LCD 16x2 I2C - is there sleep mode

Hi all,

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?

Yes, you would need to re-init the LCD on each wakeup. Is that really a problem?

I've powered a 16x2 LCD from an Arduino output pin through a 100 ohm resistor. However, this was a standard parallel LCD and the current consumption was more like 3mA. You need to make sure that the I/O lines between the Arduino and the LCD are low while the LCD power is off. For an I2C LCD, this would mean connecting the pullup resistors to the switchds power source.