I had trouble with a CCD application where the infrared light from my source was getting so deep into the silicon that it got into the pixels that were buried under some AL for the black reference. It took a while to figure that one out. I assumed that black was black. - -Mark >>> Paul Mathews 4 December 1996 9:58 pm >>> D. L. Davis wrote: > > Everything works great with one big exception.... the PIC is > extraordinarily sensitive to light! > This doesn't surprise me at all. Silicon is photoconductive, regardless of whether you are talking about junctions or MOS capacitors (i.e., gates). BTW, ordinary black electrical tape is not opaque to near IR. The old silver write-protect labels for 5.25" floppies work well, or, you can get 3M opaque black crepe tape or something similar.