# Drone torch



## Mad_mat222 (Sep 9, 2018)

Hi all,
Firstly I apologise for my lack of knowledge and the forum tag of “unenlightened” is well deserved, but I’m willing to learn.

Project: create a powerful light to mount on a drone. Aka drone night sun.

Considerations: weight is a major factor. The project needs to weigh as little as possible, will need a run time of about 30mins, the simpler the better because I’m way out of my league if I need to start calculating and designing complicated circuits.

Idea thus far: I have been trawling through the mountain of info on here(bit overwhelming for a newb)
From my reading I think the XHP70.2 might be the go. I’m not sure if bigger is better but it seems really efficient which means more power for less. I came across Vestureofblood’s write up “The XHP70.2 8,000 Lumen BLF-GT.” That is some serious light. For my needs I would prefer a flood type setup that when deployed 20-50m above ground, would produce an area of concentrated light approx 20m (I just pulled that out!) in diameter. Bright enough to have people reaching for their sunnies and not to much spilling out past that.

The light will run off independent power. At this stage the only function I need is on/off. Might need adjustable down the line. I’m thinking it will be switched on/off remotely off the drone circuit. 

Any assistance would be much appreciated. There is some much knowledge here it’s hard to find exactly what you need. The other issue is that all the lights I’ve seen have no weight restrictions.

cheers
Mat


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## Arif (Sep 9, 2018)

Fantastic project dude. What base quadcopter might you have in mind? Budget?


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## Mad_mat222 (Sep 9, 2018)

Whoops. DJI Mavic Pro. Checked a couple of vids and it’s capable of a 1kg payload. That would abviously burn your motors,batteries and circuits real quick. If you aimed for 10/25%of that, you only get 100-250 grams not a lot to play with. Could use plastic reflectors with poly carbonate less or go bare back. Not sure if there’s tricks to saving weight on drivers and then there’s batteries. Because I flight time is 30mins or under I don’t need the torch to run longer than that so can use a battery/s that are much small than would be normally practical if someone wanted it to run for hours. The weight of say an 18650 is 50grams. If aim for 10% then I’ve already eaten half my desired payload and I don’t even know if that battery would be good enough. 

heat sink will probably be the issue. So it becomes a trade off with output vs heat and required heat sinks. And ordering a whole heap of stuff to Australia to just try doesn’t seem very smart.


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## Timothybil (Sep 9, 2018)

Places like Mountain Electronics sell LED/driver/heatsink combos and individual parts for mix and match. The also offer reflectors as well, but you might be better served with an aspheric lens.

I'm assuming your drone uses the standard LiPo battery pack for power. I would suggest that you acquire one or more of the same to power that light. That way you can use the same charger for both the drone and the light, and would be easier to mount as cargo than regular cells and a holder.

There was some video running around about a year ago showing a drone with a REALLY bright LED array that would be extreme overkill for your needs, but it could give you some ideas you could massage and transfer to your needs. Definitely let us know how things turn out, hopefully with pictures or video!


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## archimedes (Sep 9, 2018)

Moved to _Special Application Lighting_

OP, just let me know if you'd rather have this in "Spotlight" or "Transportation" or somewhere else, if you think it more appropriate.


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## DIWdiver (Sep 9, 2018)

Let's run some numbers for a sanity check.

An XHP70.2 can put out (highest bin in the data sheet) 1830 lm at 12V, 1050 mA, 85C. Let's say you want 6000 lm, just as a nice round number. Calculating from the previous numbers, you'd need 3443 mA. Since the efficacy drops a bit at higher current, let's say 3500 mA. But the data sheet says a max of 2400 mA, so you'd be way overdriving this LED. Since there's tremendous air flow in the area, and we don't expect the LED to live a long happy life, maybe this is okay.

That would require 3.5A x 12V = 42W. Since you want it to run around 1/2 hour, that means 21 W-h. Due to driver efficiency, let's say you need 24 W-h from the battery.

LiIon cells have an average voltage of around 3.7V, so to get 24 W-h you'd need 6487 mAh. That's doable with two 18650 cells. I've never really looked into it, but I suspect pouch-type LiPo cells might be lighter for the same capacity.

Now the illumination. 20 meter diameter is a little over 300 m^2. So our 6000 lm would give almost 20 lm/m^2, or 20 lux. Getting a uniform spread would be nearly impossible, so you would have brighter and darker areas. A quick google search gave estimates of an overcast day being anywhere from 1000 to 30,000 lux.

So while your torch could be built by someone skilled and/or ambitious enough, you'd have to lower your brightness goals a bit.


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## Mad_mat222 (Sep 10, 2018)

😳 😳😳 And that’s why I posted. Thanks DIWdiver. I was reading your response and just went wow. As previously stated I have absolutely no idea and seeking guidance. I have seen some lights throwing light over a kilometre away. I just figured it would not be unreasonable to take similar setups but condense it down to much shorter distances. 

Your first point of the data sheet stating max 2400mA. Why not just aim for that then. Not sure what you meant by air flow. Wouldn’t that be a good thing to help disparate the heat and make everything last longer?

as for the 70.2 perhaps, are 2 smaller emitters are better than one. Again no idea. But would think one emitter is less parts such as drivers and mounts. I’d sucrifice lumens for weight. 

Like I said (and continue to state) at the start, I just don’t have the knowledge you guys possess in this area. I just want to start the discussing and get some help.

my project is to create the brightest light I can. That will be limited by weight otherwise I’d just tape one of those giga throwers on. If the best available option is 1000 lumen because of the weight so be it, but with the know how on here I’m sure a pretty cool solution can be constructed. 

I think this project is a bit unique to most of the others I’ve read because there is a specific target distance, diameter and output but severley constrained by weight. I’ve aimed right up high and if the bar needs to be lowered a couple thousand lumens that’s ok as long as it’s the best solution v weight. 

Could any any further response please be like this:

idea of using 70.2 is rubbish (similar to above) you should try 35’s instead or

aiming for x amount of lumens is impractical but x amount of lumens might work. 

Critism with with some constructive feed back would be really appreciated.


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## Ken_McE (Jun 10, 2020)

Mad_mat222 said:


> Not sure what you meant by air flow. Wouldn’t that be a good thing to help disparate the heat and make everything last longer?



What I believe he was saying is that your diodes will be heat sensitive and will last better if they run cooler, and that having lots of air flow over your heat sink will help cool it which will make the electronics work better.




> my project is to create the brightest light I can.



For whichever light you choose, check to see if the cool-white version is the brightest.


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