LED flasher

Discussion in 'The Projects Forum' started by kuxz2008, Nov 18, 2009.

  1. kuxz2008

    Thread Starter Member

    Nov 16, 2009
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    i would like to know what is the least number of component to use in order to allow the 2 LED to flash at the same time.

    how do i then connect the LED flasher to a tamiya car motor if i want the LED to flash only when the motor has stop and when LED to stop flashing when the motor is moving?
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Sounds simple. Define 2 LEDs at one time. Alternate, or together?

    The other problem is how to sense when the motor is moving.

    Something like this could be a starting point...

    [​IMG]

    Pin B will stop the oscillator, So will pin A. If alternating is what you want this will do it.

    [​IMG]
     
  3. Robin Mitchell

    Well-Known Member

    Oct 25, 2009
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    Hey bill, i though it was impossible to get a 50% duty cycle on a 555
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Mitch,
    There are many ways to get various duty cycles on a 555 timer.

    With the "typical" R1/R2/C1 configuration (R1 to Vcc, pin 7 connected between R1/R2, R2 connected to 2,6, C1, other side of C1 to ground), you're limited to >50% duty cycle. You can get a much wider range of duty cycles by adding a diode across R2. Another way is to use the output (pin 3) to charge C1 via a resistor; but with that method you really need to adjust the control voltage downards.
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    [​IMG]

    Even with the second oscillator you can get very, very close. For normal use 50.3% is indistinguishable from 50% exactly as seen by the eyeball.

    As for the first schematic, I covered this in detail in my 555 Hysteretic Oscillator article. Interestingly, a 7555 doesn't have this problem, but then it can't drive the LEDs either.
     
  6. kuxz2008

    Thread Starter Member

    Nov 16, 2009
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    the LED should be flashing at the same time but not alternate.
    so which 1 should i use?
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    Either, both. What is your power supply, and what are your LED specs (color matters)?
     
  8. kuxz2008

    Thread Starter Member

    Nov 16, 2009
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    power suply-either 3v or 9v, yellow colour...
    Is there any simpler circuit 2 use other than tis... n is it possible nt 2 use a 555timer?
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    uhhh, have you looked at the schematics? Both are 555 timers. The first uses one resistor and one capacitor (not counting LED and resistor), the other 2 resistors and one capacitor.

    I strongly suggest you read this article, 555 Hysteretic Oscillator, it doesn't get any simpler.

    If you want to know how to connect your LEDs I have another article, LEDs, 555s, Flashers, and Light Chasers, that will show you how to do it. You can have two yellow LEDs in series and one resistor, in which case I would recommend a 9V battery.
     
  10. kuxz2008

    Thread Starter Member

    Nov 16, 2009
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    i hve try out the oscillator 2 n it work. Nw i wanted 2 led 2 flash at the same time. Hw do i connect the second led?
     
  11. Wendy

    Moderator

    Mar 24, 2008
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    Try not to use shorthand in your writing, it only makes things harder to read, and this isn't a phone.

    Depends on your power supply. If you have enough voltage put a second diode in series, otherwise put a second resistor/LED next to the first.
     
  12. SgtWookie

    Expert

    Jul 17, 2007
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    Just get a flashing LED, and a regular LED. Connect them in series. The flashing LED will turn them both on and off.
     
  13. kuxz2008

    Thread Starter Member

    Nov 16, 2009
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    i wanted to connect this flasher to a tamiya motor so that it will only flash when the motor has stop nt flashing when motor is moving. How do i then connect this?
     
  14. SgtWookie

    Expert

    Jul 17, 2007
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    We do not know how your tamiya motor is wired, or what voltage the motor is using.

    Please post a schematic.
     
  15. kuxz2008

    Thread Starter Member

    Nov 16, 2009
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    i have posted the schematic. motor run on 3v battery. motor changes direction when relay(RLY) is on.
    how do i then connect the flasher to the motor?
     
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  16. Wendy

    Moderator

    Mar 24, 2008
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    At 5V you'll need 2 resistor/LED circuits.
     
  17. kuxz2008

    Thread Starter Member

    Nov 16, 2009
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    0
    I wanted to connect this flasher to a tamiya motor so that it will only flash when the motor has stop and not flashing when motor is moving. How do i then connect the flasher circuit to the motor?
     
  18. SgtWookie

    Expert

    Jul 17, 2007
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    It looks like the motor will only be stopped when S2 is open.
     
  19. kuxz2008

    Thread Starter Member

    Nov 16, 2009
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    is there any other way tht cn stop the motor other then off the s2 switch?
     
  20. SgtWookie

    Expert

    Jul 17, 2007
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    Sure. I'm thinking a big hammer, a large concrete block, fire, earthquake, or tsunami would all likely do the job.
     
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