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Re: 2mHz to 6mHz signal generator

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  • orvillefpike
    The PWM from a uC wouldn t work because, as stated, the frequencies selection is too coarse. A uC controlled oscillator, like a AD9833, could work though. I
    Message 1 of 33 , Oct 16, 2011
      The PWM from a uC wouldn't work because, as stated, the frequencies selection is too coarse. A uC controlled oscillator, like a AD9833, could work though.
      I think I solved the oscillator problem, for now, by using a 74HC4046. Now my problem is, I want to drive the two legs of a center tap transformer and feeding each leg alternatively with a positive pulse and I also need a dead time so the two transistor don't conduct at the same time.
      A SG3525 would do if it went hihg enough in frequency.

      --- In Electronics_101@yahoogroups.com, "rtstofer" <rstofer@...> wrote:
      >
      > This might be possible with one of the DSS capable microcontrollers like the Analog Devices Blackfin but I don't think it is possible with just an Arduino.
      >
      > The Arduino runs at 16 MHz (Blackfin at 500 MHz) and if we wanted only 8 steps in a synthesized sine wave of 6 MHz we would need to set the analog output at a 48 MHz rate. And that's just 4 steps on the positive side and 4 steps on the negative side of the sine wave. Or, 2 steps on the rising slope and 2 steps on the negative slope of each half.
      >
      > Creating an arbitrary frequency (like 5.379 MHz) is very difficult with binary division of a clock. There is no direct way to divide by anything other than whole numbers so the very first bit divides the clock in half. What is needed is a phase locked loop (PLL) which can generate somewhat arbitrary frequencies by first multiplying the incoming clock up to, say, 600 MHz and then dividing. The limiting factor is how fast the voltage controlled oscillator (VCO) can run.
      >
      > And I think that is what the signal generator chips are all about.
      >
      > Richard
      >
      >
      > --- In Electronics_101@yahoogroups.com, Gavin Dingley <gavin.dingley@> wrote:
      > >
      > > Well, you could use a
      > > microcontroller in the first place; with such a low frequency you can
      > > use pulse width modulation, with a pulse frequency of ten times the
      > > highest frequency of interest. As a first cut you could use a Aduino,
      > > which has analogue ouputs that are pwm. Write a program that generates
      > > the sine wave values and send them to one of the analogue pins, then a
      > > low pass filter is used that has a cut-off at the pwm frequency, which
      > > should give use the desired waveform.
      > >
      > > Gavin
      > >
      > >
      > > ________________________________
      > > From: orvillefpike <orvillefpike@>
      > > To: Electronics_101@yahoogroups.com
      > > Sent: Tuesday, 4 October 2011, 16:16
      > > Subject: [Electronics_101] 2mHz to 6mHz signal generator
      > >
      > >
      > >  
      > > Is there an IC that could generate a signal from 2mHz to 6mHz?
      > > Ideally this IC could be controlled by a microcontroller, but this is not a must.
      > >
      > > Thanks
      > >
      > >
      > >
      > >
      > > [Non-text portions of this message have been removed]
      > >
      >
    • orvillefpike
      The PWM from a uC wouldn t work because, as stated, the frequencies selection is too coarse. A uC controlled oscillator, like a AD9833, could work though. I
      Message 33 of 33 , Oct 16, 2011
        The PWM from a uC wouldn't work because, as stated, the frequencies selection is too coarse. A uC controlled oscillator, like a AD9833, could work though.
        I think I solved the oscillator problem, for now, by using a 74HC4046. Now my problem is, I want to drive the two legs of a center tap transformer and feeding each leg alternatively with a positive pulse and I also need a dead time so the two transistor don't conduct at the same time.
        A SG3525 would do if it went hihg enough in frequency.

        --- In Electronics_101@yahoogroups.com, "rtstofer" <rstofer@...> wrote:
        >
        > This might be possible with one of the DSS capable microcontrollers like the Analog Devices Blackfin but I don't think it is possible with just an Arduino.
        >
        > The Arduino runs at 16 MHz (Blackfin at 500 MHz) and if we wanted only 8 steps in a synthesized sine wave of 6 MHz we would need to set the analog output at a 48 MHz rate. And that's just 4 steps on the positive side and 4 steps on the negative side of the sine wave. Or, 2 steps on the rising slope and 2 steps on the negative slope of each half.
        >
        > Creating an arbitrary frequency (like 5.379 MHz) is very difficult with binary division of a clock. There is no direct way to divide by anything other than whole numbers so the very first bit divides the clock in half. What is needed is a phase locked loop (PLL) which can generate somewhat arbitrary frequencies by first multiplying the incoming clock up to, say, 600 MHz and then dividing. The limiting factor is how fast the voltage controlled oscillator (VCO) can run.
        >
        > And I think that is what the signal generator chips are all about.
        >
        > Richard
        >
        >
        > --- In Electronics_101@yahoogroups.com, Gavin Dingley <gavin.dingley@> wrote:
        > >
        > > Well, you could use a
        > > microcontroller in the first place; with such a low frequency you can
        > > use pulse width modulation, with a pulse frequency of ten times the
        > > highest frequency of interest. As a first cut you could use a Aduino,
        > > which has analogue ouputs that are pwm. Write a program that generates
        > > the sine wave values and send them to one of the analogue pins, then a
        > > low pass filter is used that has a cut-off at the pwm frequency, which
        > > should give use the desired waveform.
        > >
        > > Gavin
        > >
        > >
        > > ________________________________
        > > From: orvillefpike <orvillefpike@>
        > > To: Electronics_101@yahoogroups.com
        > > Sent: Tuesday, 4 October 2011, 16:16
        > > Subject: [Electronics_101] 2mHz to 6mHz signal generator
        > >
        > >
        > >  
        > > Is there an IC that could generate a signal from 2mHz to 6mHz?
        > > Ideally this IC could be controlled by a microcontroller, but this is not a must.
        > >
        > > Thanks
        > >
        > >
        > >
        > >
        > > [Non-text portions of this message have been removed]
        > >
        >
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