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LED flashing pen

Discussion in 'Electronic Design' started by Leon Heller, May 28, 2004.

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  1. Leon Heller

    Leon Heller Guest

    I was given a similar pen to this as a freebie on the PCB-Pool stand at the
    NEPCON Show in Brighton, UK, yesterday:

    It's a retractible ball-point pen with a transparent plastic barrel and
    three bright LEDs (R,G and B) mounted on a PCB, with a sort of light guide
    in the centre of the barrel. It's powered by three button cells. There is a
    switch on the top part which when pressed once, illuminates one or more of
    the LEDS. When pressed a second time, they are turned off. Repeating the
    on/off action causes it to cycle through about six colour combinations,
    including one where each combination is cycled rapidly, about every 1/2
    second. There seem to be lots of similar gadgets around - does anyone know
    how the LEDS are controlled? My guess is an ASIC, given the large volumes

  2. Guy Macon

    Guy Macon Guest

    My guess is a 4-bit Asian microcontroller. Usually Cheaper than an ASIC.
  3. They are made molded right into the LED housing. I believe the dies
    are Asian-origin ASICs.

    Best regards,
    Spehro Pefhany
  4. Not with these pens, three normal leds, and a small PCB with
    a blob. The program has 8 modes, 7 steady colors, and the 8th is
    animated flashing going through the entire rainbow.
  5. Interesting. I can get 7-color and similar) LEDs as components with
    about ten variations, some with a trigger pin. Possibly the same die
    with different packaging. I've also seen it on little plastic pendants
    that people buy at street fairs etc., though I have never dissected
    one. Very nice effect and dirt cheap. They are making millions for

    Best regards,
    Spehro Pefhany
  6. I have a collection of leds now, most of them from Ebay. Among them
    is one that fades through all kinds of colors, and then goes flashing
    madly, and goes back to crossfading again - and again. Quite nice,
    but not very powerful. No trigger pin, the 'program' just runs forever.

    The pen has three 3mm leds and gives a lot more light. Blue, red and
    a yellow one - I would have expected a green one. I'll post a picture
    of the PCB on ABSE, in a minute.
  7. Ardent

    Ardent Guest

    X-No-Archive: yes

    All these stuff come from China. I bought Rice Lights for Christmas -
    this has three strands of LEDs red, green and blue. It is controlled
    by a match box sized unit, has eight programs, seven are single
    programs of lighting sequences and the eighth goes through all the
    seven modes.

    Opening the control box I found a small switch to change the program,
    a blob and three drive transistors and of course a basic rectifier to
    provide the DC.
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