This week we focused on learning a completely new (to us) thing, PCB manufacturing! A PCB is a Printed Circuit Board, it’s the thing covered in small digital components you see inside electronics, and it’s typically green. Smart phones, tablets, laptops, desktop computers, entertainment systems (console and handheld), TVs, stereos, microwaves, and smart refrigerators…they all have PCBs!
We are going to offer “learn to solder” demo sessions in our upcoming open house and felt it would be great if participants could take something with them when they are done with the demo. The soldering demo sessions will involve attaching two small blinking lights (called LEDs) and a battery clip to our custom designed PCB we have nicknamed robbienano. This lil’ robot is roughly 2” x 2” and is designed to be worn as a lapel pin, but we think it’ll look great just whether it’s hitching a ride with you or relaxing on your bookshelf.
To begin the project, we had our code cadet sketch out a quick robot using nothing more than good old fashion construction paper and pencil. Once we had the drawing in hand, we took a picture with our smart phone and copied the image onto the computer. We used Adobe Photoshop to trace the drawing and added a little color.
From this point, we had to do a serious deep dive into Autodesk’s Eagle, which is used to create the PCB layout and schematic. Following Eagle’s Schematic Basics Part 1 guide, we learned how to create a schematic by finding parts and connecting their positive and negative terminals together. Fortunately, robbienano’s schematic is very straightforward - just two LEDs (labeled LED1 and LED2) and a battery clip (labeled G1)!
After our schematic was complete, we pulled up the Autodesk PCB Layout Basics Part 1 guide and began designing our board. At this step we took a big deviation from the guide and reviewed a few other resources regarding PCB art. This was hands-down the hardest part of this week’s project. We had to design art with four colors, reference multiple tertiary guides regarding basic functionality within Eagle, translate techniques between InkScape (a seemingly integral component used to manipulate art in Eagle) and Photoshop because InkScape isn’t natively supported in the latest version of OSX, and navigate through process holes that exist because the online resources assumed a familiarity with EDA (electronic design automation) software (aka Eagle) and until this week we weren’t even aware of the EDA acronym! Serious. Challenge.
But, when we had fully digested everything as best we could the PCB layout process came down to these steps:
Create an outline of robbienano and import it into layer 20 (Dimension) in Eagle which represents the overall shape of our PCB.
Add art to the following layers:
21 (tPlace) which represents the white outline on top of robbienano
22 (bPlace) which represents where the white logo will go on the bottom of robbienano
29 (tStop) which represents where no color, or soldermask, will go and thus reveal the copper of robbienano’s eyes, teeth, and chest
41 (tRestrict) which represents where no copper will go which will create a darker purple color for robbienano’s shirt/pants and arm sleeves
Place the components from our schematic onto robbienano and flip them so they will be soldered on the bottom
Trace a giant polygon on the top, around the shape of robbienano, which will be a ground (GND) “signal” for the ground plate, effectively filling the entire shape of robbienano with copper
Route the electrical connections between LED1, LED2, and the battery clip, which is almost like digital soldering
With all the art work in place and the electrical connections routed we just needed to upload the PCB board and have it fabricated. We settled on OSH Park, a fabrication house here in the States that offers cheap prices, fast turn around, and fast shipping. We placed the order today and our first, custom designed PCB for “learn to solder” classes should arrive next week! Hurray!