Re: Is there such thing as a resistor that bends?

There are resistors that can be used for your stated pupose.  They are called 
Force Sensing Resistors (FSR).  You can design you door so as it opens, a 
spring applies  increasing pressure to your resistor.


websites about Force Sensing Resistors (FSR):
 http://www.hku.nl/~pieter/HARD
/FSR/FSR.htm

http://stage.itp.tsoa
.nyu.edu/~hs420/pcomp/fsr.html

interlink store


There are some other approaches you can take.

1)  Use a potentiometer (variable resistor) that has shaft that turns.  Mount 
the body to one side of the hinge and the shaft to the other side of the 
hinge.  You can get these many places including Radio Shack.


2)  Use polarized film and a white LED and a light sensitive resistor.  Use two 
pieces of polarized film (PF).  One attaches to one side of the hinge and the 
second to the other side of the hinge.  As the two pieces of PF rotate with 
respect to each other, the amount of light they transmit varies.  I picked a 
white LED as the transmitter because the light is easy to see.  The light 
sensitive resistor is called cadmium sulfide (CdS) cell.  click photonics link 
photonics lookup


Once you pick your approach, if you want help with a circuit, let me know.

Gus Calabrese