Using 555 to strobe led array on ultralight aircraft.

Discussion in 'The Projects Forum' started by jolupot2000, Apr 22, 2009.

  1. jolupot2000

    Thread Starter New Member

    Apr 22, 2009
    a friend of mine builds his own ultralights and airplanes, and gave me a bit of a project to work on. he wants highpower led lighting for the exterior of his newest plane. i'm not nearly an expert but i have done some projects,mostly Rc cars and moddong my x-box, so i have a grasp of the fundamentals. so far ive been doing reasearch and putting a parts list together. the one area im caught on though is the 555. ive read all the tutorials and faqs i can find but im still not sure i have it. the strobe array is powered via a 12v system very much like a car. three CREE High Brightness LED Lamps (Forward Current:500mA, Forward Voltage:3.5V) with 3.3 ohm 1 watt resistor, powered via 500 ma buckpuck ( what ive been trying to do is strobe the leds by attatching a 555 circuit via the control on the buck puck. now for the 555 i was thinking of using FAIRCHILD SEMICONDUCTOR - LM555CN ( what i need to accomplish is on off time of 600 to 900 milliseconds and an on time of about 10 milliseconds (or as long as is needed for a vissable strobe.) i was thinking its gonna be an astable with R1 2000 (K Ohms) R2 20(K Ohms) C .47(Microfarads). i also need the compunants to be as small as humanly possible. if you guys can tell me how far off i am and offer any help it would be much appreciated.
  2. KMoffett

    AAC Fanatic!

    Dec 19, 2007
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
    How many LED's are you driving? Is the 12V battery charged in flite?
  4. SgtWookie


    Jul 17, 2007
    Use the SA555; it has an extended temperature range.

    This is for a critical safety device, and shouldn't be "cheaped out" on.

    Note that the control voltage input maximum is 10v; according to the graphs in the datasheet, no apparent benefit is achieved by exceeding about 4.3v; at which point the output current falls to zero.

    Basically, you need a brief LOW output, followed by a relatively long HIGH output from the 555 timer.
    Here is a schematic that approaches your specifications:

    For more standard values, use 2MEG for R1, and 33k for R2; this should give you a 1.3Hz rate (760mS) with a 10.7mS pulse. C1 should be a metal poly film cap with 50v or better rating. Use a ceramic cap for C2; exact value is unimportant. You will also need a 0.1uF and a 220uF cap across the Vcc and GND terminals of the timer.

    You will need to use a voltage regulator to supply the 555, as the output should not approach 10v as to not exceed the ratings of the puck. A 7806, 7807, 7808, 7809 or 7810 will be sufficient. You could use a properly configured LM317, but the parts count will be higher. Note that the output of a bjt 555 will be 1.2v to 2v lower than it's supplied Vcc, depending upon the load.
    Last edited: Apr 22, 2009
  5. Wendy


    Mar 24, 2008
  6. Audioguru


    Dec 20, 2007
    Flying an Ultra-light airplane at night?? Birds don't even do it.
    Does the pilot own a brightly lighted field for night landings?
  7. SgtWookie


    Jul 17, 2007
    The lighting our OP is talking about is generally just used in the vicinity of airports or other aircraft, whether day or night. The strobes flash with a low PRF just to attract the attention of other aviators in the vicinity to help minimize the possibility of midair collisions.

    AFAIK, ultralights don't generally fly at night; nor do most pilots who are not IFR (instrument flight rules) rated.