Refreshable Braille Display

Description

Of 40 million blind people in the world, only 10% can read and write braille.
One of the primary reason for this is because braille hasn't yet found its footing in the digital era, due to the sheer cost of such devices, as well as the affordability matrix of the visually impaired.

Low-cost braille displays have been sought after for quite a while with no avail.
Commercially available braille displays employ peizo-electric actuated pins, which are very expensive.

Due to the sheer expense of braille technology, and the scarce availability of books in braille, the medium is slowly falling out of favour. But many agree that braille literacy is paramount for the empowerment of the blind for education and employment.

The display would be used along with https://hackaday.io/project/10745-brailler-style-keyboard to make a full modular braille computer

Details

I have been working with braille for about 3 years now. My first attempt at a prototype used a dot-matrix printer head: http://www.angadmakes.com/my-portfolio/virtual-brailler

At Makerfaire Bangalore, I met Paul D'souza and was amazed by his innovative designs for refreshable braille displays. One of his designs used these vibrator motors.

Im looking to build on that brillant idea and build a system that is more robust and can be understood and reproduced and improved by people all over the world for the visually impared , similar to how the open source prosthetics movement have helped so many amputees.

The method of working is as follows:

Motor+Cam :

The heart of the mechanism is a series of pico-motors that are commonly used as vibration motors with a weight on the end.

We modify the weight to have a profile similar to the above so that is may act like a cam, when shaft axis is verticle.

Motor holder + Stoppers:

The motor holder holds all the motors in the appropriate positions to actuate the pins. There are stoppers that prevent the cam from rotating continuously that are integrated into the design.

At the particular position where the cam followers are placed, depending on the rotation of the motor, the cam follower will he higher, when motor rotates one direction, and is lower in the other. The stopper make the motors behave in a "binary" fashion. The functioning will become clearer once the cam follower is explained.

Cam follower + Lever + Spring + Pins:

The cam followers, that will be riding on the motor's cam is shown in the first image( the three projections). The cam follower is attached to the lever bar, that is fixed on one end ( the large rectangular part). The level bar has the braille pins on the other end.

The material used for this part would be ABS, or Nylon, that would be slightly flexible without causing fatigue.

Thus the movement of the cam, wold cause the cam follower to move up, that flexes the lever pushing the braille pin upwards and the lever is displaced from its natural position. when the cam causes the cam follower to fall, the level bar falls back to its natural position and thus acts like a spring.

Everything is assembled in the above fashion. Two lever arrangements and six motors make up a single braille cell.
Faceplate+ Pin Guide:

The faceplate forms the surface on which the pins pop out.

One module contains two refreshable braille cells( like above).Modules will be linked together to make a full braille display. i.e, for a 20 character refreshable braille display, 10 modules would be used.

The below image illustrates the working better. the white arrows indicate direction of motion.

Files

cern_ohl_v_1_2_howto.pdf

Cern Open hardware Licence 1.2

Adobe Portable Document Format - 55.06 kB - 04/19/2016 at 18:53

Preview

Download

cern_ohl_v_1_2.pdf

Cern Open hardware Licence 1.2

Adobe Portable Document Format - 95.73 kB - 04/19/2016 at 18:53

Preview

Download

Components

Project Logs

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Motor-gasm : The most amazing motor on earth!
Vijay • 07/12/2016 at 20:20 • 9 comments

The micro stepper motors I ordered just arrived, and god are they brilliant!
I did some rudimentary experiments about the amount of torque it has, and if it would suffice for my application, and I think it would, although i'm afraid it might miss steps.

I'm driving this straight out from the Arduino pins that should be ~40mA source and sink. Possibly some more juice from a proper driver will do the torque some good.
Let me know what you think. I would also like to thank all those who responded to my earlier log, especially @HTCPCP 418, whose micro stepper motor driver approach, ill probably be taking.

Ill be uploading CAD data for these motors in a few days if anyone is interested.

