Introducing Arduino – a simple Raspberry Pi alternative

For those whose projects have space restrictions, another attractive option is the Arduino Nano, a compact version of the Uno measuring only 18.5mm by 43mm. In addition, a specialist version of the Arduino, designed for wearable electronics projects, where the device is wired into a circuit using conductive thread, has been created by Adafruit Industries as the Flora, while the extremely compact Femtoduino model is barely larger than a fingertip.

Other third-party interpretations of the Arduino concept include the Netduino family, which swaps out the C programming language for Microsoft’s .NET Micro Framework, and the Nanode, designed by the London Hackspace community, which provides integrated Ethernet connectivity and a serial bus designed for remote sensing applications.

It’s also possible to build your own Arduino: an ATmega328 microcontroller chip, as used in the Arduino Uno, costs around £3 and can be easily loaded with the Arduino firmware –known as a “bootloader” – to work as an Arduino-compatible “brain” for projects where a fully fledged Arduino board would be a waste.

How to build a custom macro keypad

One of the best features of the recently released Arduino Leonardo is its ability to act as a USB human interface device (HID) as standard. With simple code, it’s possible to use a Leonardo to control a desktop, a laptop, a server or even a tablet. One of the easiest ways to demonstrate this is with a macro controller that allows you to set up one-button control of your favourite applications. To build the macro keypad (at a cost of £32), you’ll need:

• An Arduino Leonardo
• A breadboard
• Four push-button switches
• Jumper wires

1. Building the circuit

The Arduino can be connected to a variety of different components, but for this mini-project you’ll need only switches – the simplest active components there are. Using the illustration below as a guide, take the four push-button switches – making sure they’re momentary switches, meaning they go back to the off state when you remove your finger – and insert them into the middle of the breadboard at regular distances.

The switches we’re using have four legs, which need to be inserted so that the flats of the legs are aligned horizontally and straddle the centre line of the breadboard. If the switches won’t stay in the breadboard, put a small piece of Blu-Tack or similar under the body of the switch. If you’re using switches with two legs, such as arcade buttons, make sure they’re all connected to one side of the breadboard and on different rows.

One leg of each switch needs to be connected to a common ground; this provides a signal that the Arduino can monitor for changes. Take four short jumper wires – preferably black, for ease of identification – and insert one end of each into the same row as the bottom leg of each switch. The other end of each jumper wire should be connected to the breadboard’s common ground; this is on either side of the board, identified by a blue line and, in some cases, a minus symbol.

Next, take another four jumper wires, preferably of different colours, and connect one end of each to the same breadboard row as the top leg of each switch. These wires will provide the signals to the Arduino. The other ends should be connected to digital pins 2, 3, 4 and 5 on the Arduino Leonardo. Try to make sure the top switch is wired to pin 2, the next to pin 3 and so on. Don’t be confused by the numbering: the Arduino’s pins start at 0, not 1.

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