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Help with LED overheating. "What??" you say.

Discussion in 'Pro/Adv Discussion' started by VoicOfReason, May 23, 2015.

  1. VoicOfReason

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    I broke down and cracked open my Phantom 3. By the way, I don't recommend it. The top cover does NOT slide easily off like the Phantom 2. It is a royal pain in the neck to get it off. I mean really, really hard. It has plastic clips all around and you have to squeeze the case. Anyway, with much fear and trepidation I soldered wires to the power Pos/Neg and ran a wire out to attach accessories.

    So, I have an LED light I used on my Phantom 2. When I hook it up to the 15v source, it is unbelievably bright and gets so hot within a matter of seconds that you could get burned. So, this doesn't seem right to me. Can these LED's really operate safely at that temperature at 16v? Anyone know of a 16v capable LED?

    (By the way, I just ordered a step-down regulator to bring voltage down, but that adds some extra weight.)
     
  2. IflyinWY

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    Most of the small LEDs I deal with prefer 12 volts. You may end up melting something... :(
     
  3. VoicOfReason

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    Yeah, that's what I thought. But, I don't want a 14gram down regulator, either. Trying to save on weight. Any other options?
     
  4. IflyinWY

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  5. RedHotPoker

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    I thought 10w LED DIODES were the max...

    Seen plenty of 5w Diodes in LED panels.
    Not sure about voltage capacity...

    RedHotPoker
     
  6. IflyinWY

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    Watts & Volts
    Apples & Oranges

    LED = Light Emitting Diode

    I'm confused about what you were trying to say. :confused:
    The OP is trying to find a LED that will operate on P3 battery voltage.

    http://www.dji.com/product/phantom-3/spec
    Intelligent Flight Battery
    Capacity

    4480 mAh
    Voltage
    15.2 V
    Battery Type
    LiPo 4S
    Energy
    68 Wh
     
  7. RedHotPoker

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    Hahaha, Yeah, LED, a buddy of mine owns California Light Works down in sunny California...
    They produce a unit called SolarStorm 880.

    Been there and already done that...
    Anyway... You are Sifu, and I am, but a mere grasshopper.
    Should I like your critical tone?

    RedHotPoker
     
  8. IflyinWY

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    Ah, lets call it focused. :D
     
    dirkclod likes this.
  9. locoworks

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    if it is a really bright cree LED it will get HOT, normal ones, the type that have been around for years don't
     
  10. RedHotPoker

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  11. 4wd

    4wd

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  12. TonG

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    You can try a single resistor but you have to experiment with it to find the right value. With the right value I mean its noted resistance(Ohm's) and the capacity to dissipate the generated power/heat(wattage). You can find these values with very simple calculations. Ohm's law.

    But I have to say that I'm not sure of it will work in a good way. The reason??
    A led needs an an certain current to emit light. The more current the more light. (the voltage over the bare led always remains the same: 2,7Volt) so leds have/needs current regulators instaid of voltage regulators. In practice you find often a combination of both. A general voltage regulator followed by individual ( for 1, 2 or 4 leds) current regulators.

    So a single extra resistor between your Lipo and led system can work a little bit tricky because the voltage/current regulator comes into play. But it can work! Try it, experiment. It is not dangerous for your leds or the Lipo.

    For to make a rough estimate of the value of the resistor ( because the voltage regulator interacts with the resistor) you need to know the wattage of the existing led system. Divide the wattage by 12 ( the voltage) and you know the current.
    This current is the key. Your system worked on 12 V and the Lipo is 14,5V. So you have to loose 2,5 volts. So divide this voltage by the calculated current and you find the value in Ohms for the resistor.
    But choose the wattage of the resistor high enough otherwise the resistor will burn out. ( the wattage of a resistor have no influence on you circuit/system.)
     
    #12 TonG, May 23, 2015
    Last edited: May 23, 2015
  13. Dome

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    What kind of LED have you bought ? Have you a link ?
    If that is a simple LED you need a resistor to be applied and calculated accordingly to your input V. LEDS does work in current, not in voltage. If it's a LED with embedded internal drop resistor you need to calculate the dropping V in a different way (mostly as @TonG has told). Otherwise you melt all the stuff... beware !!
     
  14. RedHotPoker

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    I can see why someone would want to do this customization with LED.






    So cool!!

    RedHotPoker
     
    mad in nc likes this.
  15. N017RW

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    LED biasing sometimes shows up on electronics certification tests.

    Others have touched on it but you only need three items, LED, resistor, Power source. Some LEDS have the resistor internal and just need to be connected to the rated power source, done.

    If you have a 'generic' LED (no internal resistor), than you need it's 'forward voltage' rating. This will equal the voltage across the diode (also called voltage drop) during operation. We'll use 2.7v as TonG mentioned.
    Also needed would be the maximum forward current. This is typically 20-40 milliamps. We'll use 20mA for this example.
    Finally we'll use the P3 battery voltage as our PS, power source, 15.2v.

    So we'll figure out the value of the resistor needed to use our generic diode on a Phantom 3:


    First, subtract the forward voltage from the power source- 15.2v - 2.7v = 12.5v

    Now to get the proper resistor to supply the 20mA forward current our diode needs we divide the 12.5v by the 20mA, 12.5/0.02= 625 ohms.

    However 625 is not a standard value so you might have to go to 680 ohms or down to 560 ohms.

    This is how you calculate a simple biasing LED resistor.

    If you don't wish to do this manually you can go to this page and just plug in your numbers...

    http://led.linear1.org/1led.wiz
     
    #15 N017RW, May 23, 2015
    Last edited: May 23, 2015
  16. mad in nc

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    RedHotPoker - I like the light ring..... My next winter project..
     
  17. BigPig

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    Sorry to get off topic, but do you have any pointers/gotchas (other than not doing it at all...LOL!) for removing the cover, as well as a pic of where you pulled your new accessory cord to on the outside? I'm thinking of doing something similar. Thanks!


    Sent from my iPad using Tapatalk
     
  18. VoicOfReason

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    I started posting some tips here but decided to make a new thread for it. Enjoy and hope it helps!

    http://www.phantompilots.com/threads/tips-on-opening-your-phantom-3-cover.42890/
     
  19. delirious

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    I think as said before. Soldier in a resistor or put on a variable resistor. Might be more weight. Or tap into the LED that already exists. That way, you can control the light. There's a menu in the pilot app that will allow you to turn off the front two red lights. Get a meter and see what voltage those are under. I bet they are close to what you want.
     
  20. N017RW

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    None of that is sound electronic advice esp. for a new P3.

    Variable resistors are big and heavy compared to the properly selected bias resistor. Plus they may lack the resolution to set the proper value and are prone to becoming mal-adjusted due to vibrations, etc.
    It's kinda 'kludgey'.

    Tapping in a parallel fashion to existing devices is dangerous.

    One thing goes wrong on your main PCB and your grounded.

    Best strategy, if you must, is to derive the power from the battery and apply proper regulation or other power conditioning. Including a fuse.
     
    #20 N017RW, May 23, 2015
    Last edited: May 23, 2015