reverse sawtooth generator

Discussion in 'General Electronics Chat' started by mxabeles, Jun 23, 2010.

  1. mxabeles

    Thread Starter Active Member

    Apr 25, 2009
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    is there any simplistic way of creating a reverse sawtooth waveform. Maybe using a network of 555s or some opamp configuration (single sided supply preferably ? I would like to use this as an LFO for a square wave to make a digital kick drum kind of sound.
    Thanks,
    M
     
  2. mxabeles

    Thread Starter Active Member

    Apr 25, 2009
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  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    You could follow that circuit with an inverting amp, or you could do something like this...

    There is probably a simpler way to do it. Seems like every time I post a design, someone else comes up with the identical function using nothing more than a diode and a resistor.:(
     
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  4. Wendy

    Moderator

    Mar 24, 2008
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    An upside down 555? Actually I could do it with a 7555, 2 transistors, couple of resistors and a cap. The transistors are to charge the cap with constant current and discharge the cap, similar how the 555 does it. Basically it is a polarity thing, you're charging to ground instead of Vcc.

    An inverting amp after your sawtooth would do it.
     
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  5. mxabeles

    Thread Starter Active Member

    Apr 25, 2009
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    awesome, i'll try using the 555 sawtooth to inverting amplifier.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    This experiment out of the AAC book was not one of mine, but it is worth stealing.

    555 ramp generator

    It will linearize your ramp nicely.
     
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  7. SgtWookie

    Expert

    Jul 17, 2007
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    I'd whipped up this 555-based ramp generator awhile back.

    It outputs both a forward and reverse sawtooth.

    Not perfect, but cheap.
     
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  8. Ron H

    AAC Fanatic!

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    Q3 looks pretty shaky to me.:rolleyes:
     
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  9. mxabeles

    Thread Starter Active Member

    Apr 25, 2009
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    great ! great.
    one question : sgt., in the schematic there is node with the abrv. IC above it and it looks like the electrical connection is circling around it. What is this device?
    Thanks,
    M
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    Yeah, the schematic I posted was from a couple years ago when I was still pretty rusty - just happened to think of it and threw it up there.

    Max,
    that is a SPICE "initial condition" statement. It simply establishes a voltage at the start of the simulation. It would not be in the actual circuit.

    I added it because you are somewhat familiar with 555 timers already. It really needs more work before it would be usable.
     
  11. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    Most function generators also have a "symmetry" adjust where you can twiddle a ramp to be anythng from a sawtooth to a triangle, to an inverted sawtooth wave
     
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