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'[EE] how to obtain cosine'
2006\06\02@083217
by
Dorsey Fahlstedt
Hi group,
What would be an easy way to obtain a 90 degrees phase shift
from a transformer output (50/60Hz)
Thanks
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2006\06\02@110840
by
Russell McMahon
> What would be an easy way to obtain a 90 degrees phase shift
> from a transformer output (50/60Hz)
Pure L or pure C gives this. Not sensibly realisable in most cases.
In practice multiple stages with less shift per stage may be used.
Using active components this can be done very easily.
or you could do it digitally.
Or ...
You really need to provide more information about what you need to
achieve with what.
RM
2006\06\02@114948
by
Harold Hallikainen
>> What would be an easy way to obtain a 90 degrees phase shift
>> from a transformer output (50/60Hz)
>
>
> Pure L or pure C gives this. Not sensibly realisable in most cases.
>
> In practice multiple stages with less shift per stage may be used.
>
> Using active components this can be done very easily.
>
> or you could do it digitally.
>
> Or ...
>
> You really need to provide more information about what you need to
> achieve with what.
>
The pure L or pure C approach would be an integrator or differentiator.
You could have the sine wave drive a capacitor whose other side is
connected to an op amp current to voltage converter (noninverting input
grounded, feedback from output to inverting input, capacitor connects to
inverting input). The output will be the inverted derivative of the input.
The derivative of a sine wave leads by 90 degrees. When inverted, it
appears to lag by 90 degrees. The differentiator has a 6dB/octave
(20dB/decade) rising frequency response. This can be limited by putting a
small resistor in series with the capacitor (making it not an ideal
differentiator, but will be close at frequencies far below 1/(2*pi*R*C)
where R is the added resistor.
Similarly, integrating a sine wave results in a lag of 90 degrees with a
6dB/octave falling frequency response. You can make an inverting
integrator by grounding the noninverting input of an op amp, putting a
capacitor between the inverting input and output, then a resistor from the
noninverting input to your sine source. The integrator "accumulates" the
voltage over time, so any DC offsets (and there will be some) will result
in the integrator ramping towards the rails over time. This can be limited
by putting a resistor across the capacitor, which limits the frequency
response at very low frequencies (like DC). The frequency response of the
integrator approaches infinity as the input frequency approaches zero.
Finally, this is an inverting integrator, so the output lags the input by
90 degrees, but is inverted, so it appears to lead by 90 degrees.
Harold

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2006\06\02@123233
by
Spehro Pefhany

At 01:32 PM 6/2/2006 +0100, you wrote:
>Hi group,
>What would be an easy way to obtain a 90 degrees phase shift
>from a transformer output (50/60Hz)
>Thanks
At a fixed frequency (eg. 50Hz *or* 60Hz) you could use a simple
RC low pass filter. Or an LC filter, but inductors for such low frequencies
tend to be bulky and expensive. If the frequency varies, the phase shift
and output amplitude will change.
For a wider range, an allpass filter can be used, for example:
http://www.maximic.com/appnotes.cfm/appnote_number/112
Hilbert transformers can be implemented digitally or with analog means,
and can be designed to work over a given frequency range.
If you need high power, as to run a 2phase motor, the AC can be rectified,
filtered, and converted back to AC to generate what you want. Usually a
2phase ("split phase") motor uses a simple run capacitor for the phase shift.
I'm really just guessing at your needs, it really depends what you are up to,
but searching on some of terms I've mentioned above should allow you to get
started.
>Best regards,
Spehro Pefhany "it's the network..." "The Journey is the reward"
spam_OUTspeffTakeThisOuTinterlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
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2006\06\02@124538
by
Marcel duchamp
Harold Hallikainen wrote:
>>>What would be an easy way to obtain a 90 degrees phase shift
>>>from a transformer output (50/60Hz)
>>
If you have a transformer with a center tapped secondary, (or two
secondaries that can be wired this way), then with one RC network, you
can generate a signal with 0 to 180 degrees of phase shift.
Label the secondary as X = top, Y = center tap and Z = bottom.
Place a resistor from X to a capacitor that then goes to Z. Label the rc
junction as the Output.
Take your signal from Y to the Output. As the resistor value is
adjusted, the phase *relative to one end of the transformer* will vary
from in phase to 180 degrees out of phase. Somewhere in the "middle"
will be found the 90 degree point.
2006\06\02@124954
by
Steve Smith
With a 3 phase system :
Use a star delta tx this will give you 30 deg shift. Add red and blue this
gives 120 deg shift (12030=90) ups sensing circuit for control electronics
(1 x lm348) or scott wound transformer for power...
Or rectify then invert (speed controller with mods..)
Steve ..
Original Message
From: .....piclistbouncesKILLspam@spam@mit.edu [piclistbouncesKILLspammit.edu] On Behalf Of
Dorsey Fahlstedt
Sent: 02 June 2006 13:32
To: .....piclistKILLspam.....mit.edu
Subject: [EE] how to obtain cosine
Hi group,
What would be an easy way to obtain a 90 degrees phase shift
from a transformer output (50/60Hz)
Thanks
Send instant messages to your online friends http://uk.messenger.yahoo.com
2006\06\02@125505
by
Dwayne Reid

