My First PCB! – Laura Lindzey
Designing a PCB and sending it off to fab is surprisingly accessible and seems like an excellent energy.
I’d been intimidated for years, however lastly jumped in.
Additionally, I like residing sooner or later! For <$20, you’ll be able to design a PCB, have it manufactured in a manufacturing unit, and get it mailed to you.
This nonetheless appears insane to me.
This submit describes the trail I took to get my first PCB manufactured, with an emphasis on not getting sucked into optimizing each determination.
I’m assuming you have already got a circuit drawn out or breadboarded, and also you need to immortalize it.
I estimate that going from “what’s KiCAD even” to ordering your first PCB might be an affordable one-day challenge for a easy circuit you have already got sketched or breadboarded.
It solely took me just a few days as a result of I used to be paying a variety of consideration to the aesthetics of the board.
My Circuit
Whereas doing a mini batch on the Recurse Center, I turned fascinated by the oscillator circuit that powered the RC Christmas ornaments.
I like how easy the circuit is, whereas producing visually-interesting habits!
I needed to play with various the frequency of the oscillator through the use of totally different values of resistors and capacitors, so I made a protoboard wired up with feminine header to make this straightforward.
It seems that LED colour additionally makes a distinction!
I dislike breadboarding for something extra prolonged than a proof-of-concept (it’s the bodily incarnation of spaghetti code) and protoboard is usually a ache to work with.
So, I figured an oscillator circuit with feminine headers for the entire elements might be a enjoyable first PCB to have fabricated.
Early implementations of the oscillator. Left: on breadboard, Proper: on protoboard.
CAD software for PCBs
I actually like KiCAD as a design software as a result of it decouples documenting the circuit logically from laying it out on a board.
That is nice for after I need to have professional-ish schematics of issues that I’m solely ever going to implement in protoboard.
I feel Eagle is the principle competitor, however it has a good coupling between the logical schematic and the bodily structure that compelled me to care about element packaging and footprints method too early (like 2 years too early), so I bailed on it rapidly.
Plus, KiCAD is open-source, which makes me joyful.
There are 3 major phases to designing a PCB in KiCAD:
- Use EESCHEMA to generate a schematic on your circuit. This might be a digital model of the hand-drawn circuit from above.
- Use CVPCB to affiliate every ingredient within the schematic with a selected element’s footprint. For instance, resistors are available in many styles and sizes, and earlier than laying out a PCB, that you must select which resistor to make use of. The footprint specifies its bodily dimension, connections to the board, silkscreened define, and generally even 3D view.
- Use PCBNEW to outline the board’s boundary, organize the footprints on the board, add traces connecting elements, and add annotations that might be silkscreened.
This video tutorial by Widsor Schmidt was effectively finished.
He walks you thru the entire course of (opening KiCAD for the primary time to completed PCB structure) in 20 minutes.
I watched it repeatedly on 2x pace, pausing so I might observe alongside.
Schematic
I don’t keep in mind what tutorials I used for studying find out how to arrange a schematic utilizing KiCAD’s EESCHEMA program, however Schmidt’s video additionally covers that.
I first used it just a few years in the past, and recall that I spent a night to go from “KiCAD appears attention-grabbing” to “hand-sketched emergency cease schematic for my robotic is now laid out properly”.
Right here’s my oscillator circuit as represented in EESCHEMA:
Element Choice
Subsequent, we have to affiliate the symbols on the schematic with a real-world element that matches the required specs.
This requires each selecting the precise elements you’ll use throughout meeting and specifying the footprint they want on the board.
If you wish to use elements that aren’t in one in all KiCAD’s built-in libraries, you can also make your personal footprint.
I’ll must be taught this ultimately, however since my plan was to solder feminine headers to the board so I might swap elements out, this was irrelevant.
To avoid wasting time in your first board, you’ll be able to simply use through-hole elements with bendable leads (which you in all probability have already got from breadboarding!) or footprints which might be already within the libraries.
For those who’re determined/lazy, simply use the footprints from the connector library — they’ll work for something that you simply have been in a position to make use of on a 0.1” pitch breadboard!
The exceptions to this are the ability swap and battery, each of which took me a very long time to search out and aren’t a part of a typical breadboarding package.
