board+pieces design & components!

Discussion in 'General Electronics Chat' started by Eric007, Sep 23, 2012.

  1. Eric007

    Thread Starter Senior Member

    Aug 5, 2011
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    Hi All

    I am trying to design a electronics chessboard (and pieces)!

    Well the purpose of this thread is more to help me get the *exact/right* components as drawing schematics is just a matter of a few hours...

    Basically, the board will have 64 reed switches underneath (with the 64 diodes)...I had a look at digi-key but I was confused as there are different ones. So which ones would be appropriate?

    The reed switches work together with "magnet" . So my plan is to have 32 magnets under the 32 pieces...I will buy those chess pieces and customize them with magnets underneath.

    Another concern is...the circuit board will be PCB but now the chess pieces cannot be put straight on top of the PCB, there should be a layer between the PCB and the pieces (I think), so which layer (glass, plastic,..) would be appropriate without affecting the reed switches and the magnets? (Hope I make sense).

    Also, another 32 magnets will be needed on top of each piece for the arm (that will have a solenoid) to lift/drop them (replacement of gripper)

    Well a MCU will be interfaced so as to scan the board and send the changes to the PC. Hardware interface between chessboard and PC will be FTDI Basic Breakout - 3.3V +USB cable. https://www.sparkfun.com/products/9873

    And most importantly a power supply to power all the circuit that has different components (operating at different voltages)

    Well so far, a part from the microcontroller and the FTDI chip, the part list is as follows:

    - 64 reed switches;
    - 64 diodes;
    - 32 magnets (to work with the reed switch);
    - 32 magnets (for arm to grab and drop pieces);
    - solenoid (for arm)
    - power supply

    I think I can stop here for now...this thread is to help me *order* the right components. If I'm wrong somewhere (anything that does not make sense) please correct!! Im planning to order all these components at once from digi-key or..

    The schematics will be posted a bit later...

    Thanks for all your comment
     
    Last edited: Sep 23, 2012
  2. Markd77

    Senior Member

    Sep 7, 2009
    2,803
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    I'd just go for the cheapest in the reed switches section. As long as the material in between the magnets and reed switches is non-metallic, it doesn't make much difference - it probably should be thin because distance matters.
    I like the new addition to your signature.
     
  3. BMorse

    Senior Member

    Sep 26, 2009
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    Why does the chess board need to be made out of PCB material? There are thousands of chessboards available in the market, so why re-invent the wheel? If it is just for the purpose of holding the reed switches in place, you can easily carve out a niche under a wooden board to "implant" the reed switch and secure them in place with epoxy or even hot glue......

    As for the magnets for the arm....... why not use an electromagnet on the arm, and use some magnetic material on the pieces? Trying to use a solenoid to dislodge a magnet will most likely "toss" your pieces down with a jolt and may not land right where you need it to be for the reed switch to pickup the magnet..... if using an electromagnet, you can place the piece in place, and de-energize the electromagnet to release the piece.... since you are already going to use a solenoid, just use a coil from a solenoid as the electromagnet (since that is what they are....)

    You just seem to make things way too over complicated for what their intended purpose is...... try to follow the K.I.S.S. standard when prototyping, then you can elaborate on it once you have a working prototype to improve on things....

    I still think that working on getting the arm working would have been top priority with this project, since that is going to be the most complicated to do (with software and hardware), but you are still stuck at trying to re-invent the wheel with building your own pieces to start with, then now a PCB for a Chessboard?? Just trying to point out some things here...
     
  4. Dyslexicbloke

    Active Member

    Sep 4, 2010
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    64 diodes, what for?
    If you scan the board by activating rows and looking for columns you don't need them.
    Obviously if you are planning diagonal intersects, to identify a single square that is a different matter but since each move is only one piece, apart from castling. if you track lifts and drops you will always know what is in the players hand because you know where it was lifted from.

    You may struggle with reed switches because they are only work when correctly oriented with the magnet.

    Hall effect sensors would be a better choice, the scan would be the same, power up a row and look for the column. You could also bias them so that you can tell north from south, which makes detecting black took white much easier to deal with than it is with move tracking alone.

    I expect that if you wanted to be reality clever you might have different magnet heights within the pieces to denote type based on field strength, there are only 6 after all.
    You could detect correct set-up that way.

    If you use an Arduino Leonardo or Mega you will have enough IO pins and an on-board USB interface that will supply power to the uP and its IO, the board. Even a Nano would do the board but there probably wouldn't be enough left for the arm.
    NB) USB would not power an arm but it will power am arms controls

    Lastly I agree with the comments above the arm is by far the most challenging aspect of the project, except possibly writing a program to actually play chess.
     
    Last edited: Sep 23, 2012
  5. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Sounds like you've decided how you want to do this. If you're set on reed switches, I think you'll need a thin, probably non-metallic, material for the board so the reed switches will be tripped. The strength of the magnets will help with this, but if they are too strong, one magnet may trip multiple reed switches.

    If you're not set on reed switches and you're planning to use a microcontroller anyway consider using a capacitve touch sensors. These can be designed onto your board without the need for too many extra parts.

