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Under the hood LED install using mercury tilt switch

Discussion in 'Lighting' started by acdronin, Jul 5, 2013.

  1. acdronin

    acdronin [OP] Well-Known Member

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    SO I've been wanting to add a dedicated circuit of super white LED's under the hood, I've seen a bunch here and elsewhere so that's nothing new, I want to have the power source connected to the posts underneath the terminals so that you can disconnect the battery cables and still have lighting under the hood. I was thinking of different contact switches and another member mentioned mercury tilt switches. Intrigued I picked one up and started screwing around with it. It seems like a little bit more of a challenge and I don't think I've ever seen anyone else do it. For those of you that don't know what a mercury tilt switch is, it's a tiny little glass cylinder with a drop of mercury and two electrical contacts inside one end of it. As the cylinder tilts, the mercury slides down and closes a circuit by contacting both contacts at once.

    Mercury switch.

    [​IMG]

    Switch installed inside of a gutted ball-point pen

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    Switch has two wires coming out of it, I installed the switch in one end sheathed by some shrink tubing to act as a shock dampener and ran the wires out the other end with more shrink tube on it. I heated the pen to cock it at angle that I will explain later.

    [​IMG]

    The switch and LED's I got a Fry's Electronics but I'm sure you can find these online. The LED Cree bulbs are sealed in an epoxy resin for "splash-proof".

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    For the install I have 18 ga wire, 14 ga wire, zip ties, harness tubing and a butane soldering torch with lots of extra butane.

    First was to prep and solder up the LED's I used shrink tube for each connection and a larger piece of shrink tube to create a 'boot' over the wires where it connects to the LED pod.

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    Now I had pre-cut the wires to about how long i think they needed to be to all solder at the same point to one larger wire, I could have daisy-chained them too but it would have taken longer (don't ask me how I know). The pods come with some 3M adhesive on the backs of them which came in real handy in holding them in place to drill the holes.

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    After mounting the pods with sheet-metal screws and being very careful not to accidentally drill a hole through the top of the hood, I then could mock up the wires to where they will run and then cut them all off at the same spot. I then uninstalled the pods and set to work on the 4 into 1 (4x18ga into 1 14ga), solder connections, with everything shrink tubed I then installed everything into the harness tubing. The trick was to have the pods sticking out of the harness tubes at approximately the right spots. I started with the longest run first, installed it back to the 4 into one and put a zip tie at the pod end to hold the tubing still, then I worked my way down to the shortest pod wire run. At each of the last three pods I put a zip tie on the harness tube to hold the pod in place but I didn't tighten the zip tie all the way so that I would have wiggle room when I reinstall the harness.
    This is the finished harness ready to be installed, It long enough to go all the way back to the battery and all i have to do is fish the hot wire out of the harness at the point where I will mount the mercury tilt switch.

    [​IMG]

    That's all I got down tonight, will finish the install and write up tomorrow:)

    Ok, finally the stupid heat wave broke and I finished this

    So, I mounted the lights back up under the hood and began to mount the harness tubing with 3/8 clamps and sheet metal screws.

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    When I got over to where the switch is going to go, I fished out the how wire and soldered the switch into it and tucked the extra wire back into the harness tubing. Now I had wired up the circuit with the switch and played around with it to see where the right "tipping" point would be for the switch to close. I figured out that the right angle would have meant that the pen would end up mounted at a weird angle so I bent the pen to around 22*, what I wanted was the lights to come on when the hood was lifted but not come on when driving up a hill or over bumps. The bend meant I could securely mount the switch and still get the angle. With the 3/8 clamps on the pen, it's snug but I can still swivel it in case i need to still get the lights to go on with the truck facing downhill.

    [​IMG]

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    Switch solders

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    ALWAYS fuse your circuits, no matter how small the amp draw!

