Sensor to detect how high or low above a given point, any Ideas?

... Does anyone know a sensor that detects the height of your hand above a given point? ... ... Or does anyone know a laser device that can detect the position of the hand above it? ...

.. I want to apply it on my Laser Harp idea, to control the Volume of the speaker.

Mainly the idea is, the position of the hand above the device that produces a laser line will control the volume; if in high position high volume, if in low position low volume, etc.

. Tnx if you guys can comment, suggest, advice. XD

Several sensors allow you to measure range. Ultrasonic range finders and IR sensors come to mind. If you've done any research on laser harps, I'm surprised you haven't found how others have done it.

IR sensors and Ultrasonic rangefinders will both do what you want. You just have to figure out which one is right for you in terms of price and sensing distance. Here's a nice article about IR Rangers and how they work: Check the two related articles at the bottom of the link for more information about actually using them.

These sensors are available at Acroname, Sparkfun, and many other places.

Also, try doing a search on "theremin" for additional ideas.

I agree with others, that IR or ultrasound distance sensor would be easy to interface and program, OTOH price will go up sharply if you need keyboard 49 or let say 88 key. 500$ - 1000$ ??? Alternative, about 40$ CCD camera (could be less) plus arduino, than plus 1$ per 1 key (laser pointer) is to build a laser harp based on distance measurements I outlined in my project: You arrange 49 lasers beam spreading them up, like real harp, and cam taking measurements from below (facing up also). On average 880 "tick" per arc of 52 degree, you can get 10 volume levels per one key for 88 overall. Other way, lasers could be arranged not all of them in one single line, but 4 - 8 arcs, which represented 1 octave of 12 notes. May be difficult to play such church organ ! You will have to add a pedals.

I think you have to use a device named PING))) Ultrasonic Distance Sensor also known as ping)))sensor. The Parallax PING))) ultrasonic length sensor provides accurate, non-contact distance measurements from about 2 cm (0.8 inches) to 3 meters (3.3 yards). It is very simple to attach to micro-controllers such as the BASIC StampĀ®, SX or Propeller chip, requiring only one I/O pin. The PING))) sensor works by broadcasting an ultrasonic burst and providing an output pulse that relates to the time required for the burst echo to return to the sensor. By measuring the echo pulse width, the length to target can easily be evaluated.

This is another topic that is discussed endlessly and repeatedly.

See here in Sensors:,112868.0.html

And other more recent threads .. but all the same really.

Use search -- look for other similar threads before posting.

This is another topic that is discussed endlessly and repeatedly.

Not really, there is substantial difference in detecting distance, and detecting distance to multypoint (Harp). That word , probably should be included in subject line. Thinking little bit more on this, I came to conclusion that ultrasound is not applicable to measure multypoint due low angular resolution.

Parallax method, using linear CCD and laser spot.
Probably not in Arduino territory though.