Änderungen
Aus Hackerspace Ffm
The powersupply goes in at the left side, the diodes prevent that current will be flowing back to the power supply and the resistors R5/R6 limit the current at startup rushing into the Supercaps (otherwise the diodes or the power supply might die).
The supercaps C1/C2 must be connected in series and the resistors R1/R2 are used that the voltage over the caps will be distributed evenly(balancing), otherwise the caps may degrade quickly. The resistors also discharge the caps slowly when the circuit is not powered (but within a quite long time) that is also good to lenghten the live of the supercaps.
With R3/R4 the input voltage of 5V is simply divided by half and connected to GPIO pin 7. When the main power supply fails the level at this pin quickly drops to a low-level, otherwise the Raspi will detect a high-level. A simple shell-script using the "gpio" command is polling every second the state of this pin and trigger a shutdown if the level goes to zero.
== Warning ==
The EDLCs used from Nesscap are specified with a maximum ESR of 16mΩ - charged at 2.5V this will result in a minimum discharge current of >150A. So don't short circuit them when they are charged, otherwise something might burn or became welded...
== Pictures from quick'n'dirty hack ==
