Dynamic Braille display using SMA coil actuator and magnetic latch

Braille points are varied arrangements of raised dots representing characters which are identified by touch by visually impaired people. A dynamic Braille display which presents Braille points by the up-and-down movement of pins using shape memory alloy (SMA) coil actuators and a magnetic latch has been developed. When the SMA coil actuator is heated by the flow of an electrical current, the compressed SMA extends, causing the pins to move up or down. The magnetic latch mechanism keeps the pins in an up or down state and solves the problem of heat storage and power consumption of the SMA actuator. Six Braille points (2 x 3) represent one character, the distances between the points being 2-3 mm. In order to fabricate a dense array of the SMA-actuated dynamic pins, Ni electroplating is utilized for batch forming of electrical connections between the SMA coil and the electrode on printed circuit boards. Displacement and latching power of each fabricated pin are sufficient for dynamic Braille. Sixteen pins representing two characters and two cursors are modularized to realize a line of dynamic Braille characters by lining up the modules. A control circuit and a driving circuit are mounted on each module to reduce the number of lead wires. (c) 2004 Elsevier B.V. All rights reserved.