How to hook up a CdS Photoresistors?

Question

http://www.radioshack.com/product/index.jsp?productId=2062590&cp=&sr=1&origkw=photoresistor&kw=photoresistor&parentPage=search

What is the simplest way to hook this up so it can give out a voltage?

also do i need anything for it to measure a color like blue or red?

Answer 1

They have no technical specs whatsoever, so you will have to play with them. You can use an opamp, or a transistor. Simplest is a voltage divider across a 9v battery, a resistor in series with the cell and both across the battery. Try different values of R from 1000 ohms to 100kohms. Try different values of light.

we do know "resistance decreases with increasing incident light intensity"

"a simple CdS cell can have a wide range of resistance from less than 100 Ω in bright light to in excess of 10 MΩ in darkness. Many commercially available CdS cells have a peak sensitivity in the region of 500nm - 600nm (green light). The cells are also capable of reacting to a broad range of frequencies, including infrared (IR), visible light, and ultraviolet (UV). They are often found on street lights as automatic on/off switches. They were once even used in heat-seeking missiles to sense for targets.

Standard cadmium based LDRs have a frequency response that varies according to light level, but typical fall times range from 15ms to 25ms and typical rise times range from 50ms to 70ms, so they may be unsuitable for data links and picture scanning. Silicon based photodiodes and phototransistors are orders of magnitude faster."

Answer 2

Specs/info:

http://en.wikipedia.org/wiki/Photoresist...

http://www.4-direct.com/resistor/photo-c...

http://www.allproducts.com/manufacture98...

http://www.extremenxt.com/cds.htm

Circuits:

http://www.societyofrobots.com/schematic...

http://books.google.com/books?id=V4eMpaB...

http://209.85.215.104/search?q=cache:Bpv...

http://archilochus.netfirms.com/

http://www.leang.com/robotics/info/artic...

http://www.robotshop.ca/home/new-arrival...

http://www.vishay.com/photo-detectors/da...

Enjoy.

Ron