Building DIY switches from household material
Article By : Clive Maxfield
By constructing homemade versions of components like switches and potentiometers, it should be possible to reduce the cost of a new Arduino kit.
I suppose it's only fair to warn you that, it's title notwithstanding, the purpose of this column is not to tell you how to build DIY switches and potentiometers from household materials—rather, it's to ask you for your ideas and suggestions as to how to create these little rascals.
This all came about when I attended the Embedded Systems Conference (ESC) in Silicon Valley last December. Following one of my presentations, I ended up chatting with the Vice President of Operations from Arduino.org.
One of the topics we touched on was the importance of getting younger folks interested in science, technology, engineering, and math (STEM). I mentioned that there are a lot of great Arduino books and kits out there, but that sometimes they cover so much ground so quickly that the reader ends up knowing how to do something without really understanding just what it is they are doing and what's happening "under the hood."
First, a little background…
I've taught several people how to use Arduinos, with ages ranging from 12 to 60+. The one thing all these students had in common was that they had no previous exposure to electronics, microcontrollers or programming. Learning all this stuff at once can be daunting, so we started with the fundamental concepts and worked our way up.
The first thing we did was to connect a 9V battery to an 18V incandescent light bulb and observe that it had only a weak glow. We also swapped the battery leads to the bulb's terminals and noted that the bulb lit up both ways, thereby concluding that it's a non-polarised component. Next, we used two 9V batteries in series to present the bulb with 18V, and we observed that it glowed much brighter. All this this led us to the concepts of voltage, current and resistance and how they are interrelated.
The next step was to take a LED, connect it to one of our 9V batteries, and observe it glow very brightly for a very short time. This led us to the concept of current-limiting resistors. Using such a resistor (with a new LED), we discovered that the LED is a polarised component that has to be connected the right way round, while the resistor is non-polarised. A further experiment revealed that it doesn’t matter whether the circuit is +5V → resistor → LED → 0V or +5V → LED → resistor → 0V.
Next, we introduced the concept of single-pole single-throw (SPST) and single-pole double-throw (SPDT) switches, including pull-up resistors, and we used these little scamps to control our LEDs. It was only after laying all this ground work that we powered up our Arduinos and proceeded to the next stage in the game.
How to rule the world with Arduino
The upshot of all this is that I've been invited to write a collection of Libretto ("booklets") that are designed to teach the fundamentals of electronics, microcontrollers and computer programing. Each of these booklets will be thin and non-threatening, and each will build on its predecessors. In addition to use by individuals, there's talk about using these booklets in schools and also using them as the basis for weekend workshops around the world.
The umbrella title for this series will be How to Rule the World with Arduino. The rational for this somewhat audacious moniker is laid out in the first paragraph of the first book, which I started this past weekend. This first paragraph reads as follows:
If you can use a microcontroller to read the value from a sensor (say a switch), make a decision based on this value, and control something (say a light), then you can rule the world. This is the basis for all the computer-based systems we see around us, from smartphones to tablet computers to robots to space probes. They all do the same things; they just do more of them.
There's also a footnote that explains what we mean by the term "microcontroller," because we can’t take anything for granted. Just two paragraphs later, half-way down the first page, I say:
I don’t know about you, but I get bored if I'm not making something beep, squeak, flash, or explode—sometimes all at the same time—so let's perform our first experiment.
At this point we plunge headfirst with gusto and abandon into performing some fun experiments and learning all sorts of cool stuff.
The reason I'm waffling on about all of this here is that we want to keep the costs down as much as possible, which is why I'm asking…
What do you suggest?
In addition to the Arduino and a small breadboard, I know that we're going to have to include things like a couple of 9V battery clips, a brace of 18V incandescent bulbs, a bunch of LEDs and a horde of resistors in the kit accompanying these books. The total cost of these parts will probably be only a couple of dollars assuming we buy in bulk.
We could also provide things like switches and potentiometers, but the cost will start to mount if we're not careful, because we're going to need a couple of SPST switches, a couple of SPDT switches, at least five momentary push buttons and at least three 10KΩ potentiometers (or trim pots).
Quite apart from anything else, it will be more educational—and it will give the reader a greater understanding and sense of achievement—if we construct these components from the ground up out of everyday objects. For example, I had wondered about creating a potentiometer around the lead from a mechanical pencil, but I fear this might be too fragile.
So, this is the point where I hand things over to you—do you have any capriciously cunning cerebrations and cogitations you would care to share?
This article first appeared on EE Times U.S.