1. OPTOELECTRONICS

2. Photoresistors up close and personal CdS

3. Changing light = changing resistance 0.2 lux = emergency lighting 300 lux = sunrise 1000 lux = overcast day. ~15000 lux = full daylight

4. How do they work?

5. All colors of the rainbow work?

6. Introducing the phototransistor Same old resistor, except now photons can drive current in the base

7. The specs Peak sensitivity 830 nm Higher intensity drives more current Characteristic curves 19 mA

8. Where you find ‘em

9. Communication Link

10. Citations  ladyada.net/learn/sensors/cds.html (graphs of R vs illuminance and spectral response)  www.societyofrobots.com/schematics_photoresistor.html (pictures of Cds cells) www.societyofrobots.com/schematics_photoresistor.html  Tutorvista.com (atomic energy levels)