Hacker News Reader

Comment by bbayer | Hacker News Reader

I want to learn PCB design, mostly with ARM and ESP based designs. How would I learn basics? I know theory part but I really couldn't figure out why they determine which component and which value they have to use. I mean there are resistors, capacitors all over the place but I really want to learn reason behind it. Also I guess there are some basics related power, battery, UART, USB etc. Is there any source that covers all of these concepts?

View on HN

There are certain usage patterns that you will find all over the place, e.g.:

- Current-limiting resistors

- The resistor divider (two resistors between e.g. 3.3V and GND. The point between the two resistors will be between 3.3V and 0V, depending on the resistor values. Sometimes you need a certain voltage. For example to bias transistors.

- Delays, using a resistor and a capacitor. The values will determine the delay.

- Capacitors next to oscillators

- Filters, using a resistor and a capacitor. The order and the values will determine the cutoff frequency.

- Most capacitors on a PCB probably sit right next to a chip. Often, at least one per chip. They get rid of noise already on the line, and act as short-term energy storage for the chip next to it.

- Decoupling capacitors to get rid of the DC component of a signal (i.e. if there is a signal fluctuating between 4.5V and 5.5V before the cap, it'll be -0.5V and 0.5V behind the cap. Often, you need to add a DC component and later remove it, so that's two capacitors already.

Obvious but it never occurred to me that experienced person sees far fewer parts than layman when looking at the board, for expert its like yeah "file read there", "serialization here" (if I were to use programming analogy) but layman sees gazillion little parts magically working together.

"You get used to it, I don't even see the code. All I see is blonde, brunette, redhead."

I think cockroach, beetle and woodworm is more appropriate when talking about code.

They were quoting "The Matrix". But you're probably correct, even in the movies the existence of "The One" was a pretty serious security bug, and the entire need for "agents" was a workaround for other bugs.

Also worth mentioning are pull-up or pull-down resistors. They give a pin a default state when nothing is driving the pin. You will often see them on reset pins and on inputs from buttons.

"if there is a signal fluctuating between 4.5V and 5.5V before the cap, it'll be -0.5V and 0.5V behind the cap" if there's a resistance to ground after the capacitor. I've accidentally planned an audio amp with input decoupling capacitors, didn't add ground resistors before the capacitors, so if you plug it into an audio output with DC-blocking capacitors but not resistors to ground, the voltage in the middle could be anything.

> I mean there are resistors, capacitors all over the place but I really want to learn reason behind it.

There are some good YouTube channels that go into this. EEVBlog[1] has made a lot of really nice videos about the fundamentals, as has w2aew[2]. And I found MicroType Engineering[3] to be a good source of practical information on designing circuits.

Capacitors next to ICs are almost always for decoupling[4]. Similar to how the cistern in your toilet provides a large amounts of water in a short amount of time without affecting the water pressure in the rest of the house, hence decoupling the local water flow from the main supply, decoupling capacitors can supply a lot of current for a short amount of time.

However what values to use can seemingly be a bit of a black art[5], not helped by the fact there's so much outdated information and rules of thumb out there from the days of through-hole components which just doesn't apply to modern surface mounted components (like needing multiple different values).

On the other hand, resistors on a data line can be there to protect against ESD events[6], for example.

Some of it might be a bit more advanced than what you need right now, but there's definitely some good stuff for people starting out. If for nothing else highlighting areas you should be aware of.

[1]: https://www.youtube.com/@EEVblog/playlists

[2]: https://www.youtube.com/@w2aew/playlists

[3]: https://www.youtube.com/c/MicroTypeEngineering

[4]: https://www.youtube.com/watch?v=BcJ6UdDx1vg

[5]: https://www.youtube.com/watch?v=k7aPb585Y6k

[6]: https://www.youtube.com/watch?v=6OxE06n6n44

Also Phil's Lab, especially for PCB design specifically (though he covers schematics too, I'd say it's typically not as beginner-friendly/a faster-paced run-through so you understand what he's laying out).

As an EE I can vouch 100 times for Phil's Lab. He really knows his stuff and honestly is as close to the actual job as it can get.

Make: Electronics by Charles Platt will take you through all the whys and wheres, starting at the very basics. I highly recommend it.

Also, I'll recommend the "Follow the example" approach of just looking at the data sheets for various components and modules. Especially stuff like the Arduino Uno - It's got a microcontroller, and then everything around it is just support. You start to see patterns where there (for example) a 10uF and 0.1uF Capacitor around power inputs. And they're everywhere so even if you don't know why (yet) you do know that you need capacitors around power inputs.

I started by building a programmable mechanical keyboard based on this macropad tutorial (see link). If you want to simplify it somewhat, replace all the microcontroller circuitry (oscillator, capacitors, USB interface, etc.) with an Arduino, and use through-hole diodes. It's a really cool feeling to finish your design, order custom PCBs from jlcpcb, do a bit of soldering, and end up with a useful, working keyboard.

https://wiki.ai03.com/books/pcb-design/page/pcb-guide-part-1...

I followed this to make a very basic PCB and had it shipped to me, worked fine. Guides you through all the basic steps with KiCad.

https://youtube.com/playlist?list=PL3bNyZYHcRSUhUXUt51W6nKvx...

Read the datasheets. They usually have recommended layouts and configurations.

Yes, this is the way. Datasheets and application notes will tell you nearly everything you need to know. If you don’t understand why something is done or how something works, look it up at that point. Starting from fundamentals is going to be a much slower path than just following manufacturer examples.

For designing with basic components I recommend starting with microcontrollers on a breadboard. There's plenty of great youtube channels that talk about this stuff as well, like GreatScott and Ben Eater

Phil's Lab on YouTube has great PCB design tutorials that cover how to think about layout and design, how to use Kicad, and even how to turn your design into a real product.

https://youtube.com/@PhilsLab

So you want to learn electronics? I suggest that you take the time to actually learn the theory behind it and learn how resistance, capacitance, inductance affects the system. It is hard but helps a lot. If you want to understand digital systems, then learn how digital basic components work and how you combine them to create more complex systems. Had electronics as my major in my bachelor's degree, and the mental model is really important when it comes to electronics, and the only way to really understand it and get the correct mental model is by repeatedly analyzing the networks and the change over time (resistance,capacitance,inductance) and all of sudden it makes perfectly sense!

Underlying theory is important, but seeing practical examples that _explicitly applies theory_ has been critical in my particular electronics adventure. There are more ways to apply Ohm's Law (or Kirchhoff's Laws) than you can shake a stick at and seeing someone explicitly do the math and apply it while explaining a circuit that I am interested in has helped me get better at applying it.

I think the hardest things for me so far been (a) getting my head around the idea that everything in a circuit is happening all at once (rather than iteratively like an algorithm) and (b) "input" and "output" are convenience terms, e.g. an opamp can sink current through its "output". Both of these insights have come from seeing real circuits analyzed on YouTube.

In addition to the other replies which list a number of good resources, I've found reddit.com/r/PrintedCircuitBoard interesting to watch. It's mostly people asking for reviews of their projects, and there's a lot of tips and tricks to pick up in the review comments.

You can also see a nice progression there from beginner PCBs to more advanced things.

Reply on news.ycombinator.com