Is there a device which can be 28V (or USB) powered, and which starts recording (to mp3) from a line input when the power comes up, and stops (and closes the file) when the power disappears?
Not exactly what you are looking for, as it records chunks of 10 minutes and doesn‘t recognize power out, but maybe configurable to your needs?
http://www.solo-system.org/home.html
I could imagine a simple circuit which keeps it powered for 10 minutes after shutdown in between could be enough.
That’s a dead URL but this one works.
Interesting… yes there is no doubt one “can” build such a device, using some off the shelf board. One would need a “proper” OS because stuff like recording mp3 and writing to an SD card is a huge amount of code to do from scratch. And there is a possibly less than trivial task of closing the file when a loss of power is detected; action cams do this right when their battery goes flat.
There are many devices that are activated by sound and will go on recording until the sound stops. One such device was the mini disc recorder. It recorded each section of sound as a track on the disc. It is not to difficult to rip each of these tracks to an mp3 file.
On the other hand the device is small ie it fits into the palm of your hand it wouldn’t be huge if connected to an mp3 recorder to record directly as mp3 files through the inputs and outputs.
Rapberry pie? Write everything raw and then compress later.
Or write everything raw in chunks and compress the last one as the next one starts?
That way you can commit to disk the mp3 and then delete the raw file.
If you add a small rechargeable battery (to be able to stay on for the next 5 min), that should be enough I think.
There are many devices that are activated by sound and will go on recording until the sound stops.
The problem with that is that you lose track (no pun intended) of time. I need something which starts when aircraft power comes on and runs continuously.
Obviously it can be done with any of the board products, but it’s a lot of work.