The link to this motor is : http://www.aliexpress.com/item/50pcs-2-Phase-4-Wire-Micro-15-Step-Motor-Screw-Rod-Stepper-Stepping-Motor-Free-shipping/32222560547.html?spm=2114.13010608.0.78.tjruAc
Help needed driving multiple stepper motors.
Vijay • 06/26/2016 at 07:02 • 16 comments

We are trying to figure out the best way to drive as many stepper motors simultaneously ( for the actuation system mentioned in the last post ) .
-There are 40 stepper motors in total for a 20 cell braille display, two per each cell. They preferably need to be actuated simultaneously.

-The motors do not require too much current ( unknown amount since there is no datasheet, motors will arrive in a couple of days)
-The motors are 4 wire- Bipolar steppers, with 15 step a rotation.
-it takes roughly 25 rotations of the stepper motor to reach from one end of the linear selector system to another.
Some of the approaches friends have suggested:

-Using many stepper drivers like allegro or TI's solution each connected to a slave MCU like an attiny85, that takes serial input. ( i.e, each braille cell has stepper motor controller and a MCU)
-Using a I2C, SPI port expander connected to a main MCU
-Using an LED driver
Any suggestions for this problem?
! New Actuation System !
Vijay • 06/22/2016 at 20:42 • 3 comments

I've been straight at it, thinking about alternatives for the last actuation system after last weeks events. I think ive got a good robust system this time, that actually is simpler than the last one in terms of components and size. Lesser parts to be 3D Printed, and more that can be bought off-the-shelf

Using
Micro Stepper Motor
+
3x2 Pogo pins
=
Using retractable pogo pins, that are engaged/disengaged using some sort of linear motion ( servo/ stepper/spring/solenoid for up and down motion) that pass though a pin-selector slider mechanism that allows only some select pins to pass actuated by the micro stepper motor.

note: once an array of these is built, the engaging/disengageing ( up and down) motion of the pogo pins can happen simultaneously( for all braille cells together) with a since actuator.

What do you think?
Discontinuing work on current actuation method
Vijay • 06/18/2016 at 20:51 • 3 comments

Hi all,
As mentioned in my previous post, it’s been brought to our attention that features of the open source refreshable Braille display project have already been covered under a patent application filed by Paul D’souza on 5th November, 2014.
Paul’s patent describes the use of “micro-motor actuated pins, the pin cantilever design, the mechanical stop to limit rotor rotation, motors with rotors or cams, mounted vertically or horizontally used to lift pins directly or via an interposer, low force selector etc” - many of these are featured we have included in this device.
Paul has requested we discontinue the project in the interest of potential manufacturers and licensees of his patent, as well as to avoid any legal obligations he may face with the patent office. As a result, the CERN Open Hardware License the project was released under has effectively been invalidated and so I have discontinued work on this current method of braille pin actuation. The patent will severely restrict any global (and particularly local) impact we can make with this project, which was our whole motivation.
However, I would like to make clear that the designs and documentation we have released have been created from scratch, sharing only the working principles of Paul’s patent. My intention has always been to make a completely 3D printable refreshable braille display that anyone can access and I have been working on braille technologies for the past three years. As part of this work, I have developed software to convert text documents to braille and built two refreshable braille display prototypes, one using micro servo actuators and another using a hacked dot-matrix printer head. At that time, I was still a kid in college and didn’t have much knowledge about production techniques or skill in design, CAD, and electronics.
Things have changed a lot since then. Going through the process of setting up and running a 3D printing and product design startup, I’ve learned exactly what I need to know to create just about anything. I actually met Paul at a local Maker Faire and we instantly connected because of our shared efforts on braille and I was amazed and intrigued by his genius ideas for actuation. This meeting resparked my passion for braille and I began using cell-phone vibration motors as a method of actuation along with my experience with FDM 3D printing and product development to create a solution that anyone in the world could potentially have access to just by downloading the files.
What’s more, I was lucky enough to have the opportunity to show one of my early braille display prototypes to the president of India, Dr. APJ Abdul Kalam, before he passed away. He made me promise that I would do everything in my power to ensure the project would reach the people that it matters most to and that has become my life's mission ever since.
Since the 3D designs and documentation are my own original intellectual property, I will be releasing everything under Creative Commons Attribution-shareAlike 4.0 International. This is an open source license that allows anyone to use, modify, and share the documentation and 3D designs under the same license. However, anyone wishing to manufacture and distribute the device itself should contact Paul D’Souza on pgdsouza@gmail.com. I have done this to ensure that people can make a personal copy for studying purposes.
I will certainly not stop working on the refreshable braille display due to this hiccup. I have seen some amazing motors from Aliexpress while buying motors for the current system and I am confident that by collaborating with other members of the open hardware community we come up with a “patent infringement free” solution that is feasible, scalable, and will achieve my goal of bringing digital literacy to the visually impaired all around the world.
I wish @PAUL DSOUZA all the best, he has been incredibly supportive on this project, and multiple others my team and I have been working on. I...
Read more »
Updates!
Vijay • 06/17/2016 at 15:26 • 1 comment

