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LED strobe light

Discussion in 'Electronic Design' started by Jamie Morken, Feb 11, 2006.

  1. Jamie Morken

    Jamie Morken Guest

    Hi,

    What would be the simplest circuit to control the frequency and
    brightness of an LED (100Hz maximum at 1watt max power) with
    microcontroller control.

    cheers,
    Jamie
     
  2. John_H

    John_H Guest

    Simplest:
    Microcontroller directly drives a logic-level-input MOSFET, turns on at
    the 100Hz (or lower) repitition rate, turns off at a time to determine
    brightness. If you turn on the LED for 1 ms, it will be half as bright
    than if you turn it on for 2 ms. Current limit the LED from a fixed
    supply through an appropriate resistor.
     
  3. Pooh Bear

    Pooh Bear Guest

    The *simplest* circuit hardly requires a microcontroller !

    Graham
     
  4. Then use a PIC, slightly better than a 555


    martin
     
  5. Pooh Bear

    Pooh Bear Guest

    A 555 has enough oomph to drive a led directly at a decent current
    though.

    Graham
     
  6. Typical 1W Luxeon LEDs need 350mA, which is a bit much for a 555.


    Best regards,
    Spehro Pefhany
     
  7. Pooh Bear

    Pooh Bear Guest

    Is that '1W rating' a typical Luxeon spec ?

    Graham
     
  8. Boris Mohar

    Boris Mohar Guest

    Yes and there are also bigger ones. If you really want to go nuts try
    Lamina which can go over 100W (red) Digikey 521-1006-ND
     
  9. Kind-of. They have I/II/V models that have input power of roughly
    1W/3W/5W, and that's how they are often marketed. The V Star type are
    700mA at 6.8V typical. The I Star ("1W") are only 350mA @ 3V-3.4V
    typical.



    Best regards,
    Spehro Pefhany
     
  10. Keith

    Keith Guest

    Nonsense! Perhaps you'd better read the requirements statement
    again; "with microcontroller control".
     
  11. Pooh Bear

    Pooh Bear Guest

    Which is why I phrased my answer as I did.

    Graham
     
  12. Keith

    Keith Guest

    Geez Pooh, I thought you were a businessman. He asked for a solution
    *specifically* using a microcontroller and here you are telling him that
    it's the wrong solution. Perhaps he already has one in the design?
    Sometimes a microcontroller *is* the right answer (particularly when the
    customer asks for one).
     
  13. Especially when it only costs $1 and can control BOTH the perceived
    brightness (via high rate PWM) and the strobe rate. You'd need a 556 to
    do that and they're $1.44 single qty at DigiKey. ;-)
     
  14. Pooh Bear

    Pooh Bear Guest

    I have often found that ppl are chasing the wrong solution, usually on the
    basis of bad advice or incorrect assumptions.
    The OP asked for simple.

    Quite often ppl get 'wrapped up in technology' for the sake of it and simple
    becomes not so simple. If we knew *why* he wanted a uC maybe it would make
    more sense ?

    Graham
     
  15. Pooh Bear

    Pooh Bear Guest

    You have some funny ideas ideas about the price of commodity ICs.

    Graham
     
  16. Keith

    Keith Guest

    Perhaps it's you who have the incorrect assumptions?
    UCs *are* simple. Transistors are free. It's the packaging that cost$. ;-)
    It makes sense because that's what he asked for. Maybe you want to ask
    for the whole problem, rather than assume a UC is the wrong solution?
     
  17. How's that? What are you paying for 556's? It seems only natural as
    micros come down in price that they will displace more and more of the
    specialty market. This can only drive the price up further on those
    parts. I'd say that you need to face the fact that microcontrollers are
    going to be the chip of choice for the future, even if it does seem like
    overkill.
     
  18. Here here! I get the idea that Pooh doesn't "dig" micros, period.
     
  19. Pooh Bear

    Pooh Bear Guest

    You'd be very mistaken.

    I have actually designed in micros where they once would have seemed an
    unusual choice.

    It's a question of the right tool for the job.

    Unless the strobe led needs to be remote controlled, I see no reason for a
    uC.

    Graham
     
  20. Pooh Bear

    Pooh Bear Guest

    Farnell has them in ones for GBP 0.26.

    Digikey has them at a qty prcing of USD 0.14

    Show me a uC for under 50 cents ( never mind under 14 cents ).

    Show me a uC that has 200 mA drive capability.

    Graham
     
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