This is a set of simple, small form-factor, mini-shields that I created almost by accident. As I made more and more of them, I realized that they could be really useful. What started out as a way to use some spare parts, turned into a standardized form factor for a versatile, miniaturized Arduino shield. The added benefit is that they also make a great kit for traveling, or simplified prototyping or for educating kids and beginners about Arduino.
I have been building some custom shields and modules for a while now but while I like the modularity of a shield, they are a little too expensive and large if all you want to add is just a little piece. The modules I make are all small and have to be plugged into a breadboard, which doesn't have that satisfying, finished feeling I'm looking for. I buy a lot of perf board, but the Arduino boards have this annoyingly unusual spacing between the digital pin banks so you have to modify the pins to make them fit. I needed something that was more flexible, lighter weight, and allowed me to change the pins used more easily to avoid conflicts with other shields.
The Mini-Shield Standard
I started making these small modules with standardized pinouts that are mostly plug and play. I call them Mini-Shields and they include everything you need for almost any application. The first 3 pins from the right of each board are connected to the 5v, ground and Digital 2 pins from the Arduino. All of my mini-shields use the following standard and they work pretty well with each other.
Pin | Pin Function
1 | 5v
2 | Gnd
3 | Digital 2 (Hardware Interrupt)
4 | Analog *
5 | Digital (PWM)
6 | Digital (PWM)
7 | Analog **
8 | Digital
9 | Digital (PWM)
* the Real Time Clock module requires analog pin 4
** the Real Time Clock module requires analog pin 5
I liked the idea that these little modules could be added to almost any other shield and you could swap them out as needed. I would then also be able to reuse them in different projects without too much effort. The standardized pinout meant that every one of them could be used in place of the others if everything was wired correctly. Once they are built, they make a good little, rapid prototyping set that would also work as an entry level set for Arduino beginners.
Shield of Mini-Shields
I made a single shield with space for any 3 mini-shields to be connected at the same time. Each mini-shield uses 2 analog pins, and 4 digital pins (plus digital pin 2 which they all share since I have dedicated it for the hardware interrupt feature). I needed to dedicate analog pins 4 and 5 to slot A to ensure the Real Time Clock module would work. Of the 14 digital pins, there are only 6 PWM pins available, so I have dedicated slots B and C to be the PWM mini-shields, so things like the speaker and the full-color LED won't work well if they are plugged into slot A.