I'm a total novice to electronics, I know my way around basic analog circuitry (which is why I managed to design a guitar amplifier) but I have no idea where to start with PCB design.
I'm using KiCAD and I've drawn the schematic (simulates well in LTSpice); now, some info on how to translate the schematic into a PCB would be nice.
I would be using through-hole components (because how the hell am I going to work with SMD anyway?) and I'd like the amplifier to be as quiet as possible, no ground loops (OK, use a star ground, or at least a "one-way ground rail" connecting stages sequentially), no oscillations, etc. I know that with a single-layer PCB you can't really use ground planes, and ground planes can be sort of overkill when it comes to audio anyway, but where can I start?
I'm using KiCAD and I've drawn the schematic (simulates well in LTSpice); now, some info on how to translate the schematic into a PCB would be nice.
I would be using through-hole components (because how the hell am I going to work with SMD anyway?) and I'd like the amplifier to be as quiet as possible, no ground loops (OK, use a star ground, or at least a "one-way ground rail" connecting stages sequentially), no oscillations, etc. I know that with a single-layer PCB you can't really use ground planes, and ground planes can be sort of overkill when it comes to audio anyway, but where can I start?
That wasn't my biggest concern. I'm talking about good practices in designing PCBs. Some I already know (try to keep power lines and signal lines at a right angle, place filter capacitors as close to opamps as possible, try to implement a star ground, keep signal ground and power/digital/switching ground separate, connecting in one point only on the chassis itself, possibly use separate PCBs for power supply and preamplifiers). But in general, I'd like to have a more comprehensive education on the matter.
Obviously I'm not a PCB-designer and this was written for Eagle which means the workflow is a little different than Kicad, but I have written a couple of blog posts some years ago about my approach to designing boards. The real "science" of what makes a good design you can easily find online, but understanding how to start out on the puzzle took me a while to work out 🙂
https://theslowdiyer.wordpress.com/2015/08/01/pcb-layouts-part-1-workflow/
https://theslowdiyer.wordpress.com/2016/11/28/evolution-of-a-design/
https://theslowdiyer.wordpress.com/2015/08/01/pcb-layouts-part-1-workflow/
https://theslowdiyer.wordpress.com/2016/11/28/evolution-of-a-design/
Draw a clear, logically flowing block diagram, and try to lay out the pcb in a similar way.
Place the connectors in their best positions first.
Then the main devices and their power connections.
Place the connectors in their best positions first.
Then the main devices and their power connections.
Most of the projects I do have PCB layout by JPS64 or Jhofland. I do manual layout with graphics from a draw program or PowerPoint and home etched iron on transfer PCBs.
Nowadays, PCBs from JLCPCB are so cheap it doesn’t make sense to etch at home if I’m willing to wait for a week or so.
Nowadays, PCBs from JLCPCB are so cheap it doesn’t make sense to etch at home if I’m willing to wait for a week or so.
The key to SMD is use an oven - I adapted a very cheap sandwich toaster by moving both heating elements to the top, and I run the temperature profile by hand using a stop watch and watch for the solder paste to reflow through the window - remarkable simple but effective.
You can get solder paste in syringe to apply solder paste to pads, or better get a solderpaste stencil (these can be laser cut from ordinary paper if you have access to a laser-cutter!).
And if you stick to SOIC and 0805 passive components its pretty doable. With a stencil you can go down to 0.65mm pitch or so reasonably reliably: http://sphinx.mythic-beasts.com/~markt/DRV8711-stepcard-x-sm.jpg
If necessary, the SOIC package is easy to hand solder, as are 1206 resistors.
Component layout is the most important part. Place the components to keep the sensitive nodes as short as possible. Always take care of the current return path; keep the important current contours tight. Don't be too dogmatic about star grounding - return current magnitude is the criteria. E.g. low current arms can share same ground return if it's more important to keep the distance short.
In my last few projects, I've used veroboard and point to point connections. It worked surprisingly well with TTH discretes and few ICs. First, I've spent many days in optimizing the layout. Then, in most cases the uncut leads of the components were long enough to reach the next point. It took me only few wire links.
