Why am not able to get a grasp of PCB designing?

[redgear]

I am trying to design a powerbank myself. This is my first electronics project.
After completing the schematic and deciding on the components with a lot of help from this forum, I started working on the PCB Layout. I watched many videos but I just couldn't get started. Idk why.
I just get blank when all the components gets populated with the messy rat's net. The datasheet has given some layout rules which I am not able to follow.
DAE felt the same when you started? Do you have suggestions for resources that I can start with?

[I wanted a rude username]

Set yourself a series of tasks.

For the first task, just push and rotate stuff around until the number of connections that cross each other is minimised. Don't even worry about being restricted to a board size/shape or routing any traces at this stage.

Post a PNG of your layout at that point and ask for guidance on meeting the design rules.

Make mistakes.

[redgear]

Set yourself a series of tasks.

For the first task, just push and rotate stuff around until the number of connections that cross each other is minimised. Don't even worry about being restricted to a board size/shape or routing any traces at this stage.

Post a PNG of your layout at that point and ask for guidance on meeting the design rules.

Make mistakes.

Thanks! I will try doing it and post the png

[Rerouter]

My method is to break any design down to chunks, e.g. this is a charge IC, it has X number of components that belong to it, so lets group them together and lay them out as best I can, Then the next group, and so on,

Then after they are all grouped up i start connectiong up and positioning those chunks

This way you never have to try and take the entire project in your head at once, Its always smaller and simpler chunks, It also helps prevent routing yourself into a corner as it usually results in the least connections needed between chunks.

[redgear]

My method is to break any design down to chunks, e.g. this is a charge IC, it has X number of components that belong to it, so lets group them together and lay them out as best I can, Then the next group, and so on,

Then after they are all grouped up i start connectiong up and positioning those chunks

This way you never have to try and take the entire project in your head at once, Its always smaller and simpler chunks, It also helps prevent routing yourself into a corner as it usually results in the least connections needed between chunks.

Thank You.

The component I working with is a SOC, so all the components in the schematics are connected to it. Is there an option to selectively populate the PCB from the schematic? May be I can try breaking into blocks and layout in groups

[Rerouter]

I use Kicad, which groups by schematic pages, don't know what your specifically using,

Ok to follow my example, is there any 2 parts of the design you can split to reduce how much your working at once? e.g. power in / power out

[redgear]

I use Kicad, which groups by schematic pages, don't know what your specifically using,

Ok to follow my example, is there any 2 parts of the design you can split to reduce how much your working at once? e.g. power in / power out

Im using Kicad too. I got everything in a single schematic.
Yep, A boost network, output ports

[Rerouter]

Then any way to split it 3 ways? etc,

And if not now that its half as big of an issue, pick the one your more compfortable with and start placing out those components. work to reduce crossings and keep lengths minimal,

[redgear]

Then any way to split it 3 ways? etc,

And if not now that its half as big of an issue, pick the one your more compfortable with and start placing out those components. work to reduce crossings and keep lengths minimal,

Alright, I will try it.

[ebastler]

Then any way to split it 3 ways? etc,

And if not now that its half as big of an issue, pick the one your more compfortable with and start placing out those components. work to reduce crossings and keep lengths minimal,

I may be underestimating the complexity of a powerbank -- but splitting it into multiple schematic pages seems a bit over the top to me. And if most of the components (or little functional blocks) are connected to a central microcontroller, then the placement of that controller and all the components interfacing to it is a central part of the layout task, and will need to be done with all relevant components in the picture.

Also, the placement of connectors and user interface components (LEDs, buttons, or more complex parts) often creates an additional layout constraint. Again, I would want to see all these parts in context. It's OK to start with a larger-than-needed board, but I want to get an idea of what goes on the front and back, how much room the connectors take there, etc.

Could you share your schematic and non-routed ratsnest to give us a better idea of the complexity? Preferably as a picture or PDF, since not everyone runs KiCAD. Thanks!

[NivagSwerdna]

Im using Kicad too. I got everything in a single schematic.

set PCBCAD_Wars ON
Try DipTrace.  Work through the tutorial. 
set PCBCAD_Wars OFF

PS
re: Layout... In my DIY hobby experience as long as the main current paths are nicely flooded it normally works.

[Rerouter]

ebastler, I did not mean split the schematic, I meant group up parts into smaller sections, and just attack section by section, to reduce how "overwhelming" the project feels to the OP

Nivag, Why would anyone want to lock themselves in with software that limits what they can do, e.g. pay $1000 USD to not be limited, vs spend an amount of time learning the tool like approaching diptrace would involve. I'm personally unclear what diptrace offers that would make me be willing to pay that amount + the time investment to relearn a locked down tool?

