As you know, if you use Raspberry, the operating system on SdCard is very fragile, that the reason you need to power off properly the system to avoid corrupt files system. This small circuit can help you.

There is no PCB, all component was recycling, coming from old stuff, 10000uf capacitor, 3A diode from computer power supply, the battery from cell phone or old wearable device, except the StepUP converter and the battery charger are from ebay, for 1$ (shipping included).

The main power supply feed the relay coil and the Raspberry through D3, big capacitor is here to avoid voltage drop out, and D3 is here to avoid voltage feedback and latch delay for the relay.
Vcc 5.5v is converted to 6.5v. During this time the TP4056 li-po charge the battery. If main power fail, the relay RL1 turn to initial state, 3.7v from battery can feed MT3608, and keep supply the Raspberry, in my test i can still have Rpi under good power condition during around 10min, so it’s work fine with « short » power failure.

I plan to implement a power management system to power off properly the Raspberry (through GPIO), 10 minutes or more is just enought, may be with a Arduino Nano, or with a simple timer with capacitor and transistor.

My testing conditions was with a Rpi B1, and wifi dongle, with LCD touch screen, the power was +5.5v 2A.

Optiloader is a sketch designed for bulk upgrading of Arduino board
bootloaders using another Arduino as a device programmer. It stores
multiple copies of the optiboot bootloader in program flash memory. When
run (ie by hitting reset), it probes the target device, figures out the type
of CPU (ATmega8, ATmega168, ATmega328, ATmega328P) and initiates upload of
the bootloader and appropriate fuse programming. Since optiLoader runs
entirely with the Arduino and there is no communications with a host PC
required, this can procede very rapidly, and is not subject to interference
of (for example) avrdude with auto-reset.

The internal copies of the bootloader are prepare manually from the .hex
files compiled in the bootloader directories. (There’s an easy editor macro
process, but it is manual.)

While communication with a host PC is not required, the sketch does send
status information to the serial port at 19200bps.
Continuer la lecture de Burn a Arduino bootloader to a blank Atmega 328 with optiLoader →