Does anyone know where to find these optical sensors or how to make them? I have some cds photocells but I dont know how I would make one from that. Now i have it set for the analog input to receive power from a digital pin and I only have it check every 40 seconds. It works well and even after left for hours in a small container of water the corrosion is not visible at all. Also I now use graphite rods insted of wire ends. I dont think the corrosion is at a harmful level now but if i could find an optical sensor I would switch. Thanks.