The following list shows different types of sensors that have been used in Scratch Sensor Board projects. (They are typically attached to alligator clip-heads plugged into sensor board jacks A, B, C or D.) Visit the vendor site for pricing and ordering information.

Name; Description ; Vendor  Part Number

Switch;  Switch lever spdt 3A PCB; http://www.digikey.com SW773-ND.

Temperature; Thermisor NTC 10K OHM 5%; http://www.digikey.com 317-1258-ND.

Light; Photocell 5K-20K OHM 4.20 MM; http://www.digikey.com PDV-P9203-ND.

Magnetic switch - 1; Switch Reed 10-15AT SPST .5A; http://www.digikey.com 420-1047-ND.

Magnetic switch - 2; Switch Reed SPST .5A 12-23 A/T; http://www.digikey.com HE502-ND.

Humidity; Consists of a metal electrode on a humidity sensitive membrane mounted on a ceramic substrate; http://www.rhopointcomponents.com  SYH-1NC.

Thanks to Claudia Urrea for the initial list.

Note: When using resistive sensors with the XO microphone port, it appears that the interesting resistance range goes from around 2k to 5k. (Experimentally determined; your mileage may vary.)