How a devboard works (and how to make your own) • Hacker News Board

Re: How a devboard works (and how to make your own)

#31

Post by IndrekR » Sat, Nov 08, 2025, 12:58 PM UTC

_def wrote: post #28

exmadscientist wrote: post #8

I don't like this tutorial. It purports to teach you "what everything on the PCB fundamentally does, and what every single component on your PCB is actually for!" but it gets the reasoning for a lot of stuff wrong, sometimes badly wrong. I think every single instance of a component with a numerical value picks the value with a misleading or even completely wrong justification. Even if the tutorial gets to an OK schem…

What do people often get wrong about decoupling capacitors?

Few things for starters:

- you have to look at it in frequency domain as well;

- speed of light is too slow;

- often capacitors are inductors, even more so when mounted on PCB;

- capacitance is not what is written on the component.

I am teaching this to robotics and computer engineering MSc students. Quite nice intro book into the topic that I recommend to my students: https://www.oreilly.com/library/view/principles-of-power/978...

Re: How a devboard works (and how to make your own)

#32

Post by wronex » Sat, Nov 08, 2025, 2:03 PM UTC

exmadscientist wrote: post #26

wronex wrote: post #23

Earlier quoted context omitted.

I don’t think you’ve used KiCAD. Simply add an MPN attribute to your component and that is it. Use the built in BOM editor and exporter. Done. There are certainly ways to misuse any advanced software. But it definitely can and will produce a complete BOM without additional add-ons. Grated, the exporter is limited to CSV files. So I’m guessing your workflow requires something more interesting?

> Simply add an MPN attribute to your component and that is it. No, that's the problem, right there. KiCad doesn't have a parts library. KiCad has schematic elements you can manually tack parameters on to. And everyone does it slightly differently! There's no way to have a set of parts you can select from that are guaranteed-approved (because we used them previously or whatever). There's no way to have the software j…

The nice thing with KiCAD is that a part is simply a symbol (schematic element) with enough parameters attached. You can specify footprints, MPN, ratings, value, etc. then store it in your approved and verified symbol library for use in all your projects. Use your R_4.7k_0603 symbol an it comes preconfigured with footprint, MPN, rating etc. Making these symbols is a lot of work but very simple.

Unfortunately there is no standard name for these parameters beyond footprint, value and some others. MPN, brand, rating etc. are not default. This hinders bigger adoption I think, and makes every project unique. This should be improved.

Re: How a devboard works (and how to make your own)

#33

Post by macnetic » Sat, Nov 08, 2025, 5:19 PM UTC

rcxdude wrote: post #29

exmadscientist wrote: post #22

Earlier quoted context omitted.

What BOM flow? It doesn't bloody well have any! At no point in the entire design process within KiCad does this design ever get part numbers assigned for its resistors or capacitors (to pick one thing). That's not acceptable for professional work. A Bill of Materials ABSOLUTELY MUST DESCRIBE THE MATERIALS used in the assembly of the PCBA. Internal part numbers are perfectly acceptable: assigning a generic RES-0402-10…

>When I generate a build package in Altium, it has complete lists of every part in the design, its MPN, at least one supplier to purchase it, and the SPN for that MPN. (Sometimes internal parts don't have suppliers assigned, but then they're tracked elsewhere in the project or company organization.) There are also assigned alternates in many cases, though they are typically inadequate. Larger projects should use enti…

We use the Celestial Altium Library [1], it's really good for passive components, which make up ~80% of our schematics by count. For other parts we first try to get them through Altium Manufacturer Part Search, we vet the symbol and footprints before importing them into our internal library. Other model sources in order of preference is SnapMagic, UltraLibrarian, Samacsys. Be aware as the quality is often half-baked. Between components that meet my requirements, I will always pick the one with CAD models easily available.

With those prerequisites I only have to make 2-3 footprints from scratch per project as needed, and less so as our library grows.

[1] https://altiumlibrary.com/

Re: How a devboard works (and how to make your own)

#34

Post by kaipereira » Sat, Nov 08, 2025, 8:31 PM UTC

Hey guys, thanks for all the love :D

The website went down because of the traffic and large images, so I've temporarily switched hosting, and it should stay up now (DNS propagation might take a bit though), but I'm going to get those images smaller ASAP, thanks to everyone who posted web archives!

I'm also going to alter some of the reasoning for some of the stuff like decoupling capacitors, but the guide is still meant for complete beginners, and lots of the terminology/reasoning can be pretty overwhelming, and I still have a lot to learn about decoupling/other stuff!

I'll also add a part about what you actually need on your devboard, that's a great suggestion!

You can find a JOURNAL.md in EVERY SINGLE one of my hardware projects https://github.com/KaiPereira?tab=repositories so if you guys want to see more guides/tutorials, let me know :D

Re: How a devboard works (and how to make your own)

#35

Post by exmadscientist » Sat, Nov 08, 2025, 11:29 PM UTC

_def wrote: post #28

exmadscientist wrote: post #8

I don't like this tutorial. It purports to teach you "what everything on the PCB fundamentally does, and what every single component on your PCB is actually for!" but it gets the reasoning for a lot of stuff wrong, sometimes badly wrong. I think every single instance of a component with a numerical value picks the value with a misleading or even completely wrong justification. Even if the tutorial gets to an OK schem…

What do people often get wrong about decoupling capacitors?

Not quite a list of fallacies, but some words about how to do it well:

Me at eevblog: https://www.eevblog.com/forum/projects/location-and-value-of...

A discussion here a while back (not all of which I agree with): https://news.ycombinator.com/item?id=42830948