Right... Long time no update. But good news, the manual version is up and running. The mixstick operates as it should and the normaly closed oxygen shutoff valve (2) works. A socket (1) is connected in parrallel to the electric motor and provides power to the shutoff valve when the compressor is running. This way the shutoff prevents oxygen from pooling in the mixstick/hose when the compressor switches off (which could lead to Bad-Things[tm]). Next up is a microcontroller controlled safety shutoff at 40% O2. Parts are ordered, so stay tuned :) When that works, automatic flow control is ofcourse next! Pictured below is the compressor (Bauer Junior 100L/min) and mixstick.
Spring is here :) Time to get this page moving again soon. Still loads of other projects, but also found a compressor and other parts to get this project going. It might become a 2-step project though, as a wall-mounted system is more easy to optimize before building the mobile version..
ErikH