3 phase from func.gen. IC
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From: Bill Sloman on 11 Mar 2010 17:24 On Mar 10, 6:17 pm, Bill Sloman <bill.slo...(a)ieee.org> wrote: > 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... > > but a bit of trigometry with an AD9854 - which nominally generates > pairs of outputs in quadrature - might do the job for less money. http://en.wikipedia.org/wiki/Trigonometric_functions sin(x + y) = sin x. cos y + cos x.sin y sin(2.pi.t + 3.pi/2) = sin(2.pi.t).cos(2.pi/3) + cos(2.pi.t). sin(2.pi/3) = sin(2.pi.t).-0.5 + cos(2.pi.t). 0.866025403 which you can get with a summing amplifier, as you can with sin(2.pi.t + 4.pi/3) -- Bill Sloman, Nijmegen
From: Jamie on 11 Mar 2010 18:15 JW wrote: > On Wed, 10 Mar 2010 19:33:19 -0500 Jamie > <jamie_ka1lpa_not_valid_after_ka1lpa_(a)charter.net> wrote in Message id: > <0AWln.78156$K81.64778(a)newsfe18.iad>: > > >>Learn to code a uC chip... A Pic, AVR, ATEML, ARm etc.. >>that has at least 3 ADC outputs.. > > > ADC outputs? Do you mean DAC? Yes, of course ;)
From: Jamie on 11 Mar 2010 18:23 Michael A. Terrell wrote: > JW wrote: > >>On Wed, 10 Mar 2010 19:33:19 -0500 Jamie >><jamie_ka1lpa_not_valid_after_ka1lpa_(a)charter.net> wrote in Message id: >><0AWln.78156$K81.64778(a)newsfe18.iad>: >> >> >>>Learn to code a uC chip... A Pic, AVR, ATEML, ARm etc.. >>>that has at least 3 ADC outputs.. >> >>ADC outputs? Do you mean DAC? > > > > He never knows what he means. > > I think you should be the last one, commenting on that.
From: VWWall on 11 Mar 2010 18:03 Bill Sloman wrote: > On Mar 10, 6:17 pm, Bill Sloman <bill.slo...(a)ieee.org> wrote: >> 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... >> >> but a bit of trigometry with an AD9854 - which nominally generates >> pairs of outputs in quadrature - might do the job for less money. > > http://en.wikipedia.org/wiki/Trigonometric_functions > > sin(x + y) = sin x. cos y + cos x.sin y > > sin(2.pi.t + 3.pi/2) = sin(2.pi.t).cos(2.pi/3) + cos(2.pi.t). > sin(2.pi/3) > > = sin(2.pi.t).-0.5 + cos(2.pi.t). 0.866025403 > > which you can get with a summing amplifier, as you can with sin(2.pi.t > + 4.pi/3) > Once you've got two sine waves in quadrature, getting three phase is simple. Just use a Scott-T transformer. These were once use for power applications, but since two phase power is almost extinct, they are now used for connecting servos that use synchros to those with resolvers. http://en.wikipedia.org/wiki/Scott-T_transformer -- Virg Wall, P.E.
From: Michael A. Terrell on 11 Mar 2010 18:57
Jamie wrote: > > Michael A. Terrell wrote: > > > JW wrote: > > > >>On Wed, 10 Mar 2010 19:33:19 -0500 Jamie > >><jamie_ka1lpa_not_valid_after_ka1lpa_(a)charter.net> wrote in Message id: > >><0AWln.78156$K81.64778(a)newsfe18.iad>: > >> > >> > >>>Learn to code a uC chip... A Pic, AVR, ATEML, ARm etc.. > >>>that has at least 3 ADC outputs.. > >> > >>ADC outputs? Do you mean DAC? > > > > > > > > He never knows what he means. > > > > > I think you should be the last one, commenting on that. When did you start thinking? -- Lead free solder is Belgium's version of 'Hold my beer and watch this!' |