The Arduino OLED Dice project is a digital way of rolling dice with auto power OFF function. Aside of a typical push button switch, it uses a tilt switch sensor to start rolling the dice as shown on its display. Also, it uses an OLED for its display that enhances a graphic visual display instead of having a typical LED monitor.
The auto power OFF function circuit of this Arduino OLED Dice project comprised of several components hence it manages a 9V supply from a battery. A combination PFET and an NPN transistor is used to achieve ON/OFF switch with auto power OFF. The PFET serves as a switch of the supply before the voltage regulator. It is triggered by a push button switch S1 by providing a drop on its gate, and the NPN transistor, which is also connected to the gate, is used for an auto power OFF feature. The NPN transistor set the PFET gate LOW that correspond to the input send by the microcontroller having its base set to HIGH. The 7805-voltage regulator stabilizes the voltage to 5V and the two diodes prevents the 9 V from the battery to reaches the micro controller. The switch S1 is also used to control the digital input on the controller in which it serves as a Roll button and it is quite suitable for a tilt sensor with a specified capacitor for latching function. A Piezo is used for warning signal so that the user has time to trigger the switch again in order to reset the timer. The microcontroller is also used for storing the latest number into the EEPROM memory together with the selected number of dice/dices and the sound state, considering those values are recalled upon the next start of the dice. Another switch is used for the selection of the rolled digital dice that is also connected to the MCU.
Arduino OLED Dice is a good starter application for electronics development considering it uses several components not limited to an MCU. Some basic components needs to be included in which it gives an opportunity to the developer in order to experience specifically an actual components for switching.