3 phase from func.gen. IC
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From: Bill Sloman on 10 Mar 2010 12:17 On Mar 10, 5:42 pm, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Wed, 10 Mar 2010 10:52:55 GMT, kevinl...(a)hartley.com (Kevin Lang) > wrote: > > >What would be the simplest way to derive a simultaneous three phase > >output from a sine wave produced by a single function generator IC ... > >that does not change as the frequency is varied? > > >Specifically, two additional sinewaves remaining 120 and 240 degrees > >out of phase with the original as the frequency is varied between > >100Hz and 1KHz. > > >Kevin Lang > > Given a single-phase sine wave as input, you could make an all-pass > network that would give two outputs that are 90 degree phase shifted > at all frequencies, then do some analog summing to make 120 and 240. > There are some allpass phase shifter circuits used in ham-radio type > SSB transmitters that aren't too horrible. > > It could also be done with an integrator to make a 90 degree shift, > some sort of AGC to restore the amplitude, and some analog mixing. > > And a few other terrible ways. > > But it's probably easier to build a generator that inherently makes > quadrature or 3-phase sine waves. Analog Devices do multi-output DDS chips that would probably do the job. A quick look suggests that a pair of synchronised AD9958 chips would do the job http://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/ad9958/products/product.html but a bit of trigometry with an AD9854 - which nominally generates pairs of outputs in quadrature - might do the job for less money. -- Bill Sloman, Nijmegen
From: Tim Wescott on 10 Mar 2010 12:19 Kevin Lang wrote: > What would be the simplest way to derive a simultaneous three phase > output from a sine wave produced by a single function generator IC ... > that does not change as the frequency is varied? > > Specifically, two additional sinewaves remaining 120 and 240 degrees > out of phase with the original as the frequency is varied between > 100Hz and 1KHz. > > Kevin Lang No one's answered your question yet. Phase lock two function generators together, 90 degrees apart, and use resistor networks to generate the +120 and -120 degree shifted sines. This assumes that you can make one of them the slave. Or if you must have three individual signals (maybe you want one sine, one triangle, and one square?), then phase lock two generators to the one, with appropriate phase offset. But I think most folks feel you asked the wrong question... Had you asked "3 phase from some collection of integrated circuits" then most of the other answers you've gotten would be better: make something up. Either make it digital, using a DDS chip if you need signals up to the MHz range, or using a microcontroller if you just need signals up through the audio. Or make it analog, with a three-stage circuit that produces a 120 degree lag (or an inversion and a 60 degree lag) at each stage, with some sort of AGC on at least one stage and all three stage's frequency-determining components ganged. Or make a two-stage circuit with 90 degrees shift in each stage and an overall 180 degree inversion. I'll bet that with care and some thinking you could come up with a Wien bridge circuit that'd put out pair of signals in quadrature at the same amplitude, then you could use your resistor network to get your three phases. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
From: whit3rd on 10 Mar 2010 16:00 On Mar 10, 2:52 am, kevinl...(a)hartley.com (Kevin Lang) wrote: > What would be the simplest way to derive a simultaneous three phase > output from a sine wave produced by a single function generator IC ... > ...l as the frequency is varied between > 100Hz and 1KHz. The only easy way uses four function generator ICs. Run one at 6x the frequency you want (easy, just select a smaller integrator capacitor), and divide down its square wave with three stages of twisted-ring-counter connected flip/flops. That gives you three accurate phases of square waves, and an approximate current-program source to run the slaves. Then using the same control current for the three slave generators, phase or pulse-lock them each to one of the square wave phases. Injecting an error signal current into pin 7 of XR2206 would be a typical ploy. XOR gates and RC filters are adequate phase comparators for the square wave outputs of generators.
From: Jamie on 10 Mar 2010 19:33 Kevin Lang wrote: > What would be the simplest way to derive a simultaneous three phase > output from a sine wave produced by a single function generator IC ... > that does not change as the frequency is varied? > > Specifically, two additional sinewaves remaining 120 and 240 degrees > out of phase with the original as the frequency is varied between > 100Hz and 1KHz. > > Kevin Lang Learn to code a uC chip... A Pic, AVR, ATEML, ARm etc.. that has at least 3 ADC outputs.. The smaller family chips use a PWM (Pulse width modulator) that can form a Sin wave on the output.. You code the math to generate the first base sine and then, offset the other outputs at the proper angle.
From: John Fields on 10 Mar 2010 20:44
On Wed, 10 Mar 2010 21:56:59 +0530, "pimpom" <pimpom(a)invalid.invalid> wrote: >Kevin Lang wrote: >> What would be the simplest way to derive a simultaneous three >> phase >> output from a sine wave produced by a single function generator >> IC ... >> that does not change as the frequency is varied? >> >> Specifically, two additional sinewaves remaining 120 and 240 >> degrees >> out of phase with the original as the frequency is varied >> between >> 100Hz and 1KHz. >> >> Kevin Lang > >How about this: >http://www.techbriefs.com/content/view/1839/32/ --- That doesn't supply the OP's request for something which will generate two sine waves displaced from a driving sine wave by +/- 120 degrees. It does, however, provide a way to generate three sine waves displaced from each other by 120 degrees which is way more complex than the way I posted. JF |