signal generator,3waves.

Discussion in 'The Projects Forum' started by goxuard, May 7, 2010.

  1. goxuard

    Thread Starter New Member

    May 7, 2010
    hi guys!

    I'm new to the forum. i hope you can help me. I have to do a signal generator that generates a square wave, another sawtooth, and sine.
    As I have understood, once achieved the square wave, sawtooth integrand obtained, and then putting this in a wien bridge, the sine.

    I'm stuck, here I leave my simulation in Multisim.

    Let's see how they see it, any help is appreciated.

  2. SgtWookie


    Jul 17, 2007
    Let's start with your 555 timer.

    R1, in my opinion, is too low of a value.
    The DIS pin (7) is an open collector current sink. My "rule of thumb" for R1 is a minimum of 100 Ohms per 1v of Vcc; since Vcc=5v, R1 should be >= 500 Ohms.

    If you decrease C1, you can use larger values for R1 & R2.

    If you connect a diode across R2 (anode towards Vcc) you can achieve less than a 50% duty cycle.

    If you change R2 to a pot, and move the connection of pin R7 and the diode's anode to the wiper, you can adjust the duty cycle of the output over a very wide range.

    Your LED on the output would be better to connect between Vcc and the output, rather than the output to ground. This is due to the idiosyncrasy of the 555 output having a Darlington voltage follower; it will go to nearly 0v, but won't rise above around Vcc-1.3v without a pull-up resistor.

    Adding a 300 Ohm to 330 Ohm pull-up resistor to the 555 output will help the latter situation significantly.

    It will help you a lot if instead of running wires everywhere, you use node labels for things like Vcc, Vee, GND. That way the signal path can be followed much more easily.
  3. Audioguru

    AAC Fanatic!

    Dec 20, 2007
    1) The output of a 555 does not go near its supply voltage (+3.5V when the supply is +5V) but it goes close to ground.
    2) A linear integrator converts a square-wave to a perfect triangular wave. Your intergrating capacitor has a low value resistor (1k) in parallel that makes it non-linear.
    3) A single RC makes a very poor filter. Your circuit is missing something to smooth the "triangle wave" into a sine-wave.
    4) Your second opamp has an input resistor that has its value way too low so that an opamp cannot drive it. Use 100k plus another 100k for the feedback resistor. The second opamp can also be an integrator.

    Multisim makes a schematic that has lines all over the place.