Does anyone know if those 1602 LCD displays have a sleep mode?
I am using HD44780-based 16x2 LCD display with PCF8574-based I2C interface, on a battery-powered instrument, where battery life is important, and where the instrument should go low-power if the keypad is idle for 30 s. I am putting the Atmel chip to sleep with Nick's approach described here: http://arduino.cc/forum/index.php/topic,132947.0.html. The lcd.off() command turns the display off, but the LCD module then still consumes 5.5 mA, while the rest of the circuit, including Arduino, uses about 0.1 mA while in sleep.
The only thing that comes to mind is powering the LCD logic from an Arduino digital output. Arduino can digitalWrite LOW to the LCD power line before going to sleep, and HIGH on wakeup, but that would cause LCD startup, and would require initializing the LCD (?) on every wakeup... Does anyone have a better idea?