High Frequency Component in Square Wave questions
emma
I learnt that square waves for examples produced by power
interver has high frequency components. What's the typical
value of the frequency supposed the source is 110 volts,
60 hertz. Is there no way to remove the high frequency
components? How does it affect the load?
emma
ji...@specsol.spam.sux.com
> emma
http://en.wikipedia.org/wiki/Square_wave
http://www.allaboutcircuits.com/vol_2/chpt_7/2.html
--
Jim Pennino
Remove .spam.sux to reply.
St. John Smythe
> I learnt that square waves for examples produced by power
> interver has high frequency components.
Yes. That's what makes them square waves. Remove the high frequency
components, and you have sine waves.
> What's the typical
> value of the frequency supposed the source is 110 volts,
> 60 hertz.
Theoretically, multiple frequencies, extending to infinity.
> Is there no way to remove the high frequency
> components?
Yes, but not if you want to continue to have a square wave.
--
St. John
Uncle Al
Bandpass filter.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
mme...@cars3.uchicago.edu
>Hi,
>
>I learnt that square waves for examples produced by power
>interver has high frequency components.
Of course. They have to.
> What's the typical
>value of the frequency supposed the source is 110 volts,
>60 hertz.
There is no such thing as "typical value", it depends how close to
suare you want them to be.
> Is there no way to remove the high frequency
>components?
Of course. You can filter away all but the fundamental. In which
case you're back to a sine wave.
> How does it affect the load?
>
That depends on the load.
Mati Meron | "When you argue with a fool,
me...@cars.uchicago.edu | chances are he is doing just the same"
Solarman
>
> Hi,
>
> I learnt that square waves for examples produced by power
> interver has high frequency components.
That's why radios don't work well on with square wave A.C.
> What's the typical value of the frequency supposed the
> source is 110 volts, 60 hertz.
> Is there no way to remove the high frequency
> components? How does it affect the load?
>
The more expensive invertors let you switch from
square wave to sine wave when you want to run
something like a radio.
Power efficiency comes at a cost.
http://www.solarexpert.com/PVinvtinfo.html
Tm
"Uncle Al" <Uncl...@hate.spam.net> wrote in message
news:42C1FE4B...@hate.spam.net...
> emma wrote:
>>
>> Hi,
>>
>> I learnt that square waves for examples produced by power
>> interver has high frequency components. What's the typical
>> value of the frequency supposed the source is 110 volts,
>> 60 hertz. Is there no way to remove the high frequency
>> components? How does it affect the load?
>
> Bandpass filter.
>
start with if you expect to get a 110 volt sine.
TM
emma
I tried building a power inveter using two transistors as push-pull..
meaning if one is one, the other is off, this is connected to
12-0-12 transformer to produce 110 volts.
So as I understand it, when the transistor is in saturation, the
current is supposed to form the square wave amplitude. It is
not possible to raise it instantaneously that's why there is an
increasing effect. Now how does the high frequency component
got generated?? Also when it is in the maximum amplitude, how
does it generate the high frequency component in the square
waves?
What would it take to build a square wave power inverter that
totally eliminate the high frequencies riding in the square wave??
Thanks.
emma
Jerry
> Guys,
>
> I tried building a power inveter using two transistors as push-pull..
> meaning if one is one, the other is off, this is connected to
> 12-0-12 transformer to produce 110 volts.
>
> So as I understand it, when the transistor is in saturation, the
> current is supposed to form the square wave amplitude. It is
> not possible to raise it instantaneously that's why there is an
> increasing effect. Now how does the high frequency component
> got generated?? Also when it is in the maximum amplitude, how
> does it generate the high frequency component in the square
> waves?
Try playing around with this Java applet:
http://www.aw-bc.com/ide/Media/JavaTools/srfoursq.html
If your browser doesn't support Java, read these
explanations:
http://cnx.rice.edu/content/m0041/latest/
http://www.geocities.com/ac_dc_ac/FourierEng.html
> What would it take to build a square wave power inverter that
> totally eliminate the high frequencies riding in the square wave??
Jerry
St. John Smythe
> What would it take to build a square wave power inverter that
> totally eliminate the high frequencies riding in the square wave??
A repeal of some fundamental physical laws. As has already been
explained to you, when you remove the high frequencies, you no longer
Jan Panteltje
<mrandmrsr...@yahoo.com> wrote in
<1120009031.5...@g43g2000cwa.googlegroups.com>:
>Hi,
>
>I learnt that square waves for examples produced by power
>interver has high frequency components.
Any square wave can be thought of as an infinite amount of sine waves.
In practice you will have some harmonics, f, 2f, 3f, 4f etc.
Look up Fourier analysis.
Some inverters make a near square wave, some a modulated pulse width
that is filtered into an approximate sine wave, some just combine some
smaller square waves to make something that looks a bit like a sine.
Some make really good sine waves.
>What's the typical
>value of the frequency supposed the source is 110 volts,
>60 hertz.
120, 180, 240, 300, etc, with varying amplitude.
>Is there no way to remove the high frequency
>components? How does it affect the load?
Yes, LC filter, but you will lose some power.
If you for some reason need a pure sine wave, get a converter that does that.
Many applications / appliances do not need a real good sine wave, as these
have their own power processing / power supplies - those could handle square
waves even.
In fact in some cases square wave could be beneficial.
emma
Jan Panteltje wrote:
> On a sunny day (28 Jun 2005 18:37:11 -0700) it happened "emma"
> <mrandmrsr...@yahoo.com> wrote in
> <1120009031.5...@g43g2000cwa.googlegroups.com>:
>
> >Hi,
> >
> >I learnt that square waves for examples produced by power
> >interver has high frequency components.
