The Arduino is an amazing small single-board computer. The standard current generation Arduino Uno is roughly the size of a deck of cards: 3″ x 2″ x .6″, which is pretty darned small for a powerful self-contained computer. It’s much more powerful than the computers that controlled the Apollo spacecraft that went to the moon, for example!
But…for many projects for Steampunk and Cosplay that’s still too big to hide!
So, “back in my day” (2 years ago!) for projects like my (like my Tesla Cane) the only choice was to use an Atmel ATTiny, the little brother of the Arduino’s microcontroller, the Atmel ATmega328, as a bare chip. The ATTiny is indeed tiny (an 8 pin chip) and I didn’t bother with any of the normal Arduino parts, such as a USB port for programming (and power), various power options (battery, etc), breaking out each pin, etc. Just the bare chip, power, and the single output to the LED. It is important to note that the chip cost me about $4 and a full Arduino Uno runs about $25.
Importantly…I didn’t do several other things that I should have, like a 1uF capacitor to prevent power bounce, voltage protection, a reset pin, etc…My cane is the absolute barebones you can get. One day it’ll likely die for no reason at all because of something I didn’t do. It is, in fact, kind of the completely bad way of doing things…but at the time, I really didn’t have a choice because of the size! You should do all these things, but doing them yourself with a bare chip is a pain and not worth it! There is a better way!
Today there are a fair number of full Arduinos and “sub” Arduinos that are amazingly small…many not much bigger than the ATTiny I used, and all much better!
These include Adafruit’s wonderful Trinket and Gemma use the ATTiny like my cane does. The Trinket is designed more for permanent installation in objects while the Gemma (and it’s big sister, the Flora) are designed for wearables and clothing, but both work equally well for props. The most amazing part is the cost! The Trinket and Flora both run $7.95! There is no way I would have bothered with my barebones ATTiny if these things had been around then!
If you need a little more memory for your complex program or, just as likely, more pins take a look at the Sparkfun’s Pro Mini – it’s a full-blown Arduino in a tiny package, and it’s $9.95!
Lastly, just how many Arduinos do you need? It’s a trick question! All of them!
I have about 8 of them: A full size Arduino I’ve dedicated to programing the ATTiny chips, a couple of specialty Arduino clones I’ve purchased via Kickstarters, a pair of Arduinos with built-in special radios for a home automation project, a Gemma I just got to experiment with (love it!), and a specialty Arduino on order (via another Kickstarter) that has a tiny video screen just because it’s darned cool!
My future projects will be built almost entirely on Trinkets, Gemmas, and Pro Minis…for their cost it just isn’t worth trying to do them yourselves with a bare chip!