To the OP, the other thing that may help is you can adjust how the routing works, my personal preference is in the attached image, when routing a wire, right click and you will see "Interactive routing settings"

[redgear]

I may be underestimating the complexity of a powerbank -- but splitting it into multiple schematic pages seems a bit over the top to me. And if most of the components (or little functional blocks) are connected to a central microcontroller, then the placement of that controller and all the components interfacing to it is a central part of the layout task, and will need to be done with all relevant components in the picture.

Also, the placement of connectors and user interface components (LEDs, buttons, or more complex parts) often creates an additional layout constraint. Again, I would want to see all these parts in context. It's OK to start with a larger-than-needed board, but I want to get an idea of what goes on the front and back, how much room the connectors take there, etc.

Could you share your schematic and non-routed ratsnest to give us a better idea of the complexity? Preferably as a picture or PDF, since not everyone runs KiCAD. Thanks!

Yep! Almost everything is connected directly to the microcontroller. Sure, I'm attaching the schematic and ratsnest here.

To the OP, the other thing that may help is you can adjust how the routing works, my personal preference is in the attached image, when routing a wire, right click and you will see "Interactive routing settings"

Thanks, I will see if that helps.

[ebastler]

Yep! Almost everything is connected directly to the microcontroller. Sure, I'm attaching the schematic and ratsnest here.

Alright, I can see how that looks intimidating at first.

I would start by giving myself lots of room (i.e. pretend that the PCB will be huge), and roughly arrange the components: Connectors to the sides of the board where you want them, passives in loose groups (grouped by function according to the schematic). Roughly shuffle things around to untangle some of the wires.

Quite a few of your ratsnest wires will be for GND connections. Not sure how KiCAD handles this, but I would create a GND layer early on to take care of these, to clear up the remaining picture a bit. You might even create a "temporary" GND layer on the top layer, such that KiCAD auto-connects all the GND pads and removes these ratsnest lines. (Eventually, you probably want your GND pour on the bottom, and most of the other connections on top. Then you will need to place vias near the SMD pads which need to be connected to GND.)

[redgear]

Yep! Almost everything is connected directly to the microcontroller. Sure, I'm attaching the schematic and ratsnest here.

Alright, I can see how that looks intimidating at first.

I would start by giving myself lots of room (i.e. pretend that the PCB will be huge), and roughly arrange the components: Connectors to the sides of the board where you want them, passives in loose groups (grouped by function according to the schematic). Roughly shuffle things around to untangle some of the wires.

Quite a few of your ratsnest wires will be for GND connections. Not sure how KiCAD handles this, but I would create a GND layer early on to take care of these, to clear up the remaining picture a bit. You might even create a "temporary" GND layer on the top layer, such that KiCAD auto-connects all the GND pads and removes these ratsnest lines. (Eventually, you probably want your GND pour on the bottom, and most of the other connections on top. Then you will need to place vias near the SMD pads which need to be connected to GND.)

Thanks... Let me try and post the progress.

[NivagSwerdna]

Nivag, Why would anyone want to lock themselves in with software that limits what they can do, e.g. pay $1000 USD to not be limited, vs spend an amount of time learning the tool like approaching diptrace would involve. I'm personally unclear what diptrace offers that would make me be willing to pay that amount + the time investment to relearn a locked down tool?

Useability.
But shockingly I just checked and it is no longer free!  Not For Profit (500 pins, 2 signal layers) is still free if you ask them nicely.

[cgroen]

Also remember that many times you can move I/O around on the CPU to get a cleaner layout!
Other than that, experience, experience and experience. Start with something simpler, make a lot of layouts. Eventually you will "just do it"

[jhpadjustable]

Also remember that many times you can move I/O around on the CPU to get a cleaner layout!
Other than that, experience, experience and experience. Start with something simpler, make a lot of layouts. Eventually you will "just do it"

OP misspoke. It's not a SoC and it's not a microcontroller. It's just a switching converter with a lot more pins and power steering than one might be used to.

[NivagSwerdna]

OK... I'll try and be a bit more constructive...

 

Looking at the datasheet and schematic suggests that you should (as some suggested earlier) forget about size constraints for now and work radially out from the chip.

e.g. the LEDs all need to live on the side nearest their pins, etc. and likewise each output should be put radially out from where they connect

... so put the chip in the middle and arrange the connections around them at an angle that reflects the majority of their connections.