At 06:32 AM 6/2/2006, Dorsey Fahlstedt wrote:
>What would be an easy way to obtain a 90 degrees phase shift
>from a transformer output (50/60Hz)
An easy way starts off with a highvoltage AC signal, followed by a
RC low pass filter. My early dimmers used to do this to get an
almost perfect 90 degree phase shift.
The stuff I did back then was optimized for 120Vac line. Assuming
neutral is circuit common, 470K resistor from 120Vac input to 100n
film capacitor, other end of capacitor tied to circuit
common. Adjust value of R so that signal on capacitor is desired
amplitude (12V pp in the design I did way back then). Then add
another resistor of equal value from 12V rail to junction of R & C to
shift the bias point to midsupply.
Simple, easy, very effective.
Note: this was on a design that was completely optoisolated from any
outsideworld terminals that an enduser could touch (linepowered
type of stuff).
dwayne

Dwayne Reid <EraseMEdwaynerspam_OUTTakeThisOuTplanet.eon.net>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 4893199 voice (780) 4876397 fax
Celebrating 22 years of Engineering Innovation (1984  2006)
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2006\06\02@150456
by
Dorsey Fahlstedt

> If you have a transformer with a center tapped secondary, (or two
> secondaries that can be wired this way), then with one RC network, you
> can generate a signal with 0 to 180 degrees of phase shift.
>
> Label the secondary as X = top, Y = center tap and Z = bottom.
>
> Place a resistor from X to a capacitor that then goes to Z. Label the rc
> junction as the Output.
>
> Take your signal from Y to the Output. As the resistor value is
> adjusted, the phase *relative to one end of the transformer* will vary
> from in phase to 180 degrees out of phase. Somewhere in the "middle"
> will be found the 90 degree point.
Hi, I will try to do this, do you mean that the phase shift will be relative
to Vxz ? or to Vxy ?
p.s.
The reason for my question is that I want to see this circle when connecting
sine and cosine in scope xy mode, just curious to see it.
Thanks

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2006\06\02@152100
by
Herbert Graf

On Fri, 20060602 at 20:04 +0100, Dorsey Fahlstedt wrote:
{Quote hidden}> > If you have a transformer with a center tapped secondary, (or two
> > secondaries that can be wired this way), then with one RC network, you
> > can generate a signal with 0 to 180 degrees of phase shift.
> >
> > Label the secondary as X = top, Y = center tap and Z = bottom.
> >
> > Place a resistor from X to a capacitor that then goes to Z. Label the rc
> > junction as the Output.
> >
> > Take your signal from Y to the Output. As the resistor value is
> > adjusted, the phase *relative to one end of the transformer* will vary
> > from in phase to 180 degrees out of phase. Somewhere in the "middle"
> > will be found the 90 degree point.
>
> Hi, I will try to do this, do you mean that the phase shift will be relative
> to Vxz ? or to Vxy ?
>
> p.s.
> The reason for my question is that I want to see this circle when connecting
> sine and cosine in scope xy mode, just curious to see it.
Well, for something like at just using a cap will give you something
close to a circle. Try different caps to see the difference.
TTYL
2006\06\02@153737
by
Spehro Pefhany

At 03:21 PM 6/2/2006 0400, you wrote:
{Quote hidden}>On Fri, 20060602 at 20:04 +0100, Dorsey Fahlstedt wrote:
> > > If you have a transformer with a center tapped secondary, (or two
> > > secondaries that can be wired this way), then with one RC network, you
> > > can generate a signal with 0 to 180 degrees of phase shift.
> > >
> > > Label the secondary as X = top, Y = center tap and Z = bottom.
> > >
> > > Place a resistor from X to a capacitor that then goes to Z. Label
> the rc
> > > junction as the Output.
> > >
> > > Take your signal from Y to the Output. As the resistor value is
> > > adjusted, the phase *relative to one end of the transformer* will vary
> > > from in phase to 180 degrees out of phase. Somewhere in the "middle"
> > > will be found the 90 degree point.
> >
> > Hi, I will try to do this, do you mean that the phase shift will be
> relative
> > to Vxz ? or to Vxy ?
> >
> > p.s.
> > The reason for my question is that I want to see this circle when
> connecting
> > sine and cosine in scope xy mode, just curious to see it.
>
>Well, for something like at just using a cap will give you something
>close to a circle. Try different caps to see the difference.
Use a series R and C to ground for X channel and
series C and R to ground for Y channel (you could reverse the two, of course).
Use 27K and a 0.1uF film cap for the R & C in both cases.
>Best regards,
Spehro Pefhany "it's the network..." "The Journey is the reward"
speffspam_OUTinterlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
>>Test equipment, parts OLED displys http://search.ebay.com/_W0QQsassZspeff
2006\06\02@155324
by
Peter
On Fri, 2 Jun 2006, Dorsey Fahlstedt wrote:
> Hi group,
> What would be an easy way to obtain a 90 degrees phase shift
> from a transformer output (50/60Hz)
> Thanks
A RC group (two R and two C is easiest)
Peter
2006\06\05@075042
by
Dorsey Fahlstedt
> If you have a transformer with a center tapped secondary, (or two
> secondaries that can be wired this way), then with one RC network, you
> can generate a signal with 0 to 180 degrees of phase shift.
>
> Label the secondary as X = top, Y = center tap and Z = bottom.
>
> Place a resistor from X to a capacitor that then goes to Z. Label the rc
> junction as the Output.
>
> Take your signal from Y to the Output. As the resistor value is
> adjusted, the phase *relative to one end of the transformer* will vary
> from in phase to 180 degrees out of phase. Somewhere in the "middle"
> will be found the 90 degree point.
>
Do you have some theory behind this? I would like to understand how
it works before building it.
thanx.
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2006\06\05@113020
by
Marcel Duchamp

