2017-11-14, 03:31 PM
(2017-11-13, 02:06 PM)shark24 Wrote: Unfortunately most of the UPS solutions won't work for me. On the boat the pi is fed by the 12v system and should be shutdown when I kill the main power. After the shutdown the pi needs to be cut of the UPS's battery because it won't turn off completely. The pi still sucks some current in shutdown and fires the GPIO pins so the UPS wouldn't last very long. I haven't figured out yet how to detect whether the pi has finished the shutdown completely. Because of that i need some sort of timer like shipahoy wrote. First I was going for a NE555 and a relay but recently I've tested a MOSFET and a capacitor at the gate. I'm a total newbie when it comes to electronics and I'm trying to figure everything out by myself and not follow some DIY-guide. I hope I'll have a working solution in the next weeks. Currently I'm waiting for the delivery of last parts from china.
For the parts you are describing, you might find it easier to deploy an Arduino Pro Mini, and just do the appropriate programming to detect voltage states, do timing, etc. You'll probably find that the actual board real estate required for something like that would be less than a 555, capacitors, etc. It's also a lot easier to implement some logic in that configuration.