The maximum current of the PWM output of the Arduino Uno
used in this study is only 50 mA whereas typical high-power LEDs
can be driven with currents ranging from 350 mA up to several
amperes. The use of proprietary LED driver makes the system more
modular, allowing the stimulator system to be equipped with the
most suitable LED driver for the desired application. Most LED
drivers in the market are designed to produce constant-current
output for driving LEDs in contrast to previous voltage-controlled
schemes with complex feedback circuits (Watanabe et al., 1992).