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[Reply #15 on:]

The capacitance sensor is a really cool idea and best of all, no moving parts. I haven't worked with capacitance sensors before, have done a bit of googling, but still have a couple questions:

 * How much wire would have to be at the top of the stone? (i.e. would the shoe have to come in contact to trigger or just be close enough to it)
 * Would the sensor pickup capacitance of a rubber shoe?

It would also be cool to have part of the program setup to react to slow changes so we could get a light show in the middle of a rain shower!

Personally, I would cast some wire into the top bit of the stepping stone and use a capacitance sensor with some auto-sensitivity code.
Someone's foot would change the capacitance quickly, while weather conditions and such would change it much more slowly.
When the arduino detects a sudden change, it fires the lights (a note:  The lights will almost certainly pin the cap. sensor at full, turn off the auto-sensitivity code while the lights are on!).
In the following code the cap sense bits have been hacked out to just leave the (very simple) auto sensitivity code, the variable "fout" is the output from the capsense code.
Change the interval variable to change how fast the capacitance change has to be to set the lights off.

Code:

if (millis() - previousMillis > interval){
   old4 = old3;
   old3 = old2;
   old2 = old1;
   old1 = fout;
   recent = (old1 + old2 + old3 + old4) / 4;
   previousMillis = millis();
 }
 
 if (fout - recent > 10){
 digitalWrite(3, HIGH);
delay(1000);
digitalWrite(3, LOW);
 }
 

[Reply #16 on:]

Also, is there a preferred sensor to use for this? Would this one from SparkFun work? http://www.sparkfun.com/products/9695

[Reply #17 on:]

And there was the accelerometer idea, wich is very very good, it might need some analyzis of materials, mountings, soil-damping and so on it was so interesting it made me think of a similar idea but with a michrophone instead.

tilemic by swetrack, on Flickr
Think of it, when you put a glass to a wall and your ear to the bottom of it, it amplifies the smallest taps to almost painfully loud noise. I thought you could make it similar with the tiles but maybe with a can or so. In the bottom of the can you put a small michrophone. It will be easy to make a hole in the soil so the can and mic will fit. It will take some testing first and probarly lots of software debugging, but hey, thats half the fun.
It will be like AC-coupled though, people needs to move to make it light and rain will probarly trigger it to. But maybe that would be cool?

I did not mean to step on anyones toes here, this is just my thoughts about it.
And sorry about flickr spam but dont know any other way to put in pictures here.

Wow, thanks for creating a couple 3D mocks! The microphone is an interesting idea. I like how it could react to the sound of the rain falling. It would have to be calibrated to not fire at any loud sound.

[Reply #18 on:]

That has quite a lot of promise! I wonder how long those foam things will last before they loose their "bounce".

I wonder whether this conductive foam pressure sensor hack would work for your application:

http://www.instructables.com/id/How-to-Make-a-Ridiculously-Cheap-Analog-Pressure-S/

-br
http://bitlash.net
http://entropymouse.com

[Reply #19 on:]

Would fluid work?

[Reply #20 on:]

Any chance you could use ambient light detection, by casting another clear in and sensing underneath.??

Mark