Electromechanical Refreshable Braille Module

Description

The big drawback to refreshable braille devices has always been their cost. The loose rule of estimation applied to these products has translated into something like $100 to $150 per braille cell. A 40-cell display, in other words, may cost $4,000 to $6,000, while an 80-cell model will cost $8,000 to $12,000. And so it has been that, while desirable, braille computer access has been out of reach for many users of assistive technology.

It is thus of great value to lower the cost of individual braille cells in order to manufacture Refreshable Braille Devices at a price that is affordable to the Visually Impared community.

While commercially available braille displays use expensive piezo-electric actuated pins. This project employs an electromechanical system with off-the-shelf and easily manufacturable components, leveraging the accessibility of high-quality 3D Printers and micro-magnets to keep the cost low without compromising functionality.

Details

HackadayPrize Video:

Table of Contents:

Subsystem	Links to Log/Document
Mechanical Development & Testing	• 1st 3D Printed Prototypes • 3D Printing: The Devil is in the Details • Assembly and Single dot test • Two dot test • Single Dot Test on PCB • 12th time is the charm
Electronics/Firmware Development & Testing	• Braille Cell Array Drive Circuit • Updated Drive Electronics • PCB Design of Braille Cell Evaluation Board • Braille-Module & Driver PCB's • Testing Electronics • Single Dot Test on PCB
Solenoid-Coil Winding Tool	• Coil Winding Tool for Micro-Electromagnets • Updated Winding Jig for Ferrite Cores vs Steel Cores
Technical Documents	• References & Previous Work • BOM & Cost • CAD Design • PCB Source Files

Working Principle:

Fig. 1 Braille Cell Actuation Test

This is a 3D Printed, electromagnet-based braille display module that can represent braille characters.

The key working principle is a cam actuator, consisting of an eccentric cam that has a rare-earth magnet embedded into it which is rotated to two stable positions by the action of an electromagnetic that changes its polarity. The rotation of the eccentric cam causes a braille dot to be lifted up or taken down.

Fig. 2 Braille Cell Working Principle

Once the Braille pin is lifted, and the cam rotates to its stable position, the weight of a finger on the pin (while reading braille) cannot back drive the cam. This not only satisfies the need for protrusion force of the braille pin but also that the electromagnet need not be powered once the pin has been lifted resulting in lower power consumption.

Fig. 3 Protruding Force Test

Construction:

Fig. 4 Braille Cell Construction

Prototyping is done using a high-resolution SLA 3D Printer as there are many thin-walled sections.
PR4 Resin on a 3D Systems Figure4 machine is being used for its ability to achieve 0.4mm wall thickness. Craftsman resin from Anycubic, on an Anycubic Photon Ultra, was tested to work as well.

Fig. 5 Micromagnet

The micro 1mm x 0.5mm NdFeB magnet is what makes this project possible. Luckily there are now a handful of vendors around the world keeping these in stock as they are also used for things like jewelry clasps on thin bracelets, Kingdom Death miniatures, super thing Games Workshop miniatures, and more.

Fig. 6 Coil Winding Tool

The electromagnets are constructed with 50-micron enamel-insulated copper wire with a ferrite core. A 3D Printed winding tool makes winding such small electromagnets easy.

Apart from the winding tool, all standard assembly & soldering tools are sufficient to build your own braille modules.

Fig. 7 Three Dot Array

Up to 3 Braille cells were tested to work together, no reason by more won't work as well. As only one pin is actuated at any time, only 1W of power is consumed at any point of time.

The only drawback of the drive system was that it takes at least 100ms to change the state of one pin, and this stacks up if more cells are added up. If we were to change the drive electronics so all pins of a single module can be driven simultaneously, then the refresh...

Files

Braille Cell V12.f3z

Latest CAD for Braille Cell

f3z - 2.05 MB - 10/10/2023 at 14:08

Download

Coil WInding Tool V2.f3z

Assembly for the coil winding tool used to manufacture the coils needed for the individual dots. Second Version

f3z - 970.05 kB - 10/10/2023 at 13:52

Download

Braille Cell Eagle Library.lbr

.lbr file for footprint and schematic of a braille module for eagle

lbr - 14.22 kB - 09/26/2023 at 16:57

Download

Braille Evaluation Board Eagle Source Files.zip

Eagle BRD and SCH files for Braille Evaluation Board

x-zip-compressed - 102.99 kB - 09/26/2023 at 16:52

Download

Braille Cell Eagle Source Files.zip

Eagle BRD and SCH files for Braille MOdule PCB

x-zip-compressed - 7.32 kB - 09/26/2023 at 16:52

Download

Components

Project Logs

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12th time is the charm
Vijay • 10/10/2023 at 14:02 • 1 comment

Having access to a printer directly made all the difference when iterating for 20-30 um tolerances. At these sizes, you can't really trust the CAD software anymore, and every assembly has to be empirically tested by printing it out.

