In this lesson you’ll learn how to turn it up to 11 with an audio amplifier and speaker. At the heart of the circuit is the LM386 IC which takes an input signal and outputs an amplification to the speaker.
This might be your first crack at designing a printed circuit board (also known as a
PCB), or you may be a seasoned veteran just looking to learn about a new IC.
Regardless of your starting knowledge, this lesson is for you. You won’t have to design everything from scratch. Instead the lesson focuses on the essentials of the circuit and will get you comfortable working with the
You’ll be introduced to a preselected set of components as well as a schematic that shows the electrical connections between them.
You’ll learn about each of these components, how to read a schematic, and then use your newly developed skills to layout your PCB — that is, place the components wherever you like.
This lesson comes with all the components you'll need to build your badge, but it's good practice to get familiar with the components you're using.
In the table below you'll see details about all the components. To learn more about each component, check out the glossary entry by clicking on the component name.
|Component Name||Patchr Symbol||Schematic Symbol|
|Barrel Jack Connector|
At the heart of the Speaker’s circuit is the LM386. When the chip receives an input from the audio jack, through pin #3, it is able to amplify that input through the speaker. Of course, to make a functioning speaker that you can turn on and off and control the volume requires a few more components.
The volume is controlled by a potentiometer that is connected between the audio jack and the LM386's input pin (pin #3). As the potentiometer is rotated, the resistance changes and with it, the volume.
The on/off switch for the speaker uses a SPDT switch that is connected between the LM386's power line and the battery pack. When the switch is open, no power flows through the switch and thus the speaker is off. Flip the switch and the circuit is closed, supplying power to the LM386 and the rest of the components in the circuit.
Pin #5 is the output pin, through which the sound travels before it plays through the speaker. The ceramic and electrolytic capacitors remove any unwanted noise making sure your speaker sounds crisp and clean!
Speaker customization begins with the board shape. In this step you can create a custom board shape using the built-in drawing tools found in the left toolbar or you can upload a custom SVG file from your computer using the toolbar on the right of the screen.
Regardless of which customization tool you decide to use, there are a few things to keep in mind while designing.
The custom board cannot exceed 100x100mm. The design window shows this with light red shading and OUT OF BOUNDS text. If your shape exceeds the boundary, you will get an error notification and be unable to advance to the next step in the design process.
The white area inside the red shading denotes the space you have to work with for your board shape.
The dotted red lines that make a small rectangle indicate the minimum size your board can be — if you made your board any smaller than this area, you would not be able to layout your components or route them.
Zooming in and out can be done with the icons in the left toolbar or by using your mouse's scroll wheel.
To reorient your design workspace, hold the right mouse button down and drag the workspace to your desired location.
To move your custom board shape, click on the Move Selected tool in the left hand toolbox. Then click and drag your shape to the location you want.
The toolbox on the left of the screen features the draw polygon path, draw freehand path, draw rectangle, and draw circle tools. These tools allow for simple shape customization within Patchr.
Once you have a shape drawn, you can use the tools on the right side of the screen to scale up or down your shape and rotate it.
When you are happy with your custom board shape, click on the NEXT > button to advance to the layout step.
To really get the most out of board shape customization, you can upload single-path SVG files into the editor.
- First ensure your SVG is using a single path.
- Click on the Choose File button under the Upload SVG heading in the right hand side toolbar.
- Assuming your SVG is compatible, you should see your custom board shape in the editor. You may need to use the scaling and rotation tools — also in the right hand side toolbar — to tweak the placement and size of your SVG.
- Once you're happy with the size and shape of your custom board, click the NEXT > button to advance to the layout step.
Note that SVG files are a specialized type of image file which are made up of vector coordinates. If you're new to vector files and vector drawing, check out Inkscape, which is a popular free and open source vector drawing program.
Welcome to the layout step. Your PCB Editor window now shows a list of components at the bottom of the screen.
To add a component to the PCB, simply click on the one you want to add and drag it onto the PCB.
If you don't have the placement right the first time. Want to move the component a smidge? Just click and drag it to the spot you want.
When you're designing a PCB every millimeter matters, that's why sometimes it's helpful to be able to rotate the component footprint to maximize layout efficiency.
To rotate in the Editor, click the rotate tool in the toolbox and then click on the component you want to turn. Then click, hold, and drag the component to the orientation you want.
Once you have all the components on the PCB, it's time to route the electrical connections between the components.
Click the NEXT > button and the Patchr Editor will check to ensure all the components are on the PCB and their footprints don't overlap.
Don't worry if you discover during routing that a component's layout needs to change, just click the < BACK button and you can edit the layout.
Routing a PCB design is where you make the electrical connections known as traces between the components on the PCB.
When routing, you'll want to refer to your schematic as you work. The schematic shows you what components need to be connected. However, that doesn't always mean copy the exact shape of the routes between them.
In fact, most of the time the traces that you route between components will have completely different shapes than the schematic, and that's OK.
With the trace tool selected from the toolbox in the PCB Editor, click on a pad of the component you want to route.
You'll then be able to drag a teal line that indicates the placement of the trace.
It's unlikely that all your traces will be straight lines from one component to another. To create an angle in your trace, click on the PCB while using the trace tool.
When positioning a route between components, make sure that the route you are creating doesn't block the way for other routes needed for nearby components. You may find your layout of a component wasn't ideal and you want to move it, just click BACK > and make the layout adjustment.
Start by routing your power and ground traces.
Focus on components that use multiple traces, since they will require more complex routing.
Routing is as much an art as a science. As you route more PCBs, you'll begin to develop your own habits and patterns.
Last but not least is the silkscreen for your PCB.
A silkscreen layer is typically used for marking where components go and adding company logos and product names to a PCB. It's also an easy way to add the
reference designators from the schematic onto your PCB — making assembly much easier since you'll know which component goes where.
But, silkscreens can also be used to bring your board to life and give it some extra pizazz.
Once you have your PCB looking the way you want. Click NEXT > and your board will head to your teacher for review before manufacturing.
Congratulations, your custom speaker is almost ready for soldering!