Creating Circuits with EAGLE
OK, so you’ve got your Othermill and you want to make circuit boards! However, an obstacle remains between your ideas and cutting out those traces on the mill: learning EAGLE.
EAGLE is powerful software for making circuit boards, and its creators have made it free for boards under 4"x3" , which works great for most Bantam Tools™ Desktop PCB Milling Machine projects. Bantam Tools™ Desktop Milling Machine Software can import many kinds of files, but EAGLE is the most common for circuit boards. The support for EAGLE is so complete that all you have to do is drop an EAGLE .brd file into the software, install an end mill, place the PCB blank on the machine bed, and click the "Start Milling" button.
However, EAGLE itself has a somewhat steep learning curve because it has the power to make incredibly complicated, multilayer designs for circuit board manufacturers, and with that power comes some unfamiliar ways of doing things. Luckily, you can get started making boards by learning only a few of EAGLE’s capabilities. We’ll show you which ones and how to use them.
In this tutorial, we’ll go over the complete process of building a very simple LED circuit. This circuit may seem like a lot of work considering that it only has three components and just turns on an LED, but once you understand the process, you can scale it up to make much more complex designs. Hang in there and it will be well worth it!
- Start by downloading and installing EAGLE.
- Then download the Adafruit component library (adafruit.lbr) and unzip it.
- Go to your Documents folder and open the EAGLE folder (created when you installed EAGLE).
- Create a new folder called “libraries” and put adafruit.lbr into it.
Step 1: Tools and Materials
- Computer with Bantam Tools™ Desktop Milling Machine Software installed
- Flat end mill, 1/32"
- LED, 2.0 forward voltage, 20mA forward current
- Resistor, 47-ohm
- Battery, 3-volt, CR2032
- Battery holder, CR2032
- Circuit board blank, FR-1
Note: These are the materials we used, but you can use whatever LED, resistor, and battery you may have as long as they match up. See this tutorial if you’d like more information on matching your battery, LED, and resistor.
Step 2: Navigating the Interface
Before we get started, there are a few things that will help you move smoothly through your first EAGLE experience.
EAGLE has a peculiar aspect to its interface not found in most other software: no dragging. To move something, you click it once to pick it up, then click again somewhere else to put it down. The same holds true for drawing lines, placing components, etc.
You may also encounter a bug where you’ll click something and expect it to move with the mouse, but it won’t. To fix this, simply switch to another application on your computer, then switch back to EAGLE. I like to hit Cmd+Tab twice.
EAGLE also uses layers, which function in some ways like layers in Photoshop and Illustrator, except each layer has a specific purpose. The software can read all the layers, which allows for awesome things like two-sided machining and solder stencils. To keep this tutorial simple, we’re mostly going to use two of the layers: the “1 Top” layer and the “20 Dimension” layer. The Top layer is what the software uses for cutting circuit traces, and the Dimension layer is what it uses to cut the outline of your board.
Step 3: Make a Schematic
First, we’re going to make a schematic. This allows you to see your circuit by itself and helps you make sure everything is connected properly.
- Open EAGLE.
- In the Window menu, select Control Panel, if it’s not already selected.
- Make a new schematic by clicking File > New > Schematic.
- Expand the window so it fills the screen.
- In the Library menu, select Use.
- Locate the Adafruit library you put in Documents/Eagle/Libraries (adafruit.lbr) and click Open to load it in EAGLE. You won’t see anything happen, but trust that it is, in fact, loaded.
- Click the Add tool in the left toolbar (see the screenshot if you need help finding it), and find the Adafruit library in the list that pops up. Expand it to see all the components, and make sure the Name column is wide enough that you can see the component names.
- Locate the CR2032 section and expand it to find CR2032THM (the description is CR2032-THRU).
- Click OK. The window will close.
Now, if you click anywhere on the page, you’ll place the part there. Click somewhere in the middle to place it. If you click again, you’ll place another one, but don’t do that because we haven’t covered how to delete things yet!
- Hit Escape to return to the components window. Still in the adafruit library, find the LED section and locate LED5MM. Click OK and place one on the page and hit Escape to select another component.
- Now scroll down and find the resistor library. In the resistor library, expand R-US_ and select the R-US_0309/12 resistor component.
- Place the resistor, then hit Escape twice, which will exit from Add mode. You should have three components on the page: a battery, a resistor, and an LED.
Why did we choose that particular resistor? Since we’re using through-hole components and a simple circuit, hole spacing isn’t that important. This component is roughly the size we need. However, if you’re using surface-mount components, choosing the right ones is much more important, and you’ll have to match the component type with exactly what you’re using (for example, 0805 resistors).
Step 4: Use the Draw, Move, and Delete Tools
Let’s draw some lines between the components:
- Select the Wire tool. There are several wire bend style buttons to choose from in the toolbar across the top of the screen. The first one is a good place to start. Take a look at the screenshot to see where everything is.
- Again, there’s no dragging. You click to start drawing, click again to start a new segment, and hit the Escape key on your keyboard to stop drawing.
Draw a line between one of the positive terminals on the battery and the positive end of the LED. (The positive terminals are on the right side of the battery component.)
Try moving the components:
- Click the Move tool, and click on a component. It will turn bright red, and you can move it around.
- Click again to place it somewhere. If you’ve drawn wires between them, they should stay connected.
Now let’s try deleting:
Click the Delete tool, and click the middle of a line segment to delete it.
- Try clicking a corner where two lines meet. It won’t delete it; instead it will select one of the lines connected to that corner and ask you if that’s the one you were trying to delete.
- Along the bottom of the window, you’ll see “left=yes, right=next, ESC=cancel”. This means that if you click the left mouse button (one finger tap on your Mac trackpad), it will delete the selected segment. If you click the right mouse button (two-finger tap or “secondary click” on your trackpad), it will select the other line segment under your mouse. If that’s the one, then click left mouse or single tap to indicate “yes.”
- If you didn’t mean to do this in the first place, hit the Escape key.
This principle of “click until the correct thing is selected” also applies to the Move tool and other manipulation tools.
If you haven’t already, complete the circuit by drawing lines between all the components.
If you’re not sure how to complete the circuit, check out this tutorial.
You can also download our schematic for reference.