In the final few iterations, I made the Cam assembly with the Braille Lower assembly independent of the Braille Upper, so that I could laser into the hole-shaft tolerance needed between the cam shaft and the hole it fit into.

Depending on the Resin, and printer used to print, I suspect the tolerances in the CAD design may need to be altered. Ive linked the final (so far) of the Braille Cell design below for FUsion 360. You should be able to navigate to the design history and change the hole size as needed if the cam is having a hard time fitting, or is too loose.

V12 CAD designs can be found here.
Updated Winding Jig for Ferrite Cores vs Steel Cores
Vijay • 10/10/2023 at 13:30 • 0 comments
I was initially using 1mm steel cores harvested from paperclips, but experimentally found that the steel core doesn't take well to fast voltage changes, and heats up the coil so much, that I had a few failures while testing operational parameters.

So I went back to high school science trying to understand magnetic permeability, and properties of soft iron (and WTF is soft iron anyway) and finally found these Ferrite Rods on Digikey:

they turned out to be a lot more brittle and needed more care in assembly. The metal chuck of the first iteration would just snap the ferrite rod.

So I redesigned a complete 3D printed chuck, that IMO works even better than the earlier one, and sits nice and centered

Ive updated the Instrusions section with details of how to use the new Coil Winding Jig.

The braille cells made of the ferrite core were found to be:
- Run cooler & with lesser power requirement
- Faster max refresh rate, from 200ms to 50ms
- Overcomes the issue when the cam magnet is too close to the core, the natural attraction overcomes the opposing magnetic flux, and the cam refuses to flip. the natural magnetic attraction to a ferrite core vs the steel core felt like it was less than half of it.
THe main drawback of using ferrite cores, however, what that if you are not careful with the winding jig, the core would snap.

In the future, I see this process automated, with the same process used to wind small inductors.
The updated CAD design for the winding jig can be found here.
Two dot test
Vijay • 10/05/2023 at 15:05 • 0 comments

Two Dots work!! a big achievement, and proves that the concept works as intended.

A few issues that I want to rectify before assembling the rest of the dots though:

-Steel core gets TOO hot too fast, it doesn't like too many polarity changes in a short amount of time, which is a big drawback if I'm trying to active fast refresh times. I will switch to a soft iron/ferrite core for the next iteration.

- Assembly is a real pain in the current version, with the cams wanting to stick to each other before I get the upper and lower halves of the assembly together. Will change over to snap-fit components.

-Will move the magnets closer to the center of the rotation on the cams, i.e., reduce the concentricity, to reduce the effect of the cam <sometimes> interfering with the other, but works 80% of the time.
Single Dot Test on PCB
Vijay • 10/05/2023 at 14:42 • 0 comments

A couple of logs back, we tested the overall mechanism working with a single dot in isolation with the PCB designed and then verified that the PCB boards designed were working with LEDs
Now it's time to assemble them to see if the designed electronics can successfully drive at least one braille dot.
And it works! The assembly process for the braille module can be found in the instructions, so check it out there.
Read more »
Testing Electronics
Vijay • 09/27/2023 at 07:35 • 0 comments

I tested out the driving electronics using two LEDs connected in opposing polarities, and adjusting the LM317 output to bring down the voltage so as not to burn the LEDs out.

This is what the code looks like running. The via placement for the coils just happened to be the right size to mount a few 0603 package SMD LEDs, so I converted one of the braille module PCBs into a tester.

The code below shows the functions I'm using to select which pin of which module to actuate. MOD_X and PIN_X are the pin numbering for the input pins of the decoder IC.

Read more »
Assembly and Single dot test
Vijay • 09/27/2023 at 07:09 • 0 comments

Assembling such tiny components was proving to be quite tiresome on the eyes, so I decided I'd gear up. I got one of these, and am very happy with the purchase, It's almost like I have superpowers!
Read more »
3D Printing: The Devil is in the Details
Vijay • 09/26/2023 at 20:21 • 0 comments

Fig 1. Version 3 Braille Parts printed on a Figure4 3D Printer by 3D Systems
Getting the design right has been a bigger challenge than I initially thought it would be. I had to go through 7 iterations before things were getting to something that fit together satisfactorily.
Fig 2. The various versions of the braille cells printed in SLA in different orientations
I initially was outsourcing to an external vendor who had a 3D systems figure machine with ProBLK 10 resin that produced pretty strong parts at extremely high detail. Even though I was very impressed at first, I quickly realized that things were either too snug a fit and wouldn't allow for easy motion or that there was too much tolerance and the mechanisms would not actuate predictably.
Read more »
Braille-Module & Driver PCB's
Vijay • 09/26/2023 at 14:21 • 1 comment