> Any square wave can be thought of as an infinite amount of sine waves.
> In practice you will have some harmonics, f, 2f, 3f, 4f etc.
> Look up Fourier analysis.
>
> Some inverters make a near square wave, some a modulated pulse width
> that is filtered into an approximate sine wave, some just combine some
> smaller square waves to make something that looks a bit like a sine.
> Some make really good sine waves.
>
>
> >What's the typical
> >value of the frequency supposed the source is 110 volts,
> >60 hertz.
> 120, 180, 240, 300, etc, with varying amplitude.
>
> >Is there no way to remove the high frequency
> >components? How does it affect the load?
> Yes, LC filter, but you will lose some power.
So the high frequency can be removed. I thought they can't.
How complicated is the LC filter design to remove 100% of
the high frequency component in the square wave?
>
> If you for some reason need a pure sine wave, get a converter that does that.
>
> Many applications / appliances do not need a real good sine wave, as these
> have their own power processing / power supplies - those could handle square
> waves even.
> In fact in some cases square wave could be beneficial.
In pure line Alternating Current (sine wave) from power companies.
Is there any high frequency component in the sine wave or is it
pure 100% 60 Hz AC??
emma
Jan Panteltje
<mrandmrsr...@yahoo.com> wrote in
<1120042632.4...@z14g2000cwz.googlegroups.com>:
>So the high frequency can be removed. I thought they can't.
>How complicated is the LC filter design to remove 100% of
>the high frequency component in the square wave?
There are 2 ways, one is a low pass filter, the other a resonant
system.
Low pass is the simplest, it filters out everything above 60Hz
in this case.
It could be as simple as an inductor (L) in series with a capacitor
to ground.
But there are a lot of catches....
For this reason it will almost always be simpler to buy a converter that
already outputs a -reasonable- sine wave, simpler and cheaper then
designing and building one (given some initial likely failures).
First you will have to decide how 'pure' your sine wave should be.
How much power from harmonics should be allowed?
Perhaps it would be better if you specified what you need the
output for (what sort of equipment).
>In pure line Alternating Current (sine wave) from power companies.
>Is there any high frequency component in the sine wave or is it
>pure 100% 60 Hz AC??
It is a pure sine wave, but because of various loads it will carry
some distortion.
For example thyristor controlled devices can cause pulses, some
power companies send extra higher frequency signals over it for control,
some even for internet these days.
A TV with a rectifier will cause flat tops on the sine wave.
So do not expect a very clean wave!
Neither is the voltage always exact.
emma
Jan Panteltje wrote:
> On a sunny day (29 Jun 2005 03:57:12 -0700) it happened "emma"
> <mrandmrsr...@yahoo.com> wrote in
> <1120042632.4...@z14g2000cwz.googlegroups.com>:
>
> >So the high frequency can be removed. I thought they can't.
> >How complicated is the LC filter design to remove 100% of
> >the high frequency component in the square wave?
> There are 2 ways, one is a low pass filter, the other a resonant
> system.
> Low pass is the simplest, it filters out everything above 60Hz
> in this case.
> It could be as simple as an inductor (L) in series with a capacitor
> to ground.
> But there are a lot of catches....
> For this reason it will almost always be simpler to buy a converter that
> already outputs a -reasonable- sine wave, simpler and cheaper then
> designing and building one (given some initial likely failures).
>
> First you will have to decide how 'pure' your sine wave should be.
> How much power from harmonics should be allowed?
>
> Perhaps it would be better if you specified what you need the
> output for (what sort of equipment).
The output is feed to a resistive coil. I'm analyzing the magnetic
field produced by plotting it in 3D.
Suppose I have pure AC from the power lines. How would I add
high frequency component to it? Suppose I want to add 300 Hz
to ride on the sine wave, any idea how I can do that??
Another. Suppose I feed a function generator to a power amplifier.
Would the power amplifier introduce distortions to the signal
produced in the function generators? What's the worse distortion
that the power amp can introduce to it?
Thanks.
emma
Jan Panteltje
<mrandmrsr...@yahoo.com> wrote in
<1120046125.2...@g43g2000cwa.googlegroups.com>:
>> Perhaps it would be better if you specified what you need the
>> output for (what sort of equipment).
>
>The output is feed to a resistive coil. I'm analyzing the magnetic
>field produced by plotting it in 3D.
Now 'resistive' and 'coil' are 2 things that contradict a bit.
Any coil will behave as an inductor (and have some resistance).
So you can view it as a R in series with an L.
(so Z = R + jwL, were 'w' stands for omega or 2 x pi x frequency).
From this you can see the 'impedance' depends on the frequency applied.
>Suppose I have pure AC from the power lines. How would I add
>high frequency component to it? Suppose I want to add 300 Hz
>to ride on the sine wave, any idea how I can do that??
You have to decouple the 300 Hz from the mains, and also block
the 60 Hz from the driving amp.
At these low frequencies that requires large inductors and capacitors,
not very practical.
--- L---
60Hz ---- --------------------------- load
--- C--- |
300 Hz stop |
parr resonant |
-----
| |
L C
| | 60 Hz stop parallel resonant
-----
|
300Hz
>Another. Suppose I feed a function generator to a power amplifier.
>Would the power amplifier introduce distortions to the signal
>produced in the function generators? What's the worse distortion
>that the power amp can introduce to it?
