You could also get away with 3 wires for each P.B. if you use the same common for P.B. and LED.
Max.

Yes, that seem to be a great idea!

 

Can I assume that the tablet was someone else's idea and you want to improve on it? Because to me it seems that the tablet solution is the better solution and if you had come up with the tablet solution you would realize that going for buttons is taking a step backwards.

If the tablet is too small, get a bigger tablet. Or get a large touchscreen monitor and cheap computer. The benefits of a tablet or touchscreen computer are many:
1. It can be easily reconfigured as employees leave/join the company, or as work rooms are added/removed from the building. If another workroom is added, all the work is done for you already, just copy the program; with switches you need to make an entire new board.
2. it can be easily networked and integrated with management systems
3. there are more but I am out of time

Sorry for the misunderstanding. That is my mistake.
(English is not my native language)
I meant "table" and use real picture.
A tablet will be much more expensive.

 

To be sure, A is meant "Alternate Operating".
A16L-J[]A-5D-1
I don't have this kind of buttons right now.
Does this button only has two wires for LED?
and when the button is pressed, the LED will ON?
I need to make sure before ordering lots of them.

 

The P.B. and LED socket connections are separate.
You need to switch the LED with one of the switch sections.
DPDT

Max.

 

Well, then each button will need a DPDT relay?
And why DPDT not SPST?
With this kind of buttons (A16L-J[]A-5D-1), when it is pressed it will keep that state and doesn't return to the original position?

 

DPDT is two switch sections as opposed SPST is only one N.O. section, you need two for switching the remote and local LED, you would need DPST at least, but the DPDT will do it for you and this is how they come.
If you are going to purely hard wire it with no type of controller then one switch could be used for both LED's, it depends on how you intend handling the Logic.
The A style is Maintained as opposed to the M which are Momentary.
Max.

 

I this system I use only one LED built-in with that button. So, SPST will be enough?
But with this way, I will need about 40 SPSTs and that seem much more cumbersome.

 

Either way you need to 40 switches and Led's to begin with.
Or just one RFID and 40 cards or Fobs

 

Either way you need to 40 switches and Led's to begin with.
Or just one RFID and 40 cards or Fobs

Or you could just walk around and see who is at work and who is not. 40 people is not all that hard to learn to recognize. Plus while walking around you just might even talk with a few and get to know far more about thema whether or not they are at work.

 

Sorry for the misunderstanding. That is my mistake.
(English is not my native language)
I meant "table" and use real picture.
A tablet will be much more expensive.

Oh sorry for the misunderstanding.
But, this is good to know. Your conceptions about price are way off, and I think that even though you meant "TABLE", "tableT" is a much better option.
How much did you budget for this project?
Do you know how much those switches cost?
Do you know how much an enclosure big enough for 40 buttons costs?
Do you know how much your time is worth to build it (man hours * $/hr)?

I think you will find a tablet much cheaper to implement than your button board.
Those buttons cost $20USD/ea.
That's $800USD just for the buttons.

assuming you already have the expensive panel hole punches needed...
An enclosure large enough would probably cost at least $100USD.
I figure one 12hr day for punch holes, assembling, and wiring @ $10USD/Hr = $140 (factoring overtime)
a 12V power supply figure $20USD
Wire & misc : $20USD

So that's $1080 so far to build your enclosure.
You can get a winbook 10" tablet with full-blown windows 8 for $179USD
Hang that on the wall and spend a couple of days learning how to make a super (SUPER) simple program in Visual Studio (FREE) to emulate the flipping tiles. Done. Much cheaper, much more flexible, much better period.

 

Either way you need to 40 switches and Led's to begin with.
Or just one RFID and 40 cards or Fobs

Yes, 40 buttons (with built-in led) is enough.
How can I do that using RFID?

 

Or you could just walk around and see who is at work and who is not. 40 people is not all that hard to learn to recognize. Plus while walking around you just might even talk with a few and get to know far more about thema whether or not they are at work.

But at each morning before working, we have a meeting and need a quick summary who is absent.

 

Morning,

How much did you budget for this project?

My first thought is to take advantage lots of buttons available at the store of our company.

Do you know how much those switches cost?

Each button is about 20USD so total (for 40 buttons) is about 800USD same as your estimate.

assuming you already have the expensive panel hole punches needed...
An enclosure large enough would probably cost at least $100USD.
I figure one 12hr day for punch holes, assembling, and wiring @ $10USD/Hr = $140 (factoring overtime)

Yes, all these things are almost available on the store.
....and as your calculation, it costs a lot!!!

You can get a winbook 10" tablet with full-blown windows 8 for $179USD
Hang that on the wall and spend a couple of days learning how to make a super (SUPER) simple program in Visual Studio (FREE) to emulate the flipping tiles. Done. Much cheaper, much more flexible, much better period.

I have never thought about that. WinBook is far cheaper and much more flexible! With that I can add/delete and edit anytime.
Thanks for the idea. Tomorrow, I will discuss with other people about this idea and ask for budget.