HELP! PCB Layout Guidance

[Robert]

Do you have a ground plane on the opposite side of the board as well? If not, are your ground net ratlines hidden?

Your ground pads don't have solid connections between them but there are no ratlines indicating broken connections. For example the two square GND pads on the left have no connection to the three GND pads on the right.

Did you draw a schematic first in DipTrace, or did you do this all by hand in the PCB editor?


The reason I ask is that you can, of course, just draw the entire PCB from scratch in the PCB editor but it's risky... It's much easier if you draw the schematic first in the Schematic Editor then "Convert to PCB". This will display ratlines as a guide to ensure you don't accidentally forget a connection (or make an incorrect connection). Then you can run a series of tests from the Verification menu to check your layout for errors.

Check Design Rules ensures no traces, pads, or holes intersect or get too close to each other (or the edge of the board)

Check Net Connectivity ensures that all of the proper connections are made

Compare to Schematic verifies your layout against your schematic to ensure all components are present and of the correct type (and that all connections match your schematic)

It's always a good idea to run all three of these before exporting a PCB to be fabricated.

 

[Chuck D. Bones]

I see isolated ground islands. Those are undesireable so either erase them or connect them to the ground plane on the opposite side (which is not visible in your views) with vias.

I also see a problem with the schematic. I don't know where C2 and C5 are supposed to connect, but where you have them is wrong. It is never good to connect a capacitor from the - input of an opamp to ground unless you are trying to build an oscillator.

Have you breadboarded this circuit?

 

[JamieJ]

This is a great thread. Now it’s been revived I want to keep this conversation alive.
There is some great info here.

What would you recommend for trace width?
0.3mm for audio traces, then 0.6mm for power traces is what I’ve been using.

 

[Grubb]

This is a great thread. Now it’s been revived I want to keep this conversation alive.
There is some great info here.

What would you recommend for trace width?
0.3mm for audio traces, then 0.6mm for power traces is what I’ve been using.

I started out with different widths for power traces and audio traces, and it's probably good practice, but I've stopped doing it. The circuits work either way in my experience so far. I think I got the trace widths I started with from a Madbean article that was worthwhile reading.

I know symmetry absolutely does not matter, but I can't help myself:

(These are boards I did for a friend, one is a Green Matamp and the other an Orange Rockerverb.)

The other thing I try and do is put horizontal traces on one side of the board and vertical traces on the opposite side. It's not a rule but a principle that helps make routing easier.

Like the OP, I'm coming at this with a background in visuals rather than electronics, so I'm sure my boards contain a number of sins that would grate a purist.

 

[JamieJ]

This is my first go at designing a PCB other than doing some super simple ones to get a feel for diptrace.
@Grubb - that symmetry is super impressive. That is very hard to do. Im just trying to make sure my design works first of all. Big shout out to @cooder for helping me work out diptrace.

 

[Grubb]

This is my first go at designing a PCB other than doing some super simple ones to get a feel for diptrace.

I taught myself DipTrace by copying some of @PedalPCB's layouts for simple circuits. I think that's where the symmetry rubbed off, and also probably where the habit of placing outside rows of caps and interior rows of resistors comes from. It's a good strategy.

@Grubb - that symmetry is super impressive. That is very hard to do. Im just trying to make sure my design works first of all.

Thanks Jamie I find doing board layouts super satisfying, like I've just completed a tricky puzzle. Awesome brain workout.

I hear you on the "just make it work" front. My first test production board was based on an incorrect schematic from the interwebs and it only kinda worked. Thankfully it was a good learning process.

You seem like you've gone all in on the Omnidrive though, there's a lot going on there, I'd love to hear more about the project!

 

[JamieJ]

Yeah I have really enjoyed the challenge of trying to make a layout. My work is all about problem solving and that’s something I love doing so this really engages that part of my brain.

This build is nothing revolutionary- I love a blues breaker and boost together so I wanted to combine it in one effect.

It’s basically a morning glory with soft clipping and hard clipping mods on switches and hi cut mod on a DIP switch. That then goes into an ep booster with some of PedalPCBs mods on dip switches. I got rid of the charge pump and I’m using codas relay bypass.

 

[Robert]

I started out with different widths for power traces and audio traces, and it's probably good practice, but I've stopped doing it.

