skuller
Posts: 5
Joined: Thu Jan 23, 2014 8:47 pm
Location: Bourges, France

A bluetooth chessboard

Thu Jan 23, 2014 9:10 pm

Hello,

I want to build a chessboard that can act either independently or as a bluetooth device.
I am already in possession of an "auto-sensory" chessboard composed of 64 reed switches / 64 leds organized like this:


Image



I thought about this:


Image

https://www.modmypi.com/protect-your-pi
(this extension board will be plugs directly into the GPIO connector)
http://cgi.ebay.fr/ws/eBayISAPI.dll?Vie ... 0911409078
http://cgi.ebay.fr/ws/eBayISAPI.dll?Vie ... 0846780100



Does it'll work? what do you think?
Last edited by skuller on Sat Jan 25, 2014 11:44 pm, edited 1 time in total.

danjperron
Posts: 3402
Joined: Thu Dec 27, 2012 4:05 am
Location: Québec, Canada

Re: A bluetooth chessboard

Fri Jan 24, 2014 11:59 pm

I will assume that one or 2 leds will be on at the same times.

Your bluetooth device should be on the 3.3V. If it is the same that the one I got. Anyway serial is 3.3V on the PI so 3.3V it is.

I don't think that 2 AA batteries will be able to supply 1A for a long period. Even not sure it they will supply 1A. Don't forget if you step up from 3V to 5V, the power is the same and at 3V , the efficiency will be around 75% . The Input current should be roughly double on the battery side.

I suggest to opposite, use 6 batteries with a step down regulator. It will be more effective since battery could be a little bit discharge and still gives enough power.

A step down regulator like OKI-78SR, which will be around 90% efficient around 9V input voltage.

http://canada.newark.com/murata-power-s ... st=72R3616

I think your project is doable.


Ok let's be weird. What about using a pcb with pad like a keyboard. Each chess piece will have a metallic plate at the bottom
and will close contact (capacitive way). Maybe an old USB keyboard with the cpu stripped and the matrix reconnected to the chess board. This way you could just check the scan key to figure out which piece was lift and where it was put back on the chess board.

Daniel

skuller
Posts: 5
Joined: Thu Jan 23, 2014 8:47 pm
Location: Bourges, France

Re: A bluetooth chessboard

Sat Jan 25, 2014 11:25 pm

ok thank you for your response.
I forgot to mention that I have a model A.
I will assume that one or 2 leds will be on at the same times.
exactly
Your bluetooth device should be on the 3.3V. If it is the same that the one I got. Anyway serial is 3.3V on the PI so 3.3V it is.
well that's strange because i think that there is only one model and they said here that it should be on the 5V:
http://blog.miguelgrinberg.com/post/a-c ... spberry-pi
I don't think that 2 AA batteries will be able to supply 1A for a long period
ok. I already ordered the adapter so i'll try with 4 AA battery (i update the pic). apparently this is enough for ~3h.
Ok let's be weird. What about using a pcb with pad like a keyboard. Each chess piece will have a metallic plate at the bottom
and will close contact (capacitive way). Maybe an old USB keyboard with the cpu stripped and the matrix reconnected to the chess board. This way you could just check the scan key to figure out which piece was lift and where it was put back on the chess board.
well in fact i already have a mephisto modular chessboard with magnetic pieces and reed switches:

Image

So what you describe is what i'll do ;)
what i want to do is close this (except that here the board is only use as an usb device and so run with a teensy board):
http://www.meca-web.es/articulos/usb_board.htm

danjperron
Posts: 3402
Joined: Thu Dec 27, 2012 4:05 am
Location: Québec, Canada

Re: A bluetooth chessboard

Sun Jan 26, 2014 12:48 am

I checked the bluetooth specification and you need 3.3V.

All GPIO on the Raspberry Pi are 3.3V anyway. I did you use it and it is working very well. So Just 3.3V instead of 5V.

