Doctoring the mouse

5 min read

Amid the blizzard of statistics and market research that accompanied its latest product launch in August, Logitech revealed one startling fact. Researchers discovered that the average PC user spins the scroll wheel on their mouse around 26ft (8m) every day.

The statistic is more than just a depressing indictment of our sedentary lifestyles. It is an indication of the mouse’s importance — a humble palm-sized piece of plastic that has practically become an extension of the average office drone’s body.

The Logitech MX Revolution is being marketed as the ‘world’s most advanced mouse’, a bold declaration perhaps, but one which hints at some of the interesting technologies that its designers have somehow managed to cram inside its small plastic body. According to its product designer Dennis O’Keeffe, the sophistication of the Revolution puts it well ahead of any other mouse on the market.

‘We were looking to deliver the ultimate performance in a mouse,’ he said. ‘We wanted to find a way to help people with the overload of information on the PC, as well as making something that was a truly iconic, high-performance product.’

Iconic might be a bit much to ask of a mouse, but the Revolution is certainly striking. The sculpted curve of the ergonomic thumb rest gives easy access to the ‘Quick-Flip’ thumb wheel, which allows users to flick between different applications much as the Alt+Tab function works on PCs, and also works as an easy-to-use zooming tool for photo-editing applications.

However, it was the problem of endless scrolling that led to the Revolution’s key innovative feature — the MicroGear Precision Scroll Wheel. A series of brainstorming events at Logitech’s design headquarters in Cork led to the decision that the wheel had to be completely redesigned to create a smooth scrolling effect without adding any messy extras such as touch pads or joysticks.

‘We had been on the periphery of this problem for a number of years,’ said O’Keeffe. ‘We knew we wanted to keep it simple, as the wheel is a very intuitive, easy-to-control idea, that allows you to accelerate the scrolling speed. We had a number of different ideas on how to do this, including using a small DC motor, but we went for the idea of a heavy wheel that uses inertia.’

The scroll wheel is designed so that users can ‘hyper-scroll’ through endless pages of Excel spreadsheets in a single spin. In free-spin mode the wheel will spin for up to seven seconds in a single frictionless burst. This is the equivalent of more than 9,000 lines in a spreadsheet, or 200 pages in a Word document — a process that would take 500 spins and up to seven minutes with a conventional mouse.

The specially-designed brass wheel that makes this possible is almost seven times as heavy as a conventional injection-moulded scroll wheel, which was deemed too light to fit the exacting engineering specifications that had been set. A low-friction bearing mount and ratcheting hub are fitted inside the precision-moulded chassis which ‘floats’ on a series ofpin-like hinges and a tiny calibrated compression coil spring, like a form of suspension for mice.

Almost a hundred parts make up the SmartShift system, which allows the MX Revolution to scroll either in click-by-click or free-spin mode

Although larger than most mice, the Revolution’s design was heavily constrained by size, with power consumption strictly limited. This meant that O’Keeffe’s team had to come up with innovative ways of integrating the wealth of new technologies into the product within a tight power budget. Aligned with the development of the free-spinning scroll wheel — and adding to the potential power burden — the next big step was the development of the Smart-Shift technology, a unique invention that allows the function of the mouse to automatically change depending on the application the user is in.

The bi-directional 2.4GHz wireless technology allows the mouse to communicate with the PC and the embedded microprocessor detects the active window and applies the scrolling mode that is best suited for that application. The system allows a ratcheted line-by-line scroll while looking through a PowerPoint presentation, but defaults to free-spin when in Word, for example. It can even detect how fast the wheel has been spun so, in Excel, it will operate on a line-by-line basis until the wheel is spun hard when it will change to free-spin. A simple idea perhaps, but one that necessitated a complex bit of engineering. O’Keeffe admitted that developing the technology was a massive challenge.

‘We took the precision ratcheted scrolling function and the free inertia scrolling to a lead person in the marketing department. He said: “That’s great — now can we get them both in the same product?” Integrating them into the same mechanism was tough.’

The design team concluded that the most cost-effective way of doing this was to use a tiny DC motor which could change between the two modes. In total the Smart-Shift system comprises nearly 100 individual components. To operate in free-spin mode the internal ratchet mechanism — a small steel ball embedded in a spring-mounted ratchet arm — must be disengaged. In normal precision ratcheting mode this ball rides over the indentations in the wheel’s hub to give the click-by-click scrolling feel.

However, when the processor has detected that free-spinning is required, it activates a solid state switch, the H-Bridge, which applies a tiny electric current to the motor. Instead of spinning at hundreds of revolutions a second like other motors, it only rotates its central shaft by 275°, just enough for the cam on it to nudge the ratchet arm and the steel ball clear of the hub. This entire process is said to take no more than 40 milliseconds.

With the ratchet arm disengaged the scroll wheel is in free-spin mode but as the wheel comes to a halt the motor rotates in the opposite direction and re-engages the ratcheting system — operating much like a mini-clutch.

The Revolution also comes with another time-saving gadget — the ‘Touch to Search’ function. A small button behind the wheel allows the user to highlight a word or phrase in a document and automatically search using their preferred search engine, with the results displayed in a pop-up box on the screen without having to move to their internet browser.

Designing an object so fundamentally tactile, Logitech discovered that people’s perception of how smoothly a mouse is moving is often very different to the reality. When designing its Teflon feet, the company found that people wearing headphones have a different perception from people who are not — all based on the sound the mouse makes. So, the feet were designed to be some 50 per cent quieter than any of Logitech’s previous mice.

‘We realised that the sound of a mouse has a massive influence on how people perceive the smoothness of its movements,’ said O’Keeffe. ‘So it was really important that we deliver not just a really smooth precision scrolling experience, but also the right sounds to accompany it.’

The team also went for tiny dampeners at the end of the ratcheting arm so that at low speed a satisfying metallic click accompanied each scroll, but at high speed the sound could be muffled and so would not be too intrusive.

While styling was extremely important in the design, so too was robustness. so the mouse was repeatedly dropped a metre on to a steel plate and baked in an oven at 70°C for hours on end. The MX Revolution may look pretty but it is also designed to last.

Its counterpart, the equally sleek-looking VX Revolution, is specially designed to be used with laptops and is a smaller, slightly more pared down version of its sibling with the same scroll wheel, but lacking the SmartShift system.

‘I knew we’d got it right when, after I’d used the prototype version, I had to give it back and go back to using my old mouse — it just felt all wrong,’ said O’Keeffe.

Logitech will be banking on the fact that the deskbound masses in offices around the world, scrolling themselves into early RSI, will feel the same.