A system is implemented to collect data from a plurality of different sources. The alloy can include Cr, B, Ta, Nb, C, Mo, Ti, V, W, Zr, Zn, Cu, Hf, O, Si or N. The light sensor senses the ambient luminance and outputs a sensing signal to indicate whether the luminance is greater than a predetermined quantity. The outputs of an element switch to opposite voltage levels. The p-side region is provided around each of the n-side regions at the second surface. The barrel includes a depression and a number of cavities communicating with the bore, to slidably receive the longitudinal rib, and to limit the barrel to rotate relative to the longitudinal rod, and to retain the longitudinal rib in either of the cavities of the barrel, and to position the barrel relative to the longitudinal rod at selected angular position.