Component Sourcing and Library Management Guide for https://github.com/UWARG/hardware primarily intended for new members of the WARG Electrical subteam as it doesn’t dive into advanced topics.
This writing assumes you have completed the Electrical bootcamp and have a basic understanding of how to use Altium Designer. If you do not, resolve that before proceeding and interacting with our github!
Currently a WIP
Github Repository & How to use it with Altium and Discord
Our Github page for hardware for electrical can be found here https://github.com/UWARG/hardware if you do not have write access just @ a lead on discord and they can hook you up provided they are confident in your understanding or something idk.
If you don’t know how to use https://git-scm.com/downloads I highly recommend using https://desktop.github.com/ as it holds your hand and has the required features you will need. I will explain how to use Github desktop briefly below, but I will not be explaining how to use Git. Git has more features (primarily for our application, the ability to revert commits, although there are many more) and is the industry standard so if you want to learn it yourself, go for it!
You will start by cloning our repository from “origin” or https://github.com/UWARG/hardware onto your local files. Then you can open up the project with Altium and manipulate it. Be sure to include a commit message following our scheme. Examples of commit messages can be found here https://github.com/UWARG/hardware/commits/master so just try to blend in 
. For a more general guide to writing commit messages please at least skim https://chris.beams.io/posts/git-commit/ if you are new to Github.
Be sure to pull from origin before beginning work and push to origin after committing, failure to do this will result things I’m not going to describe how to fix here, but just know they aren’t fun. Further, remember to hit the save button in Altium before committing to ensure all your changes are included in the commit you make. Check the origin Github website to be sure your commit actually went through! Further, we have a system in which we use the #git channel in discord to say what files are busy. This is because the files for Altium are referred to as “binaries” and are therefore not mergable! So only one person can work on each file at once since there is no way to merge like there is when you are writing code. Same thing as commit messages, try to blend in, the git channel is filled with examples on how to do this. “Busy” means you are working on something, “Free” means you are done editing and have committed and pushed all your changes.
Be sure to only use components that are a part of our repositories libraries, mistakes can be make if you have your own repository. When creating new projects or files or anything really, always look at previous stuff and copy paste as much as you can. Sometimes the previous stuff is wrong, but if you don’t know copying previous stuff is fine, also, don’t be afraid to ask questions. Don’t waste your time doing something you’re not sure is correct when someone could answer the questions in a few seconds. Nobody is going to make fun of you, we all learned by questions.
All Components
When sourcing products 99% of the time stick to http://digikey.ca as that’s what we do and they have most things. Always sort by in stock primarily and when you are sourcing search for things that are not only in stock, but are also “well in stock” this means there are at least ten thousand of them available. This is because we will likely order the components weeks or months after you first sourced the part so we want to be sure they will be in stock then and not just in stock when you are sourcing them.
Always be sure to select the “Cut Tape” packaging option for the Digikey part number as the other methods are intended for orders of thousands of the component which we never do. This aspect is primarily for entering in the component into Altium as Digikey puts all shipping methods under each product.
Next, we prefer components that are cheap! For common components I’ve listed typical price ranges below, but for other components just be sure you’re going with the cheapest option that still meets the required specifications.
Capacitors
For capacitors we prefer Murata due to their nice capacitor simulation tool, https://ds.murata.co.jp/simsurfing/index.html?lcid=en-us , that show us how the components will behave through graphs and whatnot. They have most components in stock, but if they lack something, Kemet is our backup. There is a reason for this, probably previous good experiences with these companies, but I’m unsure of the specifics. If you want to deviate from these, check with a lead.
For capacitor voltage rating, be sure to go about 2-3x your expected operating voltage as a rule of thumb. More specifically, however, on a 3V3 application 25V capacitors is ideal and with a 5V board or if 25V capacitors cannot be found for a 3V3 application, 50Vs will do. This is because you want a little overhead just in case, but if you go too high you get poor “DC Bias Voltage” behavior. This means that if you have a 250V 10uF capacitor and you are operating it at 3V3 the actual capacitance will differ from 10uF significantly more then a 50V 10uF capacitor being operated at the same 3V3. To see this behavior, checkout the simulation tools on Murata!
For package we prefer 0603, especially if large amounts of the capacitors are needed, for example, when the capacitor will be used as a decoupling capacitor. This is because they are small and standard. 0805 capacitors are also acceptable as a backup and may be used when better DC Bias Voltage behavior is needed as they often preform better, although, you may want to check the simulations on Murata for the specific capacitor and do your own research regarding this. 1206 capacitors are far too big for standard capacitors so check with a lead before including one. If other capacitor sizes are needed, check with a lead.
Capacitance is often very picky, so when sourcing a capacitor for an application check the datasheet for the exact value required and use it as a search filter on Digikey. For tolerance, plus or minus 10% is what we look for and is fairly standard. Less then 10% is fine if necessary, although watch the budget!
For Temperature Coefficient, we prefer X7R, although X5R and C0G are acceptable as well. This coefficient also plays a significant factor in DC Bias Voltage behavior of a capacitor.
Most capacitors should cost less then $0.75 a piece with your average capacitor right around $0.45 in my experience. If you’re spending over a dollar on a capacitor you should look for alternatives, especially if many of them will be required.
For making the capacitor symbol, assuming you’re grabbing an 0603/0805/1206 package, just copy paste the generic symbol and fill in the parameters with information from the datasheet. These must be filled in perfectly as failure to do so will mess up the bill of materials (“BOM”). The footprints are already made for these packages as well so this should go pretty quick.
Headers
Resistors
Other non-standard components
Symbol Making
parameters
can copy for common packages of common components
Pins can (and should for aesthetic state) go in any position you want as long as the number and name are correct according to the part datasheet.
Naming scheme, blend in
For the drawing itself you can copy from other libraries as long as it is clean
Footprint Making
Correct pin numbers, no need for top overlay except for dot on pin one on components in which pin1 is important.
Can copy from other components or other libraries, make it clean, must be perfect, download 3d body from digikey or make sure it is 100% the exact component, then use the 3d body to ensure your pins are in the correct position