traces for power and grounds, 16 mm for signals. Thank you both for pointing out the undersized traces, it's very much the kind of feedback I was hoping for.

1611446469939.png
 

Thread Starter

bignobody

Joined Jan 21, 2020
80

BobaMosfet

Joined Jul 1, 2009
1,776
@bignobody Something to consider going forward- don't use square corners on traces. Always bend them at 45-deg angles. When you make a square corner, you create a point for energy to bounce and make emf noise. Other than that, very nice.
 

jpanhalt

Joined Jan 18, 2008
11,088
Until you get to very high frequencies, that old adage does not apply:
http://montrosecompliance.com/wp-content/uploads/2014/09/corners-USA.pdf
Also published here (1998): http://ieeexplore.ieee.org/Xplore/login.jsp?url=http://ieeexplore.ieee.org/iel4/6068/16215/00750154.pdf&authDecision=-203

In the days of olde when PCB's were laid out with sticky tape, making a 90° angle was a problem.

The only real reason for thin traces appears to be mechanical robustness. Now, if you look at reference designs for many modern, high-frequency chips, you will see large, 90°cornered copper areas used.
 

wayneh

Joined Sep 9, 2010
17,152
Success! I had this manufactured.
Can I ask where? I know there’s a thread here somewhere that polls members’ opinions on various vendors. Just curious where you went and your opinion.

I’m finishing up 3 identical builds on protoboards right now and have more or less resolved, “never again”. It’s just too tedious. I’ve already started playing with Eagle but have a long way to go.
 
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nsaspook

Joined Aug 27, 2009
8,390
Can I ask where? I know there’s a thread here somewhere that polls members’ opinions on various vendors. Just curious where you went and your opinion.

I’m finishing up 3 identical builds on protoboards right now and have more or less resolved, “never again”. It’s just too tedious. I’ve already started playing with Eagle but have a long way to go.
They look like JLCPCB. The manufacturing zip file that eagle generates can be dropped directly into their web job folder.
 

Thread Starter

bignobody

Joined Jan 21, 2020
80
They look like JLCPCB.
Good eye, you are correct.

Can I ask where? I know there’s a thread here somewhere that polls members’ opinions on various vendors. Just curious where you went and your opinion.
As nsaspook noted, I had them manufactured by JLCPCB. I originally got a quote to have them produced in Canada (where I live) - they wanted $50 to set up and $375 for 2-5 boards, which was way more than I wanted to gamble on something I wasn't even sure would work.

JLCPCB manufactured 5 boards for $21, and most of that cost was for shipping... Quality seems good to me (the only errors were my own), but being the first boards I've had made I have little to compare it to. I will say the recommendation to use them came from my brother's friend, who's an actual Electrical Engineer and uses them frequently.


I’m finishing up 3 identical builds on protoboards right now and have more or less resolved, “never again”. It’s just too tedious. I’ve already started playing with Eagle but have a long way to go.
This is pretty much why I resolved to learn how to make PCBs in January. I built a lot of circuits on protoboard last year. It was great for learning and building up my soldering technique, but yes, it can be very tedious.

You might not have as far to go with Eagle as you think. I was able to get a working board manufactured and I still only have a basic understanding of the software. Good luck!
 
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jpanhalt

Joined Jan 18, 2008
11,088
I am a long-time user of Eagle starting with version 4.03 through 7.7.0. I have not installed the Autodesk versions. It has handled everything I have needed to do. However, my impression from Autodesk as well as users here and on other forums, is that for someone just starting and wanting a free version, KiCad might be a better choice.

The programs are definitely different, and I like the way libraries are handled in Eagle. Some users hate that feature. For myself, I don't want to rely on anything subscription or cloud based.
 

Thread Starter

bignobody

Joined Jan 21, 2020
80
For myself, I don't want to rely on anything subscription or cloud based.
I understand this. It's actually the reason I avoided Eagle for months, but in the end since I'm just a hobbyist and have no plans to sell any thing I build, I figured Autodesk could have my email address in exchange for their software ;)

I will give KiCad a look - I don't mind learning new software. Thanks!
 

Dmm

Joined Apr 13, 2015
47
Nice work on your first attempt! I'm barely ahead of where you are...2 working circuits fabricated, 1 rework for an error on my part. One thing I learned is to look for the limitations on the fabricators website you are going to use. They may vary from one to the next, such as the small trace mentioned that you started with. I first started out with the default settings (using KiCad) not knowing you can and should change it. It was pretty small traces. Some threads I've read saying make the traces big if you have the room. And if you are running any sort of power through the trace to use a trace width calculator to make sure you can run the current through the trace at a given width. Very nice to see others beginning like me, and showing a final working project. Thank you for sharing!

My thoughts on KiCad, I've been able to make footprints and parts easily. I'm sure like any other software out there just look for a helpful video and you will be fine. I've enjoyed KiCad and will continue using it. IIRC, I think one thing users don't understand right away moving from Eagle to KiCad is the foot prints are not tied to schematic symbols. That makes sense in my head, but I thought I read once someone had issues adjusting to that methodology. Keep it in mind if you give KiCad a try.
 

Thread Starter

bignobody

Joined Jan 21, 2020
80
Thanks, @Dmm ! I especially appreciate you sharing your experience of moving from Eagle to KiCad. I am more than giving it a try - I'm building my next project with it (which I will also post about here when it's ready!).
 
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