In my last few projects, I've used veroboard and point to point connections. It worked surprisingly well with TTH discretes and few ICs. First, I've spent many days in optimizing the layout. Then, in most cases the uncut leads of the components were long enough to reach the next point. It took me only few wire links.
You can find my workflow here: https://www.diyaudio.com/community/threads/pcb-design-tool.391094/post-7143873
Tom
Tom
A brief overview of how to translate your schematic into a PCB design using KiCAD, while keeping your specific requirements in mind. PCB design can be a bit complex, but I'll break it down into key steps to help you get started:
- Import Schematic: Start by opening your schematic in KiCAD's schematic editor. Make sure all components and connections are correctly placed and labeled.
- Footprint Selection: For each component in your schematic, you need to associate it with a physical footprint (through-hole in your case). KiCAD provides libraries with a wide variety of footprints for through-hole components. You can assign footprints manually or use the "Assign Footprints" tool to speed up the process.
- Create PCB Layout: After assigning footprints, launch the PCB layout editor. The components from your schematic will be imported into the layout editor. They will appear as a cluster of components initially.
- Placement: Arrange components on the PCB layout, keeping in mind their connectivity and signal flow. Place components close together to minimize trace lengths and reduce noise.
- Routing: Route traces to connect components based on the connections defined in your schematic. Try to keep signal traces as short as possible to minimize signal degradation and noise. For audio applications, you might want to avoid running signal traces near noisy components like power supplies.
- Grounding: Since you're concerned about ground loops and noise, it's important to have a solid grounding strategy. You mentioned a star ground or a sequential ground rail – these are good approaches. Connect all ground points together in a single location (star point) or using a dedicated ground trace running through each stage. This helps reduce ground loops.
- Power Supply: Ensure that the power supply traces are appropriately sized to handle the current requirements of your circuit. Keep power and ground traces wide to minimize voltage drops.
- Copper Pours: While you can't use full ground planes on a single-layer PCB, you can still create copper pours that function as pseudo-planes. Create large copper areas for both ground and power and connect them to your ground and power traces. These areas will help improve noise immunity.
- Component Clearances: Maintain proper clearances between components, especially for through-hole components with leads that might stick out. Avoid overlaps and ensure components don't obstruct each other.
- Design Rule Check (DRC): Run the DRC tool in KiCAD to catch any design rule violations such as trace width, clearance, and other potential issues.
- Export Gerber Files: Once your design is complete, you need to export Gerber files. These files are used by PCB manufacturers to fabricate your board. KiCAD provides an option to generate Gerber files along with other necessary files like drill files.
- PCB Fabrication: Send your Gerber files to a PCB manufacturer for fabrication. They will create the physical PCB based on your design.
1) There is no reason to use single layer unless you are etching the board yourself. Two layers make much better layouts and fewer dry joints
2) Star grounding is rarely a good idea, they cause RFI problems. Just be aware where large currents are flowing, especially Class B output stages.
2) Star grounding is rarely a good idea, they cause RFI problems. Just be aware where large currents are flowing, especially Class B output stages.
Regarding grounds, its important to learn about and consider where currents are going to flow. One app note of possible interest:
https://www.analog.com/media/en/technical-documentation/application-notes/AN-202.pdf
Also, for mixed-signal systems there are a number of app notes, such as for example:
https://www.ti.com/lit/an/slyt499/s...90931&ref_url=https%3A%2F%2Fwww.google.com%2F
https://www.analog.com/media/en/tec...14948960492698455131755584673020828AN_345.pdf
Beyond that type of thing there are whole books on grounding and on "electromagnetic compatibility engineering."
There is no good reason to use a single layer is there? The cost is the same for two layers, so why not use them both thoughtfully?
I had bad experiences with using big groundplanes just to use the second layer. I had unwanted oscillations, HF pickup, crosstalk etc in audio circuits. So just using a layer for groundplanes can give a lot of more trouble. You need excactly when to use those big groundplanes or otherwise it is better to leave them.