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mellisphone Make Your Own Cellphone

David Mellis from the MIT Media Lab has been designing and refining his DIY cellphone, one that you can build yourself from his open source design files and code. A “difficult, but potentially do-able project,” the phone has the basic features that you’d expect: you can make and receive calls and text messages and it has a phone book for storing numbers. To coincide with CES, we got an update from David on his homebrew consumer electronics device.

What was the biggest design challenge?

Balancing the desire to make a functional phone while keeping it as easy as possible to assemble by hand. Mostly, this was a question of sourcing the right components: parts small enough to fit into a reasonable overall size but still big enough to solder manually. For example, I was lucky that the GSM module on the Arduino GSM shield (the Quectel M10) was both fairly small but with reasonably big solder joints — unlike many GSM modules with 0.5mm pitch connectors. Finding a small and robust screen was also a challenge: the LCD I used initially would break after a month or so of use. The LED matrix I’m using now has been fairly stable, but only shows eight characters. Similarly, I managed to find a nice small speaker, but the audio quality isn’t amazing. In general, there’s been a lot of tradeoffs: balancing functionality against ease-of-assembly. This problem is a lot harder when you’re trying to make something that you’re going to carry in your pocket every day.

What’s the next feature or improvement that you would implement?

I’m less interested in adding specific improvements to the phone itself than in exploring other ways to help people make their own devices. For example, I’m working on a GSM module that’s effectively a cellphone and an Arduino in one, so people can build their own cellphone interface or form factor. I’d also like to find ways to make PCB design appealing to new groups of people; making simple boards doesn’t seem that hard, so I’m curious to see how we might be able to place it in a design context rather than an engineering one. Finally, I’m also interested in finding ways to get the phone itself out to more people, whether by having them build it themselves or otherwise distributing it.

David's cellphone module allows people to build their own cellphone interface or form factor.

David’s cellphone module allows people to build their own cellphone interface or form factor.

Can you talk about the process of refinement on the design?

The phone has gone through a lot of iterations — circuit, enclosure, and software. The changes to the circuit itself have mostly been small tweaks and additions: for example, adding a reset button in case the software crashed, or connecting the buzzer straight to the microcontroller so I could use it as an alarm (not just a ring tone). For the enclosure, it’s been a lot of playing with different materials and fabrication processes — some by me, but also by a lot of others. People have made cases from cardboard, 3D-printed plastic, CNC-milled wood, even silk-worms. The software is probably the area which has had the tightest back-and-forth between design and use: I’ve discovered lots of problems and missing features while using the phone. Early versions were just missing a lot of features (for example, it didn’t even show the name of a person when they called) and I’ve gradually added the most pressing. In part, though, using the phone everyday has also made me realize how much functionality you can live without. The current version of the software doesn’t save old text messages, for instance, and I’ve just gotten used it.

Were there any capabilities that turned out to be harder or easier than expected to implement?

I’ve been surprised as how reliably the phones connect to the network. I am using an off-the-shelf antenna, and I borrowed the circuit for connecting it to the GSM module from the Arduino GSM shield — but still, I expected the RF portions of the circuit to present more of a problem.

If you could make an open source version of another consumer electronics device, what would it be and why?

While I started, to some extent, by creating DIY replacements for existing devices, I think the most interesting possibilities are in creating new, custom devices. With the increasing accessibility of embedded computation and digital fabrication, it’s more and more possible for an individual to create not just prototypes, but robust, reproducible devices they can use in their daily lives. So I think we’ll see increasing numbers of unusual, one-off or small volume devices that appeal to specific people or needs but that don’t make sense for mass production. For example, I’d personally like to build a couple of devices that perform specific, internet-enabled functions, like showing the weather or playing a particular podcast. I don’t see these particular devices as the next big thing (even for my own work) but simply as examples of the many different kinds of things it’s now possible to build.

Have you heard from anyone that’s tried to make the phone for themselves?

A number of people have emailed me to say they’ve made the phone themselves. Some have asked for help with various aspects but, in general, I’ve been impressed with the extent people have been able to make the phone independently. To me, it’s a sign that the digital files really do capture a lot of the design — meaning there’s real value in sharing them with others, even though there are still a lot of steps needed to turn them into a functioning device.

Thanks David!

Matt Richardson

Matt Richardson

Matt Richardson is a San Francisco-based creative technologist, Contributing Editor at MAKE. He’s the co-author of Getting Started with Raspberry Pi and the author of Getting Started with BeagleBone.


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