This is the best system, and you could then take 60 Hz from the mains,
attenuate, and simply add 300 Hz from a signal generator, via a resistor
network:
60Hz ---- R------------ amplifier ---------- load
|
300Hz ----R------
|
R
|
//// ground
We have seen that the 'impedance' of the coil you use is very low
at low frequencies (practically near its resistance in Ohms), while
at higher frequencies it will have a higher impedance.
The amplifier should be able to drive the low impedance, say if the
coil is 4 Ohm, and the amplifier can drive 4 ohm speakers this should
be possible.
You will have to keep the output amplitude below clipping to keep a sine wave.
At the 300Hz, what the impedance is, depends on the inductance of the coil,
that is set by the number of turns and if there is some metal core.
How much current you can drive into the coil at frequency f is set by
the impedance and the peak to peak undistorted output from the amplifier
you use.
Here is a power amp I use for experiments, it is quite rigid and protected
against overload (within reason).
http://panteltje.com/panteltje/amplifier/
emma
Jan Panteltje wrote:
> On a sunny day (29 Jun 2005 04:55:25 -0700) it happened "emma"
> <mrandmrsr...@yahoo.com> wrote in
> <1120046125.2...@g43g2000cwa.googlegroups.com>:
>
> >> Perhaps it would be better if you specified what you need the
> >> output for (what sort of equipment).
> >
> >The output is feed to a resistive coil. I'm analyzing the magnetic
> >field produced by plotting it in 3D.
> Now 'resistive' and 'coil' are 2 things that contradict a bit.
> Any coil will behave as an inductor (and have some resistance).
> So you can view it as a R in series with an L.
> (so Z = R + jwL, were 'w' stands for omega or 2 x pi x frequency).
> From this you can see the 'impedance' depends on the frequency applied.
When I say resistive coil. It's not one load. I used an electric
bulb in the output.. then the coil is put in series to it. The
coil has reading of 1.7 ohms.
Do you know of a program where I can input the waveforms (i.e.
sine or square and its micropulsations) and it can output or plot
the magnetic field of the waveforms in 3D? I have to do it manually
and need something for comparison.
> We have seen that the 'impedance' of the coil you use is very low
> at low frequencies (practically near its resistance in Ohms), while
> at higher frequencies it will have a higher impedance.
>
> The amplifier should be able to drive the low impedance, say if the
> coil is 4 Ohm, and the amplifier can drive 4 ohm speakers this should
> be possible.
That means I can't use any 100 ohm lamp in the output of the speakers.
I can't find any AC resistor 110 volts at electronic stores. The
most they have is a 1 watt resistor for used in circuit. What's the
other names for AC resistors? Are their power amplifers that don't
have resistance limit in their output?
> You will have to keep the output amplitude below clipping to keep a sine wave.
> At the 300Hz, what the impedance is, depends on the inductance of the coil,
> that is set by the number of turns and if there is some metal core.
> How much current you can drive into the coil at frequency f is set by
> the impedance and the peak to peak undistorted output from the amplifier
> you use.
> Here is a power amp I use for experiments, it is quite rigid and protected
> against overload (within reason).
> http://panteltje.com/panteltje/amplifier/
I won't build the amplifier. I have wasted so much time constructing
pcb, circuit, soldering for a function generator and variable power
inverter and it's only up to 9 khz. I want something as large as 10
megahertz. Can commercial function gen create very clean sine wave?
What's your function gen?
About the power amp. I want to buy a commercially available one.
Are older transistor based solid state circuit better or worse
compared to modern ic based power amp in preventing distortions
in the waveform sent from the function gen input?
What do you call power amps where it is not used for audio only
but also for function gen amplification??
I need to get very clean source so I can prevent any contaminations
of frequencies in the output.
Many thanks.
emma
ji...@specsol.spam.sux.com
> I tried building a power inveter using two transistors as push-pull..
> meaning if one is one, the other is off, this is connected to
> 12-0-12 transformer to produce 110 volts.
> So as I understand it, when the transistor is in saturation, the
> current is supposed to form the square wave amplitude. It is
> not possible to raise it instantaneously that's why there is an
> increasing effect. Now how does the high frequency component
> got generated?? Also when it is in the maximum amplitude, how
> does it generate the high frequency component in the square
> waves?
Is this supposed to mean soething?
> What would it take to build a square wave power inverter that
> totally eliminate the high frequencies riding in the square wave??
As has been said by several others, put a filter on the output
and you get a sine.
Jan Panteltje
<mrandmrsr...@yahoo.com> wrote in
<1120055529.6...@g47g2000cwa.googlegroups.com>:
>> So you can view it as a R in series with an L.
>> (so Z = R + jwL, were 'w' stands for omega or 2 x pi x frequency).
>> From this you can see the 'impedance' depends on the frequency applied.
>
>When I say resistive coil. It's not one load. I used an electric
>bulb in the output.. then the coil is put in series to it. The
>coil has reading of 1.7 ohms.
>
>Do you know of a program where I can input the waveforms (i.e.
>sine or square and its micropulsations) and it can output or plot
>the magnetic field of the waveforms in 3D? I have to do it manually
>and need something for comparison.
I am still a bit puzzled to what you are trying to do.
Here are my questions:
If you say 'magnetic field' what field are you referring to,
the one from the coil? So then you have a probe, and measure everywhere
near and in the coil the magnetic field, and plot that?
