Quick Test
This is the display board for a slave thermostat. In the picture there is a B/W 5110 LCD and Dallas DS18B20 digital thermometer fitted. The switches provide for manual override of the local temperature and return to automatic control (up/down and auto).
The LCD has a specification of 3V3 max and the Arduino is a 5V part so on the reverse of the display PCB are resistive dividers to form the level shifter from 5V to 3V3.
The 3.3V backlight is driven directly from an Arduino port with a series resistor to limit the current. Backlight activates on the 1st press of any button and runs for 10sec after the last key press. This allows the measured or set temperature (or date or time) to be queried by pressing a button once without permanently illuminating a room.
Quick Test
This is the display board for a slave thermostat. In the picture there is a B/W 5110 LCD and Dallas DS18B20 digital thermometer fitted. The switches provide for manual override of the local temperature and return to automatic control (up/down and auto).
The LCD has a specification of 3V3 max and the Arduino is a 5V part so on the reverse of the display PCB are resistive dividers to form the level shifter from 5V to 3V3.
The 3.3V backlight is driven directly from an Arduino port with a series resistor to limit the current. Backlight activates on the 1st press of any button and runs for 10sec after the last key press. This allows the measured or set temperature (or date or time) to be queried by pressing a button once without permanently illuminating a room.