LEDs (big, serious LEDs) brightness control

having used LED strips, ive found theyre great in low light (or at night), but completely useless in bright sunlight.

now that im getting parts together for a new custom frame, im going to try some seriously big LEDs giving a single point of light at the end of each arm.  these are favourite so far: http://www.ebay.es/itm/130702285270 as they are rated for a 12V socket i assume they have a resistor in series with the LED inside that case, but i will test them before wiring everything up.  

the thing is though, just as the small LEDs in strips are pretty much invisible in full sunlight, im sure that these will be _complete_and_utter_overkill_ at night - that ill have people calling the police because theyve seen a UFO etc..  ideally i would like to be able to regulate the brightness all the way from full power to a faint glow.

reading a little about voltage regulation it seems that it can be incredibly wasteful trying to do this with a simple cicuit, and so i really need a switching BEC to power them at the lower voltage.  if it turns out that the brightness at 5V or 6V is just right for flying at night then thats no problem, i can plug the lighting circuit into a tiny switching BEC and all is good.  but i wonder if i might want even less power to the LEDs, and ideally it would be nice to be able to be able to select brightness all the way from 1V to 12V.

so my questions:

  • does anybody know of a cheap, lightweight voltage regulator with a wide range of adjustable output?
  • if 5V is just the right voltage, and i want to use the BEC currently supplying APM, could the change in load with LEDs blinking disrupt the voltage supplied to APM? - assuming 200mA of current to the LEDs
  • is there anything else to consider here? 

regards,

james

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  • SMD5050 x6 on a PCB with built in 12v regulator. Can't beat the price either. I LOVE mine! They're insanely bright and not too bad on battery usage.

    I run one at each corner or SMD5050 waterproof strips (they usually have black PCBs so look better)

    Here are the 6 LED modules:

    Up front in white, SMD 5050 Waterproof strips in the rear (15m roll for $30)

    IMG_8690.JPG

    My Bambucopter mini quad with 4 of the Digitron Modules. SUPER bright!

    IMG_1446.JPG

    My gigantic carbon Rusty quad with 4 Digitron Panels pointing up at the props to light them up for orientation. This worked real well!

    IMG_7086.JPGIMG_7082.JPGIMG_7088.JPG

    VC-20-450 Quad with 4 digitron panels on the tips of the arms, and SMD 5050 Strips on the arms as well. This was BLINDING. I had to remove the panels...

    IMG_6167.JPG

    Without Still visible from afar.

    IMG_3268.JPG

    The SMD5050 Lighting panel in Green on the rear on my y6 Bolt, I'm waiting on my blue panels for the front. I may light up the rear prop as well. Also have plans to run the outer rim of the frame with green EL wire with a sequencer, and holding the EL wire with zip ties.

    Here she is now, the green is the back. Visible for up to 2 miles easily.

    IMG_1828.JPG

    With flash on

    IMG_1829.JPG

    The 6 LED cluster 12v Panels are available at http://www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDrillDo...

    for $7-12

    And the rolls of waterproof black adhesive backed SMD 5050 Strips in different colors and even RGB I get at this vendor on ebay. I suggest ordering a few. They're very useful. I even lit part of my house in 4300kv warm strip LEDs on a dimmer.:

    http://stores.ebay.com/ledview?_trksid=p4340.l2563

    -Dane

  • VERY simple.....   Brushed motor speed control.

    12V input.  PWM output.

    saw it on an issue of "flitetest" on youtube

    https://www.youtube.com/watch?v=cdEHGw2UeYw&feature=plcp

  • You're right about those LEDs--they have resistors in series, and are wasting most of the energy. As such, using an external buck regulator isn't a good option--it will require >12 V in order to put 50mA through the LED + resistor.

    Your best bet is to go with high-brigthness cree LED modules (or something similar) + a current source (like a buckpuck, which are kinda lame). They also make LED drivers with inputs for brightness control, but they are more expensive.

    If you want to save weight, it might be simpler to buy discrete medium-power LEDs (ie, they are brighter than normal ones, but still in regular packages), with diffuse lenses--normal LEDs clear lenses. These will work a lot better as indicator lights, since they have a huge angle, with pretty consistent power output throughout. You can then drive them directly from your battery or regulator (depending on how many you want to put in series) along with a resistor.

  • FWIW, I use these on my helicopter.

    http://www.hobbyking.com/hobbyking/store/__16383__12_LED_Cluster_Gr...

    or:

    http://www.hobbyking.com/hobbyking/store/__16381__4LED_Strip_WHITE....

    They are very visible during the day when roughly pointed at you (maybe a 25-45deg included angle).  At night they are quite bright, but not obnoxiously so.  I know the 3 LED strips can be driven directly from the 2560 with no external circuitry.  I haven't really determined the amperage of the larger units.

  • Are you sure that this bulb it much brighter than little piece of typical LED strip?

    From ebay link i can see some mystical numbers is specs:

    Specification:
    Voltage: 12V DC.
    Work current:45-50mA
    Power:1W

    12V * 0.05A = 0.6W... And it's not 1W :)

    Typical led strip have power 5W/1 meter.. I can decide that one little piece of LED strip will have same power and brightness as this LED bulb.

    If you want something really visible at daylight, you can try using something like Cree MC-E - it really have about 2.5W power

  • thanks to you both, 

    it makes sense to drive the leds with a constant current, and now i see theres a whole range of products specifically for this!

    the BuckPuck looks ideal and at a reasonable price, but now that i know about these things i will look around some more.

    james

  • Google around for diy bicycle light projects. There are a number of controllers that provide brightness adjustment for high-current LEDs. The BuckPuck (ledsupply.com) comes to mind.

    Knut

  • Hi James,

    The best/right way to power leds is with stable CURRENT.....not voltage! The forward voltage drop across the led is a consequence of a flowing through current. So, all manufacturers give Vf as a function of forward current. For higher current I'll recommend you use a PWM with current sensing feedback.

    If you like I can recommend you some manufacturers I use in my business.

    Best regards

    Nick

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