The piezoelectric actuator seems to be driven even when playing a null waveform (consisting of only zeros).
Date Added: 2018-11-23
This occurs on firmware revision 2.1 when DIP Switch 1 is set to OFF. The selected voltage range is -10 V to 60 V. In this range, voltage gain is 35 V and offset is 25 V. When playing waveform values of 0, the BOS1901-Kit will force 25 V on the BOS1901 output, thereby producing a voltage step from 0 to 25 V on the piezo actuator which can be felt as the actuator being triggered.
This gives the impression that a wave or pulse is played on the actuator while it is in fact a matter of playing the appropriate value.
Note that even when applying appropriate negative value so the BOS1901 output is driven to 0V, Audacity® adds 0 values before starting the wave, therefore a 0-25 V square pulse is still played on the piezo actuator. To be sure no 25 V step occurs, you can select the ±95 V symmetrical range by setting DIP Switch 1 to OFF. However, using a TDK PowerHap 2.5G, be sure to limit the waveform so no voltage higher than 60 V is produced, and avoid triggering the sensing and feedback (this would playback a 95 V pulse on the piezo actuator, likely damaging it).
Since firmware revision 2.2, the gain and offset are fixed at 95 V and 0 V respectively for all voltage ranges. However, the -10/60 V unipolar range will clip the input signal if it is out-of-range. This solves the offset issue causing voltage steps on the piezo and makes codes consistent between ranges.