Need Help with Project

Discussion in 'Embedded Systems and Microcontrollers' started by repobounty, Sep 30, 2007.

  1. repobounty

    Thread Starter New Member

    Aug 12, 2007
    Hello all
    Please excuse my layman terms on the subject.

    Here is what I am trying to achieve:
    I need is to be able to light up 6 super bright high intensity LED’s that require 4v each.
    Image a box with a hinged lid [like a toilet lid]… this device will attach to the underside of the lid… when the lid is closed the led’s will light for 3 minutes, If you lift the lid before the 3 minutes are up then the led’s will turn off. Otherwise if the lid remains closed the led’s will turn off after the 3 minutes are up .
    Then to recycle the led’s… you would lift the lid and close it again to start the timer and light the led’s for another 3 minutes.

    But the catch is I need to keep the dimensions within 3 inches long x 2 ½ inches wide x 3/8 deep. Also the battery life needs to last for 1 year if used for 30 minutes a day!

    The LED’s Specs are HERE

    The batteries I have chosen are HERE Not because I know anything about batteries, but because they fit in the specs and are 12v. I was able to get 3 weeks of steady run time using this battery but on 25 LEDs that were a 10th of a watt each so the total wattage was 2.5. With the new LEDs they will be 6 total watts 1 watt each

    I have been looking at the 555 timer but was told to maybe try a microcontroller but I know even less about them.
    Anyone think they can build it?
    What is the best way to go?

    Any help would be greatly appreciated?
  2. mrmeval

    Distinguished Member

    Jun 30, 2006
    You can extend battery life if you pulse width modulate them, intensity will be lower but since they are only on a percentage of 'full' battery life is extended. Adjust the on to off ratio so it looks acceptable.

    You can extend battery life if your PWM controls a mosfet that then turns on the LEDs (mosfets draw little current when off).

    This is a resettable circuit that has all but the PWM part, see about a low current 555 timer for that.