On suggestion from @Yann Guidon / YGDES I've scaled the mechanism by 1.1 times. It changes the dimensions by a very small amount (0.6mm over a character) so that I can accommodate 4mm motors for the time being since the 3mm ones are proving hard to find. I shall maintain another copy of this version of the mechanism in another folder.
Using the prize money from the "Anything Goes" round ( YEY!) ive purchased the following motors and eagerly await their arrival:
http://www.aliexpress.com/item/5Pcs-DC2-3V-1500RPM-4mm-Dia-Coreless-Vibrating-Motor-for-Mobile-Phone/32637931060.html
The electronics design will take advantage of the spring leads of the motors to have a "solder-less" connection to the driver board. As mentioned in an earlier post, it driver circuitry will be similar to that used in Flip-Dot displays (Thanks Martin )

I have been requested by @PAUL DSOUZA to make everyone aware that the features mentioned in this Project thus far are covered under a patent application filed at The PatentOffice, Chennai, by him on 05Nov2014 …5559/CHE/2014. If anyone wants to exploit features of this design, they would need to get in touch with Paul or his patent attorneys (Origiin IP Solutions LLP), as rules require that even the Patent Office to be kept informed of activities in regards to patents.

I have also been toying with the idea suggested by @Keith Minsel using cams to drive the pins. After finding some really cool motors on aliexpress (God bless China) Ive made up my mind to make a prototype using a stepper-cam system to lift pins up and down.
I'm considering using either a linear compound cam, on a circular one. I hope people can decipher the drawings above, The prongs are the same cam followers that I have currently on the design, only the motor block would be replaced. Any help with making the decision is appreciated( circular or linear)

The stepper motors: http://www.aliexpress.com/item/hot-salow-price-20pcs-extra-Micro-stepper-motor-DC-Stepping-motor-with-Screw-Dia-3-3mm/2053510670.html?spm=2114.10010108.100009.4.UGX6T0
I guarantee the size would surprise you.
Thats one tiny motor!
Vijay • 05/12/2016 at 17:30 • 0 comments

I found a single 4mm dia motor from somewhere, and am in the process of modifying to see if it works. it struck me how small these things are!

I'm also in the process of working out the electronics, looking at how Flip Dot displays are run, and probably follow the same method for the driving circuitry.

Using the following resources for that ( Thanks to Martin for the idea) :
http://www.dhenshaw.com/Art/Dottie/start.htm
https://wiki.attraktor.org/FlipdotDisplay
Pin actuation looks promising!
Vijay • 04/29/2016 at 12:06 • 2 comments

I couldn't get the motors I need, but was able to source a 6mm dia version (double the size I need) to see if the cam+follower thing would work, I just couldn't take the suspense of not knowing!

I was too lazy to CAD anything for the test, I had to know IMMEDIATELY!

so I ground the weight to a shape I wanted, got my friends iPhone to record in slow mo, and it looks promising!
I can't be 100% sure the final would work, since the actual motors I need to use are smaller, but I feel it's got a fighting chance!

