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  1. #1

    Join Date
    Dec 2011
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    Milwaukee, WI
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    Led lights for Mcfoamy



    The golf dome we fly R/C in is very large, but not lit very well. The lights are all bright enough right at the line where the golfers stand, but as planes get further away to the back of the dome, they can get hard to see. I couldn’t help but notice some of the other flyers using strip led lights that they got from HobbyKing as they were very bright. I found what appear to be the exact same lights at my local hobby shop, Greenfield News and Hobby, marketed by BP Hobbies. The install is fairly simple, just use small gauge servowire with the unneeded 3rd wire peeled offand solder to each strip after cutting them to the length you need. They are self adhesive and can be cut into strips as short as3 lights. I’m using 18 leds total, two yellow6 light strips for each wing, wrapping them around the wing tips with 3 lights on top and 3 on the bottom, and for the tail 12 violet leds stuck on the trailing edge of the rudder.



    Powering them was a bit more complicated. They are rated to run off 6 to 12v, an in fact an attempt to run off 5v resulted in them not lighting up at all, killing my first idea to just power them directly from the reciever. The other plane I saw at the domefly solved this by usinga seperate bec to run his lights, but I wanted to do it more simply, and since I was running two cells lipo, there was a easy way.



    I ran a connector right to my lipos balance tap. I used a connector from a servo extension,the one thatgoes to the servo itself, and pulled off the plastic ” female ” housing.This leaves the innner plastic housting which looks just likethe other end of the servo extension exceptthat it has the 3metal pins sticking out. Theseplug directly into the balance connector, and I used the two outermostpins. This gave the full 8.4 volts from my two cell batteries.



    The full 60 led strip is rated at400 mah at 12v, so using 18 at 12v would be 119mah. However, since I’m running at only 8.4v, this drops current even more to 2/3rds or about 80mah. In the normal 6 minute flight, this means that the lights are consuming about 1/10th of this or 8mah from the 450 batteries. Not enough to make any difference in flight time.



    I belive this very low draw should make it possible to use this same connector idea on 3s batteries even though its pin spacing won’t allow usingall three cells. While this would seem to be creating a problemwith cell balance, I think that the very low draw won’t have much chance to get the battery very far out of balance, and then the balance charger will make them exactly even again after every flight. Caveat: I have not tried this myself yetso proceeed with caution.



    These lights, while runningdimmer than if I was at 12v, are bright enough to allow true night flying, ( next summer),and will make the domeflying more fun as well.



    Dean


  2. #2

    Join Date
    Dec 2011
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    RE: Led lights for Mcfoamy



    I was looking forward to flying the Mcfoamy at last weeks domefly with my newly installed lights. As I mentioned previously, I used a converted servo connector to allow me to run 8.4v right off my 2 cell batteries balancing tap. This was an easy and lightweight way to run the lights, and while not as bright as running off of 12v, it was good enough. The problem showed itself right after takeoff. While the yellow wingtip lights were working fine, the violet taillights weren’t on. I figured that something had come disconnected, so I landed for an inspection. I then found that the lights were back on. My buddy Jason was having the same problem with his identical setup, and noticed that they went dim and then out as throttle was added. Apparently, the batteries voltage drops far enough under load from the motor that the violet LED’s go out, and then come back on as soon as the motors shut off.



    I’m guessing that the LED’s spec’s of 6 to 12v are nominal, and that the violet ones actually need more than 6v to light up, while the yellow ones still work fine. I have taken a look at the wiring on the LED’s, and found that they are wired three at a time in series with a small chip inline that I belive is a diode. Knowing that LED’s have no electrical resistance of their own and the diode is normally added to keep the circuit from acting like a dead short, I thought at first that I might be able to bypass the diodes and add an appropriate resistor to feed the whole circuit. Some probing with my multimeter however showed a voltage drop across each LED, indicating that there must somehow be a resistor in each LED junction. This makes any ” quick and easy ” solutions impossible.



    I will be instead be taking the easy way out and just swap out my violet LED’s for more yellow ones.



    Dean



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