Overview
Welcome to the hardware at Midnight Sun! This introductory boot camp is a continuation of Hardware 101 and will go through the basics of our flow for hardware design.
Getting Started
Please drop a message pinging @Hardware Lead in the #hw-onboarding channel indicating that you’d like to start your onboarding process! Include the email you would like to have associated with your Altium account, or the email you already have associated with an account. If you do not yet have an Altium account, do not create one by yourself. We will create an account for you with access to the team licenses. Otherwise, you will have to request an educational license on your own.
Once a lead has responded to your message indicating that they have added you to our Altium workspace, you will be able to begin!
Installing Altium
[Coming Soon! Hopefully this was covered during HW101]
Navigating the UI
Most UI elements you will interact with are housed in “Panels”. They are synonymous with windows, you can resize them and drag them around, even off to a second screen. You can select which ones are visible using the panels tab in the bottom right corner.
Project
You will be creating a board out of the simple “battery tester” circuit that you’ve seen in Hardware 101. When powered off a 12V source, a battery can be connected to see if it is between 10V and 15V. If it is not, an indicator light will illuminate to show the error.
Creating a new project
In the Altium program:
Create a project by right clicking on the Midnight Sun workspace in the projects panel (usually on the left of the screen)
Set the project name to “<term> <waterloo-userid>”, ie. “F24 f39zhou”
Leave version control checked, and constraint manager unchecked
Under advanced options, click the 3 dots for the folder location and select Projects → Onboarding
The project should now appear in the projects panel! This is a blank project, so we will need to add some files where we will later create the design. Right click the newly created project (.PrjPcb file) in the sidebar and add the following new items to the project:
Schematic: A diagram which shows all the connections between components. It is not a physical representation of the hardware, just a logical representation of what’s connected.
PCB: The physical design of the circuit board that you are making. Where exact component placement, trace routing, silkscreen labels, etc are defined.
ActiveBOM: A bill-of-materials that will be used to generate the files necessary to order the components.
All these files are created with default names. When you click “Save to Server” in the projects window, you’ll be prompted to name the file. Generally we will name it the project name, and any identifiers as needed (if there are multiple schematic pages, for example).
Schematic
The schematic is where you will create the drawing for your circuit with all the logical connections, like what was done in the onboarding activity.
Template
We use templates to keep the page size standard and add in the Midsun title block. With the schematic open, select the Letter sized template under Page Options, → Formatting → Template. If a larger page is required in other projects, you can switch to the B or Tabloid template.
While you are in the properties panel, you can verify that the units are set to mils, and that the visible and snap grids are both set to 100mils. The default shortcut to change the grid is “g”, and it’s also displayed in the bottom left corner.
Adding Existing Components
Components on a schematic are sourced from the Midsun component library. We have a large collection of parts that have been added to the library for previous projects, and these components can be reused by searching for them in the components panel.
We can start by adding a few standard components to our schematic. Search for the following components from the panel. Double clicking a result will lock it to your cursor, where you can then drag and place it onto the page. Note that searches are not caps sensitive, you can type everything in lowercase!
2POS Microfit: The Molex Microfit series is our standard connector. We’ll need 2 of these for battery input and output, with each connector having 2 positions (+ and -). You may find 2 results come up, we will use the normal upright one rather than the right angled (R/A) connector.
SOT23 Comparator OC: The comparators we will be using. These are open collector (OC), which means instead of the two output states being high (connected to power) or low (connected to ground), it is either not connected (floating) or low.
0603 Resistors: Grab the resistors needed for the resistive dividers. Note that in the example slides, a 1k/5k divider is used, but 5k resistors are not common. It can be swapped for 2k/10k, which has the same ratio. Websites like Voltage Divider Calculator (ti.com) can be used to calculate which standard value resistors will get you closest to the desired ratio. Try using the E24 series first, if nothing is a perfect fit, you can see if using E96 resistors will get you a lower error.
0.1uF 0603 Caps: These capacitors help to ensure the power rail is smooth, without any unwanted oscillations. Generally we want at least one per set of power/gnd pins. Since we have 2 comparators and each comparator only has 1 set of pwr/gnd, 2 caps are sufficient here.
Clear Red 0603 LED: To serve as an indication when our battery is outside operating conditions (over/under voltage).
Adding New Components
When a required part is not already in the library, you will have to add a new one yourself. In this case you will create a resistor to add in series with the LED.
Placing Components
Any time you have a component locked to your cursor in drag mode, you can:
press space to rotate
press x or y to mirror about different axes
You can place and orient the components in such a way to make the wires neater. For more complicated circuits, it would be divided into smaller sections for organization.
Drawing
At the top centre of your schematic page window, you’ll see a toolbar containing schematic elements you can pick from. Right clicking each option will reveal related elements.
Wires
To start placing a wire, you can click the wire icon or press ctrl+w. Generally wires are used within a small sub circuit to clearly show connections. Since our circuit is quite small, we can use wires to make most of the connections. For larger circuits with multiple sub circuits, each block is generally connected with wires, and all the nets between blocks are connected with net labels. Wires generally should not cross, a net label should be used instead.
No 2 pins should also be placed so close that they are connected with no visible wire segment. They should be placed at least one grid apart and connected with a wire.
4 Point connections should also be avoided, the WARG design team has a good article on it here: Schematic Four Point Nodes - Electrical - WARG (atlassian.net)
Ports
Immediately to the left of the wire icon are the port icons. You can right click to select between power and ground ports. Ground ports generally don’t need to be renamed, while power nets follow our Power Net Naming Standard. Since the battery voltage is variable, we will name it “VBAT”.
