He used several components and built simple prototype board that can be connected to Arduino with Ethernet Shield. By sending a single signal to relay audio signal input can be switched between two outputs. Sound really simple indeed. Interesting part is a software which is actually pretty easy to write as there are libraries like webduino that allows to write pretty complex tasks with a few code lines.

Of course using Arduino and Ethernet Shield seems to be to expensive tools for such a simple task, but if you have spare lying around and gathering dust – why not. And don’t limit to audio only – relay can switch other things like lights, motors and other that comes to your imagination.

However, nothing is impossible, especially in this bizarre 21^st century, where many wacky-doo stuffs available in the market. Well, thanks to the Drawdio, the magical tool that turns your ordinary pencil into a music drawer.

Some of you here must be wondering, “How Drawdio got its name?” Actually, Drawdio is the combination words of “Draw + Audio”. It cuts away the ‘Au’ part, and combined it became “Drawdio”!

To be honest, it’s one of the most amazing devices that being invented in the early 21^st century. For your information, it’s definitely a great tool, especially for the beginners. There are many possibilities can be created by using the Drawdio.

Drawdio is a very simple musical synthesizer. It uses the conductive properties of pencil graphite to create different sound effects. A single AAA battery can operate the Drawdio for many hours, even the “nearly dead” batteries will work fined with the tool. In this case, you can use the battery till its last drop! It’s truly an environmental friendly device as well.

You’re wondering, “What’s the specialty of this wireless accelerometer based mouse and why I should build it?” Well, you might be haven’t notice that this project is using CYWM6935 wireless integrated module with antennas. It can act as “Transceiver” at the same time.

1. The CYWM6935 wireless USB LR Radio Module is very awesome, as it offers a complete radio module solution. Some of the reasons why you should use the CYWM6935 transceiver are:
2. It’s a single-chip 2.4 GHz direct sequence spread spectrum (DSSS) base band modem radio. It means it can be used to connect directly to a microcontroller via a simple serial peripheral interface (SPI).
3. It has the ability to support up to 78 channels of 1MHz.
4. It can be used for Point-to-Point and multipoint communication.
5. It has the normal/double data rate with 32 chips or 2 bit.

By the way, the SPI allows high-speed synchronous data transfer between the microcontroller and peripheral devices. Once the SPI is activated, the data transfer for this wireless accelerometer based mouse could be as smooth as silk!

Do you know that a microcontroller’s GPIO (General purpose input/output) pins cannot handle higher power requirements? An LED was easy enough, but how about the large power items such as light bulbs, toaster ovens or blenders that required more circuitry?

In this case, a relay is wanted in this situation. However, building a 5V controllable power outlet can be handy for many applications, thus a relay is the perfect choice for this project! For your information, a relay is a large mechanical switch, where the switch is toggled on or off by energizing a coil constantly.

By applying the relay in the project, it will ensure your safety. Let’s take an example, if you have 120VAC running through the paddles, you don’t have to worry about that 120VAC will sneak back into and vaporizing your microcontroller that connected to the coil, as the paddles are capable of carrying very large currents! Furthermore, you can use the relay to control a DC motor or an AC lamp if you want to.

Well, isn’t doing an electronic project should be a fun test? You can immediately change the above unhappy moment into a joyful moment.

How? Well, all you have to do is create the simple negative power supply for your own need!

I’m know building a -5V from a battery is a little bit tough. For this problem, I’ve decided to build a small device, which it will provide either -5V, -12V or -15V easily.

You can use the MAXIM 764/765/766 series, a little modification on the chip needs to be done on it, for the good output results.

As you can see it at the below schematic, we will use four capacitors in this project which:

C1 – 120µF, 20V

C2 – 0.1µF

C3 – 0.1µF

C4 – 68µF, 20V

However, for a greater current output, we should choose to use the 220µF instead of the 120µF.

Isn’t this is a cute and small gig? [source]