I know symmetry absolutely does not matter, but I can't help myself:

The other thing I try and do is put horizontal traces on one side of the board and vertical traces on the opposite side. It's not a rule but a principle that helps make routing easier.

The only time I bother with increased trace width is when a trace will be carrying higher than normal current. (Vibe lamp, Power rails of the ProtoBoard/Auditorium, etc)

You don't have to justify symmetry to me.

Perpendicular traces is an excellent idea, not just for ease in routing, it reduces the amount of signal crosstalk between traces. I can't always stick to this like a rule, but I try my best to avoid long runs of traces that might interact running parallel to each other.

 

[Blooze]

I see isolated ground islands. Those are undesireable so either erase them or connect them to the ground plane on the opposite side (which is not visible in your views) with vias.

I also see a problem with the schematic. I don't know where C2 and C5 are supposed to connect, but where you have them is wrong. It is never good to connect a capacitor from the - input of an opamp to ground unless you are trying to build an oscillator.

Have you breadboarded this circuit?

I’ll rework this over the weekend as I have time.

I haven’t breadboarded it yet. Was really just messing around to get a feel for Diptrace. Others have though.

Seamoon (Anderton) Fresh Fuzz gut shots

Another oldie from around 73 or so, the Anderton designed Fresh Fuzz. I find this interesting for a couple of reasons, First it is one of the earlier dirt pedals using the JRC4558, it does not have a clipping section but just overdrives the op-amp, and

www.freestompboxes.org

I think I’ll start a new thread on this particular circuit so we can keep it all together.

 

[Chuck D. Bones]

The other thing I try and do is put horizontal traces on one side of the board and vertical traces on the opposite side. It's not a rule but a principle that helps make routing easier.

That's good practice for the reasons Mr. PedalPCB stated and as you say, it makes the routing easier. Auto-routers (the good ones, anyway) follow the same process. Doesn't matter much on a board with a small number of connections, but on a board with ICs and/or a high parts count, the horiz / vert method is essential.

 

[fig]

Auto-routers (the good ones, anyway) follow the same process

Are there good ones available to mere mortals?

 

[benny_profane]

Are there good ones available to mere mortals?

For circuits the size we’re working with with pedals, I don’t think autorouters add much advantage. In my experience, you can use them to get a general layout, but they should be adjusted. We don’t have to worry about any of the issues that high-speed designers do.

 

[Chuck D. Bones]

Agreed. With low-level analog circuits, parts placement is very important. I don't trust an auto-router to do that well.

 

[vigilante398]

Are there good ones available to mere mortals?

Altium's auto router started getting usable a few years ago and is now actually quite good, but not really "mere mortal" pricing unless you can get a license through school or work.

 

[Grubb]

That's good practice for the reasons Mr. PedalPCB stated and as you say, it makes the routing easier. Auto-routers (the good ones, anyway) follow the same process. Doesn't matter much on a board with a small number of connections, but on a board with ICs and/or a high parts count, the horiz / vert method is essential.

The other thing I do is try and always have traces on opposite sides crossing each other at 90° to one another. Sometimes I have to make individual traces less optimal for this to happen, is that the right priority?

 

[Chuck D. Bones]

You can angle the traces, they don't have to be 90°. Short, direct traces are the priority.

 

[Grubb]

I'm using codas relay bypass.

Now you have me mulling over midi controlled relay bypass switching again. One day I will work out how to do it.

 

[JamieJ]

Now you have me mulling over midi controlled relay bypass switching again. One day I will work out how to do it.

Don’t blame me, blame @cooder

Coda Effects: Relay Bypass: final code

Learn more about electric guitar related electronics: DIY guitar pedals, from fuzz faces to delays and reverb, cables and circuits theory

www.coda-effects.com

Coda Effects: Relay Bypass: conception and relay bypass code

Learn more about electric guitar related electronics: DIY guitar pedals, from fuzz faces to delays and reverb, cables and circuits theory

www.coda-effects.com

 

[JamieJ]

Any tips for how to “not connect” a pin of an op amp in diptrace? I’m using a Mac and it won’t let me right click to try and press no connect as the diptrace forums suggest.

 

[finebyfine]

Any tips for how to “not connect” a pin of an op amp in diptrace? I’m using a Mac and it won’t let me right click to try and press no connect as the diptrace forums suggest.

You're in the schematic editor right? Does the pin get highlighted red like this?