part 0 44 bytes
his is a multipart message in MIME format.
part 1 1571 bytes contenttype:text/plain; charset=ISO88591; format=flowed (decoded 7bit)
Dorsey Fahlstedt wrote:
{Quote hidden}>>If you have a transformer with a center tapped secondary, (or two
>> secondaries that can be wired this way), then with one RC network, you
>> can generate a signal with 0 to 180 degrees of phase shift.
>>
>> Label the secondary as X = top, Y = center tap and Z = bottom.
>>
>> Place a resistor from X to a capacitor that then goes to Z. Label the rc
>>junction as the Output.
>>
>>Take your signal from Y to the Output. As the resistor value is
>>adjusted, the phase *relative to one end of the transformer* will vary
>>from in phase to 180 degrees out of phase. Somewhere in the "middle"
>>will be found the 90 degree point.
>>
>
>
>
>
> Do you have some theory behind this? I would like to understand how
> it works before building it.
> thanx.
I'm not so great at explaining this stuff but maybe a graphic analysis
will help. In the attached gif, the bottom line XYZ represents the
center tapped secondary. VR is the voltage on the resistor, VC is the
voltage on the capacitor and VO is the output voltage.
The phase angle is ALPHA. As the R and C values change (for a fixed
input frequency), the VO vector will sweep out a 180 degree angle.
THETA represents the phase angle obtained from just the RC components.
If anyone sees a mistake here, please by all means, point it out.
Derivation of the pertinent equations is left as an exercise for the
student.
part 2 4043 bytes contenttype:image/gif; (decode)
part 3 35 bytes contenttype:text/plain; charset="usascii"
(decoded 7bit)
2006\06\07@160050
by
Barry Gershenfeld
>p.s.
>The reason for my question is that I want to see this circle when connecting
>sine and cosine in scope xy mode, just curious to see it.
Agree! That was me, 30 years ago after I got my first 'scope. And...there
was a magazine article where they took some zener diodes, and clipped the
waveforms...and made a square! I just HAD to try that one.
Barry
2006\06\16@090932
by
Dorsey Fahlstedt

{Quote hidden}> >>If you have a transformer with a center tapped secondary, (or two
> >> secondaries that can be wired this way), then with one RC network, you
> >> can generate a signal with 0 to 180 degrees of phase shift.
> >>
> >> Label the secondary as X = top, Y = center tap and Z = bottom.
> >>
> >> Place a resistor from X to a capacitor that then goes to Z. Label the rc
> >>junction as the Output.
> >>
> >>Take your signal from Y to the Output. As the resistor value is
> >>adjusted, the phase *relative to one end of the transformer* will vary
> >>from in phase to 180 degrees out of phase. Somewhere in the "middle"
> >>will be found the 90 degree point.
> >>
> >
> >
> >
> >
> > Do you have some theory behind this? I would like to understand how
> > it works before building it.
> > thanx.
>
> I'm not so great at explaining this stuff but maybe a graphic analysis
> will help. In the attached gif, the bottom line XYZ represents the
> center tapped secondary. VR is the voltage on the resistor, VC is the
> voltage on the capacitor and VO is the output voltage.
>
> The phase angle is ALPHA. As the R and C values change (for a fixed
> input frequency), the VO vector will sweep out a 180 degree angle.
> THETA represents the phase angle obtained from just the RC components.
>
> If anyone sees a mistake here, please by all means, point it out.
>
> Derivation of the pertinent equations is left as an exercise for the
> student.
>
I got VO= V * ( JWCR  1) / ( 1  W^2 * C^2 * R^2 )
Is this correct?

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