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3 lamp light chaser

Discussion in 'Electronic Basics' started by bob, Nov 7, 2004.

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  1. bob

    bob Guest

    Im looking for a circuit to control 3 lamps in a
    "back & forth" motion, ideally I would like the
    first lamp to take about 0.5 second to reach full
    brightness, stay illuminated for about 1 second,
    and 0.5 second to dim and switch off.
    Then the second lamp does the same, then the third
    followed by the second lamp again etc etc.
    The lamps I want to use are 12v 21w automotive type.

    Im sure this is a simple circuit, and ive looked on the web
    but cant find a 3 lamp controller

    Thanks in advance

  2. What type of lamps - mains, DC, LED...?

    BTW, here's a small gift of 4 apostrophes, as I see you were plumb out
    of them when you posted the above: ' ' ' '
  3. bob

    bob Guest

    Thank you for the apostrophes, I will save them for later.

  4. Brian

    Brian Guest

    A PIC chip would be ideal for this. You might be able to find a ready made
    circuit (that you can modify), to make it do what you want. Look at, they have some chaser
    circuits there.
  5. john jardine

    john jardine Guest

    (Terry, can't see you missing it ... "12V, 21Watt automotive type" :)
  6. Sorry, my bad - a glass too many of Sainsbury's Cava!
  7. Brian

    Brian Guest

    If that is no help (and you can't find a chip that will do what you want),
    I dew up a circuit that should work for you. If you would like to go this
    route, I will add the values and component numbers for you. You can see it
  8. bob

    bob Guest

    Thank you for taking the time to draw up the diagram for me, but it
    seems it there is no need for the 0.5 second ramp up/down, the lamps
    just need to light for 1 second in sequence in a back and forth motion.
    Is there a simpler solution for this arrangement?

    Many thanks

  9. Buy

    1) a 555
    2) 2 470k, and 1 10k resistors
    3) 1uF capacitor, 1 0.1uF capacitor
    4) a 4017 chip
    5) 2 diodes
    6) 2 N-MOSFET transistors.

    I assume you already have the lamps.

    Hook up the 555 as shown in the datasheet (google 555 datasheet) as an
    astable, using a 470k resistor as both Ra and Rb, and the 1uF capacitor
    as C. That will give you a 1 second (+- 20%) clock. Put the 0.1uF cap
    from the ctl input to GND to prevent false triggering.

    Hook the output of the 555 to the clock of the 4017 (again, google for
    the pinouts of the 4017). Hook the Q4 output of the 4017 to the MR input
    (this will reset it after 4 counts; it'll go Q0, Q1, Q2, Q3, Q0, Q1,
    Q2... etc each for 1 second)

    Now, hook each of the 3 lamps up between the 12V input, and the drain
    output of the transistors. Hook the source of the transistors up to GND.
    Hook the Q0 up to the first transistor's gate, and Q2 up to the third
    transistor's gate. Hook the diodes up pointing from the Q1 and Q3
    outputs to the gate of the second transistor. Hook the 10k resistor from
    the gate to ground.

    Hook the Vcc on the 555 and 4017 up to the 12V, and the GND to ground.

    Fire it up. If the transistors get too hot, you'll have to heat sink
    them. However, they should be fine if they have a low Rds. If you can
    touch them while its running, they should be fine. If they are too hot
    to touch, find a bit of metal, and screw them down, making sure to
    insulate them from each other.

    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
  10. Brian

    Brian Guest

    I put the ramp up and down in, because that is what you said you wanted
    (in your first posting). The circuit will now be simpler, because you can
    take out the integrater amplifier and the transistor above the three lamps.
    Now the 555 timer will only go to the stepper circuit, reduce the duty cycle
    to about 5% and frequency to 1 Hz. The top of the lamps will go directly to
    the +12 volt supply. The stepper circuit will light each lamp the way you
  11. Brian

    Brian Guest

    Hi Robert,

    I believe Bob wants it to go Q0, Q1, Q2, Q1, Q0, Q1. That was the reason I
    put in the extra J-K flip flop. Unless I am missing something, wouldn't the
    way you describe, be counting up in binary. Wouldn't that need some
    decoding, to turn on the lamps in a stepping sequence? Pardon me if I missed
    something. :)
  12. bob

    bob Guest

    Hi Brian/Robert

    Yes that is sequence I want, and I think it will work like that with Roberts design
    He has hooked Q0 to transistor 1, Q2 to transistor 3, Q1 and Q3 to transistor 2
    via a pair of diodes, then it resets on Q4.
    This looks like what I need, I did ask for a 0.5 second delay, but I have since been
    told the delay is not required now. Thanks for taking the time to work out a diagram.
    Just one more question, then I will leave you clever people alone,
    could you suggest a suitable mosfet for this project?

    Many thanks

  13. I thought the sequence you wanted was "back & forth"? That's what Bob
    Monsen's circuit will do: Q0, Q1, Q2, (Q3 very briefly to switch off),
    Q0, Q1, Q2, etc. Because of the steering diodes, that will correctly
    light lamps L1, L2, L3, L2, L1, L2, L3, etc. That's not what Brian
    says above!
  14. Brian

    Brian Guest

    I would suggest an IRF520N power FET. You can get it from Digi-Key for
    about 89 cents. It turns on to about 0.27 ohms, which would make it drop
    about 0.47 volts and burn about 0.83 watts.
  15. The 4017 counts up sequentially, 0 1 2 3 4 5 6 7 8 9 0 until it's reset
    by the MR input. Thus, if you connect the Q4 output to MR, it'll go 0 1
    2 3 0 1 2 3, just like your flip-flops.

    If you look at the schematic shown in the 4017 datasheet, it's just a
    set of serially connected flip-flops.

    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
  16. Brian

    Brian Guest

    Thanks Robert, I knew I was missing something.
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