Hi
I have built a guitar onboard pre-amp, which runs on a 9V battery. I also built for it a small power conditioner/regulator, which converts the battery 9V into +/- 15V, and +5V, for powering the various preamp elements. But I will also sometimes be connecting to the guitar a 13-pin cable (for MIDI), which has lines for +/- 7VDC and ground, as supplied by an outboard synthesizer unit.
What I'd like is to be able to "detect" the presence of the +/- 7V power, and if it's "live", then have my power unit switch from drawing on the battery, to drawing on the +7V. Basically, just disconnect the battery. I could just use a physical switch, but I'd rather have it function automatically.
The thing is, I'm really in the dark as to how to go about building such a thing. One consideration that boggles me is considering which source would be powering the switching circuit - I'd think it would have to be... either one!?! I could start making some guesses, but rather than just demonstrate my ignorance, I thought I'd ask for help. Anybody? Even just a simple "go look at this" link would be a nice start.
* an additional consideration will be that it might be best to convert the bipolar 7V into unipolar. But more on that later. First, I just want to know if the switching idea can work
I have built a guitar onboard pre-amp, which runs on a 9V battery. I also built for it a small power conditioner/regulator, which converts the battery 9V into +/- 15V, and +5V, for powering the various preamp elements. But I will also sometimes be connecting to the guitar a 13-pin cable (for MIDI), which has lines for +/- 7VDC and ground, as supplied by an outboard synthesizer unit.
What I'd like is to be able to "detect" the presence of the +/- 7V power, and if it's "live", then have my power unit switch from drawing on the battery, to drawing on the +7V. Basically, just disconnect the battery. I could just use a physical switch, but I'd rather have it function automatically.
The thing is, I'm really in the dark as to how to go about building such a thing. One consideration that boggles me is considering which source would be powering the switching circuit - I'd think it would have to be... either one!?! I could start making some guesses, but rather than just demonstrate my ignorance, I thought I'd ask for help. Anybody? Even just a simple "go look at this" link would be a nice start.
* an additional consideration will be that it might be best to convert the bipolar 7V into unipolar. But more on that later. First, I just want to know if the switching idea can work