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newbie: Simple microcontroller circuit gone bad

Discussion in 'Electronic Basics' started by SEB, Dec 12, 2004.

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  1. SEB

    SEB Guest


    First post and just beginning in microcontrollers and electronics, so please
    excuse the dumb questions. I have built a circuit with an Atmel 2051 that
    simply makes 4 leds flash quickly (about 400 hz), using the standard circuit
    set up for the 2051. It works fine but when I run it off of two 3volt watch
    batteries, they are dead after about 1 minute. My understanding is that
    this circuit should run for many hours with these batteries.

    I've been over the circuit lots of times looking for short circuits, but
    can't find any.

    a) is this normal behaviour or do I need to use some low power circuitry
    b) where could I find examples if I need a different low-power schematic?

    Can anybody point me in the right direction?

    Thank you.
  2. Watch batteries don't have much capacity to drive an LED, let alone 4
    of them. How much current are you sending through each LED? First
    change would be to go to very high efficiency LEDs and drive them with
    low current ( a milliamp or 2).
  3. CFoley1064

    CFoley1064 Guest

    Subject: newbie: Simple microcontroller circuit gone bad
    Hi, Sean. Get 4 "AAA" batteries and a battery holder to give your 6V. Watch
    batteries aren't made for that kind of current draw. Even if your LEDs are
    flashing sequentially, you're probably drawing at least 10mA, which is at least
    100 times the recommended maximum current for a watch battery. Even getting
    high intensity LEDs and running them at a couple of mA won't be good enough,
    and watch batteries are pretty expensive.

    BATTERY HOLDER FOR 4 AAA CELLS Radio Shack P/N 270-413 $1.99

    These should last for a day or two, at least.

    Good luck
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