overview
The Pi project’s power system is based on the Arduino Watchdog timer with RTC module. The ATMega 328p with Uno bootloader is used to check the time from the RTC module, If the returned time matches the defined times in the Arduino code, the raspberry Pi is activated via the relay, else sleep for another 8s
Items
1x ATMega328p with Uno Bootloader
1x 16MHz Crystal Oscillator (comes with ATMegga328p)
1x 100 µf Capacitor
1x RTC Module
6x AA battery
some hookup wires
Instructions
- The ATMega328p is powered by 3 sets of 2 parallel AA batteries connected in series, producing 4.5V.
- chip comes with a 16Mhz oscillator, which is connected across pins x1 and x2. Power is supplied via pins Vcc and GND.
- Pin A5 is connected to SCL of the RTC, pin A4 is connected to Pin SDA of the RTC
- Pin D8 of the Arduino is connected to one side of the LED in the photocoupler, the other side of the LED is connected to GND of the Arduino via a 50 Ohm resistor. on the other side of the Photocoupler, one side of the transistor is connected to the power supply for the Raspi, the other side is connected to one side of coil of reed relay, the other side of the coil is connected to negative of Raspi power supply.
one side of the reed switch s connected to the Raspi power supply, the other side will be connect to the voltage regulator for the raspi.
the battery connection for the Arduino is bridged by a 100uf capacitor. a 100 ohm resisitor is bridging relay connection from the photo isolator to the negative for the Raspi
First test
the first run of the system used the power source from the Arduino Uno and a frequency generator to provide the necessary current.
For more detail: Raspberry Pi power circuit