I passionately hate Digikey’s search interface.
It’s shockingly unhealthy at having the proper metadata for filtering to be efficient.
Mouser is usually higher, however I am nonetheless not a fan.
So, listed below are some good-enough choices:
- I used these breadboard-friendly switches from Sparkfun. I additionally just like the C&K JS202011CQN, which has a footprint within the KiCAD Button_Switch_THT library.
- I used a coin cell battery to energy my challenge. There are KiCAD footprints for the Keystone 3000 (12mm) battery holder and Keystone 3008 (24mm). I favor the Harwin S8211-46R for a 20mm battery as a result of it’s simpler to get the battery in/out, however there isn’t a built-in KiCAD footprint.
If you wish to scale down elements to make the ultimate board smaller, you’ll must spend time buying … and cutting down in dimension additionally means determining find out how to do surface-mount soldering with tiny elements.
I could get to that sometime, however not but.
Board Structure
The following step was to put out my circuit as it might seem on a PCB.
I fiddled with the structure lots (totally redoing it 3x), and had numerous drudgery determining find out how to get the silkscreening to look virtually proper.
I nonetheless don’t have a course of that I like for that … I imported public domain electrical symbols as bitmaps, however it was onerous to get their results in have the very same width to match.
This is the illustration of my board from pcbnew, exhibiting the entire layers without delay:
I don’t keep in mind when/how I got here up with the concept for making the circuit diagram a part of the PCB design, however I think it was influenced by having seen Star Simpson’s Circuit Classics in some unspecified time in the future.
Fabrication
When you’re proud of the circuit structure, head over to OSHPark and add your kicad_pcb file.
Their interface is unbelievable, and offers a pleasant rendering so that you can do a last examine on every layer, along with what the entire stackup will seem like when manufactured:
Renderings of the entrance (left) and again (proper) of my PCB, generated by OSHPark.
I did not spec out the total market of accessible fabricators as a result of OSHPark hit a candy spot for me on the intersection of “low cost sufficient to do on a whim” and “caters to hobbyists/small batches, performs exceedingly effectively with KiCAD”, with a bonus of “the EE at work makes use of them for customized boards for our a number of million greenback robotic, so high quality should be OK”.
Severely, really putting the order was the simplest a part of this entire course of.
Their automated import (straight from KiCAD’s .kicad_pcb format) automagically labored.
My first model of the structure was going to value $7.85 to get 3 copies of the board.
I made it larger for aesthetic causes, so I wound up spending $20.05, and transport is free.
Outcomes!!
OSHPark did an incredible job, they usually’re prettier than I anticipated!
I assembled two out of the three — one with header so I can swap out and in totally different elements, and one with blue LEDs tuned to flash at about 1 Hz.
Assembled boards!
The tough bits across the edges are mousebites, that are added by OSHPark with the intention to connect my board to others in the course of the fabrication course of.
Afterwards, the skinny tabs break simply, separating the boards.
I don’t actually need to sand fiberglass, so I could strive protecting them with clear nail polish.
There are just a few points that I might repair in a v2:
- One of many vias is beneath the battery, and for some cause, it is not coated with solder masks. Provided that it’s kind of recessed, it in all probability would not have made contact, however to be protected, I put down a bit of kaptan tape. I feel “tented through” often is the proper key phrase right here?
- The destructive battery pad can be recessed, and the battery is not making contact. For now, I utilized a little bit of solder to boost it up. I feel the true repair could also be to re-design the battery footprint such that the central pad is greater and/or has a wider border of no-copper round it.
- My LEDs do not flip off as rapidly because the RC decoration one did. This has nothing to do with PCB design, and all the pieces with me not but absolutely understanding how totally different elements have an effect on the circuit. The header check board is supposed to make testing my understanding simpler!
Nevertheless, I’m fairly proud of this! Whereas I nonetheless have heaps to be taught, the workflow appears stable. My subsequent step might be determining find out how to add my very own footprints so I can use any element I need.
Acknowledgements:
Enormous because of the neighborhood at RC for uplifting each the challenge and the writeup! Aaron Strick & Noah Zachary Gordon offered the unique inspiration and encouragement to submit this. Veronica Hanus & Robert Schuessler commented on an earlier draft.