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.

Too many post above...I will have to analyze each one of them but I am happy we getting somewhere...having a look at your schematics...you just drew it now? wow...

thanks!

 

Reed switches can be hard to trigger from small magnets.

Ideally to trigger a reed switch you need a bar magnet, with N and S at the bar ends, and the magnet much be lined up with the reed switch.

Getting a long reed switch to trigger from a small round magnet (like an ebay magnet) is almost impossible. However you can get 3pin hall switch IC's for about a dollar, which will trigger very well from a tiny magnet S pole, wihtout needing to be lined up perfect N-S like a reed switch.

 

I just made a little video, if the reed switches are mounted vertically under the board there is no problem with orientation.
It's a sensor from an old cycle computer, because I couldn't find my reed switches, but it's definitely a reed switch, I can hear it clicking.
At the start of the video you can see the wrong way, the switch only activates with the magnet near the ends of the reed switch, but not in the middle. Then I move the magnet onto the axis of the reed switch and it works fine, probably a smaller magnet than this 10mm diameter, 5mm thick one would be better. Right at the end is one of my 14mm cube magnets, just for fun, they are scarily strong.
http://youtu.be/BlG1wxVkyuM

 

No, not a ready to use electronic chess board !

Oops...Lol...

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.

I get it now...

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....

Ok! reed switches discarded...I will buy a wooden chessboard to work on...

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 )

Ok! here we talking about the lifting and dropping the pieces...
that solenoid/elecromagnet will be used to attract the pieces...those 'metal thumb tacks' will be put on top of each piece...wooden pieces preferably, correct?

But why you sayin "if you were going to use a solenoid" as if you prefer something else...

As for the comment in bold...do you mean that solenoid will be put inside the tip of the arm or what...pardon my english...I speak french!

So the above items will be bought...

Thanks!

 

I just made a little video, if the reed switches are mounted vertically under the board there is no problem with orientation.
It's a sensor from an old cycle computer, because I couldn't find my reed switches, but it's definitely a reed switch, I can hear it clicking.
At the start of the video you can see the wrong way, the switch only activates with the magnet near the ends of the reed switch, but not in the middle. Then I move the magnet onto the axis of the reed switch and it works fine, probably a smaller magnet than this 10mm diameter, 5mm thick one would be better. Right at the end is one of my 14mm cube magnets, just for fun, they are scarily strong.
http://youtu.be/BlG1wxVkyuM

Just watched you video...thanks for the experiment...looks like everything is to be considered plus they are not even expensive...I'll buy them but that will be alternative 3.

thanks!

 

...Reading all Dyslexicbloke links...for better understanding...then I can comment or ask questions!

Thanks Dyslexicbloke!

 

try these, all the biasing and conditioning is on board all you do is give it a supply and read the output.
http://download.siliconexpert.com/pdfs/2010/5/27/4/31/31/422/alg_/auto/1301.pdf

Drawing on the way

I am trying to buy everything from the same place (Digi-key) so I want to make sure that this http://www.digikey.com/product-detail/en/A1302KUA-T/620-1022-ND/1006597 is the correct one?

Thanks!

 

That has an analog output centered around half it's supply voltage and changing by 1.3mV per Gauss.
I would think you would need a digital output hall switch that is either 0 or 5V output. I'll have a look for one.

I'm thinking this one (I assume you don't want surface mount):
http://www.digikey.com/product-detail/en/TLE4906L/TLE4906LINCT-ND/954453
In "Magnetic - Hall Effect, Digital Switch, Linear, Compass (ICs)" section, I think you want either unipolar or omnipolar switch, unipolar will only switch with one pole of the magnet, omnipolar will switch with either pole. I didn't look into the sensitivities much, but this is more sensitive than a couple of cheaper through hole ones.

 

That has an analog output centered around half it's supply voltage and changing by 1.3mV per Gauss.
I would think you would need a digital output hall switch that is either 0 or 5V output. I'll have a look for one.

Alright! Would you please providing a digi-key link for it...as I said ...trying to buy everything from same place!

thanks

 

Ok! here we talking about the lifting and dropping the pieces...
that solenoid/elecromagnet will be used to attract the pieces...those 'metal thumb tacks' will be put on top of each piece...wooden pieces preferably, correct?

Yes, you are correct. Wooden pieces will work, but just be careful not to split the wood when pushing them in, you might have to drill small pilot holes in the wood first, then glue the tacks in place. Or if you used plastic pieces, you could heat up the tack and melt it into the pieces...

 

But why you sayin "if you were going to use a solenoid" as if you prefer something else...

As for the comment in bold...do you mean that solenoid will be put inside the tip of the arm or what...pardon my english...I speak french!

So the above items will be bought...

I had said that because you already said you were going to use a solenoid to release the piece from the pickup magnets. But as an alternative I was suggesting you use your solenoid as an electromagnet, like this, maybe this will make it a little clearer >>

The solenoid I showed in the link is just one example, you may want to search for a smaller more lightweight one to put on the end of the arm.

 

Just thought I'd mention that if you look at other ones, check their turn on time, I found one that was 125ms, so it would take a second to scan the whole board (bad).
Also they will need bending 90 degrees so the correct face of the sensor points towards the magnet.

 

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.