Fig 1: Individual Braille Cell PCB's

I had to max out the PCB fabs capability and took a few risks in the design by overriding my tried and tested DRC(Design Rule Check) file in Eagle when it came to the distance of the traces to the edge of the board, drills, and pads, but it seems to have worked. Nothing is shorted, or disconnected, so big win!
Read more »
Coil Winding Tool for Micro-Electromagnets
Vijay • 09/25/2023 at 13:01 • 2 comments

I figured that the trickiest parts of the build would be the winding of the ultra-small coils, so I designed a coil winding tool to help with this process and make it easier
Read more »
PCB Design of Braille Cell Evaluation Board
Vijay • 09/24/2023 at 13:02 • 0 comments

I created an 8 - Braille cell board to evaluate the braille cell functionality.
Read more »

View all 14 project logs

Build Instructions

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Coil Winding Setup

Step 1 :

Lock one end of the 50um wire into the groove of the chuck and loosely tighten the chuck tightening screw

Step 2 :

Place about 1-2mm of the Ferrite core into the chuck, then with the spacer jig, push the ferrite core in at the exact distance into the chuck using the tailstock.

Step 3:

Tighten the chuck to clamp down on the ferrite core, and then remove the spacer and the tailstock

Step 4:

Place the 1mm spacer on the other end of the Ferrite core, and gently flush the tailstock to the spacer. Tension the copper wire through the wire guide.

Winding the Coil

Step 1:

Manually wind the first few turns neatly and make sure there is adequate tension in the copper wire

Step 2:

Turn on the motor, monitor the coil winding, and guide the coil if required to evenly spread the diameter of the winding.

Step 3:

At the end of the winding, using a paintbrush, apply some PVA-based glue to the coil

Step 4:

Carefully remove the tailstock, and the spacer. Then loosen the chuck and remove the finished coil. Allow for glue to dry

Step 4:

Marvel at the fruits of your labor

Cam Assembly

Step 1 :

Using a Xactro knife, remove individual 1mm magnets from its stack, and place them on a magnet. Mark a side of the magnet with an identifier, so you can make out the polarity, and hence know the polarity of all the micromagnets. you just need to make sure all are polarised in the same direction.

Step 2:

Remove a cam from the 3D printed support tree, and clean the area where the support was stuck.

Step 3:

Using a tweezer pick up a coil, keep track of the magnetic orientation, and press-fit it into the 3D Printed Cam

Step 4:

Marvel at the fruits of your labor

Discussions

richsmith0707 wrote 4 hours ago

do you have stl file?

Are you sure? yes | no

Razvan T. Coloja wrote 11/14/2023 at 04:52

I can't state well enough how much I appreciate your efforts. I have been trying to create an affordable Braille display for years. I've thought of tens of design, from tiny tubes involving air pumps to purely mechanical rotors that would push and keep up the pins. Your design is ingenious, I must say. And keeping the cost of production so low is incredible.
Thank you for making the world a better place.

Are you sure? yes | no

TRAN.VINH.QUANG wrote 11/11/2023 at 09:00

Great job! Could I translate your work to vietnamese and share to our community with original link include ?

Are you sure? yes | no

Vijay wrote 4 days ago

You are very welcome to!

Are you sure? yes | no

Paul McClay wrote 11/10/2023 at 03:15

*Table* of contents... Elegant approach to big HaD project navigation. I might be stealing that. And congratulations on your 2023 HaD Prize win!

Are you sure? yes | no

kelvinA wrote 11/11/2023 at 13:22

After seeing this project make a table, and discovering #YGREC8 which writes the logs in a list, I'm also going to pilot-program this too. I'm also going to try writing tags under them, as the titles alone usually don't mention all of the highlights.

Are you sure? yes | no

Yann Guidon / YGDES wrote 11/11/2023 at 15:15

I maintain a formatted list of logs on most of my projects, after 2 or 3 logs, it must be a habit because things can quickly get out of hand :-)
I do this also to help my (now-broken) project downloader/scraper: it's easy to parse with grep/sed/wget.

I wish HaD had this feature to automatically create such a list. Some of my projects exceed the 100 logs and it becomes *very* useful after a while.

Are you sure? yes | no

Vijay wrote 4 days ago

Thankyou!

IMO Project documentation on HaD should be rethought from scratch. There are so many great projects where it is so easy to get lost in the logs, I hope the log navigation becomes a thing, it's all yours 😆

Would love a similar approach to GitHub Docs where you could add documentation to various sub-systems of a project as you go.

