Tact-Tiles

It's been a long time, but I have some good news:

In this video you can see the assembled prototype running a simple demo test of the touch sensors array:Hope you liked! :D

Finally I finished the prototype, everything is working as expected, apart from the Bluetooth module (I still have to buy a new one). It was the most interesting build that I have done and I am pretty happy with it. Hope you like it:

This night I will be working on the software, so the new video will be up to date. Tomorrow I will post a simple video showing the progress and on Monday I post the new one. Thank you for your support!

I’m only a few hours to finish the final prototype, but I wanted to share the current status with the community. Here are some photos from last night.

I’m still thinking in how I will be able to demonstrate in the new video the vibration of the pads. In the last video if you watch carefully I think you can notice the vibration but on last night’s test I wasn't able to tell which one was vibrating by looking at it, only by feeling and hear it. If you have some idea on how to show this on a visual demonstration please let me know!

Here are some pictures of the assembling of 16 pads:

Note the little bumps made for reading the cell letter in Braille:

Making all these pads was a very time consuming task that took me almost five hours to finish. I had no time to make mistakes, luckily just one of the 80 very thin wires broke, but I was able to identify and fix it.

I used 5 minute Epoxy for keeping everything in place. I never had used it before, but the results was satisfactory.

My test on the Bluetooth module did not work, It can send messages to my cellphone but it always receive “0” when I try to reply them (displayed as a blank line after the letter in the image below).

Oddly I found that every time that I sent a “y” it returned a “@”, this made me realize that it might be a software problem, but when I tried the same code in my Arduino Mega 2560 it worked... So I still don't know what it is all about, but I have some guesses:

• Maybe I overheated the uC during soldering
• Maybe the board has some design error (probably not due the simplicity of the track, see image below)

I also tried to make a serial connection between my Arduino Mega and the board and got the same results.

I think this is a problem with this unity only, so tomorrow I will assemble another board and see if this is really the case.

If someone has an idea about what can it be, please share! ;)

UPDATE: I assembled a second board and got the same results, I also tried making a connection with my Arduino Mega again and it worked! So probably the problem is in Bluetooth module, but is still odd that it works perfectly with my Arduino Mega. Anyway, I bought another Bluetooth module, and I will resume my tests in the weekend.

Yesterday I assembled the main board as expected, I used only one slot for the IO, making it capable of handling the first 8 tiles. I also assembled 4 tiles of random Braille letters.

... but my new soldering iron only comes tomorrow, and my flux pen on Thursday, so probably by Friday I'll have some news.

Here are some pictures:

Version 1.0 vs 2.1

The main cause that I wasn't able to build a improved prototype yet is the huge mistake of choosing the wrong footprint for the ULM2803. I couldn't find this component at my city so I wasn't able to check if it had the right size, only when it has been delivered from China one month later. So I had to create a new design and order it again, this time using my voucher from OSHPark.

I'm now in Ireland, starting a scholarship programme in Computer Engineering. I'm loving this country, but until last week I didn't have a address to order things. My boards are now estimated to be delivered on 25 of August, so until there I have to wait.

There are two exciting new improvements in this version of the main board:

• You can populate the board according with the number of pads (input and output) that you will use, e.g. 8, 16, 24 or 32:

• A unusual footprint for the ULM2803 (8 outputs) made by me is used for enabling the use of an ULM2003 (7 outputs) if you want:

I'm currently porting the PCB design for KiCad, increasing the TouchX board hardware openness! :D

2.0 version changelog:

• Added mounting holes
• Added some forgotten capacitors/resistors
• Changed position of the Bluetooth HC-06 module connector
• Added Bluetooth RX pin voltage divider selection jumper
• Fixed SOIC-18 footprint

Here are some 3D renderings of the board:

On the next project log I'll post the full schematics and PCB layout files ;)