I'm a newbie in robotics, and I'm doing a project on dynamic Braille interface. Basically it's a 8*8 array of pins, which can be either totally up or down. How to use least motor as possible?

I'm thinking of using Arduino for easy interface with computer.

  • $\begingroup$ Welcome to Robotics Dzung Nguyen, perhaps you could explain what you have considered so far, and what you have rejected. What constraints are you under? Do you have limits on how big the device can be? What are your response time requirements? What budget does your project have? As an example, you could do this a set of 64 piezo or pneumatic actuators and set each pin individually, or you could use fewer motors which set multiple pins at the same time, but there are many factors which need to be taken as design considerations. $\endgroup$
    – Mark Booth
    Apr 17, 2013 at 18:13
  • $\begingroup$ Braille itself only has 64 possible values -- 6 dots (⠃) allowing $2^6$ possibilities. Are some of the rows permanently unused, existing only for spacing purposes? In other words, you're one row of pins short of being able to represent 3 rows of braille characters; how does this affect your plan to show characters on this interface? $\endgroup$
    – Ian
    Apr 17, 2013 at 20:36
  • $\begingroup$ Thanks for the input! Actually I want to make this computer mouse for Blind people:economist.com/node/14955359. It has two 4x4 array which changes depending on mouse location. The budget should be around 100-200$. $\endgroup$ Apr 17, 2013 at 20:41

1 Answer 1


With a \$100-200 budget it's unlikely you can duplicate the functionality of a \$695 commercially-produced product. Your device may be slower, bulkier, noisier, less reliable.

One possible approach is to use dot matrix printer print-heads to drive pins. See example of pins being driven in a vimeo.com video called “Dot Matrix Print Head - Testing”. You might need to replace the pins with push wires so that you could go from a 3-by-9 pin layout to a 4-by-4 or 4-by-5 arrangement. Some fairly old (and bulky) print-heads already contain push wires.

If the print-head pins are driven ballistically they might not be able to work with the high duty cycle that a Braille dot would require. If you use push wires, you could have a cam that moves a latch plate back and forth, alternately latching wires in place or releasing them so they can move up or down. Or you could have a cam that lifts all the Braille pins at once, and a print head that drives some latch pins sideways to catch those Braille pins that that should remain up. Another cam would clear all the latch pins at the beginning of each character cycle.

There are miniature solenoids as shown below with roughly 1cm square cross-section, with a 1.5mm diameter pin that moves about 3mm. (Listed on ebay as “Miniature Electric Solenoid - 9 V - Push Type - 2 oz. Force - 3 mm Stoke”, about \$7.) The duty cycle of this solenoid is 10%, so like a ballistic print head it would require some latch mechanism, as well as a spring or gravity return. You would need to attach push wires to the end of the shaft because the solenoids won't cluster closely enough.

Miniature Electric Solenoid - 9 V - Push Type


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