Are you sure? yes | no

[deleted]

[this comment has been deleted]

Paul McClay wrote 11/10/2023 at 03:21

Great that similar designs are so widely available. Please share some links or search terms.

Are you sure? yes | no

BRUNO RAFAEL DE OLIVEIRA MARTINS wrote 10/24/2023 at 13:50

Man, what you just did is revolutionary! We've been trying to make a viable competitor for the piezo braille cells for years! Congratulations!

I'm not a specialist on the matter, but i believe you can replace the cam mechanism with a bistable compliant mechanism, i'll try to study the subject to contribute to the project! Thank you!

Are you sure? yes | no

Vijay wrote 10/25/2023 at 02:19

Thankyou so much!

Ive been thinking about compliant mechanisms early on, but couldn't figure it out. However, I'm no expert in compliant mechanisms and would love to collaborate

Are you sure? yes | no

kelvinA wrote 10/25/2023 at 12:06

I'd imagine that a compliant mechanism would achieve the reliability and durability required for the goal of having these braille modules implemented in the outside world (shops / ATMs/ etc.).

Are you sure? yes | no

Trevor Flowers wrote 10/13/2023 at 19:53

Excellent work! Would you be interested in switching away from Eagle and Fusion to all open source software so that anyone can use and contribute to the project? OpenSCAD, FreeCAD, and KiCAD are more than capable of working with these designs.
If so, I'm happy to help with the conversion and any questions that come up afterward.
- Trevor (trevor@transmutable.com)

Are you sure? yes | no

Vijay wrote 10/14/2023 at 11:19

Thank you @Trevor Flowers!

I'm always open to using open-source software, but I generally get scared of the associated learning curve, especially since I've invested time in the software I've already taught myself. However, I'm willing to collaborate to convert the project for use on open-source CAD software for both mechanical design and electronics.

Are you sure? yes | no

Blayze Millward wrote 10/23/2023 at 13:49

Since your mounting PCB for the electromechanical parts are relatively simple (compared to the other PCBs, at least) and there's a lot of repetition in the physical design, it would probably be possible to put together an OpenSCAD script that generated not only the physical elements, but also the PCB as an SVG for arbitrary sizes of actuator grids. If you take this further, I'd be interested in collaborating (do you have this up on a git repo, or are you just hosting the files here?).

As an aside, just wanted to say that I love this project! I saw it on YouTube, and the ability to hit "like" on this has literally made me make an account with hackaday.

Are you sure? yes | no

JamesCarron wrote 10/30/2023 at 15:45

I'd be happy to help out with the KiCAD conversion eg with review / prototyping etc. I'll reach out @Trevor Flowers

Are you sure? yes | no

Trevor Flowers wrote 11/09/2023 at 01:46

Hey, I'm caught up in the holiday rush so I haven't had a chance to work on this at all. So, don't let me hold you back! :-)

Are you sure? yes | no

botmayank wrote 10/11/2023 at 05:46

Great work Vijay! All the best for the prize 😁

Are you sure? yes | no

Vijay wrote 10/11/2023 at 16:45

Thankyou!

Are you sure? yes | no

Ishaan Pilar wrote 10/10/2023 at 13:18

Great project, so fascinating to see the dots move like that!

What resin & printer did you use to 3D print parts of such accuracy?

Are you sure? yes | no

Vijay wrote 10/10/2023 at 13:32

Thankyou!

Earlier prototypes were made using a 3DS Figure4 printer is PR4 resin. The shin-color parts were printed on an Anycubic Photon Ultra in Craftsman resin.

Are you sure? yes | no

Josh Joy wrote 10/10/2023 at 13:10

👍👏

Are you sure? yes | no

Vijay wrote 10/10/2023 at 13:32

Thankyou!

Are you sure? yes | no

chiranjeevi wrote 10/10/2023 at 13:02

Good job !

Are you sure? yes | no

Vijay wrote 10/10/2023 at 13:09

Thankyou!

Are you sure? yes | no

Electromechanical Refreshable Braille Module

Description

Details

Files

Braille Cell V12.f3z

Coil WInding Tool V2.f3z

Braille Cell Eagle Library.lbr

Braille Evaluation Board Eagle Source Files.zip

Braille Cell Eagle Source Files.zip

Components

Project Logs

Collapse

12th time is the charm

Updated Winding Jig for Ferrite Cores vs Steel Cores

Two dot test

Single Dot Test on PCB

Testing Electronics

Assembly and Single dot test

3D Printing: The Devil is in the Details

Braille-Module & Driver PCB's

Coil Winding Tool for Micro-Electromagnets

PCB Design of Braille Cell Evaluation Board

Build Instructions

Collapse

Discussions

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