I am a total beginner in electronics so I need your advice. Does this simple circuit provide for a safe shutdown, with two super caps of 10F?
Electronic – Safe shutdown/restart Raspberry Pi due to a power loss
lossmicrocontrollerpower
Related Solutions
There's nothing wrong with a power supply that has 10-15 connections; that's actually fairly typical for supplies in this class. You just need to understand what they're for.
For the power input, there will be connections for line, neutral and ground. There might be a separate "frame ground".
For the output, there will be at least one pair of output terminals (maybe more), possibly a pair of "remote sense" terminals (which help compensate for voltage drops in the wiring), and possibly terminals for remote adjustment or load-sharing.
The datasheet for the power supply should show how to hook it up for various application scenarios.
The circuit you designed works as specified. The issue is in you spec:
Case 3: V_usb == OFF and LBO == HIGH: Rpi is powered by the battery.
This requirement doesn't do anything to prevent the boot-shutdown-boot loop you're seeing. You could avoid this behavior by specifying, for example:
Case 3: V_usb == OFF and LBO == HIGH: If Rpi is running, keep it powered by the battery. Otherwise, don't start it.
This change makes it obvious that your system either needs to keep track of the state, or use an additional signal (RPI_RUN) which your Rpi should pull to HIGH when running. Those possibilities can be illustrated as follows:
simulate this circuit – Schematic created using CircuitLab
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Best Answer
I think this is bad idea, because:
You will be unable to use all capacitor energy. Capacitors will discharge from 5 to 4.5V or maybe 4V and your Pi will reset. In best case - 20% of capacity will be used.
Even if you change your circuit by adding some DC/DC converter - 10F 5V may be not enough. Raspberry Pi (model B) needs at least 2W. Thats 400mA at 5V.
You should consider conventional rechargeable or alkaline batteries. There are many designs with LiIon 18650 cells. One cell is 8-11Wh / watt hours. That means 3-4 hours on single cell with average efficiency DC/DC converter.