Having Fun in Smartcar Competition


In 2014 I decided to participate in Freescale Smartcar Competition with my friends. Eventually we didn’t have the time to finish our smartcar, but in preparing it I learnt a lot of things about the design of Printed Circuit Boards (PCBs), which I found was one of the most interesting and flow-producing activities. Here I’ll talk about my experience and thoughts about it.

Introduction

The competition, in brief, required participants to design a mini-smartcar that can automatically follow a race track. The faster it completed a given track, the better score it got. A team had to design and make the whole car except for its body frame. So to start, I had to design my own circuit board for the car.

Though having taken the Digital Circuit course, I found myself totally blind of the whole mechanism of PCB–how it is designed, produced and programmed. Thus I read some articles for starters and began by learning the design tool–Altium Designer. TBH, the tool itself was not the hard part. You just has to place components and connect pins.

Process

The real difficulty was to design, of course. Firstly, I had to draw the schematic. I studied the chips usually used for most functions, such as the gyro-accelerometer and driver chips for motors. You have to not only balance the price and performance, but also pay special attention to their specification details in case something was not matched. After that, a lot of efforts were put into reading every chip’s specifications. Many told me that I shouldn’t spent much time on reading them since I could just copy the schematic from others or the manufacturer’s manual. But I believed that it would ruin the whole fun of design and make it hard to debug. Reading specifications itself was also interesting. You can often found their special features you will never notice by just making copy. After getting familiar with chips, drawing schematic was easy.

In the meantime, I bought all components needed from Taobao. Physical size of all components had to be taken account in in the designing process.

(Click to zoom image)

After schematic was finished, the next steps was to draw the board. The physical models of most chips and components were already registered in the software. Some that were not could be downloaded. In rare cases I had to draw my own models according to components’ specifications. Then the software could generate a circuit board with components placed randomly, without wires connected. The followed things were to layout and connect them, which was the most challenging and fulfilling part.

Wiring may sound easy, if it is in 3D space. With double-sided boards, you are actually dancing in 2.1D (whatever number greater than 2 and less than 3 you like), where lines can cross each other, with cost. It was especially hard for myself when designing the second version of my board. You have to try your best to minimize interference from electromagnetic radiation caused by parallel wiring, wide angle turns and through holes. Other factors like current load, heat emission and physical limitations should also be kept in mind.

Results

I spent a lot of spare time drawing boards in Starbucks, or in dormitory with my cat Chui-Chui 😏.

Chui-Chui instructing me on finding best route

Version 1

Here was my first result. (The CPU, a Frescale K80, was on a prefactured board that would be attached to my PCB.)

(Click to zoom image)

I know, it looks a little rough and ugly 😂. But it worked! I sent my design to a factory and days later I received my boards (left photo). Since I had chosen big-sized SMD package for most components, soldering them was not very hard, except for the gyro-accelerometer chip which had a LGA package.

Left: produced raw PCBs. Right: after soldering and programming.

Version 2

Summarizing all the problems I had in version 1, I re-designed my board. This time I decided to challenge myself, incorporating CPU directly onto it. This decision would later cause a huge amount of difficulties in the soldering process I had not expected. However, I felt the board was simply so beautiful that I cannot help looking at it!

Unfortunately, I never had a chance to finish the soldering and following process due to rarer spare time.

Conclusion

Though I didn’t participate in the whole competition, from the process I learned from scratch the process of designing PCBs by myself. This experience has enlightened me about the beauty of electronics. I think it will be very practical both for personal hobbies like DIY stuffs and working needs.


Author: Texot
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