Variable frequency and pulse width generator with 2 x 555's

Discussion in 'The Projects Forum' started by solmil, Feb 13, 2010.

  1. solmil

    Thread Starter New Member

    Jul 19, 2005
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    Some years ago I built a circuit with two 555 (on two RS Australia 434-071 555 project circuit boards) that very nicely produced a variable frequency and variable pulse width.

    Of course I've lost the circuit! (as you do!).

    HELP!

    Can anyone give me a circuit that does this?

    Love and peace,

    Sol
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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  3. Wendy

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    Mar 24, 2008
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    There are many, many ways to do this. So many it is easier to define what you need and we'll design to spec.

    To add to what SgtWookie said,

    What is your power supply voltage?

    What are you going to be feeding this signal into?
     
  4. shortbus

    AAC Fanatic!

    Sep 30, 2009
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  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Here is an updated circuit for one I have been using for years. It puts out a signal compatible with TTL or CMOS. By changing the supply voltage, you can use it for higher voltage logic, like 4000 series operated from 15V.

    It requires only a single 555. It is adjustable over a duty cycle from about 2% to about 98%. The frequency range can be moved from ~1Mhz to a few pulses per Hour.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    A variation of post #4, something out of LEDs, 555s, Flashers, and Light Chasers.

    [​IMG]

    The frequency and PWM are completely independent of each other, but fully adjustable. A CMOS 555 works better for this design, especially for low voltage power supplies, but a regular 555 works too.
     
  7. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Bill, minor nit, but the 10K pull-up at the output is kinda whimpy if driving much fan-out.
     
  8. lmartinez

    Active Member

    Mar 8, 2009
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  9. Wendy

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    Mar 24, 2008
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    Yeah, but they'll have 3 extra LM339 comparitors to use! Besides, leave the LED off and you have a ready made driver.
     
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