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FabLearn 2015

A two-hour workshop on fabricating electronic circuits and products for FabLearn 2015.

Introductions

Who are you? Why are you here? What’s your experience with electronics and programming? (Don’t worry, none is required.) What do you make?

The DIY Cellphone

The DIY cellphone is an example of a relatively complicated device that an individual can design and fabricate. We’ll discuss the components inside it, the resources required to make it, the software that drives it, and the way it was designed.

Understanding Printed Circuit Boards

Before we get to designing our own circuit boards, let’s talk about what a printed circuit board (PCB) is. I have talk about understanding PCBs in my tutorial on ordering circuit boards. There’s also a SparkFun tutorial on PCB basics.

Designing Circuit Boards

There are many options for PCB design software, none of them great. They include:

I’ll give a brief overview of Eagle, starting with the DIY cellphone’s design files (led-matrix.zip).

Eagle Tutorials

I recommend the SparkFun Eagle tutorials, although they may not cover everything you need to know. Jeremy Blum’s Eagle tutorials are also worth checking out.

Parts Libraries for Eagle

If you want to use Eagle on your own, you’ll probably want to grab:

Ordering Circuit Boards

I have a whole tutorial on ordering PCBs. It includes a discussion of the different options involved and suggests some good online vendors.

Sourcing Parts

Figuring out which electronic components to use is an art in itself. As you can see from my cellphone’s bill of materials, I tend to order from DigiKey and SparkFun, along with Adafruit.

Packages

One basic aspect to pick the right part is getting one in the size you want. These packages have many different names, which can make the process somewhat intimidating at first. SparkFun has a tutorial on integrated circuits that discusses packages for microcontrollers and other chips. In general, I’ve found that the smallest pitch (distance between adjacent legs of the chip) that’s feasible to solder by hand is the 0.8 mm of TQFP components. That is, you probably only want to use chips that are either DIP (through-hole components), SOIC (the largest surface-mount parts), or TQFP.

Small components, like resistors, capacitors, and LEDs, come in multiple small, surface-mount packages. A common one is the 1206 package, which means the part is 0.12″ by 0.06″. They get smaller – 0603 (0.06″ x 0.03″), 0402, 0201, etc. – but you probably want to stick with 1206 unless you really need something smaller.

Understanding Datasheets

Filtering Through Parts on DigiKey

Potential Projects

Here are some links to projects that might serve as good starting points for assembling or designing your own electronic circuits and products. Many of these come in kit form for you to assemble but also provide Eagle files for you to modify.

Pre-Requisites and Scaffolding

Some thoughts on when and how circuit board design and fabrication might make sense. Note that it’s not a very exploratory medium, so it helps to have a specific design in mind before sitting down to create a PCB. So it might be good to do an Arduino or other physical computing course, and then have a follow-up course to translate people’s projects into PCBs. Or, you could do a longer (e.g. a full semester) course on interactive product design, which could include both prototyping and PCB design. See my Design for DIY Manufacturing course (at the MIT Media Lab) or the Interactive Device Design course at UC Berkeley for examples.

Chapter 6 of my dissertation has an in-depth discussion of the concepts, skills, and practices involved in the designing and fabricating a custom electronic product. It definitely involves a lot of planning, abstracting, and other engineering-mindset heavy practices. For people without much engineering or electronics experience, it might be better to start by assembling an existing design or experimenting with Arduino or another physical computing toolkit or platform.

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