We report the discovery of eleven new ZZ Cetis using telescopes at OPD (Observatório do Pico dos Dias/LNA) in Brazil, the 4.1 m SOAR (Southern Astrophysical Research) telescope at Cerro Pachon, Chile, and the 2.1 m Otto Struve telescope at McDonald observatory. The candidates were selected from the SDSS (Sloan Digital Sky Survey) and SPY (ESO SN Ia progenitor survey), based on their $T_{\mathrm{eff}}$ obtained from optical spectra fitting. This selection criterion yields the highest success rate of detecting new ZZ Cetis, above 90% in the $T_{\mathrm{eff}}$ range from 12 000 to 11 000 K. We also report on a DA not observed to vary, with a $T_{\mathrm{eff}}$ placing the star close to the blue edge of the instability strip. Among our new pulsators, one is slightly cooler than this star for which pulsations were not detected. Our observations are an important constraint on the location of the blue edge of the ZZ Ceti instability strip.