I also realised I'm using 2 simple machines, a lever and a ramp, and it oddly satisfies me for some reason.

Inferences:
- there is only a ~0.5mm lift required at the cam follower to achieve the required lift at the pin.
Hence, a shallower angle on the cam, would make it even more easier to lift the pin ( because of the shallower slope of the ramp of the cam )

I contacted sales at Precision Microdrives about sponsoring their motor, https://pmdri.zendesk.com/attachments/token/koNuCT5zcZuO6kQC6E56rh040/?name=303-103-datasheet.pdf

They got back saying they won't lower the MOQ or the price :( gotta figure out another way of getting my hands on them, or else try and change the design to use 4mm dia motors from china ( highly unlikely they will fit the requirement due to the size constraint)
A big thanks to @Anool Mahidharia for the article on Hackaday today!
http://hackaday.com/2016/04/28/refreshable-braille-display-and-braille-keyboard/
CAD design changes and improvements
Vijay • 04/27/2016 at 21:22 • 0 comments

Updated the description with the above image. As you can see, the changes in the last few logs now reflect the CAD design.

-The Cam Follower(blue) & Pin Lever(red) are different parts to aid 3D Printability
-Jig-saw type thingies on the sides, for chaining the module to create a full display
Cam followers+ Spring action working!
Vijay • 04/24/2016 at 15:45 • 0 comments

The cam followers were printed, and came out beautifully . The Spring action works just like planned.

the only thing left to test is the cam actuation with the motor.
Link and description of the motor :
https://www.precisionmicrodrives.com/vibration-motor/3mm-vibration-motor-8mm-type

The MOQ and price is a little expensive for me at the moment, I will be contacting them and asking if they will sponsor the motors for the project.
The video below shows the cam followers and the spring action pulling the pins back down after pushing the cam followers up.
The perfect tolerances: Assembly time!
Vijay • 04/19/2016 at 18:32 • 0 comments

The above image shows the shaft-lever part into the braille cell plate. It took 4-5 iterations (available on the dropbox link) to get the tolerances just right, such that the pins don't get stuck in the shaft of the braille cell plate.
The above image shows the side view of the braille cell's, along with the pin-lever part assembled and held in place with an M2 screw. the pins are "below" the surface of the braille cell plate when not pressed, due to the spring action of the lever ( by the cam follower)
In the above image, I'm applying a slight force on one of the lever, that causes the pin to move up. Quite simple really.

Now its time to test with motors!

View all 13 project logs

Build Instructions

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Discussions

Strike.Productions wrote 10/15/2018 at 20:16

hi I’m working with a group on a project to improve the blinds way of life and I believe if we could mass produce the final product these could be put in stores and various other places so the blind don’t have to rely on others or rely on product placement

Are you sure? yes | no

tonny_hoo wrote 06/14/2018 at 07:46

Great project! Eepecially for blind people. Really kind of you.

I'm a student in china and want also start a project like this to help more blind people .Now I bought the vibraiton motor you have showed <a href="https://www.vibrationmotors.com/product-catalogue/cylinder-coreless-vibrating-motors/small-vibrating-motors-bl4i2j6-x10e/</a> . Is this vibraiton motor workable

Are you sure? yes | no

teoteehsien wrote 03/30/2017 at 08:56

hi vijay, may i ask where did u buy the small linear servo? as shown in the new actuation system post?

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Vijay wrote 10/05/2017 at 09:16

https://www.aliexpress.com/item/DC-5V-Sankyo-2-Phase-4-Wire-Slide-Screw-Stepper-Motor-Micro-Stepper-Motor/32462050546.html?spm=2114.search0302.3.65.v5sqyj&ws_ab_test=searchweb0_0,searchweb201602_0_10051_10050_10053_10052_10338_10339_10055_10099_10175_10054...

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Injoip wrote 09/30/2016 at 16:06

Hello vijay, Im a student in University, I have a big interest in engineering and Im very excited about your project, Im wanna make one to present my grandpa on his birthday as a gift because he's blind. In your CAD files, it doesn't have an exact size, can you tell me the size of those things ? Im looking forward to hearing from you, thank you so much .

