[sdiy] Performance control - processing a control voltage

[Matthew Smith]

I want to use LDRs for performance control, getting a 0-5V output 
depending on the amount of illumination they receive. (There is a 
feedback element here too, as there will also be light emitters in the 
system, but that's another story.)

If I make the LDR one half of a potential divider which has 5V across 
it, how exactly do I calibrate the system so that the maximum resistance 
of the LDR is, say 0V (depending on which end of the leg it is placed 
in) and a given value of illumination is 5V?

I realise that I'm going to need at least one op amp here and, if I can 
get away with it, I'd like to power it/them with just the single 5V 
supply going to the potential divider - so I can create a simple, 
three-connection module.

As far as I can tell, I need to both amplify and offset the voltage 
coming out of the potential divider, but not entirely sure of the 
optimum way of doing this.

Ideas?

Cheers

M

-- 
Matthew Smith

Business: http://www.smiffytech.com
Blog:     http://www.smiffysplace.com
Linkedin: http://www.linkedin.com/in/smiffy
Flickr:   http://www.flickr.com/photos/msmiffy
Twitter:  http://twitter.com/smiffy

ABN 16 391 203 815