CHAPTER 3

Electronic Invention

It is beyond the scope of this book to teach you everything about electronics. For that, you will need a bigger book such as Hacking Electronics or Practical Electronics for Inventors, both by Simon Monk and published by TAB Books.

At this point, it is useful to look at the various stages that you are likely to go through, when taking your initial idea and converting it to a product. The stages are shown in Figure 3-1. Although these stages will probably all be necessary, perhaps you, as the inventor, only take it so far and then partner with someone who can continue with the final stages of the project.

FIGURE 3-1   The product design process.

First, you will have an idea of what you want to make. As an example, let’s assume that you want to make a novelty project, a musical instrument that uses an ultrasonic range finder to vary the pitch of a note generated by an Arduino board. This project is based on a project described in the TAB Book of Arduino Projects. I will not go into all the details of the whole design process, but rather use it as an example of the kind of things that you need to be thinking about as you design a project.

The Idea

Some people claim to be “ideas” people, painting in broad strokes and not really wishing to understand or be involved in the details, with the latter being a job of lesser mortals (the technicians). Time and again, I have found this to be untrue. The distinction between artist and maker is an artificial one. If you want to invent something, you will find things go much more smoothly if you can make it yourself; even if it is a crude prototype held together with electrical tape and a prayer, you should still be able to make it. All the world’s great inventors make their own prototypes. Thomas Edison was not just an ideas man. To take a more modern example, the stylish reinventor of the vacuum cleaner James Dyson made prototypes of his cyclone system.

This is not to say that there aren’t people (let’s call them artists) who have an aesthetic sensibility that allows them to make things look beautiful and stylish. This is a skill much to be admired and somewhat lacking in this author.

Generally, paper and pencil are probably the best tools for sketching out an initial idea. Figure 3-2 shows what this might look like for our musical instrument.

FIGURE 3-2   A novel musical instrument.

If you are good with a drawing or CAD package, then you may want to use it to describe what you have in mind. Generally, pictures or words on their own are not enough; you will need pictures and accompanying text that explains what your idea does.

Documentation will be useful not only to you in clarifying your ideas, but also to others to explain how the project will work. It is always worth canvassing other people’s ideas. You can ignore their suggestions, but it’s still useful to have them.

Do not spend too long specifying what you intend to make. When you actually make it and have a prototype in front of you to play with, you will probably find that your ideas change. So do just enough planning out of the idea to allow you to get on to the next stage of building a breadboard prototype.

Breadboard Prototype

It is a lot easier to use ready-made electronic modules like the Arduino or an ultrasonic range finder module and connect them to a breadboard than it is to design something from scratch. This will get us to the stage of a working prototype, but when you start to look at how you would make lots of these objects, it becomes wasteful and expensive to use modules. For now, while we are proving the concept by making a prototype, the solderless breadboard and ready-made modules are ideal.

In this case, the ready-made modules will be the Arduino, an ultrasonic range finder module, and an audio amplifier module. Figure 3-3 shows the breadboard layout.

FIGURE 3-3   Breadboard prototype.

Fritzing makes it easy for us to make a nice-looking, easy-to-follow diagram while we are connecting things on the breadboard. In Chapter 4 you will learn a lot more about using breadboards for this stage of the invention process.

Once you have built the breadboard prototype, try out the project and get other people involved in using the device for real. This experience will be invaluable. Make a list of your thoughts and feedback from others. This will allow you to refine your design. This might include such things as these:

•   It is too hard to hit just the right note. Could it be made to autotune?

•   Could you have a switch to turn autotune on and off?

•   It would be good to have another distance sensor to set the volume of the instrument, as on a theremin.

Some of the ideas can be ignored, but others would improve the project. Fortunately, at this stage, you can easily implement the kinds of changes described above. The first one is a matter of changing the Arduino software, but the other two require an extra range finder and slide switch to be added to the breadboard design.

Keep repeating the cycle of prototype and evaluation until you are happy with the design and any software involved in the project. It’s worth getting as much mileage out of this design stage as possible because it’s so much easier to change things now than in the next stage, which is a PCB prototype.

