By default, we assume you'll want the backlight on all the time. However, you may want to PWM control or otherwise turn off the LED backlight to save power. You can do this with a simple hack. On the back, look for the two backlightjumpers. Cut the trace between the VCC jumper using a sharp knife and then solder the jumper labeled Pin 3. Then you can use Digital 3 to control the backlight.