LED Circuit For Model Airplane

Discussion in 'The Projects Forum' started by TuborgDoug, Nov 21, 2010.

  1. TuborgDoug

    Thread Starter New Member

    Nov 21, 2010
    1
    0
    Hi,

    I'm trying to make a circuit for a friend and his model airplane. Its a rather large plane so although weight is a concern, there is some leeway here.

    The LEDs are for the wings on the plane. Its an older model - in the Amelia Erhart era, and I no flashing is required.

    I had two basic choices, a basic resistor-type circuit, or, using the LM334 - 3 terminal adjustable current sources.

    LED:
    The LEDs are from BIVAR SuperFlux LEDs
    Green ( Digikey - 492-1165-ND ) I=20mA, Vf=3.4V
    Red ( Digikey - 492-1172-ND ) I=50mA, Vf=2.4V

    I'll have to experiment a bit to get similar brightness on the red/green.

    Battery
    Using the CR123 (from AW at CandlePowerForums) with a built in circuit protection. I'm going to trust this circuit protection and not have any circuit protection myself.

    Is that a smart thing? The last thing I would want is to cause the plane to burn-up. But I believe the only concern with over-draining the battery is ruining it (i.e., overdraining would not cause a fire).

    Switches
    An on/off switch for sure.
    Maybe a dip-switch bank to select high/medium/low for LED current.

    Connectors
    This is my biggest challenge. I would like the main board that houses the battery/resistors/switches to be disconnectable from the LED lights. There would be wires going from the board to the LEDs.

    I'm familiar (from pinball) with the [SIZE=-1].100" Connector pins, header pins, and plastic housings, but I think these are too bulky for this application.

    I'm thinking a connector like on small AAA battery packs would be a better choice. The current/power should be low enough and these are much smaller/lighter. What is the name/part# of this connector? Is there a special crimp tool required (I'm assuming its some kind of IDC and just closing/clamping the connector causes the termination?).
    [​IMG][​IMG]

    Any advice would be appreciated. Thanks.


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    Last edited: Nov 21, 2010
  2. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    I hate buying small stuff like this because of the hassle and costs. You would do well by scavanging an old printer, fax, computer, or just about any box with electronics in it so salvage usefull parts.

    I'd stick with resistors. You could still switch in or out a resistor for brightness, or dial it in with a pot.
     
  3. Wendy

    Moderator

    Mar 24, 2008
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  4. windoze killa

    AAC Fanatic!

    Feb 23, 2006
    605
    24
    We use small connectors with our planes (not quite remote control but not big enough for a person either). The connectors are Harwin Microfit. They are supposed to have a special crimping toll but you could get away with soldering them. The have a positive latch so they won't come apart with vibration.
     
  5. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Do you want alternating lights, continual, or just blinking along?

    Blinking LEDs are available, hook up to a CR2032 coin cell in each wingtip and you are done if that is all that is desired.

    For alternating or better effects, I've seen most people use "magnet wire", 28 gauge or so enamel coated wire for making coils, as the cabling to the different LEDs.

    With the hair-thin wires, the driver for flashing (8-18 pin PIC or AVR, or a 555 timer) can be in one place with the power, and the wiring doesn't interfere with the rest of the airplane controls and assemblies.

    --ETA: For headers, the 0.1" header pins would be the easiest to locate and work with, no matter the wire type.
     
  6. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,887
    1,016
    I was going to suggest a PIC. I wrote some demo code for another forum member that flashes the lights in a certain sequence. Let me know if you are interested.
     
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