I am sure there are examples of solenoid (single layer coils) with field
lines on the net, search via google:
solenoid field lines
I find many many hits,
here
http://www.bfafairfax.com/~pfeiffer/concphys/EandM/magnetism.html
The field will be symmetrical if you coil is, so 3D = 2D
>> The amplifier should be able to drive the low impedance, say if the
>> coil is 4 Ohm, and the amplifier can drive 4 ohm speakers this should
>> be possible.
>
>That means I can't use any 100 ohm lamp in the output of the speakers.
But you could use a simple trick, add a 3 Ohm resistor is series with the
coil, and use an amplifier that can drive 4 Ohm.
This way the amp will not be overloaded.
amplifier --- 3 Ohm -- 1 Ohm coil -- ground
>I can't find any AC resistor 110 volts at electronic stores. The
>most they have is a 1 watt resistor for used in circuit. What's the
>other names for AC resistors? Are their power amplifers that don't
>have resistance limit in their output?
Resistors behave the same for AC and DC (except from very high frequencies,
many MHz, where they act like an inductor depending upon their construction).
>I won't build the amplifier. I have wasted so much time constructing
>pcb, circuit, soldering for a function generator and variable power
>inverter and it's only up to 9 khz. I want something as large as 10
>megahertz. Can commercial function gen create very clean sine wave?
>What's your function gen?
I designed my own.
Now I use an FPGA (programmable gate array) with a fast DA converter.
You calculate the waveform for say 1024 points, upload to the (very
fast) FPGA internal RAM, and then program the FPGA so it outputs at the
right speed.
Or just program the required pulse sequence (in Verilog).
You are limited by the clock speed divided by the number of samples you want.
64 samples per period at 10MHz output would require a 640 MHz clock!
Mine does not go that fast (and and neither the DA).
And 64 samples is not exactly a 'pure' sine wave.
If you just want the sine waves, use any LC signal RF generator.
If you want only frequencies in the audio range, use the PC sound card,
and a good sound editor.
In the past I have made waveforms by writing a simple BASIC program,
calculate for example some values, and write it to a raw file (binary
sound file). Then most sound editors will be able to make a wave file.
If all else fails get a good RF generator from ebay?
While you are at it get an oscilloscope, and all this is difficult to do
without being able to see the waveforms (even if just to check nothing
clips).
A 10MHz scope should be dirt cheap on ebay.
>About the power amp. I want to buy a commercially available one.
>Are older transistor based solid state circuit better or worse
>compared to modern ic based power amp in preventing distortions
>in the waveform sent from the function gen input?
If you say 'I want 10MHz' then you have a problem.
Please also state the amount of power you want (at that frequency).
The other thing is how will you detect the magnetic field at 10MHz?
You can detect LF fields very good with an old playback head, but
not in the MHz range.
>What do you call power amps where it is not used for audio only
>but also for function gen amplification??
I would call a 10MHz power amp a power amplifier with 10MHz bandwidth....
>>I need to get very clean source so I can prevent any contaminations
>of frequencies in the output.
One way of doing that is using an amplifier with as narrow a bandwidth
as possible, for example if you want 10kHz, a 10MHz wide amp will
only add unwanted stuff!
I am still not 100% clear on what you want to do, how will you measure the
magnetic field?
CWatters
"Jan Panteltje" <pNaonSt...@yahoo.com> wrote in message
news:1120059038.54704b6708a8757ecce7db46932843db@teranews...
> I am still a bit puzzled to what you are trying to do.
..and why experiment at 110V when say 9V would be a lot safer?
John Fields
<pNaonSt...@yahoo.com> wrote:
>On a sunny day (28 Jun 2005 18:37:11 -0700) it happened "emma"
><mrandmrsr...@yahoo.com> wrote in
><1120009031.5...@g43g2000cwa.googlegroups.com>:
>
>>Hi,
>>
>>I learnt that square waves for examples produced by power
>>interver has high frequency components.
>Any square wave can be thought of as an infinite amount of sine waves.
>In practice you will have some harmonics, f, 2f, 3f, 4f etc.
---
No. A _square_ wave is composed of an infinite series of _odd_
harmonics.
--
John Fields
Professional Circuit Designer
emma
Well. Let's just say that I need to know all the magnetic field
configurations of all kinds of signals... square waves with high
freq components, triangular waves, sine waves because I want to
build a radio or other circuit powered by induction (without
contact). For example, a radio put near a computer monitor that
can power itself (by induction).
Do you think all oscilloscopes can show even the high frequency
components in the square waves. Do all have the same sensitivity.
What particular feature must I look for in oscilloscopes? Single
or dual trace, etc?
> amplifier --- 3 Ohm -- 1 Ohm coil -- ground
Yes I know this configuration.
>
> >I can't find any AC resistor 110 volts at electronic stores. The
> >most they have is a 1 watt resistor for used in circuit. What's the
> >other names for AC resistors? Are their power amplifers that don't
> >have resistance limit in their output?
> Resistors behave the same for AC and DC (except from very high frequencies,
> many MHz, where they act like an inductor depending upon their construction).
Won't a 1 Watt 2 ohm resistor explode if I use it in conjunction with
a 2 ohm coil in series. I can't predict the voltage produced by the
power amp since the manufacturers are accurate on the power rating.
Suppose a buy a 100 watt power amp... connect the 4 ohm resistor
and coil at the output.. put the function gen at the input...
initiate a 200 hz sine or square wave signal... what if the voltage
produced is say 50 volts and the current is more than the load can
handle... unless the 4 ohm load would only draw the current it needs
irregardless of the voltage. Is this what you mean. But I need high
current to cause high magnetic field in the coil so I can measure
it easily and representative of computer monitor magnetic field
strength (at the sides).
