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flashing led

Discussion in 'Electronic Design' started by Tuurbo46, Jan 31, 2005.

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  1. Tuurbo46

    Tuurbo46 Guest


    Im after a little advice to a very simple problem which has got me all in a
    muddle. I am currently designing a circuit with a comparator in it, and
    when the comparator goes active high(+5V DC) on the output, i would like an
    led to flash.

    Her is the question i am going to ask. If i had 5V AC on the output i think
    i could use an RC network to enable my led to flash on and off if i
    calculated the values correctly? But on the DC version the RC circuit isnt
    going to work? At this point im thinking i could use the 5VDC output to feed
    straight into a 555 timer and allow this circuit to flash the led?

    Please could somebody help me with my basic electronic skills.

  2. Gareth

    Gareth Guest

    The easiest way to do this would be to use a flashing LED. These are
    easy to get, for example see: LED&doy=31m1
    You can use a 555 timer if you like. This would have the advantage that
    you could choose your own frequency and duty cycle.


  3. Leon Sorokin

    Leon Sorokin Guest

    i made a nice flashing circuit that works off of very low voltages....down
    to 0.9V, and uses a low voltage 555 timer can adapt it to your use.
    the schematic i posted isnt the design of the board...the board design is
    more complex because i needed control over duty cycle as well, not just
    frequency. and the mosfet really isnt needed if you arent driving a Luxeon,
    like me, i think the timer can output up to 200ma if i remember.

  4. Gary J. Tait

    Gary J. Tait Guest

    You would do this, set up the 555 circuit as normal (powered from your
    +5 supply), except have pin 4 go to the output of your comparator.
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