Earlier today someone was asking about using their Pi to play music in their car. This prompted me to consider using capacitors to keep the Pi powered until it had shut down cleanly. For that I'll need something that detects when the accessories power is switched off and then initiates a shutdown script which hopefully can complete before the power is drained.
To visualise how this may work, I downloaded an Android app and began tinkering.
I had to substitute in places because some components weren't in the app.
I also only assume I have the relay wired correct, so ignore that if its wrong.
I subsituted a lamp as a fuse coming off the battery. I am aware I put it on the wrong wire.
The thing at the bottom right (which the app called a 'voltage controlled voltage source') should be a buck converter set to ~5.1v
The lamp connected to it is supposed to represent a Pi.
All grounds are connected to the battery cathode.
What I need to know is:
- Is this accurate? I've got everything hooked up right?
- what rated fuse should I use? (relay is 30A and I may end up using more buck converters for additional Pis or USB power ports.)
What sort of capacitor (if any) would do what I want. Would multiple capacitors in parallel work or be better?
I appreciate even links to electrical forums where I coukd/should pose my question.