for an installation, i want to connect a watertap (no water connected) to arduino.
the idea is that the knob of the watertap is used as a controlling element for sound or leds.
that means i need a sensor so that i can get data about how far its turned. i was thinking about using a potentiometer and connecting it somewhere inside the watertap to get data about how far the knob is turned. but the potentiometers i found turn only 300° and a watertap-knob turns much further.
any ideas? use a different sensor? are there potentiometers that go further than 300°?
i'm thankful for any helpful answers or ideas.
A rotary encoder continuously rotates. Rather that reading a value at each position as you would for a pot, you read each step and determine if it moved clockwise or anticlockwise.
Luckily for you there are some excellent examples in the playground
There are also mullti turn or helical pots. This give there range over more revolutions. Typically this is from three to 10 turns.
The helical trim pots are the cheapest but they only have a screwdriver adjustment but there are panel mounting ones as well.
Just one warning from me 
A typical water tap "handle" is much bigger than an ordinary potentiometer knob, so it is very easy to apply more force with it. This could lead to damaging the potentiometer if people turning the tap handle are not avare that at a certain point they can not turn it any longer. So if the piece is to be part of an exibithion this should be taken into consideration.
How about an off the wall idea:-
Put a piece of conductive foam under the tap plunger with a wire inside it. As the tap turns the foam is crushed changing the resistance between the wire and the rest of the tap. Read that with the analogue input.
Or maybe a slider pot - but that would probably need to be mounted outside the tap.
Or an LED/LDR combination - as the tap spindle moves down it come between the LED and the LDR progressively causing less/more light to fall on the LDR. Set the LDR up in a voltage divider and measure the change in voltage with the ADC.
Mike
ok, i think a three turn potentiometer would do great. now i have another problem. i need a quite small one, since it's supposed to be mounted inside the watertap. 1,7cm in diameter and 2cm in height (bottom plus turning knob) is the maximum size the potentiometer could be. i haven't found a 3 turn potentiometer of that size on the internet yet, any ideas where i could find one?
This is the right size but you might have to do something clever with the mechanicals to couple the screwdriver slot into the system.
The others I have found are all a bit too wide (2.2cm dia)