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flashing led

Discussion in 'Electronic Design' started by daron, May 30, 2004.

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  1. daron

    daron Guest

    can anyone tell me a simple way to make 1 led flash
    i have a diagram for 1 led + 1 transistor + 1R
    but i cant find this transistor in any shops
    i have 555 timer chips but would prefer not to use them
    it will be for 12 car
  2. Leon Heller

    Leon Heller Guest

    Just buy a flashing LED, like the Kingbright L-976 series devices. They work
    off 12V.

  3. Activ8

    Activ8 Guest

    connect it to a battery through a resistor and a push button switch
    and keep pushing the button.
    No C? Oh, I get it. The transistor turns on and smokes the LED,
    thereby flashing it once.

    Way cool. I should've thought of that myself.
    I'll take them off your hands.
    huh? Nascar or what? What's 12 car? Viagra? DeWalt?

    try a 2n2222 or 2n3904 ( I assume this POS uses an NPN transistor. )
    If you can't find those in the shops, find other shops.

    HTH, if not, let's have some more info like what transistor you
    can't find, flash rate, and what circuit you're talking about.

    But I don't recall ever seeing the circuit you to which you allude -
    1 transistor, no cap. Check out:

    and for future:
  4. Activ8 wrote...
    The circuit mentions 5 to 12V supplies. But if a power supply
    voltage of more than about 8V is used the two transistors may
    experience high reverse emitter-base breakdown current. This
    causes a severe drop in the transistor's beta, which could then
    cause eventual failure of the circuit. Two resistors can be
    added to solve the problem. For example, connecting each 10uF
    timing cap to a tapped version of its 470 ohm resistor.

    - Win

    (email: use hill_at_rowland-dot-org for now)
  5. daron

    daron Guest

    my god clowns everywhere
    thans to all that helped
    i have a diagram here uses 1.2v-4.5v in to dc of ic part number HT-2014L-ND
    ground of ic is ground
    middle leg goes to R1 270ohm then to cathode of led
    and anode of led goes to dc in of ic
    i hope this makes sence
  6. That's an (obsolete?) Holtek IC in TO-92.

    Best regards,
    Spehro Pefhany
  7. Activ8

    Activ8 Guest

    Yeah. With V_(BR)EBO at 6V and the thing getting slammed with maybe
    -11 Vp...
    YOu know, as common as this circuit is, I never messed with it - but
    I've seen enough "blinkey lights" not fail. Some ran off 9V, too.

    I just checked a circuit for a R/C proportional controller that uses
    this same MV circuit ('cept it uses pots to vary the time constant
    on one side and each pot is driven by a decade counter to get that
    PPM signal - actually PWM which ends up looking like PPM.) THat
    circuit uses 4k7 instead of 470 at the collectors, not that that
    changes anything breakdownwise.
  8. Fred Bloggs

    Fred Bloggs Guest

    Ehhh- that's an observation - but then you screw up the timing. The
    usual technique is to drop diodes in series with the emitters.
  9. Activ8

    Activ8 Guest

    Screwing up the timing is an understatement You can't move the cap
    far enough from Vc to matter without killing the oscillations
  10. Fred Bloggs

    Fred Bloggs Guest

    It looks like the manufacturers have discontinued these LED-flasher
    IC's. You can now just buy a flashing LED- apply power and it flashes-
    also known as blinking LEDs. If you want to construct an actual circuit,
    then a CMOS 555 would be the simplest, or there are bunches of LED
    circuits here- that actually work:)
  11. My favorite is the LM3909 ic. I think discontinued, but some are still out
    there. Small little chip (8 pins). You add a capacitor to determine the
    flash rate and the LED.

    Extremely long battery life. Generally, a C-cell size battery will last 1
    year or longer flashing at once per second.

    - - - -
  12. Ken Taylor

    Ken Taylor Guest

    Just use a flashing LED and a resistor - two components. Or go to an auto
    store and get a flashing LED pre-made - a couple of bucks more but in a neat
    package with a dash-mounting bezel.

    Incidentally, yes, the '3909 is discontinued, and becoming hard-to-find.
    Sad - a nice little device.

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