    [​IMG]

    I wanted the lights to stay on even if I disconnected the battery from the rest of the truck, not the most elegant solution but it worked perfectly, an electrician would know these as 1/2 inch conduit nuts.

    (Yes that is a can of Monster that I used as a little platform to hold the wire :) )

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    Lights on and all is groovy.

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    Now I just had to wait another hour and a half for darkness till the final result! The pics are a little misleading, it's actually pretty bright, I was able to work on some other stuff without any other lights needed.

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    Oh and what was I working on waiting for night to fall?

    Moar blue LED's this time I mounted two pods under the hood scoop for moar evil blue glow coming from the hood.

    [​IMG]

    Everything on all at once and my alternator groaning under the strain :)

    [​IMG]


    Come to the light!

    At the end of my driveway 80 feet away

    [​IMG]
     
    Last edited: Jul 6, 2013
  2. dan33900

    dan33900 Well-Known Member

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    Nice.
     
  3. ian408

    ian408 Well-Known Member

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    Looking good!
     
  4. acdronin

    acdronin [OP] Well-Known Member

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    Bumpity bump, finished the install:D
     
  5. babytruck

    babytruck Babytruck, babytruck...I've got a babytruck :)

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    Looks good Chris! I like the idea of doing something so that if you need to disconnect the battery you still have light. Good going!
     
  6. babytruck

    babytruck Babytruck, babytruck...I've got a babytruck :)

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    So when are you going to do the puddle lights? If it's this week, I want to come learn please?
     
  7. acdronin

    acdronin [OP] Well-Known Member

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    Not sure if I'm gonna have the time before I go on vaca, might save that for the Mod Day
     
  8. DoorDing

    DoorDing Thank you, Nancy Roman

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    Subbed for later reading.

    Please update the thread when CHP impounds your blue light special.
     
  9. username

    username Fluffer

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    Ya but what are you going to do when it is -37.894 degrees Fahrenheit and the mercury freezes? :D
    .
     
  10. acdronin

    acdronin [OP] Well-Known Member

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    Ain't gonna happen:cool:
     
  11. babytruck

    babytruck Babytruck, babytruck...I've got a babytruck :)

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    The front lights are reflecting blue, they do not actually shine blue as this pic shows.

    [​IMG]

    Plus they are not on when driving. And that SHOULD make a difference.
     
  12. babytruck

    babytruck Babytruck, babytruck...I've got a babytruck :)

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    If it's hella hot on Mod day, I'm going with you to BAMF. I can't be in 90-100 weather for 12 hours.
     
    Last edited: Jul 6, 2013
  13. bjmoose

    bjmoose Bullwinkle J. Moose

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    Bravo. If you hit the gas hard enough, do the lights come one?
     
  14. acdronin

    acdronin [OP] Well-Known Member

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    Haven't driven yet, but how the heck would I be able to tell from inside the truck while it's moving by myself?
     
  15. bjmoose

    bjmoose Bullwinkle J. Moose

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    In the daylight, you'd never know. But at night - you might get an unexpected "close-encounters-dead-aliens-hidden-in-the-engine-compartment-glow"

    Or, you could deploy an unneeded small child to hide in the engine compartment while you're running. No, that's cruel. You'll have to use a specially trained cat.

    I better get off the internet before I get myself into trouble. :p
     
  16. acdronin

    acdronin [OP] Well-Known Member

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    Kinda like the Cat idea:rolleyes:
     
  17. Tbird

    Tbird Well-Known Member

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    SWEET...very nice job on that! Gonna have to copy. :D
     
  18. evanmb31

    evanmb31 Well-Known Member

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    Wow, nice job! I really love all the lighting on your truck it looks awesome
     
  19. DoorDing

    DoorDing Thank you, Nancy Roman

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    Doesn't matter. He'll be doing time before the end of the year. That's how they got Capone.
     
  20. acdronin

    acdronin [OP] Well-Known Member

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    Thanks Guys!

    Oh ye of little faith!
     
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