APM stabilised spotlight (SAR application)

My second flight with the hex, after a maiden inc autotune*. It's my workhorse, and it's back to work! No real issues, apparent from a faulty AR8000 rx which seems to generating some CH3 "blips" if CH8 is connected. Weird...

 

This is a very dark night (no moon, full cloud coverage), so I figured a perfect time to see how my stabilised spotlight performs. And it performs....ok. Ish. Unfortunately, it's really *really* difficult to film this, as you'll see. The nex5 struggles to pick up all the light - you can see me supposedly walking right out of the beam at one point on the film, but actually, I I was still generating a shadow!

 

1. Yes, it's stabilising, but the response on the roll axis is far too weak, both on latency and response. I might need to search more leverage vs bigger servo. What can I do with the APM, to increase "P" on the roll axis?

 

2. Both axis lack the response time and accuracy of brushless but frankly, for a spotlight, that's not too much of an issue. Just fixing my PID's will help a lot. Since it will be used to support ground searches, it merely has to track at slow speeds, and in a consistent manner.

 

3. The light itself is rated at 9,800 lumen. Chinese Lumen...But I could still do with more power. Also, a more even and round beam would be nice - it's strangely square with too much of the beam focused in a narrow beam in the centre. But it was cheap! For a much more even spread, I'm going to have to try and find a better unit. Hmmm.

 

4. The test was just stabilisation. I forgot to demonstrate the forward-looking beam (ie points forward at 45')...it's surprisingly effective.

 

5. This gimbal only has about 80' of rotation on both axis; this makes point 4 difficult to perform while moving. You won't be chasing speedboats with cocaine or joyriders with this just yet...

 

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* Autotune missed again with this one...my last two were too soft, this one is too hard! P of 0.17  and D of 0.15 for a 6S hex is too much. I've tuned it back to P0.1, but it's still too much. P of 0.09 and D of 0.010 is probably the sweet spot.

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  • Oh i forgot:

    speaking of efficiency:

    Running at ~ 2,9V, 700mA it is at 137 lm/W (which the lamp is probably running)

    At 3,3V, 3A it drops to 91 lm/W so relatively more work for the heatsink.

    At the cooling side:

    The higher the wattage the higher the portion to be dissipated in heat.

    The datasheet claims for an ambient temperature of say 40°C a maximum thermal resistance from junction to ambient of 7 °K/W (or °C/W) ths includes the heat conduction glue and the heatsink itself (maybe with a fan).

    I wont say it is doable but the needed heatsink will be heavy.

    I'd try with a cpu fan (widely availiable and cheap).

    One with a TDP of 100W should be enough, since the system consumption is 99W in total and there is Power comming out in the form of light. ;-)

    So goals for the heatsink:

    • 100W TDP max
    • as light als possible

    An advantage of a large heatsink is the possibility of easy mounting.

    For a Heatsink i would say 300-400g is realistic.

    If that is light enough depends on the application.

    So my conclusion: LEDs are not efficient enough for using with such brightness on flying machines.

    If you fly in the arctic you can design the heatsink much smaller and lighter. ;-)

  • Hi,

    a bit btt. ;-)

    i bought one of these bike lamps, too.

    Mine was "rated" at "max6000lm" by the chinese seller.

    After putting it on a wattmeter for a longer time the following came clear:

    • It definitely does not bring the full 6000lm due to far too less power consumption.
    • The datasheet of the Cree XM-L T6 claims 3A at 3.3V which results in 9,9W for the 910lm per LED.
    • The Wattmeter shows around 15W in total, which is around 2.1 Watts per LED.
    • Even running at this wattage the light gets so hot you can burn yourself by touching.

    So my suggestion is it is limited to just around 2000lm due to heat problems in the first place.

    This means if you dismantle the light (which is absolutely easy) replace the controller and upgrade the heat dissipation to something capable of getting the heat away (large sink with a fan) the 6000lm should be doable with the LEDs of this light.

    Speaking of costs: The whole light cost me less than the LEDs alone at my favorite LED shop.

    So it is a cheap point to tinker on.

  • Well, the nice thing about the MTB lights is that they have a nice housing with a wire coming out.  I like things to look a bit better than a basement hack when I can.

    I've got a WR250X supermotard.  Had a WR250F before that.  Did a bit of enduro racing, but realized I care too much about my family to ever be fast.  The fast guys are insane.  Well, it wouldn't be so bad if you didn't have to worry about a head-on with a quad using the same trails.  Anyway, the F was a bit too racey for just fun trail use and road riding.  So I traded it on the X.  I put big fat knobby tires on it for off-road.

    Not a lot of power, but it's OK.  Super cheap, nice and light.  It's actually quite a bit of fun on the slicks around town.  I'd never want to ride too fast on a highway.  I prefer to have a cage around me when I'm doing that.

    Here's my bike on a 3 day, 1000 km on/off road ride with 100 other bikers.  Great trip, even if it rained the whole time.

    3701677104?profile=original

    3701677055?profile=original

  • Yeah, as a cyclist, that's where I got the idea from in the first place :-)

    If i was clever enough, I would wire up my own CREE XML2 's in a grid, and that would be it.

  • MTB bike lights are the way ahead. They have the same requirements as your application. Light, bright, small. Not always cheap though. Here is a good comparison, even giving Lumen per gram, but this may include the battery pack (often designed to fit the bottle cage) which shouldn't be needed.

    http://reviews.mtbr.com/2014-mtbr-bike-lights-shootout-lumen-measur...

    Ive cycled with guys that light up the Forrest from something the size of a cotton reel. Unfortunately, most of the reviews and tech info often dont mention voltage,

    Its actually not that hard to buy the components and make up something that exactly fits the bill. Perhaps even with a servo drive beam focus.

  • What do you ride, R?

    He's my little monster...and his dad...the diavel and swiss roads did not mix (he was chewing a front tyre every 2,000km, and a set of toe sliders in a single day of alpine passes!), and he was slightly overpowered for Swiss speed limits. So I got the monster...and haven't slowed down by a single km/hr. I do get more out the tyres now though.

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    3701676075?profile=original

    Back to spotlights in a minute...:-)

  • Yeah, those are too expensive for me.  Even on my truck. ;)  Actually, I strongly prefer incandescents anyway. I've been wanting to add something to my motorcycle, and I might look at using the ones Euan found.

  • Thanks for the link pedals - I might have a look and see what I can use with minimal modification - I'm really keen to keep weight down to meet the "Phantom" criteria, and if it ever gets sold, I need to make it affordable too.

  • The video looks a bit like greenscreen in earlier days. ;-)

    Great progress Euan!

    I am working on two 5W Cree XP-G2 leds with a 8° reflector and 38mm x38mm standard cooler each.

    Maybe a bit over cautious but this should be usable even in highest ambient temperature.

  • You may also wish to check out http://offroad.rigidindustries.com/products.  They make 12v automotive and marine LED axillary lights.  Light output on them ranges from very bright to obscene.  They're all-weather and tough as nails.  No modification needed as long as you have 3s-4s power.  They come with bail mounts and have other mounting options available. This is what I was going to try on mine at some point.  I use these lights on my SUV as driving lights tied into my high beams. I also have one on my bicycle using a 12v lithium pack in a water bottle.  The single Dually spot model (4 LEDs, ~3 watts each) is about 1200 lumens.  They have ever increasing size and output lights up to literally like 10,000 lumens. You could keep your SAR victims warm with that thing!

    I think using something COTS (commercial off the shelf) like this would be wise. It easier for you since you don't need to design the whole thing. It is warrantied and well regarded already.

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