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From: John Woodgate
Subject: Re: How generate a 3phase sine wave ?
Date: Wed, 6 Nov 2002 16:24:34 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Wed, 6 Nov 2002 17:38:30 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Sparky wrote (in
) about 'How generate a 3phase sine wave
?', on Wed, 6 Nov 2002:
>"john" wrote in message
>> Could anyone help? I have to generate a three phase sine wave signal
>> that composes of three component, with 120 degree phase different
>> between any two components. The frequency of it has to be adjustable,
>> say from 0Hz to 5Hz. The signal will be amplified for driving some
>> device. I have no idea to start at all, could anyone help and show me
>> some hints. Is there any commercial product available for such ?
>Easiest way is probably a microcontroller with 3 dacs.
>You need a sine lookup table, you only need the first quadrant values, the
>other three quadrants can be generated by inversions.
>Basically have an n bit counter running at 2^n *4 * your output frequency.
>This output via the lookup generates your reference phase via dac1.
>The other 2 phases are generated by adding (2^n*4)/3 and (2^n*4)*(2/3)
>respectively tothe reference, and outputing via dac2 and dac3.
>In the good old days I would have used counters/adders and muxes to drive
>the LUT and dac's.
I'd very much like to see a 3-phase 0 Hz supply. (;-)
I agree that a digital solution is the right one here. You can get into
AWFUL problems with analogue at such low frequencies.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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