This is the spec for the bluetooth device (Max is 4.2V)
http://www.amazon.com/Arduino-Wireless- ... s_indust_1

Daniel

skuller
Posts: 5
Joined: Thu Jan 23, 2014 8:47 pm
Location: Bourges, France

Re: A bluetooth chessboard

Sun Jan 26, 2014 12:54 am

the description is wrong, check the 4th picture:
Image

3.6v-6V

the amazon reviews (and your experience) suggest that 3.3v can be possible but i prefer to follow the manufacturer's recommendations ;)
Last edited by skuller on Sun Jan 26, 2014 1:51 am, edited 2 times in total.

User avatar
redhawk
Posts: 3465
Joined: Sun Mar 04, 2012 2:13 pm
Location: ::1

Re: A bluetooth chessboard

Sun Jan 26, 2014 1:25 am

This project is very interesting, however I'm confused about the detection method used.
As I understand each chess piece has a magnet attached and when in close proximity to the reed switch a signal is detected on the matrix grid.

If that's the case then surely having several chess pieces on the board would also trigger other parts of the grid casing many signals to cross over??

How can you tell which chess piece is where on the board unless that is the magnet only causes momentary connections with the reed switches and not a permanent contact??

Richard S.

skuller
Posts: 5
Joined: Thu Jan 23, 2014 8:47 pm
Location: Bourges, France

Re: A bluetooth chessboard

Sun Jan 26, 2014 1:32 am

redhawk wrote:This project is very interesting, however I'm confused about the detection method used.
everything is explained here:
https://sites.google.com/site/bergerspr ... cb/sensors
Strength: We have to find a balanced value of strength, since excessive strenght may result in premature malfunction of the switches (by deformation of the reeds), in addition to not only activate the switch of its square but the others around.

danjperron
Posts: 3402
Joined: Thu Dec 27, 2012 4:05 am
Location: Québec, Canada

Re: A bluetooth chessboard

Sun Jan 26, 2014 2:01 am

Ok, not exactly the same.

Be sure that the transmit output gives 3.3V otherwise use a resistor divider to reduce it to 3.3v

Daniel

User avatar
perfo
Posts: 92
Joined: Mon Jan 30, 2012 2:42 am

Re: A bluetooth chessboard

Mon Aug 10, 2015 12:38 pm

I think that would be the problem of using a keyboard scanner in that you have 32 keys pressed at the same time...

PiGraham
Posts: 3613
Joined: Fri Jun 07, 2013 12:37 pm
Location: Waterlooville

Re: A bluetooth chessboard

Mon Aug 10, 2015 4:07 pm

perfo wrote:I think that would be the problem of using a keyboard scanner in that you have 32 keys pressed at the same time...
That's what the diodes are for. Multiple switches can be detected.

User avatar
perfo
Posts: 92
Joined: Mon Jan 30, 2012 2:42 am

Re: A bluetooth chessboard

Mon Aug 10, 2015 6:37 pm

A normal keyboard (scanner) with. Diodes at the crossing points, I'll have to think about that one (not suggesting any one is wrong of course).

User avatar
perfo
Posts: 92
Joined: Mon Jan 30, 2012 2:42 am

Re: A bluetooth chessboard

Mon Aug 10, 2015 7:13 pm

Ah yes I'm on hols and 8 pints down but it does makes sense (to me). Perfect then except only being able to Id the piece from memory only.

PiGraham
Posts: 3613
Joined: Fri Jun 07, 2013 12:37 pm
Location: Waterlooville

Re: A bluetooth chessboard

Tue Aug 11, 2015 9:44 am

Just thought...

If you made a pegboard style chessboard with 2.5mm jack sockets (think travel chess) you could wire a resistor between the pins of the jack plugs mounted on the pieces. You could then read the resistance value via matrix scanning. That should allow you to find out which of the 6 pieces is in each square. Put a diode across the resistor for all white pieces and you could detect colour by testing forward and reverse polarity.

It may not be elegant but it should work.

Maybe some sort of magnetic connector (e.g. "Magsafe") could be used to get good connections to the base of the chess pieces.

Return to “Automation, sensing and robotics”