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  1. #1
    Full Member level 4
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    atferrari's Avatar
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    Jun 2004
    Buenos Aires - Argentina
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    dual triphasic sinusoidal signal generator

    After extensively googling I found no valid circuit to generate two sets of triphasic sinusoidal signals simulating the V of a genset and its load.

    It should be able to change phase of I wrt V. Peak value 3 to 5 V is enough. I feel that something with shif registers would be the way to go. If ready made, would be better.

    Taking signals from real life, is a no no in this case.

    Thanks for suggestions.

    Agustín Tomás

    •   Alt25th August 2006, 13:13



  2. #2
    Advanced Member level 5
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    VVV's Avatar
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    Nov 2004
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    Re: dual triphasic sinusoidal signal generator

    I would use two sets of DACs. TI has some quad parts. Many other manufacturers have dual parts. Most of these parts have a pin that enables you to update all the DACs in the package at the same time (you write the data serially for each DAC, but the output does not get updated; when you have written the data to all DACs you drive the update or SYNC pin and all the DACs change their outputs).

    Using a micro with 6 DACs (two or three packages) , you can build your circuit. All the micro has to do is have a lookup table and some pointers for the sine output value. Shifting the waveforms means simply intitalizing the pointers of the "current" waveforms to another location in the array.

    Examples of dual DACs are the DAC082S085, DAC102S085, DAC122S085 from National. the /SYNC pin does what you need. The 8-bit parts are not too expensive, either.

    The only small problem with this approach is that it produces waveforms that have a DC component equal to half the supply voltage (+2.5V).
    To remove it, you would have to either use capacitive coupling, or use some opamps to add a negative offset (and possibly gainO to each of the waveforms. Capacitive coupling works fine if the loads connected to the circuit are not too heavy. A scope, for example, would be just fine.

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