THIS IS FOR AN ODROID XU4 which has 1.8V max on GPIO logic, should also work in a Raspberry Pi but untested.
Working with Super Capacitors is super dangerous, they may burn you or weld your skin to something else, or give you a very nasty shock. Be very careful not to short the capacitor + and -, or feed them at a higher rating than is suitable. Please google super capacitors and understand how they work before playing with them.
- 2 x 1.5 Ohm 5W resistor (R1, R2)
- 2 x 5A Schottky diode (D1,D2)
- 2 x 10F 2.7V capacitor (C1,C2)
- 2 x 100R resistor (R3,R4)
- 3 x 1K resistor (R5, R6, R7)
- 1 x XL6009 Step up & down convertor module
5.2V input from 5A PSU, up and down convertor is set to output 5.1V output.
+---R1---D1------+
in | >| |
+5--+--+ +-----+---+-\
| | >| | +| | -\ out
R5 +---R2---D2------+ C1 | -+----+- +5
R6 -| R3 |step|
+----<1.8V to GPIO +---+ |up &|
| +| | |down|
R7 C2 R4 -+---+-- -0
in | -| | -/ out
-0--+-------------------------+---+-/The voltage to a GPIO pin on the XU4 will be <1.8V (1.6V ish) whilst the input is 5.2V. A shell script should check the state of this pin and trigger a shutdown when the voltage drops below .5V.
Step Up Step down to provide 5.1V output no matter what the input is. Input min for this XL6009 module is 3.8V and it can be fed at 3A max.
Work in progress, this circuit is currently not working correctly.