A voltage controlling device includes an AC terminal receiving an AC voltage
signal,
a voltage dividing device adapted to divide the AC voltage signal into a plurality
of distinct voltage signals within a predetermined range, a controller adapted
to control the voltage dividing device to provide a selected voltage level based
on voltage level information and an SPD terminal for providing the selected voltage
level to a suspended particle device. Voltage level information may be provided
via an input device and/or from a photocell that monitors a light level at the
suspended particle device. A separate AC power supply may also be provided. The
controller may also monitor an SPD load voltage to control the voltage level provided
to the SPD terminal in order to prevent shocking of a user.
