What They Don't Teach You In Class

November 14, 2017

I'm Joshua Jones, returning to write a blog once more! In my last blog, I discussed, among others, how joining the team led me to my first exposure to Printed Circuit Board (PCB) design. I would like to elaborate a bit more on how I have experienced learning about design PCB over the last two years.

 

Contrary to what one might expect, I have never learned about practical PCB design at any stage of my curriculum, as usually the projects I have had to do focused more on the theoretical design than physical (final) implementation. However, in our car, and in engineering practice, designs on just paper will not do. The most common and straightforward way to produce high quality, high performance electric devices is to implement them as PCBs.

 

The first step is designing the schematics of the device you're going to make. Here, circuit components are still their familiar abstract selves; resistors are zigzaggy lines, integrated circuits are blocks with lines going to them, opamps are triangles, capacitors are two short parallel lines. All you have to do is place them and draw the lines between them. The big challenge at this stage is how to make your schematic design structured and easy to follow; you will not be the only one who will need to read your schematics. Making one big circuit on a single sheet, i.e. 'flat design', is not very conducive to a circuit that is easy to read. In this sense, it is much like writing source code in software; write it clean, write it elegant, and leave plenty of comments! In schematic design, one of main methods to achieving this is by following the principle of 'hierarchical design', which means that rather than implementing your schematic design as one big messy circuit, you divide your design up in functional blocks and draw lines between them. Altium Designer, the PCB design software suite that we use for this, is well suited to this.

 

It is after the schematic design is complete and reviewed that the real fun begins. Now, circuit components need to be associated with their real life forms. This is when you find out that there is a whole universe out there of different component sizes, packages, types, power ratings, voltages, purposes, mounting techniques (through hole or surface mount), etcetera. Your job as an engineer is to choose for each of your components which real-life component you're going to use. Not only that, but it's also your job to make sure they properly fit on your PCB; this is not an automated process. Then, all these physical components have to be placed in the board layout and connected using copper traces. Then you find out you have to account for aspects such as electromagnetic interference and thermal expansion, which again is usually not considered in the curriculum.

 

Once this is finally complete and your design has passed all the reviews, it is sent out for production. When the PCBs arrive, the long and arduous task of testing them begins. This can be quite confrontational; here you might discover just how many design errors you made - and they will always be your fault! Connectors that don't fit, transistors that are mounted the wrong way round, to name a few common ones ... However, once the testing is complete and the PCB (almost) works as intended, then you, the electronics engineer, can take some well deserved pride and satisfaction in the fact that your PCB (hopefully) not only looks good, but is also instrumental in making the car reach the finish line and doing so fast, smart and efficiently.

 

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