>
> >I won't build the amplifier. I have wasted so much time constructing
> >pcb, circuit, soldering for a function generator and variable power
> >inverter and it's only up to 9 khz. I want something as large as 10
> >megahertz. Can commercial function gen create very clean sine wave?
> >What's your function gen?
> I designed my own.
> Now I use an FPGA (programmable gate array) with a fast DA converter.
> You calculate the waveform for say 1024 points, upload to the (very
> fast) FPGA internal RAM, and then program the FPGA so it outputs at the
> right speed.
I don't want to design my own. There are so many power amps there. I'm
bad in soldering and often produced cold soldering points causing
endless hours of debugging.
> Or just program the required pulse sequence (in Verilog).
> You are limited by the clock speed divided by the number of samples you want.
> 64 samples per period at 10MHz output would require a 640 MHz clock!
> Mine does not go that fast (and and neither the DA).
> And 64 samples is not exactly a 'pure' sine wave.
> If you just want the sine waves, use any LC signal RF generator.
> If you want only frequencies in the audio range, use the PC sound card,
> and a good sound editor.
Hmm... yes.. a good idea.. Pc sound card... it can also produce
current that can cause magnetic field in the coil, right?? What's
the typical amperage of the pc sound card, I need very high
amperage so I can easily measure the magnetic field and typical
of monitor magnetic field strength.
>
>
> >What do you call power amps where it is not used for audio only
> >but also for function gen amplification??
> I would call a 10MHz power amp a power amplifier with 10MHz bandwidth....
Oh no... if power amp has bandwidth of 10-20 khz. Then I can't
use higher signals in the function gen above 20 khz??
I tried building a power inverter with variable frequency. It's
designed for 60 hz but I replace some parts so I can use frequency
as low as 1 hz to as high as 10 khz. But after some use, my transistors
always gets fried and have to replace them. Know the reason why?
I think the perfect setup for me is to get a variable frequency
sine wave power inverter. Know any commercially available ones
where you can adjust the frequency?? I don't want to construct
one from kits as so many parts need to be soldered and I always
get cold solders.
emma
Uncle Al
[snip]
> Well. Let's just say that I need to know all the magnetic field
> configurations of all kinds of signals... square waves with high
> freq components, triangular waves, sine waves because I want to
> build a radio or other circuit powered by induction (without
> contact). For example, a radio put near a computer monitor that
> can power itself (by induction).
[snip]
"Best efforts will not substitute for knowledge," W. Edwards Deming.
Old Man
news:1120009031.5...@g43g2000cwa.googlegroups.com...
You can get an estimate of the high frequency component
from the rise and fall times of the "square" wave. A low pass
LC filter will reduce the high frequencies. Expensive.
[Old Man]
> emma
>
Old Man
"Tm" <smill...@nospamcast.net> wrote in message
news:DI6dnfn9gcj...@comcast.com...
No loss in RMS power.
In principle (R_ series = 0, R__parallel = infinite), an LC
low pass filter is lossless.
[Old Man]
> TM
>
Bob Myers
> So the high frequency can be removed. I thought they can't.
> How complicated is the LC filter design to remove 100% of
> the high frequency component in the square wave?
I think you're still missing the point. A square wave has
"high-frequency components" simply by virtue of being
a square wave. Take those away, and it's not a square
wave any more. Take ALL of them away, except for the
base, or what's called the "fundamental" frequency, and you
have a pure sine wave.
Basically, you get additional components in ANY signal
in which something is changing more rapidly than it would
in the case of a sine wave at that frequency. (That's a terrible
oversimplification, but I'm hoping you'll see the point from it.)
In short, if you see any sort of "wave" with "sharp edges,"
it has high-frequency components.
> In pure line Alternating Current (sine wave) from power companies.
> Is there any high frequency component in the sine wave or is it
> pure 100% 60 Hz AC??
A sine wave is a "pure" signal in the sense that it exists, or
has components, only at one specific frequency. A 60 Hz
sine wave is a "pure 60 Hz tone," in more musical terms.
Bob M.
CWatters
> I want to build a radio or other circuit powered by induction
> (without contact). For example, a radio put near a computer
> monitor that can power itself (by induction).
Can I recommend you try placing an ordinary radio next to a computer first.
Try picking up a selection of different stations.
Jan Panteltje
<mrandmrsr...@yahoo.com> wrote in
<1120083238.0...@g49g2000cwa.googlegroups.com>:
>Well. Let's just say that I need to know all the magnetic field
>configurations of all kinds of signals... square waves with high
>freq components, triangular waves, sine waves because I want to
>build a radio or other circuit powered by induction (without
>contact). For example, a radio put near a computer monitor that
>can power itself (by induction).
Interesting.
But remember that the EM field, or rather magnetic field you use,
decreases at the third power of the distance!
So, even as the deflection current in the horizontal scan coil
of a CRT monitor maybe 10A pp, the magnetic field lines on the OUTSIDE
of that coil are extremely weak (on purpose by design), and at say
10cm from the coil (flat against the screen) VERY weak.
A tape recorder playback head wil pick these up, AFTER AMPLIFICATION
you can hear the 100Hz scan (or whatever is used).
In case of a LCD monitor there is hardly any field, maybe from
switch mode supply or back light HV generator perhaps.
>Do you think all oscilloscopes can show even the high frequency
>components in the square waves. Do all have the same sensitivity.
