How do I wire this USB/Voltmeter, 12V plug?

Discussion in 'Wiring' started by JeepinAndCampin, Jul 21, 2017.

  1. JeepinAndCampin

    JeepinAndCampin Member

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    SO i bought this on ebay and it came in with no instructions

    I watched a youtube video of a similar product but the switch only had 2 connections, not 3.
    That guy made a multi-way connection to connect the switch to the other 3 spots. He ran his 12v to one slot on the switch, and the other slot on switch was a positive that connected to the other 3. and then completed the circuit with ground connecting to other 3.
    I am assuming this switch has 2 positive and 1 negative?
     
  2. michaeltdyer

    michaeltdyer Member

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    I tried to look at your images, but I got an error
    PopUpPortal - Error
    You do not have permission to view media within this album.
     
  3. f5moab

    f5moab Retired from the Federal Government

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    Without seeing it since your photos won't work for me either. I will assume one + is for the 12 volt receptacle, the other is for the USB; or one is for both the 12 volt receptacle and the USB the other is for backlighting. (I had a factory switch in my Hummer that was like that two positive one for the switch one for the little LED idiot light.)
     
  4. Boatnman

    Boatnman Well-Known Member

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    Pictures didn't work for me either.

    If your switch has a light, then one blade is for 12VDC power in (from battery), one blade is for 12VDC out to devices, and one blade is for a ground (so the light will work).

    Now you have to decide if you want the switch to control one, two or all three devices and how you wire each option will vary. I purchased a voltmeter/USB/12v Plug combination that came with a switch. I used the switch to control just the USB. I wired the 12v plug without a switch (hot all the time). And I added a second separate switch to control the voltmeter so turn it on, check the voltage, and then turn it off.
     
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  5. JeepinAndCampin

    JeepinAndCampin Member

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    Sorry. Not sure why they didnt post
    IMG_6977.JPG IMG_6978.JPG IMG_6979.JPG
     
  6. Boatnman

    Boatnman Well-Known Member

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    That is the same one I installed.
     
  7. JeepinAndCampin

    JeepinAndCampin Member

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    Do you have any suggestions on how to wire the 3 pin switch? i have an understanding of how to connect all 3 other items.. just not sure on how to wire + / - to switch
     
  8. ny_rocking_chairs

    ny_rocking_chairs Active Member

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    If you have a DMM multi-meter you can identify the two pins the switch connects. When the switch is "On" two pins should be shorted together, when "Off" all three pins should be isolated.

    The two pins that are shorted, one gets connected to 12Vdc, the other goes to the devices. The third pin is GND.

    As someone pointed out, one of the pins is the "input" 12Vdc to turn on the LED, can identify that by trial and error on the two pins previously identified.
     
  9. Boatnman

    Boatnman Well-Known Member

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    I just went out and looked at mine. Based on my setup, the switch shown in your picture is now in the OFF position (red light down) and the ground wire connects to the blade that is furthest away from the red light.

    The easiest way to wire the switch is to ignore the ground wire at the switch for now and connect the 12v power in (from battery) to the blade closest to the red light and the 12v power out (to devices) to the middle blade. Turn the switch on (the red light won't come on yet) and, assuming the devices have been grounded, if the devices work, then you have the correct blades. You can then connect the ground wire to the third blade and the red light will work.

    The red light gets its power internally when the switch is ON, but the light needs the ground in order to complete the circuit and make it work. As I recall, the red light can only be wired so it comes on when the switch ON - it can't be wired so it is on all the time.
     
    Last edited: Jul 27, 2017
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  10. nhlakes

    nhlakes Active Member

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    upload_2017-7-28_14-13-30.png
     
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  11. JeepinAndCampin

    JeepinAndCampin Member

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    THANKS
    Perfect. Got it installed and its working! headed out this weekend to try it out~
     
  12. JeepinAndCampin

    JeepinAndCampin Member

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    IMG_7351.JPG IMG_7352.JPG
     
  13. crab

    crab 1984 Starcraft Starflyer 19

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    A fuse should be added to the hot side, yes? Would 10 Amps do the trick?

    Also, it's OK to wire this directly to your battery, yes? My feeling is that this is sort of does an end run on any other electrics you have; it's its own power center separate from everything. It's what I was planning for our camper.

    Thanks
     
    Last edited: Aug 13, 2017
  14. WeRJuliIan

    WeRJuliIan If it's "Aluminum", why not "Sodum" and "Uranum"?

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    I would definitely make sure that there is a fuse in the supply... if you connect it directly to the battery, add an inline fuse, or tap it off an existing fused 12v line from your converter/power centre.
     
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  15. crab

    crab 1984 Starcraft Starflyer 19

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    thanks
     
  16. roybraddy

    roybraddy Well-Known Member

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    I have a couple of those round BLUE SEA 12V modules installed... Like your picture is showing you can see how bright they are. Lights up the inside of my OFF-ROAD trailer big time haha... I'm glad mine has a ON-OFF switch on the panel...
     
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  17. MaeKay

    MaeKay Member

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    Oct 18, 2017
    Utah
    Does anyone know of a link for a beginner on how to install this? I get the theory but before I start cutting into my trailer walls I think I need to see it done. JeepinandCamping's photo of it below the outlet is the most helpful thing I've found so far. I think I want to see what the wires look like inside the walls before I start this project. (And maybe a picture or diagram of what an in-line fuse is and how it's installed. Never even thought of that so thanks for the recommendation!)

    Also, is it kosher to ressurect an old post? Because it contains half the info I need, thought I'd just take it one step farther. Thanks!
     
  18. Boatnman

    Boatnman Well-Known Member

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    Resurrecting an old topic is fine - for exactly the reason you stated.

    Here's what an inline fuse looks like:

    https://www.amazon.com/Iztoss-Water...512194450&sr=8-22&keywords=inline+fuse+holder

    They are readily available at most auto parts stores and are manufactured with various size wires depending on how big of a fuse you will be installing. Where the inline fuse goes depends on how you wire the various components. The wiring diagram nhlakes posted is probably how JeepinandCampin wired his - the one switch turns on all components - so the red DC 12~24V + wire connecting to the middle blade on the switch could actually be one end of the inline fuse. The other end would be connected to the wire that provides the power to the device. In other words, you want the power going to the device to pass through the fuse before it gets to the device.

    Your device probably came with several electrical connectors. You use those to connect the components together like the red wire in the diagram that starts at the top of the switch. When you have two wires coming together - like the red + on the top of the voltmeter - you simply have one connector with two wires crimped into the connector.

    I know this is vague and isn't as good as a picture but the wiring part is fairly simple if you have the one switch control all the components. As you can see in JeepinandCampin's pictures, with the switch on, the switch, the voltmeter and the USB charger are all illuminated. As roybraddy said, they light up the inside of his trailer. So if you're trying to just charge a phone at night, be prepared for a lot of light or hanging a towel in front of the device. (There are ways to eliminate some of the light, but the wiring is a bit more complicated.)
     
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  19. MaeKay

    MaeKay Member

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    Utah
    I found a video where they attach the voltmeter/USB plug to the fuse box but we don’t have slots for any more fuse boxes. An in-line fuse sounds like just the thing! Thanks again!
     
  20. Boatnman

    Boatnman Well-Known Member

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    Connecting the voltmeter directly to the fuse box or battery (with an inline fuse) means the voltmeter will be on all the time. I wired mine so the switch on the panel only turns on the USB charger. My 12v plug is wired directly to the battery (through an inline fuse). And I added a switch next to the panel (also available at an auto parts store) so I can turn the voltmeter on just when I want to check the battery.
     

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