Need help with 2 devices sharing 1 power supply

Discussion in 'The Projects Forum' started by Raymond Ploesser, Oct 12, 2015.

  1. Raymond Ploesser

    Thread Starter New Member

    Oct 12, 2015
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    I have to electronic devices that will share 1 9v power supply. Each device will have its own power button. What I'm trying to figure out is what type of relay I would need so that when device 1 gets turned on device 2s power button will become disabled. When device 2 is powered on device 1s power button gets disabled. So that both of them cannot be turned on at the same time. Space inside the enclosure is limited. So this relay or circuit board will need to be as
     
  2. paulktreg

    Distinguished Member

    Jun 2, 2008
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    Use a On-Off-On toggle switch (like this one) then only one device at a time can be on?
     
  3. crutschow

    Expert

    Mar 14, 2008
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    Is this a momentary button or an alternate action button?
     
  4. TheButtonThief

    Active Member

    Feb 26, 2011
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    Why not just use buttons/switches with both a NC and NO contact? Or button/switch with a changeover contact?

    Also, buttons are normally momentary (some are locking). are you using momentary buttons and hope to use the relays to latch the on/off function?
     
  5. Raymond Ploesser

    Thread Starter New Member

    Oct 12, 2015
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    This needs to happen automatically when either of the power buttons is pressed. The power switches themselves are of no consequence. As I had planned on disabling the power just before it enters the device. I have very tight constraints as to what I can do to the outside of the enclosure. So adding another external switch isnt an option. I know this can be done with the right relay but I do know what kind.
     
  6. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Are the existing buttons built-in to the devices?
    Do the existing buttons latch (so they stay on electrically, or are they momentary)?
    Can you get access to both contacts on the existing buttons (in and out)?
     
  7. Raymond Ploesser

    Thread Starter New Member

    Oct 12, 2015
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    Yes they are built in. One latches on the other is push button. I can access where they are board mounted.
     
  8. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    The fact that one latches makes it harder. Can you cut a trace down-steam of the pushbuttons? The input side of both pushbuttons have to remain connected to +9V at all times in order to know that the non-active button was pushed. The only way of doing that is to break the circuit after the pushbuttons using an added relay.
     
  9. TheButtonThief

    Active Member

    Feb 26, 2011
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    The function (as you've described it) has very little to do with what kind of contactor/relay you use, moreover how you wire it/them.
     
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