On Sun, May 22, 2011 at 10:19 AM, Olin Lathrop wrote: >> Olin, is the strain gauge measuring torsion, or compression? > > I don't know since the mechanical design was done when I started with the > project and I never saw the insides of a hub. =A0I think I remember someo= ne > mentioning torsion, but I'm not sure. > I took apart a PowerTap to have a look. It has four gages arranged around the outside of a torque tube. (The torque is transmitted from the right (drive) side to the left, and the wheel is actually driven from the left side of the bicycle.) The microprocessor is a PIC16F690. I would not be surprised if some of Olin's code is still running in there. Modern state-of-the-art is wireless transmission from the power sensor to the computer on the handlebars via the ANT+ 2.4GHz protocol. PowerTap was one of the first to adopt this system. Regards, Mark markrages@gmail --=20 Mark Rages, Engineer Midwest Telecine LLC markrages@midwesttelecine.com --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .