  We present a dedicated search for new pulsating helium-atmosphere (DBV) white
dwarfs from the Sloan Digital Sky Survey using the McDonald 2.1m Otto Struve
Telescope. In total we observed 55 DB and DBA white dwarfs with spectroscopic
temperatures between 19,000 and 35,000K. We find 19 new DBVs and place upper
limits on variability for the remaining 36 objects. In combination with
previously known DBVs, we use these objects to provide an update to the
empirical extent of the DB instability strip. With our sample of new DBVs, the
red edge is better constrained, as we nearly double the number of DBVs known
between 20,000 and 24,000K. We do not find any new DBVs hotter than PG
0112+104, the current hottest DBV at $T_{\mathrm{eff}}\,{\approx}$ 31,000K, but
do find pulsations in four DBVs with temperatures between 27,000 and 30,000K,
improving empirical constraints on the poorly defined blue edge. We investigate
the ensemble pulsation properties of all currently known DBVs, finding that the
weighted mean period and total pulsation power exhibit trends with effective
temperature that are qualitatively similar to the pulsating hydrogen-atmosphere
white dwarfs.
