Fig. 3. Schematics for Arduino UNO in rodent pupillometry. The digital input (D2) reads the signal initiating light stimulus corresponding to the use of mechanical Uniblitz
shutter in previous setup (Mure et al., 2007). The switch is connected to the ground (GND) via a pulldown 10 k resistor. The LED intensity is adjusted via a LED driver by
the PWM output (PWM4 from digital pin 11) of Arduino Uno. Arduino schematic was developed using the Fritzing (http://fritzing.org/) software.