PCB Prototype

Moving from a breadboard design to a PCB is a big step. An Arduino makes sense for prototyping, because you can simply plug things into it with jumper wires. However, any final product that used the Arduino would be expensive to produce. In actual fact, the main thing that you need from the Arduino is the microcontroller chip (the ATmega328). You can assume that this will be preprogrammed during manufacture or by using an in-circuit serial programmer (ICSP), so you do not need the USB circuitry of the Arduino. You will need to provide some kind of voltage regulator. Thus the basic lesson is that you can look at the open-source schematics for the Arduino and just take the parts of the circuit that you need. The Shrimping.it (see Chapter 8) approach to off-board Arduino design is a great illustration of how this can be quite straightforward. If you are considering an invention with an Arduino at its heart, then you should consider the Shrimping.it approach. The design of Figure 3-3 is repeated in Figure 3-4, but using the Shrimping.it concept.

FIGURE 3-4   Taking the microcontroller off the Arduino.

Design Decisions

These are the kinds of questions you should be asking yourself for this example project:

•   What kind of batteries will the final product use?

•   Will it have a DC power jack?

•   What sort of on/off switch will it have?

•   What kind of loudspeaker will it use?

•   Will it have an audio output jack?

The fewer external wires the project has, the simpler it will be to make. The speaker will probably be too big to fit comfortably on the PCB, so this will likely be attached with connectors. Connectors will probably also be needed to allow the second range finder to be positioned far enough away from the other range finder. The battery and switch may also be off the PCB and connected via wires, or you may decide to have them both mounted on the PCB.

Cost is also a factor to consider, and you may find yourself spending a lot of time with on-line component catalogs.

A First PCB Prototype

At this stage, you can probably go ahead and design the PCB. In all probability, you will end up making at least one further PCB prototype. So get as small a batch of PCBs made as possible, and solder a board. The Appendix includes links to companies that will make you a set of bare PCBs for as little as $1 per board.

Make sure everything still works, and once again evaluate it and decide what needs to change.

If you are selling a small number of high-value products, then the cost of all the components is not as crucial as if you wanted to sell to a mass market. The cost of the components will be a significant factor in the overall cost of the product. So if you find that one integrated circuit (IC) is particularly expensive, search and you will probably find a cheaper alternative.

Product Design

There is a big difference between a prototype and a product. You only have to make one or two prototypes, and they don’t have to be rugged or reliable. When making a prototype, you could buy an off-the-shelf project box and drill holes in the right places for the switches and sockets. Essentially, it does not matter how time-consuming or difficult it is to make. But when it comes to making a product, you have to consider these things in greater detail.

Enclosures

You need to consider the overall shape and aesthetics of the design. If you want something more than a plain rectangular box, you need to design an enclosure for the project. This is a specialized job, but there is no reason why you cannot give it a try yourself, using three-dimensional (3D) modeling software. Use of 3D modeling software is a broad enough topic to merit a book or two of its own; but if you have created the design and you have a 3D printer, you can print it yourself or send the design files away to a 3D printing service.

3D printing is time-consuming and relatively expensive in materials. Once you have a case design that is just how you want it and that matches up with the PCB perfectly, then you can get a quote from a manufacturer to produce the same design by using plastic moldings. This will be a much cheaper cost per unit, but there will probably be a minimum order quantity of at least 500 units.

PCB Manufacture

Once you have made some PCB prototypes by hand, you will probably want to get a quote for the manufacture of these boards in quantity. I have included a list of companies that supply such services in the Appendix. You will also find some links to companies offering 3D design and manufacturing services.

When you submit a PCB design for manufacture and assembly of the components, you need to provide a Bill of Materials (known as a BOM). This may have to fit into the guidelines of the company providing the quote, but will typically consist of a list of all the components including the following information:

•   The component name, for example, R1

•   The component value, for example, 270Ω ¼W 5% accuracy

•   An example source where the component can be bought

There will be other columns on the table such as the cost of the component in various quantities that the manufacturer will complete to estimate the job. The manufacturer may make up one or two of the boards as prototypes for you to test. The manufacturer may also require you to make a test harness to check that the production process is okay. All these things are covered in greater detail later in the book.

Summary

This chapter has summarized the process of creating a new electronic product. In the chapters that follow, we will explore these steps in a much greater detail, starting with the important initial step of creating the breadboard prototype.