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100w LED - drone mounted battery powered - Help

Discussion in 'LEDs and Optoelectronics' started by Ethereal, Feb 1, 2017.

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  1. Ethereal

    Ethereal

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    Feb 1, 2017
    I am wanting to build a 100w LED flashlight on a drone consisting of 10 10w LED I bought off ebay. (something like these). I was inspired by this video. The video doesn't really say how to wire everything up and what I need other than the battery he used. I don't know if I need a LED driver or something and I don't know much about electronics other than a high school physics class. Can someone help me out a bit please?
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Too bad the seller doesn't offer a datasheet or at least a set of minimum data apart from 9V...12V / 10 W.

    LEDs need to be supplied by a constant current, not a constant voltage. Otherwise you risk destruction by thermal runaway (as the LED gets hot, more current flows, heating the LEd even more..). From the power and voltage given, we can assume the LED is made to be used with 1A of current.

    So what you neeed is a 1A constant current source with the capability to supply up to 12V (this is also known as LED driver).
    You will also need a heat sink to mount the LED on. Examples are here. Without heat sink the LED will almost instantaneously burn out due to overheating.
     
  3. WarrenC

    WarrenC

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    Jan 31, 2017
    A buddy of mine has got me into drones recently. I have a cheap hubsan x4 for $40. I have heard with the bigger ones that you can buy a splitter which would allow you to connect two batteries. I would be wary of not proving the proper voltage to your drone if you are splitting the battery power off to something else. I have found this site as I am brainstorming an LED project on here myself: https://www.fasttech.com/category/1699/flashlights--lasers
     
  4. Ethereal

    Ethereal

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    Feb 1, 2017
    I will be putting another battery on the drone, not splitting it off the battery it is holding. I already have a 9.4v lipo battery that I use for airsoft, but I can also just buy a 11.1v lipo like this one. (that is the one the guy used in the video). Also getting back to a LED driver, all I can find on ebay are AC input with high inputs like 120v which I can assume are for plugging into walls which is not what I am going to do. Is there something I am missing?

    Also for the heat sink I am getting something like this. Because I am doing 10 LED that are 10w each.
     
  5. Audioguru

    Audioguru

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    Sep 24, 2016
    100W at 11.1V is a current of 9A!. Then the heavy little Chinese battery might last for 8.7 minutes (or only 2 minutes) and you will see the LEDs dimming as the voltage quickly runs down.

    Can you calculate if the heatsink will cool well enough? Will the Chinese heatsink be made of 100% aluminum or will it have 50% rice?

    Can the drone carry the battery, LEDs and heatsink?
     
    Harald Kapp likes this.
  6. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
  7. Audioguru

    Audioguru

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    Sep 24, 2016
    The 11.1V battery will be 12.6V when fully charged and be 9V when it is dead. The LEDs will be dim at 9V.
     
  8. Ethereal

    Ethereal

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    Feb 1, 2017
    Yes the drone should be able to handle the LEDs, battery and heatsink. Also 8 minutes would be a fine time for it to be on. Also about the voltage I might be wrong about this but wont the LED driver make the voltage constant 12v?

    When I tried them on a 9v battery, they seemed pretty bright, but yea they probably could be a lot brighter on 12v. If I am thinking about what the LED driver does wrong, then what would you suggest I do?
     
  9. Audioguru

    Audioguru

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    An expensive LED driver will boost a low voltage or cut a high voltage.
     
  10. Ethereal

    Ethereal

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    Feb 1, 2017
    so get a 11.1v battery with an expensive LED driver? So the drivers that Harald linked would be ok? Also if they are ok is it fine that the output is only 150ma/350ma even though Harald said they should be run at 1 A (LED driver im referencing)
     
  11. Audioguru

    Audioguru

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    The buck-boost converters do not have enough details to see if they will work but their output current is much lower than your LEDs could use.
     
  12. Ethereal

    Ethereal

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    Feb 1, 2017
    So is their current that makes them brighter or the voltage? If I run them at a lower current what will happen?
     
  13. Ethereal

    Ethereal

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    Feb 1, 2017
    also just found this. Says that the 10w should be running at 1A and 9-11 volts
     
  14. Audioguru

    Audioguru

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    Sep 24, 2016
    The ebay LEDs are Chinese and maybe the spec's are just "made up". If you cool them perfectly then they shouild survive 1A of current.
    Some LEDs use 9V and other LEDs use 11V. You need something like a power resistor to limit the current because if you connect one that is 9V to an 11V supply then it will immediately burn out. You do not know the voltage of your LEDs because they cannot make them all the same like a simple light bulb.

    It is the current that makes them bright and hot. You cannot power an LED from a voltage without limiting the current.
     
  15. Ethereal

    Ethereal

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    Feb 1, 2017
    The LED driver will limit the current right? Also will there be any problems that arise from powering all 10 LEDs at once in parallel? Also just tried running one LED with 18 volts with two 9v batteries and it didn't blow out after a couple seconds, but definitely got hotter than if it was connected up to just the 9v. Also I didn't see a noticeable change in light when it was hooked up to the 18v. It was also a bit brighter but not a huge amount.
     
    Last edited: Feb 5, 2017
  16. Audioguru

    Audioguru

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    Sep 24, 2016
    Look at the datasheet of an LED driver to see if it limits the current and see its range of regulated current.

    You must not connect LEDs in parallel unless you buy thousands of them, test them all then group them into groups so that the LEDs in a group all have the same forward voltage. That is what Chinese manufacturers of cheap flashlights do.
    If you connect 10 LEDs in parallel and one has a forward voltage of 9V and the others have higher forward voltages then all the current goes to the 9V one and it instantly burns out, then the next one burns out then the next then the next..... Each LED needs its own current-limiting resistor.

    Our hearing and vision work with logarithmic levels, not linear levels. That is why we can hear a pin drop or a loud jet airplane and so that we can see in moonlight or in sunlight.
    Double the power makes sound or light seem only a little more but the heating is doubled. 10 times the power sounds and looks like double.

    I think the current in a high power LED is too much for a little 9V battery. With two 9V batteries in series then the LED might get only 12V or less.
     
  17. Ethereal

    Ethereal

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    Feb 1, 2017
    If I can't hook it up in parallel then I would need a resistor for each LED? Also how does this guy do it in parallel? Also he is powering those LEDs at ~24v... is that just because he bought different LED or what? Also he is just using a voltage upper not a LED driver, or is the driver kinda built into the voltage upper?
     
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