PCB board question Moderators: adafruit_support_bill, adafruit

[sayagi1]

Hey guys just had a quick question. I’m going into my 3rd year of EE so I have a lot of theoretical knowledge of electricity, electronics, etc. I’m just getting into robotics and one thing that I’m finding confusing is making PCBs. Like how do you know where to put a resistor, the value of the resistor needed, things of that sort? Like I’m trying to make a IR sensor module but I have to copy other peoples work because I have no idea on how to go about designing it. Any advice on where to potentially get educated on this?

[jps2000]

A PCB is a method / technology to realize an electronic circuit physically.
So first you have to design a schematic having all components needed. Usually there is a key component like a microcontroller or other integrated circuits. Semiconductor suppliers give application information in data sheets. This is your starting point.
A good approach is also to look into existing schematics and try to understand the function of each component. Ideally with the help of a supervisor / teacher. Ofcourse not all are designed very well. Schematics of professional equipment may be superior- but not necessarily.
You may even study the related PCB and figure out why it was made like this. Sometimes there are also manufacturing constraints that are not immediately evident.
Also repairing electric electronic equipment may promote learning
Main approaches of PCB design are: as small as possible within electrical and mechanical constraints.
Experience is key (as always). And endurance of course.
No master has fallen from the sky yet.

[adafruit_support_mike]

A good approach is also to look into existing schematics and try to understand the function of each component.

Very much yes: Existing circuits are design problems that someone has already solved, so they're intellectually closed systems: there's at least one configuration where every part does exactly what the designer wanted. The dual processes of figuring out what the part does and why the designer wanted that specific behavior are incredibly instructive.

Equipment manuals from the 1960s through the 1980s are especially valuable. They go out of their way to explain the theory of operation and piece-by-piece operation of the circuits.. back then companies understood that users needed to understand the equipment to use it effectively. The Tektronix 'Concepts' manuals are some of the best technical documents ever written:

http://www.davmar.org/concepts.html


PCB design is another, separate art. It begins with toplogy.. putting related parts close to each other so the traces are as short as possible, combining groups of parts into modules that talk to each other and routing signals between them in a reasonably sensible way.. and moves on to include as much low-level physics as the circuit demands. Cell phone PCBs are electrical components in their own right, with controlled impedances, matched trace lengths, and so on.

In general, circuits in the quasistatic domain (DC to about 10MHz.. where the physical circuit is much smaller than the wavelength of the fastest signal of interest) are less demanding than RF circuits. That's the easiest place to start learning.

And just as with circuit design, learning to read existing PCBs and relate them back to a schematic is hugely instructive. Along with "what does this component do?" and "why did the designer want that?", you can also ask "why put it here instead of somewhere else?"

You can think of schematics and physical circuits as two kinds of literature. It takes time to learn to read them, and more time to read enough that you start to recognize standard features, genres, and yes, fads. And as with every other kind of literature, you'll find masterpieces, day-to-day works that are competent but not much more, and the occasional piece of absolute garbage. All of them are worth reading, if only to remind yourself that you know better.

[tepalia02]

Hi there, so you're a beginner in PCB making, right? I think this write-up will be helpful for you.

https://pcbtracks.com/basics-of-pcb-des ... beginners/

It explains what a PCB is and how PCBs are designed. It will help you learn how to make your own PCB.

[petespaco]

Re: "Like how do you know where to put a resistor, the value of the resistor needed, things of that sort? Like I’m trying to make a IR sensor module but I have to copy other peoples work because I have no idea on how to go about designing it."
From this comment, I'd suggest that you need to start with learning circuit design first. Don't even worry about PCB design until you learn how to design, breadboard and test the circuit itself.

[argonblue]

If you want to bridge the gap between theoretical EE knowledge and practical, and if you learn well from books, I would suggest reading Horowitz & Hill, The Art of Electronics. I've only read the second edition, but I've heard the third edition is even better, and Adafruit sells it.

[adafruit_support_mike]

but I've heard the third edition is even better

I have all three versions, and they're all worth reading.

Beyond the excellent descriptions of components in general, Horowitz and Hill invested the time and effort to test and characterize hundreds of parts, then create tables so you can compare the results. For the third edition they really pulled out the stops on that, so the book is full of information about devices you can buy and put in a PCB. They also provide detailed descriptions of contemporary circuits using those parts.

Manufacturer catalogs over time though, and not always for the better. A sad fact of being a TAOE fan is reading clear and well-documented descriptions of what they consider the best parts, and knowing they're no longer being made.