>What particular feature must I look for in oscilloscopes? Single
>or dual trace, etc?
This is vague, you need to mention a frequency, say the wave is 32kHz
sawtooth (as in CRT monitor), say we want to be able to see 10th
harmonic (would give sufficient true waveform display), then 320kHz
is enough.
Simplest scopes are analog 10MHz, then 20 MHz, 50MHz digital sampling
storage to 1G samples / second and 100 MHz, 1 GHz, 1 GHz analog....
it all exists.
Unless you want to power from your microwave oven, anything over 10MHz
should be enough in your case.
If you want it for the future to play electronics, go for a digital one
and 1G samples.
As for the sensitivity, what do you expect?
You want to power a radio.
Say the radio uses 100mW (very low power speaker), so you need to get
that from the external magnetic field.
You need a LOT of magnetic field! You can use a normal scope with 10mV
per division.
BUT it also depends on what you use as sensor, I asked this before, what
do you use as sensor?
>> amplifier --- 3 Ohm -- 1 Ohm coil -- ground
>
>Yes I know this configuration.
>
>Won't a 1 Watt 2 ohm resistor explode if I use it in conjunction with
>a 2 ohm coil in series.
OK some basics:
A resistor is measured in Ohms, the resistance.
When current flows through that resistor, it gets hot.
Above a certain temperature it will melt or burn.
The resistor manufacturer will specify how many Watts you can 'dissipate'
in the resistor so it just does not go kaput.
From this you can -calculate- the current.
P (watt) = U (volt) x U (volt) / R (Ohm)
or
P (watt) = I (Ampere) x I (ampere) x R (Ohm)
And U (volt) = I (Ampere) x R (Ohms)
So let us take some examples how to use this:
Say the amplifier can output 20 V sine.
And say you have a 3 Ohm resistor and a 1 Ohm coil as shown above.
The power in the total output load will be
20 x 20 / (3 + 1) = 400 / 4 = 100 W
The resistor gets 3/4 of this, so 75 Watt, the coil 1/4 so 25 W
So the resistor you need to buy is 3 Ohm 75 W, or 3 1 Ohm 25 W resistors
in series.
If you only have a bunch of 1 W 1 Ohm resistors, than we can reverse the
calculation, total load allowed now is 4W, so U x U / 4 = 4 or U is 1V sine.
Not a lot of voltage!
Anyways with Ohm's law you can calculate what components you need.
One remark: a 20 V sine wave is really a voltage swing from 20 x 2 x sqrt(2) =
56V, such an amplifier will have a total supply voltage of 60V or so, to
make the output possible.
>I can't predict the voltage produced by the
>power amp since the manufacturers are accurate on the power rating.
>Suppose a buy a 100 watt power amp... connect the 4 ohm resistor
>and coil at the output.. put the function gen at the input...
>initiate a 200 Hz sine or square wave signal... what if the voltage
>produced is say 50 volts and the current is more than the load can
>handle... unless the 4 ohm load would only draw the current it needs
>irregardless of the voltage. Is this what you mean. But I need high
>current to cause high magnetic field in the coil so I can measure
>it easily and representative of computer monitor magnetic field
>strength (at the sides).
I hope I have explained that, BEFORE you attach any load to the amp,
check the correct calculated output level with the scope (or an AC
voltmeter).
>> If you want only frequencies in the audio range, use the PC sound card,
>> and a good sound editor.
>
>Hmm... yes.. a good idea.. PC sound card... it can also produce
>current that can cause magnetic field in the coil, right?? What's
>the typical amperage of the PC sound card, I need very high
>amperage so I can easily measure the magnetic field and typical
>of monitor magnetic field strength.
Well, it depends, my creative sound cards only give line level output,
you still need an audio amplifier.
Some sound cards have 1 W or more.
>> >What do you call power amps where it is not used for audio only
>> >but also for function gen amplification??
>> I would call a 10MHz power amp a power amplifier with 10MHz bandwidth....
>
>Oh no... if power amp has bandwidth of 10-20 kHz. Then I can't
>use higher signals in the function gen above 20 kHz??
Correct.
>I tried building a power inverter with variable frequency. It's
>designed for 60 Hz but I replace some parts so I can use frequency
>as low as 1 Hz to as high as 10 kHz. But after some use, my transistors
>always gets fried and have to replace them. Know the reason why?
If it has a transformer in it, and is designed to run at 60Hz, lowering
the frequency will reduce the impedance of the transformer to its resistance
in Ohms, and your output transistors will die of too much current.
Do not mess with designs like that, it will only work in the specified range.
>I think the perfect setup for me is to get a variable frequency
>sine wave power inverter.
My personal opinion on this idea is that powering via magnetic
induction will not work (unless you are sitting under a power line perhaps).
The simple 1 W or up amplifier with PC sound card will do for the
audio range, else use the one I provided the link to, it will do 40 kHz.
Else you get into very expensive stuff, although 1MHz wide 1 W power
amp is easy to make yourself.
Have you ever considered using a ring core (ferrite) transformer in the
output of an amp to step up the current?
>Know any commercially available ones where you can adjust the frequency??
>I don't want to construct one from kits as so many parts need to be soldered
>and I always get cold solders.
Get some RF signal generator from ebay perhaps, but limit yourself to the
audio range or just above it.
What makes you think there are strong 10MHz signals (harmonics) around?
EVERY piece of equipment (except cell phones haha) these days is certified
NOT to emit any of these fields.