    Here is some info:

    ww1.microchip.com/downloads/en/AppNotes/01101a.pdf

    ww1.microchip.com/downloads/en/AppNotes/01102a.pdf
     
  6. Eric007

    Thread Starter Senior Member

    Aug 5, 2011
    1,044
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    I cannot buy a readuy to use electronics chessboard!!! it a FYP and I am required to design and build one so I can't help it...hope you understand!

    what is the problem with PCB? Ok assume I buy one chessboard from market...how do I make it electronics chessboard using the "reed switches"? coz this chessboard will have to communicate with the PC...please explain in details how you would do that...I need serious help...I need to have this thang at least partially working or else I'll be kicked out!:(

    Ok then! I will do just that. Would you please suggest one specific electromagnet and these 32 magnetic material you are referring to!! I need to order them now!!! I am running outa time! please provide links like you did for the FTDI IC chip...

    Ok I got that...I've discarded that method...

    I'll use electromagnet as suggested...

    I am not too good with electronics...that's why I am here...to get some help...another thing is learning properly while still being at school is very difficult...we doing too many thangs at the same time (and with very short time) so it kind of hard...I beleive that I will learn properly once done with school as I will have no pression no dealine....

    Believe me I am trying to make thingz as simple as possible but I am not to good with theses thangz and you guyz showing me the right direction!

    I understand Sir..and I am aware of that...and like I said I wish I could buy all these thingz but I can't...once I am done with all the ordering of components I will work on the arm...so I need quick help finishing up with the chessboard and pieces and have at least something working...coz I know the arm will take most of the time and if not done with it ...at least I'll have something to show/present!!!

    Thanks again
     
    Last edited: Sep 24, 2012
  7. Eric007

    Thread Starter Senior Member

    Aug 5, 2011
    1,044
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    Ok! but money doesn't really matter the real problem is *which ones* to use? can you point out one type from digi-key website or ...there are too many different ones...operating at different voltages!

    Thanks! this is what I have realize from experience at school...Most of my solutions are not wrong but as they sometimes arrive late although they are correct...they are considered wrong!! I have experienced this a lot...:(

    Thanks for replying
     
  8. Eric007

    Thread Starter Senior Member

    Aug 5, 2011
    1,044
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    will comment on Dyslexicboke and elec_mech in a minute
     
  9. Eric007

    Thread Starter Senior Member

    Aug 5, 2011
    1,044
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    OK! can you suggest one of these material that would do the job?

    Ok! I get it but how to solve this? I mean selecting the appropriate one that will only trigger the needed one and at the same time handle the 'thin non-metallic material'

    will those 'touch sensor' work with the pieces? will have a look at it

    thanks!
     
  10. Eric007

    Thread Starter Senior Member

    Aug 5, 2011
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    need what? reed switches/diodes?

    ok! the problem will be have a mechanism to send that information (change made on the board) to the PC...

    How would that work? how many would be needed?....

    A 40pin PIC mcu will be used...how about integrating a ower suply to the system?

    I know! the program to actually play chess is almost done! actually done...just need testing...

    Thanks!
     
  11. Eric007

    Thread Starter Senior Member

    Aug 5, 2011
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    I think one thing at a time should be tackled!
    first type of sensor to be used! assuming reed switch...which type? provide link so I can see description of it and al that goes with it...then move on to the next component...

    this starting to really stress me...as I'm still nowhere with this project!
     
  12. Markd77

    Senior Member

    Sep 7, 2009
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    I just sorted by price and the first one in stock that can be bought in quantity of 64 was:
    http://www.digikey.co.uk/product-detail/en/FLEX-14%2010-15/HE555-ND/2218213
    Go for high sensitivity (low AT value or high "must operate distance") because you can always move the playing surface higher above the sensors if you get problems with magnets triggering more than one switch - I don't think that's very likely anyway.
    Voltage, power rating, type of switch (normally open / normally closed) don't matter. They are all rated higher than you need and code can use either switch type. The only other thing is package type, choose what you are happy with.
    Hall switches would make the board layout more complicated, they require power, ground and output connections. They might not need the diodes to work, but I'm not sure what happens if the output of a powered hall switch is connected to the output of an unpowered one.
    I'd go for ~3mm thick clear plastic for the board, then you can print out the board and put it under the plastic.
     
    Eric007 likes this.
  13. Dyslexicbloke

    Active Member

    Sep 4, 2010
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    I meant you didn't need diodes, but that is only true for reed switches, if you decide on a different sensor then the configuration will be different.

    Hall sensors are just transistors ... Connected, open collector, to a rail that is pulled up, or down if they are PNP, will work just fine.

    How ever you scan you will be switching on, enabling, a row and then reading the column. You will do this 8 times per board scan its called multiplexing.
    For each row you check 8 column inputs and check to see what isn't the same as the previous scan.
    On a keyboard you would look for a single key, one column for a given row but you need to look at all 8 and then do a comparison, to the previous scan, to determine what has been added or removed.
    I would suggest that you use a two dimensional array, in the uP, that will be the easiest method I should think.
    I can draw it it will help you

    Seriously ... a reed switch will only work if the piece is placed within a few degrees of its horizontal axis. Most pieces are round, how is that going to work.
    For a reed to pull in, one side needs to be S and the other N, some switches are pole sensitive too meaning a specific side needs to be a specific pole.

