Azrael wrote:
>     The real project is designing "smart" building-blocks.  Around the size
> of Duplo blocks or other large "Lego" like blocks.  The goal is to create a
> set of blocks that can do math when connected in a correct order.  There
> will be number blocks, addition, subtraction, multiplication, and division
> blocks.  All of them are like the cars in the train.  The Equals block works
[snip]

Ok Azrael, now you just said that you can not have any electric contact
exposed, if this thing goes to be around children 3 or younger, even if
it is intended to 6 and older.

Here the suggestion is just use a coded holes or reflective mark
combination on the bottom of each block, it will means its "function",
number, math operator, etc, and then it should be positioned over a
"master" calculator bed, template, board, whatever.  The board identify
what is on top of it and do the math.

By this way, no electrical nothing on each module, and all the
electronics and batteries will be closed inside this strange
calculator... :)

Just to make little gizmos inside your brain;  I saw years ago a math
calculator using only a light beam (today it would be a laser)...and
function + number (trasparent) blocks using just reflective + prisms +
mirrors inside.  It worked just as easy as a regular "slide ruller", you
can think it to be an electronic abacus.

When using an ADD block, it just shift the original light beam position,
while a MULT block change the beam angle. Just think about a round
calculator, like a 10 hours clock, with really two hands, the short one
is the tens, while the long one is the units.

Wagner.