Are you sure? yes | no

Vijay wrote 10/03/2016 at 05:23

Hi, it very gratifying to hear that, and is something that will motivate me to finish this project.

Were you able to open the files? do you want me to save the assembly as a consolidated step file?

Are you sure? yes | no

Injoip wrote 10/05/2016 at 05:37

I opened the file, but Im didn't see any size, maybe the size is integrated and when I bring it to the 3D printing, the printer will understand, right? If I can, I would like to see the assembly as a consolidated step file too, it would be very nice. I'm working on the program, it's almost done

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Andrew wrote 06/28/2016 at 13:05

How about a tiny one of these?

http://woodgears.ca/counter/

That one is pretty big, but shows the principle of operation. Tape recorders had small ones.

Imagine 3 reels, mounted vertically, not horizontally like the counter. Each reel is a square, so it has four positions, not ten. On the facets of the reel is zero, one, one, or two dots. So different combinations of the three reels can make a Braille character cell.

Turning the first reel once makes the next reel turn by one quarter. Turning the second reel once makes the third wheel turn by one quarter. Thus, the character can be reset within 16 turns.

The first reel can be driven by a direct drive motor, or a stepper, or a solenoid. Only one drive is required for the whole cell.

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K.C. Lee wrote 06/28/2016 at 14:27

I was thinking along the same line as those music box player drum, but the actuators are stretched to linear strips and driven by the new linear stepper motor. Sort of like paper tapes for old computers except with bumps.

The top part would be like this https://hackaday.com/2016/06/27/pinjig-soldering-clamp-has-pins-seized-by-airport-security/

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Vijay wrote 06/29/2016 at 09:47

Someone send me this link just yesterday, did you check the log involving pogo pins?.

The stepper motors will be cleared from customs today, and I will CAD and post the design online as soon as it reaches here, possubly will give people more ideas.

Are you sure? yes | no

Vijay wrote 06/29/2016 at 09:44

I love this idea. Id like to explore it after the current design is done. Possibly a micro gear train done on a SLA/PolyJet machine for a size acceptable for braille.

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Stuart Longland wrote 06/27/2016 at 03:43

I wonder how hard it'd be to adapt this to "print" a page? i.e. you lay a sheet of paper across the face of the display and roll a roller over it to imprint indentations into the page.

Reason I ask is this: http://www.abc.net.au/news/2016-06-27/sa-vision-impaired-students-benefit-new-braille-printer/7546678

"The printer was not cheap, at a cost of more than $30,000, but in an era of computer-assisted technology the braille language remains vital."

Pretty sure the BoM for this display is a lot less than AU$30k, and with some adaption, I think it could easily perform both display and print functions.

Are you sure? yes | no

Gabriel wrote 06/19/2016 at 13:39

hey... how about making the dots simple contacts that pass high voltage instead of fisically moving? Avoid any mechanism pattent.

Obviously high voltage enough to feel but not to harm or be unconfortable.... this could be ajusted by the final user as a preference. I dont know what is the threshold for this to work.

Your design basically becomes a PCB with exposed pads and a "High voltage" segment diver of sorts....

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Vijay wrote 06/20/2016 at 09:13

I had the opportunity to talk to someone in the field of psychophysics, the study of the relations between physical stimuli and mental phenomena on the subject of braille. This approach is definitely one worth researching on, there are some very fascinating research in this field from Disney. Ill look more into it.

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Gabriel wrote 06/20/2016 at 12:02

This is probably the best project here.

Keep it up.

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Gabriel wrote 06/20/2016 at 12:02

This is probably the best project here.

Keep it up.

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Vijay wrote 06/30/2016 at 03:22

Thank you for the encouragement!

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zakqwy wrote 06/18/2016 at 14:18

Awesome project! Keep up the great work!

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Vijay wrote 06/30/2016 at 03:22

Thank you!

