The sketch for this project can be downloaded from my GitHub page here.
This simple board seems to be an opto isolator that can use the Arduino to drive a high brightness LED or fan. It comes in two parts the board with a USB socket and three pins to connect to the Arduino. A USB plug is fitted with two high brightness LEDS that can be used to test the board.
A simple sketch using PWM can be used. The board has three connections, Vcc, Gnd and signal. Connect Vcc to the Arduino 5 volts (or better a separate power supply). Connect Gnd to Arduino Gnd, also connect the Gnd of any external source to the Arduino Gnd. The signal pin needs to be connected to an Arduino pin that supports PWM, I used pin 3.
I decided to add a single Capacitance switch to turn the LEDs ON and OFF and the Sketch for this project can be downloaded from my GitHub page here. The capacitance switch Vcc is connected to the Arduino 5 volts, Gnd to Arduino Gnd and the output pin is connected to Digital pin 4. Upload the Sketch Arduino_with_USB_LED_driver.ino touch the Capacitance switch and the LEDs will light, touch the switch again and the LED will go out.
An Arduino Nano or Pro Mini could be used to produce a small night light etc.