And what sensor do you use for detecting the magnetic fields?
Vidar Løkken
>>Hmm... yes.. a good idea.. PC sound card... it can also produce
>>current that can cause magnetic field in the coil, right?? What's
>>the typical amperage of the PC sound card, I need very high
>>amperage so I can easily measure the magnetic field and typical
>>of monitor magnetic field strength.
>
> Well, it depends, my creative sound cards only give line level output,
> you still need an audio amplifier.
> Some sound cards have 1 W or more.
ES1371 soundcards have a TDA1517m which provides 2x6W. That is the most
powerfull soundcard I'm aware exicsts. Typically it gives 4-5W.
--
MVH,
Vidar
emma
Jan Panteltje wrote:
> On a sunny day (29 Jun 2005 15:13:58 -0700) it happened "emma"
> <mrandmrsr...@yahoo.com> wrote in
> <1120083238.0...@g49g2000cwa.googlegroups.com>:
>
> >Well. Let's just say that I need to know all the magnetic field
> >configurations of all kinds of signals... square waves with high
> >freq components, triangular waves, sine waves because I want to
> >build a radio or other circuit powered by induction (without
> >contact). For example, a radio put near a computer monitor that
> >can power itself (by induction).
> Interesting.
> But remember that the EM field, or rather magnetic field you use,
> decreases at the third power of the distance!
> So, even as the deflection current in the horizontal scan coil
> of a CRT monitor maybe 10A pp, the magnetic field lines on the OUTSIDE
> of that coil are extremely weak (on purpose by design), and at say
> 10cm from the coil (flat against the screen) VERY weak.
> A tape recorder playback head wil pick these up, AFTER AMPLIFICATION
> you can hear the 100Hz scan (or whatever is used).
> In case of a LCD monitor there is hardly any field, maybe from
> switch mode supply or back light HV generator perhaps.
I didn't say I'm gonna power a convensional radio. But something
nanotech like molecular circuitry (which I'm still exploring). For
now I just want to master the different magnetic field variations
produced by different current and voltage waveforms.
> So let us take some examples how to use this:
> Say the amplifier can output 20 V sine.
> And say you have a 3 Ohm resistor and a 1 Ohm coil as shown above.
> The power in the total output load will be
> 20 x 20 / (3 + 1) = 400 / 4 = 100 W
> The resistor gets 3/4 of this, so 75 Watt, the coil 1/4 so 25 W
> So the resistor you need to buy is 3 Ohm 75 W, or 3 1 Ohm 25 W resistors
> in series.
I can't find any 3 ohm 75 Watts at any electronics stores in my
place. The most they have is 1 watt. If I'm gonna use a load such
as bulb or heater. Are you aware of anything that is only 3 ohms??
> > >I tried building a power inverter with variable frequency. It's
> >designed for 60 Hz but I replace some parts so I can use frequency
> >as low as 1 Hz to as high as 10 kHz. But after some use, my transistors
> >always gets fried and have to replace them. Know the reason why?
> If it has a transformer in it, and is designed to run at 60Hz, lowering
> the frequency will reduce the impedance of the transformer to its resistance
> in Ohms, and your output transistors will die of too much current.
> Do not mess with designs like that, it will only work in the specified range.
I fried 4 pcs of MJ15015 Power Transistors and 9013 ordinary
transistors already. My transformer is 12-0-12 primary and
110 volts secondary. I can't understand what you mean the
transformer will reduce the impedance to its resistance and the
output transistors will die of too much current. Can you just
mentioned what is the principle called (for example, Lenz Law).
I'll just research about it so you don't have to type and explain
a lot.
I thank you so very much for the replies and all the information,
Jan. I've gained the necessary information I needed in my project.
> And what sensor do you use for detecting the magnetic fields?
My friend has a very sensitive 3D sensor where he can image the
entire magnetic field intensity and harmonics. I don't fully
understand it well yet.
emma
Jan Panteltje
<mrandmrsr...@yahoo.com> wrote in
<1120143011.8...@g44g2000cwa.googlegroups.com>:
>I didn't say I'm gonna power a convensional radio. But something
>nanotech like molecular circuitry (which I'm still exploring). For
>now I just want to master the different magnetic field variations
>produced by different current and voltage waveforms.
OK
>I can't find any 3 ohm 75 Watts at any electronics stores in my
>place. The most they have is 1 watt. If I'm gonna use a load such
>as bulb or heater. Are you aware of anything that is only 3 ohms??
Using light bulbs as load works, but light bulbs have this peculiar
thing that if cold, the resistance is about 1/10 of when hot.
Say you have a 35 W car headlight (available form any garage), 12 V
So (12 x 12) / R = 35, so R = 144 / 35 = 4.11 Ohm.
However when cold it is more like 0.4 Ohm.
It will perfectly protect your power amp though, light bulbs (with a
filament) act as a constant current source.
Most transistor amps have output power limiting.
You can increase resistance by 2 by using the dim and main light connections
only (series), divide by 2 by using both in parallel.
>I fried 4 pcs of MJ15015 Power Transistors and 9013 ordinary
>transistors already. My transformer is 12-0-12 primary and
>110 volts secondary. I can't understand what you mean the
>transformer will reduce the impedance to its resistance and the
>output transistors will die of too much current. Can you just
>mentioned what is the principle called (for example, Lenz Law).
>I'll just research about it so you don't have to type and explain
>a lot.
No it is very simple.
Suppose the transistors deliver a sine wave to the transformer.