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PAUL DSOUZA wrote 06/18/2016 at 11:55

Vijay, as K.C. Lee says, making a one off for study is ok. It becomes a problem when multiple people start wanting to produce the same not knowing a patent exists. Also, pls check Bristol Braille Technology's - Ed Rogers ---Quixote and Canute regarding the linear cams.

Are you sure? yes | no

PAUL DSOUZA wrote 06/17/2016 at 18:28

Vijay,

from the pat office rules I have been provided ... "Further , Section 146(2) of the Act and Rule 131(2) of The Patent Rules 2003 provide that every patentee and patent licensee should furnish the details of working of the patented invention in Form 27 in respect of every calendar year within three months of the end of each year"

I have no wish to enter into all the legalities with the patent office prematurely regarding whom I give permission to produce the device. It also makes it difficult to explain to potential manufacturers / licensees that permission has already been given to x, y, z.

Guys like you would, I am sure, be able to come up with something unique that can be developed in the public domain if desired. The only criteria is that you would still need to do a prior patent search.

Are you sure? yes | no

K.C. Lee wrote 06/17/2016 at 18:41

There are two separate issues. One is a patent which describe the methods/ideas only valid in the jurisdiction(s) that has been granted/recognized. The other one is the Copyright of the design. i.e. actual artwork, design files etc. The project can retains its copyright regardless of the patent issues. The only thing is that the readers need to be informed of an existing patent which might affect if/where it can be manufactured/distributed.

Patents do allow for making a personal copy for studying purposes. Sadly that this project get caught up in a patent dispute.

Disclaimer: I am not a lawyer.

Are you sure? yes | no

de∫hipu wrote 06/18/2016 at 12:48

I think it's an excellent opportunity for everyone to see for themselves and learn why so many improvements and inventions, sometimes life-saving and life-changing for the people in need of them, never see the light of day. It's because of patent squatters who "have no wish to enter into all the legalities", but had no problem with the legalities involved in registering their patent.

Are you sure? yes | no

PAUL DSOUZA wrote 06/16/2016 at 04:29

Hi Vijay,

while I have
been supportive and impressed with your efforts in trying to produce a rapidly
prototyped Refreshable Braille Display thus far, I was just informed by my patent attorneys that that I needto let you know that before you take this Refreshable Braille Display projectforward further you must be made aware that all of the features you havepublished thus far are covered under a patent application filed at The PatentOffice, Chennai, by myself on 05Nov2014 …5559/CHE/2014 . The said patentapplication for a Refreshable Braille Display covers the use of micro-motoractuated pins, the pin cantilever design, the mechanical stop to limit rotorrotation, motors with rotors or cams, mounted vertically or horizontally usedto lift pins directly or via an interposer, low force selector etc. Iprototyped just one of the variants covered by the patent that I deemed to bethe most feasible and cost effective. Amongst the peoplefollowing your project on this open forum there might be some who believe that
this design is open source, and that
prior arts and patents do not exist. I was advised that this impression needs
to be corrected immediately.

You will need
to let the public know that if anyone wants to exploit features of this design,
they would need to get in touch with me or my patent attorneys (Origiin IP Solutions LLP), as rules require that
even the Patent Office be kept informed of activities in regards to patents.

Are you sure? yes | no

Vijay wrote 06/17/2016 at 11:39

Hi Paul,

Sure no problem, I shall post a log relaying the same. Since the patent is already granted, would you be willing to put it under a non-commercial licence, so that people like me can develop the idea further? and in case anyone wants to commercially use the design they may contact you.

So far the CAD files i've released ( available in the dropbox link) are under the CERN licence (http://www.ohwr.org/projects/cernohl/wiki) let me know how best to modify it.

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de∫hipu wrote 06/17/2016 at 14:29

I'm not sure Indian patents are valid on the Internet ;-)

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Arsenijs wrote 06/06/2016 at 19:26

You might have funding for ordering enough of those smaller motors now, it seems! Cheers!

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Vijay wrote 06/17/2016 at 16:45

I went to town buying all sorts of miniature motors from China, I just hope I made the right choices :p

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tstenswold wrote 06/06/2016 at 17:34

This is very interesting and I commend you for your efforts. Have you considered the possibility of using a rotary display? Since each horizontal row of the Braille character only has four possible positions (no pips raised, left pip, right pip, both pips), any symbol could be conveyed using three cylinders with four faces each. Two symbols side by side could be accomplished with 16-faced cylinders. I understand that this would require some positioning feedback, but might be accomplished with cheap optical/mechanical encoding. It may be a way to lower the total number of motors used and thereby reduce the cost and noise.

Mind you, this is simply off the top of my head idea. Clearly you've been working hard at this for some time and are doing a great job. Keep up the good work!

Are you sure? yes | no

Vijay wrote 06/17/2016 at 16:46

Hey!

Thats a good idea, another person had suggested something similar. Check my latest log, Ive bought miniature stepper motors that may take care of the positioning.

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Mati wrote 05/05/2016 at 03:49

Great project! :)

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Vijay wrote 05/12/2016 at 17:31

Thankyou! :D

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Sandeep Patil wrote 04/30/2016 at 07:39

Brilliant work!

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Vijay wrote 05/12/2016 at 17:31

Thankyou! :D

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Keith Minsel wrote 04/27/2016 at 12:23

Have you considered driving the pin pair positions with a set of 3 8-position cams using a single servo/motor and reduction gearing?

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Vijay wrote 04/27/2016 at 15:49

Thanks for the message and drawing! it got my mind wandering

I did a little research to see what gears can be used with pico motors : http://www.didel.com/microkit/pricelist/

I don't think any of the off the shelf servo motors available would fit the size limitations. Do you know of any?

I like the idea of a single cam-train actuating multiple pins.

check http://www.ebay.in/itm/322010918960?aff_source=Sok-Goog

combining this with a linear cam that has all the combinations of crests and troughs for a number of pins.

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joe57005 wrote 04/27/2016 at 00:41

Have you considered shape memory alloys? they take more current than motors, but you could make some truly tiny actuators.

Are you sure? yes | no

Vijay wrote 04/27/2016 at 10:22

There is research regarding this (http://assistech.iitd.ernet.in/asme-15-rbd.pdf)

but has some apparent drawbacks: the refresh rate, heat produced and thus requires a cooling system current consumption, and fatigue.

If you know of any new developments in this field, do let me know!

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Karl-Wilhelm Wacker wrote 04/26/2016 at 22:13

Looking at the pin arrangement and the suggestion of using coils and magnetized pins made me think of another technology: core memory. Instead of a coil for each pin, wind rectangular coils so that you have three coils going across the [4] pins of two letters, and four coils, one for each column of [3] pins. drive an x-y pair of coils at the same time in the same 'direction, and only one pin would have the combined magnetic field to move up or down. this lets you use 7 push-pull drivers for the coils instead of 12.

Are you sure? yes | no

Vijay wrote 04/27/2016 at 10:01

I've been learning so much from people on hack a day, thankyou! I didn't know of core-memory until today! (https://en.wikipedia.org/wiki/Magnetic-core_memory)

This got me thinking of the electro-permanent magnets being used in google's project ara phone. Electric potential will only we required to change the state.

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K.C. Lee wrote 04/27/2016 at 12:00

I am thinking something like power inductors. e.g. http://www.coilcraft.com/me3220.cfm

3.2mm diameter. Use these tiny disc shaped rare earth magnets from China.

e.g. http://www.banggood.com/search/magnets.html

The inductor is on a ferrite core, so there will be some attractive force. You can reduce the force a bit by having some minimum separation between the magnet and the coil. You'll only need to apply current in one direction to repel it.

Only issue is how much current and if the current is within Irms rating for heating. If the current is small enough, there are SPI low side drivers with onchip protection etc. Just have to google for "spi low side peripheral driver chip"

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Vijay wrote 04/27/2016 at 18:22

You sir, are a genius! Using off the shelf power inductors is a brilliant idea, and keep the cost low, and makes assembly/reproducibility easy.

