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12V Lighting strips run at 15V — Parallax Forums

12V Lighting strips run at 15V

bcdebuskbcdebusk Posts: 4
edited 2014-02-07 20:28 in General Discussion
Would it blow-up the LEDs? Would they degrade quickly over time?

Has anyone tried running them with that much voltage?

Thank you in advance.

Comments

  • Beau SchwabeBeau Schwabe Posts: 6,566
    edited 2014-02-07 11:28
    That's 25% more than what they are designed for.... it most likely would not "blow them up" ... they would run hotter, and in my personal experience if they are the "sealed" water proof strips in that silicon clear gel they won't last as long as the non-water proof. The reason is because the "sealed" water proof LEDs won't be able to dissipate the heat as efficiently, and that is your killer more than anything else. IMO
  • xanaduxanadu Posts: 3,347
    edited 2014-02-07 14:38
    Which strips? Most automotive stuff is "12v" but the cars alternator can put out up to 13.7v. 15v is pushing it, you'll cut its life short. If one fails closed then the rest of the strip is done for. What is the source that is 15v? There are a lot of DC to DC converters pretty cheap these days, probably the same price as the LED strip.
  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2014-02-07 14:54
    bcdebusk wrote: »
    Would it blow-up the LEDs? Would they degrade quickly over time?

    Has anyone tried running them with that much voltage?

    Thank you in advance.
    Since there are groups of LEDs in series there isn't a lot of headroom and it is only simple resistor current limiting. I measured 180ma @12V but 340ma @15V, so that's is way too much, if you must use 15V then just run it through two 1N4004s which should knock that down to an acceptable range, I measured 210ma with this arrangement.

    EDIT:
    I also measured the forward threshold which is around 7.3V so at full brightness it might be around 9.3V (3 in series) so the "resistor(s)" is around 15 ohms which seems to correspond to the 340ma figure.
  • RickBRickB Posts: 395
    edited 2014-02-07 16:04
    Put 4 or 5 silicon diodes (forward biased) of the appropriate current rating in series with the led string to drop the excess voltage.
  • kwinnkwinn Posts: 8,697
    edited 2014-02-07 20:28
    bcdebusk wrote: »
    Would it blow-up the LEDs? Would they degrade quickly over time?

    Has anyone tried running them with that much voltage?

    Thank you in advance.

    You could also use a 555 timer and a transistor to pulse width modulate the leds.
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