Help with Sensor selection

Projects General Guidance
1

Im trying to figure out which sensors for a couple of actions.

First I want to register when someone blows on a surface (doesnt matter the measurement just that they blew on it). Im thinking a barometric pressure sensor should work but wanted to make sure

Second trying to figure out how to sense a little bit of water on a surface, if I put a few drops of water it would register it and let me know there is water there. Any ideas on how to do this? All i have been able to find is water level sensor or the plant moisture which wont really work.

2

You can use an electret mic to detect if someone blows onto it.
A baromic pressure sensor will also work.
Both methods are not very accurate, someone talking loud or someone opening a door will result into the same.

A few drops of water will be very hard to detect
How big is the surface ?
You would need a matrix of wires, spaced 1/20 of an inch or 1mm. Or something more complex with a camera and a lens.
Where is that water coming from ? Perhaps there is another way to detect it.

3

if I put a few drops of water it would register it and let me know there is water there.

Place paper that has been soaked in salt solution (then dried) on top of a wire grid.
One wire to ground one wire to a digital input.

4

Peter_n:
You can use an electret mic to detect if someone blows onto it.
A baromic pressure sensor will also work.
Both methods are not very accurate, someone talking loud or someone opening a door will result into the same.

A few drops of water will be very hard to detect
How big is the surface ?
You would need a matrix of wires, spaced 1/20 of an inch or 1mm. Or something more complex with a camera and a lens.
Where is that water coming from ? Perhaps there is another way to detect it.

Ok, for the wind i can do some testing to find a good threshold, hopefully its a big change with someone blowing directly over it.

For the water it would be a 3" equilateral triangle (give or take), the idea is that someone would just place some water on it to "activate" some lights.

For reference I want to make some working lamps that look like the stones from 5th element (see here if you havent seen the movie) and have them turn on like they do in the movie or as close as I can make it. The fire and earth ones are easy enough, the wind should be fine if I can find a good threshold that isnt to sensitive. The water is the one im having trouble with figuring out.

5
6

Yes similar to those, but those dont have sensors in them and they use a lot of their own custom stuff so cant really use them as a basis. Thats actually where I got the idea from, but I want the sensors so they activate like the movie.

7

Using a thermistor will detect wind blown when temperature changes. Someone made an electronic candle with this method. No problem with noise.

8

liudr:
Using a thermistor will detect wind blown when temperature changes. Someone made an electronic candle with this method. No problem with noise.

You dont happen to have a link to that project do you?

9

Ask this company about their demonstration of an LED candle with temperature sensor on a muffin at 2011 AAPT summer meeting:

I can't find where they host that content.