Hello there ! I'm about to start working on a project that involves detecting ripples in water, more specifically the ripples made by rain drops. Ideally the sensor would not only detect a ripple but also its proximity to the sensor, does anyone know of any sensor that is capable of such a thing ?
Many Thanks for any and all help, its really apprieciated !! 
This sounds like a much more complicated problem than you'd think.
About the only way I could think would be to do image processing.
You'd need to look for ripples that were curved and use the amount of curvature to
determine distance.
Way out of the simple Arduino project.
One other thing you might consider is to have acoustic pickups to list for
the signature of a drop sound. I suspect they have a signature sound.
Three sensors would determine the direction. The amplitude might be used
to determine the distance.
Again, more than a Arduino is designed for. It would most likely require
some DSP work.
JMHO
Dwight
Interesting project. What is the end purpose? Is it for a school/university assignment? What are your ideas for a solution and what have you found by googling?
Also, regardless of the approach (camera or whatever), I suspect that in a rain storm, when many drops are hitting the water surface and creating an essentially random "sea state" around your sensors, it will be extremely difficult, if not impossible, to calculate the distance from your sensor(s) to any particular single rain drop. And distinguishing between ripples from drops and ripples from wind (or insects, bird crap :), leaves, etc.) might be hard. But, you haven't explained enough about your situation for anyone to know what you really want to do ("...detect the proximity of a ripple to the sensor..." is ambiguous).
Camera sensor would be the way to go
The project is actually for an art piece ! I intend to make a wooden bowl, fill it with water and attach a suspended perspex box type thing to it, drilling very small holes into the perspex box and filling the perspex box with water to create drops of water that flow into the bowl and create ripples in the water, so its a very much controlled environ. I'd then measure the drops and translate these into musical notes via max MSP!
Camera sensor sounds really interesting ! I could probably hook that up to max msp and analyse the data from there... any other options incase it doesnt work out ? Ideally the equipment could be obscured or concealed from view..
I think a couple acoustic sensors at either end
might be what you want. You measure the time delay
between the impulses to determine which location had the drop.
Dwight
dwightthinker:
I think a couple acoustic sensors at either end
might be what you want. You measure the time delay
between the impulses to determine which location had the drop.
Dwight
But what about ambient noise such as people talking, foot steps etc ? Would there be a way of picking up on only the water droplets ?
Cool!
But what does this mean?
LeftHeadphone:
...I'd then measure the drops...
Funny. I wrote the same thing, about how he needs to be so much more concise in what he means.
"detect a ripple" "measure the drops" "drops of water that flow"
But the text disappeared before I could post and just didn't care.
OP guy needs to do a better job at explaining what his grand ingenious goals are.
Far as I can tell, he wants to turn on a sprinkler onto a keyboard.
LeftHeadphone:
drilling very small holes into the perspex box and filling the perspex box with water to create drops of water
How many holes. Just a few?
Beam break sensors with one 38kHz modulated IR transmitter diode and as many IR receivers as holes could detect/count falling drops.
Leo..
Detecting that a drop has occurred is pretty easy. Have a light source and a sensor set up to 'see' each other in the reflection in the water. If the reflected light changes then you know the water surface moved.
Detecting direction and strength would be more difficult. Maybe just a few of these sensors can give enough data on arrival time to make some different musical sounds.
The international terminal at Los Angeles has a musical installation which is 'controlled' by the people walking past. The musical tones are related to the position of the people. Moving too a different position changes the music. It's not entirely clear how it's done. It may be a camera looking down at the floor or it may be laser sensors beamed out horizontally. Maybe Google can find some information on it?
Projection unit and camera, can see where an object blocks/shadows the passive screen. Simple stuff, they throw that up in random seating areas in malls.
As I said, camera is the way to go. Map out X-Y coords, grid out notes however you want.
The perforated box won't work as you imagine, though. Surface tension will find only a few paths and follow them regularly.
Maybe a minature buoy arrangement with a suspended magnet dangling over a Hall effect sensor?
Surely an accelerometer in a pivoted float?
It's like some people respond based only on reading the title
INTP:
Funny. I wrote the same thing, about how he needs to be so much more concise in what he means."detect a ripple" "measure the drops" "drops of water that flow"
But the text disappeared before I could post and just didn't care.
OP guy needs to do a better job at explaining what his grand ingenious goals are.
Far as I can tell, he wants to turn on a sprinkler onto a keyboard.
Sorry for not being more clear ! So basically, i want to measure the ripple a water droplet makes in a 'well' of water, this means the ripples strength (how far it propagates and at what intensity through the water) and also where the ripple originated within the well of water. I imagine its strength could be measured by the intensity of refracted light it creates or its speed as it moves through the water ? Anyway I would translate this data in MAX MSP into different musical notes, by setting various thresholds or mapping different notes to different areas of the 'well' depending on the sensor used to aquire the data and interface it with MAX MSP.
The problem is that i am not sure what sensor to use ! I used IR sensors in the past to do much the same but it was a bit of an 'illusion' in that people were instructed to touch the water and various musical notes would be produced, but actually i was detecting their fingers and not the actual ripples they made within the water. Another problem is sensors form factor. I absolutely must be able to hide it from view, so it must be small.
I hope this helps and please if you have any more questions direct them towards me and i'll try my best to answer them.
MarkT:
Surely an accelerometer in a pivoted float?
This sounds very promising, but how does such a sensor interface with an ardiuno ? Is it possible to find a wireless solution ? As visible wires could make the artwork a bit unsightly.
INTP:
Projection unit and camera, can see where an object blocks/shadows the passive screen. Simple stuff, they throw that up in random seating areas in malls.As I said, camera is the way to go. Map out X-Y coords, grid out notes however you want.
The perforated box won't work as you imagine, though. Surface tension will find only a few paths and follow them regularly.
Yes, this seems quite do-able and i have plenty of experience on the MAX MSP side of things, thanks this really helped.
The sensor interfaces with i2c or SPI. See the sensors category at Sparkfun.com.
I imagine a small Arduino like a Lillypad or Gemma could be hidden in a floating puck with a battery, radio and of course the sensor. If you have never used a radio on an Arduino before then leave that part out and tether it to the bottom of the well. Waterproofing wires will be easier than using a radio for the first time.
Well, maybe a Bluetooth module might be easier for the wireless communications.
Hi everyone i just wanted to say a massive thank you and to show my apprieciation for the amount and variety of suggestions i've recieved !!! You guys are really great and please do keep them coming,
Again thanks for all the great suggestions so far