    If the magnet poles point to the ends of the switch it will be just fine but if you place the magnets so that the poles are rotated from that position, even just a bit, you will not see the piece.

    I am not trying to complicate your project, just prevent you from doing something that is likely to cause you a big problem.

    There are a vast array of none contact sensors that might do the job, I was simply trying to offer advice RE the simplest and cheapest solution.

    Of course if you must use reeds for some reason then you could put multiple magnets under each piece, arranged in a ring so one pole is in the enter and the other is on the outside making a toroidal field.
    Then if you place the reed so that it sits between an edge and the centre of the square it will always be correctly magnetised.
    That seems like a great of complexity to solve a problem that only requires a magnet of only a few mm and a single transistor per square.
     
    Eric007 likes this.
  14. Eric007

    Thread Starter Senior Member

    Aug 5, 2011
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    Ok!

    OK! can you also provide a link that shows the description of it?

    I know how multiplexing works...the above description would be a nice way to scan...but this will be done in software that comes later but it was good to point it out!

    You mean you can draw a schematics? That would be great!! to see...I could have provided a schematics but I was/am still unsure what to use...so it make sense that I cannot provide one at the moment.

    I understand you perfectly and *reed switches* is not a MUST...I was reading around and that's how I am talking about it. You are correct to say that I would have a BIG problem if it goes wrong and as one of my signature say "the best solution is the simpler one" I can even add the 'cheapest one' too.

    Again *reed switches* is not a MUST.

    As for the Hall sensors, How many will be needed? will the pieces have something underneath to trigger it?

    Thanks again for this post
     
  15. Eric007

    Thread Starter Senior Member

    Aug 5, 2011
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    Sounds like *reed switches* are likely to cause problems...but I'll buy them anyway even though I don't use it! it always good to have alternatives when solving a problem!

    Another thang that just popped into my mind is the dimension of each square!!! assuming i'm using reed switch* or *Hall effect sensors*...!!!
    or maybe I can buy a ~3mm thick plastic chessboard that I will put on top of my circuit!! Will try to look on google

    thanks
     
  16. Eric007

    Thread Starter Senior Member

    Aug 5, 2011
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    A guy suggested like elec_mech to use *capacitive sensors* and *dielectrics* for pieces! looks like I have 3 alternatives now. So now I think it about time to come up with a schematics for *Hall effect sensors circuit* and *capacitive sensor* circuit

    Thanks guyz!
     
  17. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    No, not a ready to use electronic chess board :rolleyes:! Just a plain wooden or plastic one, that way your "platform is already there, you just add whatever sensor you want under the board to make it an electronic one.;) Wooden or plastic ones would be easiest to work with, since you can drill holes in wood to place any type of sensor you need underneath, if you end up using reed switches, then you wont have to drill holes as long as the magnets are strong enough to penetrate the thickness of the board (and you will have to place small feet on the board to keep the switches from getting broken)...But others have already posted possible problems with using reeds switches and the orientation of the switching magnets, so you may end up using something else, but still, a wood or plastic board can be modified to fit whatever sensor you choose to use....

    as for the electromagnet, if you were going to use a solenoid, that is an electromagnet, something like this http://www.digikey.co.uk/product-detail/en/F0471A/527-1024-ND/668309, if you tape the plunger down into the solenoid, when activated, the plunger becomes a magnet, and you can place some metal thumb tacks or something else that would be attracted to the electromagnet (you can not use a regular magnet in the pieces, then they would stick to the solenoid and not come off :) )
     
  18. Dyslexicbloke

    Active Member

    Sep 4, 2010
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    Capacitive or even inductive sensors would work, although capacitive sensors are notoriously difficult to trigger with much other than a finger, just look at the array of capacitive screen pens available.

    Hal sensors are cheep and easy to use they simply respond to the strength of a magnetic field, its flux density, so they will see a single pole which means orientation is not a problem. Have a look at this demo, using a sensor and an Arduino to read it directly, its not at all technical but it shows the effect beautifully.
    http://vimeo.com/4061697
    You can see with that huge magnet that 20mm is easy on your board you could use a tiny neo magnet, in the piece, and see it easily through 10mm of wood or plastic never mind a few mm.

    Other reading ...
    http://www.jhf.com/catalog_v6/1361.pdf
    http://pcbheaven.com/wikipages/The_Hall_Sensor/
    And they willnot break the bank ...
    http://www.ebay.co.uk/sch/i.html?_trksid=p5197.m570.l1313&_nkw=hall+effect&_sacat=0

    I will do you a quick drawing ...
     
    Last edited: Sep 24, 2012
  19. Dyslexicbloke

    Active Member

    Sep 4, 2010
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  20. Dyslexicbloke

    Active Member

    Sep 4, 2010
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    Here you go ...
    Just pay attention to currents, an Arduino, and most other uP's would not need anything else as the input impedance of the analogue inputs is circa 10K.
     
    Eric007 likes this.
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