Charles: Fluid flow detection has been around a long time. Most detection is done with a paddle wheel type of device. The following web site has products which detect fluid flow. http://www.chemline.com/digiflowproducts.htm.

Yes this is true But how do you add hardware without using power. Also how does an Ir led emit light below its threshold current. I suspect that the 16 uA is average and the led is pulsed at a much higher level. I still feel that driving the operating current any lower will cost much more in design and production as opposed to adding to the available power from the battery Terry