Ok! looking at this schematics...there will be 64 capacitors between the 2 pins (5V and GND) of the sensors...now what should be that value? and what is it for?

I also see 64 diodes connected to each sensor...needed as we dealing with multiples switches connected together...guess there're zener diodes (single)...looking at digi-key...there're too many (with different voltages)...not to sure what to pick up... would you please provide a link with the correct/proper one!

I also see pull down resistor...do we need that or we can use the in-buit ones from the PIC?

I am thinking of ordering everything tomorrow...


Thanks!

 

These are the hall effect sensors I use for motor positioning and other non contact sensing applications at work >> http://www.digikey.co.uk/scripts/dksearch/dksus.dll?vendor=0&keywords=OHN3120U They are uni polar (only work with S end of magnet), but they only require a 10K pull up on the output. And if used with a 5mm or larger Neodymium magnet, you do not have to be right on top of it, you can be off by as much as 1/4" or more (depending on the size and strength of the magnet)and still activate it.... AND you do not need to use any AD converters or AD channels on the uC (less code to have to write).... you can still use the same circuit dyslexic posted and instead of having analog you will have a digital on/off signal.

 

These are the hall effect sensors I use for motor positioning and other non contact sensing applications at work >> http://www.digikey.co.uk/scripts/dksearch/dksus.dll?vendor=0&keywords=OHN3120U

Ok thanks...the above will be bought!

They are uni polar (only work with S end of magnet), but they only require a 10K pull up on the output.

Ok!

And if used with a 5mm or larger Neodymium magnet, you do not have to be right on top of it, you can be off by as much as 1/4" or more (depending on the size and strength of the magnet)and still activate it.... AND you do not need to use any AD converters or AD channels on the uC (less code to have to write).... you can still use the same circuit dyslexic posted and instead of having analog you will have a digital on/off signal.

Any link you can provide for these '5mm or..magnets' to be put under each piece please?

I think all major components have been discussed now I would have to come up with a complete schematics included everything...microcontroller and the rest...

I almost forgot...what about the power supply!?

Thanks again!

 

These are the hall effect sensors I use for motor positioning and other non contact sensing applications at work >> http://www.digikey.co.uk/scripts/dksearch/dksus.dll?vendor=0&keywords=OHN3120U

I'm not an expert on hall sensors, so could you look at the one I linked to and see if it's any good. It's less than half the price, so could save Eric a few Euros.

 

Hopefully, I will discuss the arm design very soon...but I was just thinkin...don't you think that all the pieces should have the same *height* so the arm will always bend to the same level when picking/dropping them ...?

Also the pieces should not fall when dropping them...

Can someone please address post #33?

Thanks!

 

Probably 100nF:
http://www.digikey.com/us/en/techzo...r-Hall-Effect-Sensor-ICs-for-Mobile-Apps.html

If you add a weak spring to the arm, it can accommodate different size pieces, just lower it to the position for the shortest piece and the spring will compress for the taller ones.

 

Decoupling caps:
0.1uF ceramic will be fine.

zener:
No, just signal diodes, anything that will handle a few mA

Internal PIC resistors:
I think you will find that they are pull-up resistors and small ones at that. It will depend on the Hall device you chose. If it has an open collector output then the answer is probably yes and you would be able to loose the diodes as well. See comments below.

As for the rest!

The hall effect sensors I used as an example require a positive supply and have a bipolar analogue output. If you use a device like this then you need to ensure that when multiple device outputs are connected together that one isn't sourcing current for another to sink, that's wheat the diodes are for.
Now it is most likely that as only one row will be powered on at a time that this wouldn't happen anyway but it doesn't hurt to be safe particularly as you are not an experienced designer. Without the diodes you only get to make a tiny programming mistake once and you will destroy 16 sensors.

Since my post and drawing you have talked about 3 other options, all different.
Now there is nothing wrong with that, in fact I think exploring options is a great plan especially as the example I used was just the first common device I found as opposed to being the best option, technically or cost wise.

However if you look at different solutions the the layout will change ... If your sensor is has a unipolar digital output, IE it is either on or off, then you don't need the diodes because there is nothing to protect.
If you plan to measure field strength to identify pieces or sense when they are just above the board, as feedback for your manipulation system, then you will probably want to use Schottky diodes to minimise voltage drop or even replace the diodes with current limiting resistors but that would depend on how the devices behave when not powered on.

The point is you need to DESIGN the functionality first and then source the components. IF you then find that a component cant be found, or more likely found cheep enough, then modify your design so that you don't need the functionality that you are struggling to provide.

Digi-key alone list 65 Hall effect sensors that will work at 5V including all the output topologies I have mentioned and several more besides.
You will be able to pick one when you decide what you want to do.
Remember you need a switch or an analogue output NOT a latch!

Switches will cost less but check the initialisation and switching times as was mentioned in an earlier post.
Again you need to define the design, how long a scan time is acceptable.
If one board scan per second is OK then even a slow 125mS device is quick enough.

 

I'm not an expert on hall sensors, so could you look at the one I linked to and see if it's any good. It's less than half the price, so could save Eric a few Euros.

I took a look at those, and they have a digital differential output, versus the ones I linked to that have an open collector output, which I thought would be easier to work.