Novel mechanism makes refreshable braille displays practical

Tactile displays — particularly for use as refreshable braille displays — have always been a challenge to design and fabricate, as they require so many moving parts. Every dot needs its own actuated mechanism and there needs to be dozens or hundreds of dots squeezed into a small space. Conventional micro actuators become very expensive and difficult to control in such quantities. But researchers at Monash University developed MagnePins, a new type of refreshable braille display with novel mechanisms that are much more affordable.

The MagnePins team built both general purpose tactile display and dedicated braille display prototypes. They’re similar, with hundreds of actuated pins. The only major difference between the two is the pin arrangement.

Both display types rely on electromagnets to push up pins below the dots. But it wouldn’t be feasible or cost-effective to include hundreds of electromagnets in a display like this, which is why MagnePins has a kind of “scanning” mechanism to actuate the pins column-by-column in quick succession. That mechanism slides underneath the display while the pins ride in special channels. A staggered line of pistons, actuated by 24 electromagnets, either remain low or protrude upward to change the positions of the pins as they move overheard.

An Arduino Mega 2560 board controls those electromagnets through FETs and monitors the position of the sliding mechanism using a linear encoder. Software built in Unity converts images or braille into pin positions for the Arduino to set.

In testing, the MagnePins display prototypes proved to be 99.97% accurate and the average refresh time was just 12.88 seconds. Readability was confirmed by an experienced braille reader. And, best of all, the cost to build a MagnePins display is very low, with the components adding up to a mere $231.95 USD. Furthermore, a MagnePins display can be built using tools commonly found in makerspaces.

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