Results 1 to 8 of 8
  1. #1
    mtbr member
    Reputation:
    Join Date
    Dec 2009
    Posts
    6

    OT: LED's for car interior - electrical question

    Sorry to post this here, but after building several bike lights from info on this forum, I knew that the electronics wizards here could help answer my question.

    I've replaced my car's interior lighting with LED's (looks hot!) and a well known issue is the bulbs glow very faintly even when "off". There is some amount of current going through the system at all times I guess but not enough to light the original incandescent bulbs.

    To fix the issue you can wire in a resistor parallel to the bulb. For testing I've used 1/4 watt and 1/2 watt at both 100 ohm and 220 ohm only b/c I had these left over from bike light projects. All sizes tried do get rid of the unwanted glow.

    My question is, what wattage resistor do you guys recommend for this application? I'm starting to worry that 1/4 watt, or even 1/2 watt, is too small for this application.

    Thanks!

  2. #2
    recognize the slowness
    Reputation: jbflyfshr's Avatar
    Join Date
    Jul 2006
    Posts
    481
    What did you use for the builds? I have mulled doing the same thing to my cars for a while. Would really like more light in the trunk/hood areas especially...

    JB
    "mountain biking and flyfishing, what more do you want?" - Yeah, I said it

  3. #3
    mtbr member
    Reputation:
    Join Date
    Apr 2006
    Posts
    593
    Joe, we need to know how the leds are wired, what kind of vehicle. Some vehicles have switched hot and some are switched ground. We can fix this! James

  4. #4
    mtbr member
    Reputation:
    Join Date
    Dec 2009
    Posts
    6
    It's not really a "build", I used some off-the-shelf leds.

    I used these for the dome and floor lighting - very bright (by dome-light standards that is!) - in blue:
    http://store.ijdmtoy.com/Luxer1-12-L...anel_sku53.htm

    And these for the map lights (not as bright but better than stock and better color - used cool white):
    http://store.ijdmtoy.com/SMD-LED-Map..._d42_sku23.htm

    Some lights are switched on in pairs and only needed 1 resistor per pair, the map lights can be switched on individually and needed 1 resistor per light.

    Thanks guys!

  5. #5
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    569
    I have two of these in my trunk. Not the round ones, but the longer ones. Nice even light that lights up the whole trunk. They're 12v ready too, no resistors needed.

  6. #6
    mtbr member
    Reputation:
    Join Date
    Dec 2009
    Posts
    6
    The resistors are only needed for applications where the lights glow dimly when "off". The lights work just fine as-is without the resistors.

    So, anyone have any idea what wattage is recommended here?

  7. #7
    mtbr member
    Reputation: mattthemuppet's Avatar
    Join Date
    Jul 2004
    Posts
    2,292
    can you find out what sort of current they draw when off? Then all you need to do is current squared x Ohms = power. As long as the power rating of the resistor is comfortably (25%? 50%?) than the power dissipation, then you're golden.

  8. #8
    Dirt Deviant
    Reputation: savagemann's Avatar
    Join Date
    Jan 2008
    Posts
    3,694
    I'm not really sure what the issue is, but I picked up some of these to modify the lights in my shuttle vehicle/daily commuter van.

    http://www.dealextreme.com/p/mr16-1-...0v-input-13557
    Look, whatever happens, don't fight the mountain.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •