Gemini: The Newest Thing In All Of Psion

By therefore founder, Martin Riddiford

Feb 28, 2017 · 4 min read

It’s been 25 years since I designed the first clamshell PDA, and 20 years since the Psion Series 5 — a hell of a long time in the world of technology! Over time, PDAs and other formats have been swept aside by the advances in mobile telephony and miniaturisation which has led to today’s amazing smarthones, it’s surprising then that so many people I meet still have such a fondness for the pocketable clamshell format. It’s not just nostalgia either, there is a genuine belief that it is much easier to use for generating text documents, manipulating spreadsheets and coding with a scaled down laptop, rather than cramping a touchscreen with a virtual keyboard.

I have played around with the idea of breathing new life into the PDA several times over the years, but it needed Planet Computers and Dr Janko Mrsic-Flogul’s enthusiasm for such a venture to convince me it was time to do it for real! I knew that the final design would need to compete with high end smartphones, so the start point was how to squeeze a real, properly tactile keyboard into the thinnest package. This is the type of challenge that I have tackled many times in my career whilst at therefore and before, while shoehorning electronics into ever smaller products.

The obvious arrangement of hinging a keyboard from the edge of a smartphone was never going to fly — the balance and thicknesses would be all wrong as it would be top heavy, even falling over backwards when put on a desk. Having worked through the remaining options, the most favourable from a component layout and ease of manufacture point of view was to put a large, flat battery under the keyboard. This gave a better thickness and weight distribution, but was thicker overall than some of the other options, because the lid would still be the thickness of a smartphone. I then asked a naive question: can we reduce the thickness by putting all the components on a single sided PCB, as the PCB area available to us having removed the battery was huge compared to a smartphone? The answer came back: Yes.

One final technical showstopper needed to be overcome — connecting the battery and the CPU via a flexi circuit through the hinge has always been deemed to be problematic due to power losses. However, the removal of the battery from under the display has opened up space to use a supercap to assist the battery, thereby overcoming the problem and ensuring unrivalled performance.

So now we were settled on a format which enables a workable, slim-form factor. But we weren’t finished yet! How could we drive the thickness even further? We hatched an audacious plan to squash the keys when the device was shut, saving 1.4mm in thickness. This is done with magnets on the corners which compress the keys and hold the lid and keyboard frame together.

But what about stability on a desk? I originally pioneered a series of innovative clamshell hinges over the years for Psion. Since then I have played around with and designed many over-centre hinge mechanisms. I have drawn on this experience to create a new, delightful over-centre mechanism which exudes tactile quality. The stainless steel spine artfully covers the main hinge and connection between the two halves, and is tensioned on opening to create a stable, tilted form, while urging the case to close when you have finished using it. Two separate stainless steel covers complete the high quality wrap. All three covers can be removed and replaced, enabling personalised customisation and limited edition versions.

The hinging of the spine is unusual. Rather than having a traditional cylinder (piano) hinges along its edges, it rotates about its folded-back edges. This is very strong, invisible and easy to miniaturise, whilst also allowing the spine to be easily unclipped for personalisation.

Gemini will be available for Linux and Android, and the Indigogo crowdfunding campaign has just begun!


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Founded in 1993, therefore is a multi-award winning, London based product design consultancy.