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Thread: Power inverter on/off switch question

  1. #1
    Maximum Bitrate Skipjacks's Avatar
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    Power inverter on/off switch question

    The power switch on an inverter...

    Can I use 12V DC power from a switched source (the stereo lead) to make that connection?

    There are two wires running to that switch (they are NOT the main power supply cables comming off the battery, nor do they carry alot of current through the switch. They are tiny little things.)

    My assumption is that the switch just completes a 12V dc positive lead into the body of the inverter that tells it to start doing it's thing.

    The question is can I put the switched power from my car onto the wire comming off that switch and have it turn the inverter on?

    I know that step 1 is testing all the lines to ensure that all the voltages involve match. I haven't done that yet. But assuming they do, is there any reason why this wouldn't work?

  2. #2
    Variable Bitrate
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    No there isn't any reason it wouldn't work, but the best (safest) way is to use the "stereo lead" to power a relay that shorts the wires going to the power switch. Then you don't have to worry about it.

    KyferEz
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  3. #3
    Maximum Bitrate Skipjacks's Avatar
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    Quote Originally Posted by KyferEz
    No there isn't any reason it wouldn't work, but the best (safest) way is to use the "stereo lead" to power a relay that shorts the wires going to the power switch. Then you don't have to worry about it.

    KyferEz
    Whats' that? Like a little solenoid that shorts the circuit?

    I can see that being a better set up with more stable power. Where would you get a thing like that?

    Thanks for your help!

  4. #4
    Variable Bitrate
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    Yes, a relay is like a solenoid.

    Get a relay from Radio Shack or advanced auto. One of those automotive type relays with tabs so you can use Quick Disconnect crimp on connectors.

    KyferEz
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  5. #5
    Maximum Bitrate Skipjacks's Avatar
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    Quote Originally Posted by KyferEz
    Yes, a relay is like a solenoid.

    Get a relay from Radio Shack or advanced auto. One of those automotive type relays with tabs so you can use Quick Disconnect crimp on connectors.

    KyferEz
    The Radio Shack guy looked at my like I was crazy today when I explained this. He said it was a bad idea to have unregulated power anywhere near integrated electronics...blah blah blah....and that they didn't have anything that would work for this.

    Long story short, I don't think they guy really understood what I was asking. I think he assumed I was trying to use the 12V line comming off the ignition to POWER the entire inverter. There was no explaining to him otherwise.

    Anyway...what exactly do I need? They have everything laid out in clearly marked bins so I can find it myself. But I don't know enough to pick out what I need.

    How would the part I need be labled? What would it's voltage requirments be, etc etc. I found the relays fine, but there were like 50 of them all with different output options.

    And am I going to need a ground wire comming off the relay back to the neg terminal on the battery?

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    Constant Bitrate old_lou's Avatar
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    Quote Originally Posted by Skipjacks
    The Radio Shack guy looked at my like I was crazy today when I explained this. He said it was a bad idea to have unregulated power anywhere near integrated electronics...blah blah blah....and that they didn't have anything that would work for this. And am I going to need a ground wire comming off the relay back to the neg terminal on the battery?
    You need a neg to the relay, a switch in the pos side connection and a fuse ideally
    The relay usually has a little picture on explaining how its connected up
    If anything as you are only switching the control side of the supply circuit this relay is to big.
    http://www.radioshack.com/product.as...5Fid=275%2D226
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    Maximum Bitrate Skipjacks's Avatar
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    Quote Originally Posted by old_lou
    You need a neg to the relay, a switch in the pos side connection and a fuse ideally
    The relay usually has a little picture on explaining how its connected up
    http://www.radioshack.com/product.as...5Fid=275%2D226

    Oh thanks! Is this the part I need so I can just go into the store and find it?

    And thanks again, you should know you are no officially overqualified to work at a Radio Shack.


    Is the important information just that it be powered by 12V DC? Does anything else really matter? Will any 12V DC relay with 4 prongs (2 for the switched power and ground wires, and 2 to bridge the wires on the switch) work for me?

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    Maximum Bitrate Zebelkhan's Avatar
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    Quote Originally Posted by Skipjacks
    Oh thanks! Is this the part I need so I can just go into the store and find it?

    And thanks again, you should know you are no officially overqualified to work at a Radio Shack.


    Is the important information just that it be powered by 12V DC? Does anything else really matter? Will any 12V DC relay with 4 prongs (2 for the switched power and ground wires, and 2 to bridge the wires on the switch) work for me?
    That relay will work. There are two basic kinds of relays though.

    1- Normally open - Contacts are open until power is applied
    2- Normally closed - Contacts are closed until power is applied

    Make sure the relay you get is the type "normally open". Very easy install though. Good luck.

  9. #9
    Maximum Bitrate Skipjacks's Avatar
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    Quote Originally Posted by Zebelkhan
    That relay will work. There are two basic kinds of relays though.

    1- Normally open - Contacts are open until power is applied
    2- Normally closed - Contacts are closed until power is applied

    Make sure the relay you get is the type "normally open". Very easy install though. Good luck.
    Yeah that's what was throwing me when I went to the store. I didn't know if NORMALLY CLOSED meant it was on or off when no power was applied. I mean...closed could mean the circuit is completed (like a door closed makes a solid wall) or it could mean it's 'not open for business' meaning the current won't complete the circuit.

    Thanks though. That makes this process extremily simple. I appreciate the electronics lesson!

    (It's amazing how much I've learned here. 2 months ago I could barely run my desktop system. Now I've got a fully integrated CarPC will all kinds of custom built switches and buttons and what not)

  10. #10
    Constant Bitrate old_lou's Avatar
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    Look here for info
    SPST means that there is one contact and its either, normall off or on, and will be held in the opposite state for as long as the power is switched by the coil

    SPDT means single pole double throw IE: there is one switched wire that can be in two positions either normally of and switched or normally on and switched between the two So will have three connections for the switched termials one common one normally open one normally closed and you have to choose which one you wire to.
    Ther are other variation as well some you can use a button to power up with and it will not drop the power till you drop the power from the circuit (ie turn the ignition off)

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