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Power Switch

Discussion in 'LT General Discussion' started by Toopy14, Feb 27, 2020.

  1. Toopy14

    Toopy14
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    How difficult would it be to add a power switch to the LT?

    I use an iPad with Bandhelper to control the LT and it would be nice to be able to leave the iPad plugged into the LT instead of disconnecting it each time.
     
  2. rjmmusic

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    It wouldn't be too hard if you're handy with a soldering iron. You could remove the ferrite bead (FB19) and add a switch to those terminals. This assumes that you're powering it with the AC adapter and not USB.
     
  3. Toopy14

    Toopy14
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    Sounds easy enough, unfortunately, it's the power from the USB port that I would like to turn off so it doesn't drain the iPad.
     
  4. Zach_Drummond

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    Or you could just buy a good surge protector with a short cable. Then you could turn everything on and off in case you need to reboot the system live. I've done this. Works well.
     
  5. Toopy14

    Toopy14
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    I use Bandhelper on my iPad, which I connected to the Mastermind LT, with a Lightning to USB cable. I use a power bar (as you suggested) in my rack, however, if I leave the iPad plugged into the Mastermind LT, it continues to power the unit.

    Unless there is a way in the iOS to tell the iPad not to supply power via the Lightning port?

    Thanks
     
  6. Toopy14

    Toopy14
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    I was reading up on how to hack a USB-A to B cable so it only transfers data and doesn't deliver power. I tried using a piece of tape to cover the metal Vcc tab on the USB-A connector. It worked, the iPad no longer delivers power to the Mastermind, so when I power off the D.C. power supply, the Mastermind shuts off. However, the cable doesn't transfer the MIDI data either, so I can't change presets from the iPad with Bandhelper.

    So then I tried a more direct hack, I found an older USB-A to B cable, sliced open the sheathing and cut the red wire, which is Vcc. Same thing, no power, which is good, but data transfer, which is bad.

    From what I read, as long as the USB cable has the two data pins and the ground wire connected, it should transfer data but not power. Is there something about how the Matermind LT is designed that would prevent this from working?

    It would be really nice not to have to unplug the USB cable every time.

    Thanks
     
    #6 Toopy14, Sep 8, 2020
    Last edited: Sep 8, 2020
  7. rjmmusic

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    It should still operate as long as the LT is powered in another way, but I've never tried it myself. We could probably modify an LT to not draw power from USB.
     
  8. Toopy14

    Toopy14
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    I don’t see why it won’t work either. I can see the tape experiment not working if I didn’t cover the pin properly, not a lot of room to maneuver in there, but snipping the red wire should have worked. Well, it kind of worked, ie., it stopped feeding power to the LT but I’m not sure why the MIDI data wasn’t getting through. Unless there is something going on in the iPad Lightning/USB cable that I’m not aware of.