hi guys!
just would like to ask help for our project proposal. Its a device whioch could electronically check test paper with answers in a shaded box form. We are planning to use a infrared circuits which could sense that a shaded portion exixt and convert it n digital form and compare it to the answer written by means a assemly program in the PIC. Can you give comments or any suggestion in doing our design. Or a working infrared circuits utizing reflective sensing. Thank you so much for those who are willing to help.
Neil

 

Fairchild makes several different reflective sensors (QRB11xx series and QRD11xx series). You can always get a couple and see how well they support your needs.

You may find it's necessary to place a separate track on the score sheet to indicate the places where an answer box is located. That lets the uC know where to expect a valid signal.