[Jaromir] created this astonishingly retro future device as an entry for the NXP LPC810 challenge, a contest to do the most with an ARM Cortex M0+ microcontroller in an 8-pin package. Having only six I/O pins for controlling a GSM module, display a few buttons, and the fancy rotary dial meant [Jaromir] needed to expand his I/O some way.

the rotary cell phone isn’t ready for Think Geek to do a production run quite yet.

Sumasta was showing off his Arduino Cellphone which he calls Phoenard. It lets you write phone apps the same way you write Arduino sketches. It also has a hardware connector letting you drive external add-ons like the self-balancing robot shown in the video.

[Sumasta] won the Atmel Hero contest

Here’s an interesting concept. Lets make a kit to build your own super simple cell phone. Thats basically what a group at the MIT media lab is proposing with this prototype

At$150, it isn’t really that competitive compared to the phones you’d get from your provider, but it is just a prototype.

DIY Cellphone
http://hlt.media.mit.edu/?p=2182

An exploration into the possibilities for individual construction and customization of the most ubiquitous of electronic devices, the cellphone. By creating and sharing open-source designs for the phone’s circuit board and case, we hope to encourage a proliferation of personalized and diverse mobile phones.

DIY Cellphone website
http://web.media.mit.edu/~mellis/cellphone/index.html

The DIY Cellphone is a working (albeit basic) cellphone that you can make yourself. It can make and receive phone calls and text messages, store names and phone numbers, and display the time. It builds on the hardware and software in the Arduino GSM Shield but extends it with a full interface, including display, buttons, speaker, microphone, etc. The source files for the cellphone are hosted on GitHub (hardware, software), which also includes an issue list where you can file bug reports or request enhancements.

Be careful with those Arduino GSM cards. As [James] reports, they may turn into fire starters. One person has reported a small explosion and fire already on the Arduino forums

[James] states the problem is a tantalum capacitor used to decouple the GSM radio power supply from the main Arduino supply.
Tantalum capacitors are great for their low ESR properties. However, they have a well known downside of getting very hot, or even exploding when stressed.

It’s not the Tantalum Anode that is burning. The Manganese Dioxide used as a cathode in some Tantalum capacitors is the culprit.

It comes down to voltage rating (or more aptly, derating). The Arduino GSM shield runs at 5 volts. The designers chose a 6.3V rated capacitor. While this close of a tolerance may be good enough for some types of capacitor, it is a no-go for a Tantalum cap with Manganese Dioxide.

The dielectric material in these capacitors is so thin that the stress of a reflow oven cycle causes cracks. The cracks pass leakage current, and this sets the Manganese Dioxide on the path to destruction.