You can then squish it together later

I would aim to route all non-ground nets first and come back to a ground flood later.

(The caps need to go where they are intended... so for example a decoupling cap should really be close to where it is meant to decouple... that can get lost in translation if you aren't careful)

[rstofer]

ExpressPCB (classic) doesn't do autorouting but what it does do is link the layout to the schematic.  So, when I click on a pin that might be Clk, say, all pins on that net are highlighted.  All I have to do is lay down a trace.  Inevitably, I have to reroute some traces but it usually works out fine.

That rat's nest is useless.  It provides no information about how to lay things out other than "it's a mess".

I haven't used any of the more sophisticated PCB programs, I have always been happy with ExpressPDB (classic).

[redgear]

Quite a few of your ratsnest wires will be for GND connections. Not sure how KiCAD handles this, but I would create a GND layer early on to take care of these, to clear up the remaining picture a bit. You might even create a "temporary" GND layer on the top layer, such that KiCAD auto-connects all the GND pads and removes these ratsnest lines. (Eventually, you probably want your GND pour on the bottom, and most of the other connections on top. Then you will need to place vias near the SMD pads which need to be connected to GND.)

This didn't work. I tried creating a ground fill on the top layer but the ratsnets is still the same.

OP misspoke. It's not a SoC and it's not a microcontroller. It's just a switching converter with a lot more pins and power steering than one might be used to.

I might have been wrong but that is how the company calls it. Powerbank SOC. It has a boost converter, Charge Protocol Identifiers and a Battery Gauge built in.

OK... I'll try and be a bit more constructive...

 

Looking at the datasheet and schematic suggests that you should (as some suggested earlier) forget about size constraints for now and work radially out from the chip.

e.g. the LEDs all need to live on the side nearest their pins, etc. and likewise each output should be put radially out from where they connect

... so put the chip in the middle and arrange the connections around them at an angle that reflects the majority of their connections.

You can then squish it together later

I would aim to route all non-ground nets first and come back to a ground flood later.

(The caps need to go where they are intended... so for example a decoupling cap should really be close to where it is meant to decouple... that can get lost in translation if you aren't careful)

Cool. Just arranging the components properly is difficult to me. There are some layout rules on the datasheet(that I don't properly understand) which makes it more difficult.

[tautech]

Start again with a bigger PCB.
Drag all components outside the PCB margins.
Have the printed schematic handy or on a second display to constantly refer to while placing components.
Place first components that must be in a certain place. Lock them.
Then place the most complex components.
Slowly add other active components while still shifting already placed components to make room for passives yet to come.

As others have mentioned build and finalize circuit blocks of which you can select and move/rotate for best connectivity.
All the time you need consider how any and all components will be placed, soldered or reworked and routed.
Use autoroute often to see what you can improve with better placement then un-route and move/rotate stuff.

Study old commercial PCB's......lots ! Understand signal/data connections and power rail routing.
Use a pour to connect to as many components as you can, orientate them so that you can.
Eye up bigger components that might allow traces run under them and place them where this might help you.
Be prepared to spend real time on a good layout and don't be too impatient to do so.
After a couple of PCB's there'll be no stopping you and you'll spin them out in a fraction of the time your first one took.

Post your progress layouts for marking. 

Daves good PCB guide:
http://www.alternatezone.com/electronics/files/PCBDesignTutorialRevA.pdf

More here:
https://www.eevblog.com/wiki/index.php?title=Online_Electronics_Tutorials_and_Books#PCB_layout_and_CAD

[redgear]

Start again with a bigger PCB.
Drag all components outside the PCB margins.
Have the printed schematic handy or on a second display to constantly refer to while placing components.
Place first components that must be in a certain place. Lock them.
Then place the most complex components.
Slowly add other active components while still shifting already placed components to make room for passives yet to come.

As others have mentioned build and finalize circuit blocks of which you can select and move/rotate for best connectivity.
All the time you need consider how any and all component will be placed, soldered or reworked and routed.

After dinner I’ll be back with a link to a good and full guide.

Tried it, as all connections just go to a single IC it is very difficult for me.
Thanks, I will be waiting for the link.

[redgear]

I have disabled ratsnet right now and started grouping components as per the schematic. Will post it once i am done for review

[james_s]

Maybe try some simpler PCBs first to get the hang of it? Lay out some stuff like 555 and transistor multivibrator LED blinkers, op-amp circuits, just easy stuff with a handful of components. Once you get the hang of the process it gets easier.

Some people are also just better at visualizing spacial relationships, PCB layout came quite naturally to me but I've seen a lot of people struggle with it.