I've been thinking how to wind the coils myself. I shall give this a try and let you know how it goes!

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Vijay wrote 04/27/2016 at 19:18

I did a quick attempt at trying this, I got a ~3-4mm diameter indutor+core and a 10mm dia rare earth magnet. used 5V at ~ 1 A to power the eliminator.

The attraction between the magnet and the ferrite core was more than the repulsion caused by the turning on of the coil.

Maybe one with a smaller core would work better? you think its a good idea to keep persuing this and try a few more times?

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K.C. Lee wrote 04/27/2016 at 21:20

I don't know the right answer to this. The only thing I suggested is to have a minimum separation distance - put a cardboard shim between the inductor and magnet to weaken the force a bit. There are also air core inductors for RF, but they are not designed for high currents. Beyond that, it might need a lot more turns of coils than such types of cores.

In the old dot matrix printer, they have solenoids spread around the pin head and use pieces of steel wire to redirect the force. The wires also do the printing. It is a hell of a mess to fix the head - I keep mine alive by fixing it every few months for a while until I gave up.

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Yann Guidon / YGDES wrote 04/28/2016 at 00:44

"You sir, are a genius!" He always surprises me so that must be why :-)

K.C.'s electromagnetic core proposal sounds very interesting to me.

The modified cam is a nice trick but it does not fully exploit the electromechanical properties of the tiny motor. These 3mm or 4mm motors are designed for high speed, not torque, so they will heat a lot with pretty small torque, and I suppose they would need mechanical amplification with gears (micro-planetaries ?)

OTOH Lee's proposal reuses existing power coils (cheap !) with a very well understood and simple electromagnetic circuit. It's easy to control 1A currents (or more), the voltage does not need to be high so the actual power is a few Watts during a fraction of second.

What is also missing frmo the overall design, IMHO, is position sensors. A couple of wires should indicate that the moving part has reached one end or the other, so the driving current can stop, and a safety mechanism is triggered if it stays "inbetween" after a reasonable time (indicating electric or mechanical fault). Or even if the current is too high.

Good luck, I have doubt about the micromotors with simple cams, but I hope you will prove me wrong or find a better system.

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Vijay wrote 04/29/2016 at 08:25

@K.C. Lee I know what you are talking about, with the dot matrix head. My first prototype when I started attempting refreshable braille used it.

It would heat up too much, and would scare the blind when I tried user testing, because of the heat of sound.

I'll keep trying with different inductors, lets see what works.

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Vijay wrote 04/29/2016 at 14:55

@Yann Guidon / YGDES The position sensor is a good idea and will be needed thanks!

Check out the latest log, the cam thingy look like it might work, I was skeptical myself!

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surubarescu wrote 04/26/2016 at 14:37

You can use the motors from old phones. You can find them at a phone repair shop or at companies that recycle electronics.

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Vijay wrote 04/26/2016 at 17:30

Thanks!

most of the motors I've seen so far have 4mm diameter body. The company mentioned above is the only one who makes 3mm that I am aware of.

According to the design, I can push for a maximum of 3.5mm diameter motor body.

If you have seen smaller ones let me know! :)

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surubarescu wrote 04/27/2016 at 09:45

All the phones i had opened were Nokia and they seem to share the same motor or at least same form factor motor.

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Jan wrote 04/26/2016 at 10:09

Unfortunately I can just give you one skull. Amazing project!

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Vijay wrote 04/26/2016 at 17:30

Thank you so much!

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Refreshable Braille Display

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Motor-gasm : The most amazing motor on earth!

Help needed driving multiple stepper motors.

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Discontinuing work on current actuation method

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Thats one tiny motor!

Pin actuation looks promising!

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cern_ohl_v_1_2_howto.pdf Cern Open hardware Licence 1.2 Adobe Portable Document Format - 55.06 kB - 04/19/2016 at 18:53	Preview	Download

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Refreshable Braille Display

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