[sdiy] Photoelectric String

[Harry Bissell Jr]

 it'll be a 
> single string (any reccomendations onwhat to use?
> bass guitar strings? garage 
> door cable? picture-hangingwire twisted around
> itself?) running the length of 
> a piece of wood (4or 5 feet).

Wound strings have a much lower frequency that a plain
string or cable. If you are going to play it with your
fingers... it should be smooth

Bass guitar string will be good for around 40"
length..
longer you should use a string bass string...


Towards the bottom
> it'll have a set of three 
> infrared LED'sabove and in line with the string.
> These can be turned on and 
> offindependently. Beneath the string (and directly
> beneath the LED's) willbe a 
> total of 3 photoresistors and 3 phototransistors (2
> components perLED). These are 
> varying a current being passed through them
> separatelyand then mixed together 
> before running to the output. The 'volume' ofeach
> can be changed by knob. 
> Phototransistors will output square waveswhile
> photoresistors will put out 
> slightly more sine-ish waves, andnone of them will
> be quite in phase with one 
> another, so it shouldn'tbe just a mushy square
> output.
> Okay, so now for the questions.

> 1. Am i crazy/stupid for even wasting anyone's time
> asking this?

no... its DIY ain't it ?

> 2. Any suggestions on what string type/length to
> use? (it'll be tuned/tunable 
> but fretless).
> 3. Any general construction tips?
> 4. Any clue what the decay time will be like?
depends on the mass of the string and the damping
(loss in the body / air).  You want a string with
large mass and low stiffness - a wound string is prlly
best.


> 5. Anything I've forgotten?

The Photoresistors *MAY* not work... they probably do
not have a high enough frequency response. You could
use
photodiodes or phototransistors in linear made to get
the same effect....

H^) harry
>