The impedance of the primary coil is R + jwL
The trick is in 'w', if you use 1/10 of the frequency, then the impedance
is also 1/10, and the current that flows is 10x.
In reality it will likely just switch the primary across the supply.
For any inductor goes:
I (Amperes) = U (volts) x t (seconds) / L (Henry)
This is a very very important formula.
It means that if you connect a coil of 1 Henry across a 1 V battery,
the current in the coil wil *linearly* rise to 1 Ampere after 1 second,
(and 10 Amp after 10 seconds etc), only to be limited by the resistance
in Ohms of the coil (normally quite low).
So if the switcher switches at say 50 Hz, after 1 / 50 = 20 mS a current
I will flow, if you go to 5 Hz, 1 / 5 = 200 mS, the current will be 10x
higher!
Here is where your transistors die.
The number of turns in the primary of the transformer determine the
inductance (and the core material has effect too).
For a lower frequency you need a LOT more turns, more iron in the core
perhaps, so you can only use a 60 Hz transformer for 60 Hz, not also for
6 Hz, or lower.
>I thank you so very much for the replies and all the information,
>Jan. I've gained the necessary information I needed in my project.
You are welcome.
>> And what sensor do you use for detecting the magnetic fields?
>
>My friend has a very sensitive 3D sensor where he can image the
>entire magnetic field intensity and harmonics. I don't fully
>understand it well yet.
Neither do I, what is a 3D sensor?
Ask him some time, I'd like to know.
CWatters
John Fields
wrote:
>
>"Tm" <smill...@nospamcast.net> wrote in message
>news:DI6dnfn9gcj...@comcast.com...
>> Low Pass will do it. But you will need more than a 110 volt square wave to
>> start with if you expect to get a 110 volt sine.
>
>No loss in RMS power.
>
>In principle (R_ series = 0, R__parallel = infinite), an LC
>low pass filter is lossless.
---
1. There is no such thing as "RMS power"
2. Since, for a square wave, RMS and peak voltage are the same and
since for a sine wave they're not, a lowpass filtered 120V 60Hz
square wave will yield a 120V _peak_ 60Hz sine wave. That's about
an 85VRMS sine wave.
3. Of course there's a loss in power. Where do you think all the
energy in the harmonics went, into the fundamental?
CWatters
> I didn't say I'm gonna power a convensional radio. But something
> nanotech like molecular circuitry (which I'm still exploring).
> I can't find any 3 ohm 75 Watts at any electronics stores in my
> place.
Na that won't pass the Turing test.
curiou...@yahoo.com
> Now how does the high frequency component got generated??
> Also when it is in the maximum amplitude, how
> waves?
The high frequency comes from the sudden change in di/dt in the each
square wave. You will notice that each square wave starts and ends
with a sudden pulse. That pulse is the sudden change in di/dt. A pure
sine wave is caused by a smooth changing di/dt where the peak di/dt is
at zero amplitude and the zero di/dt occurs at peak amplitude.
> What would it take to build a square wave power inverter that
> totally eliminate the high frequencies riding in the square wave??
There are countless options. It depends on the of amplifier *class*
you are using. Here's a cheap and simple idea. In series with the
output of your amplifier you could place a 7000 uF capacitor in series
with a 1 mH inductor. Again, that's a dirty cheap method though. I
only mention this so perhaps you can understand what's happening. An L
& C in series form a resonant circuit. The equation is f = 1 / [ 2pi *
(LC)^2 ] Also, such a dirty method would not waist that much energy
because the LC circuit resists all current outside 60Hz, but it's
reactive resistance. Pure reactive resistance will not consume energy.
For better options you'll need to do some study on different class
amplifiers. Try this for starters ->
http://www.bcae1.com/ampclass.htm
I would stay away from class A amplifiers since they generate dc
current. Therefore it would be difficult to filter out the unwanted
frequencies, including dc, without corrupting the amplifier. Class B
would work but are generally not used for high quality because of
crossover, which generates some unwanted high frequency. Class AB is
more efficient. Class D is extremely efficient. Class E is even more
efficient. Class G & H are less efficient than E. Here's a brief
explanation of some different class amplifiers ->
http://www.absoluteastronomy.com/encyclopedia/e/el/electronic_amplifier.htm
CWatters
John Fields
>emma wrote:
>> Now how does the high frequency component got generated??
>> Also when it is in the maximum amplitude, how
>> does it generate the high frequency component in the square
>> waves?
>
>The high frequency comes from the sudden change in di/dt in the each
>square wave. You will notice that each square wave starts and ends
>with a sudden pulse. That pulse is the sudden change in di/dt. A pure
>sine wave is caused by a smooth changing di/dt where the peak di/dt is
>at zero amplitude and the zero di/dt occurs at peak amplitude.
>
>
>> What would it take to build a square wave power inverter that
>> totally eliminate the high frequencies riding in the square wave??
>
>There are countless options. It depends on the of amplifier *class*
>you are using. Here's a cheap and simple idea. In series with the
>output of your amplifier you could place a 7000 uF capacitor in series
>with a 1 mH inductor. Again, that's a dirty cheap method though. I
>only mention this so perhaps you can understand what's happening. An L
>& C in series form a resonant circuit. The equation is f = 1 / [ 2pi *
>(LC)^2 ]
---
No, the equation is:
1
f = --------------
2pi sqrt(LC)
---
>Also, such a dirty method would not waist that much energy
>because the LC circuit resists all current outside 60Hz, but it's
>reactive resistance. Pure reactive resistance will not consume energy.
---
If you started with a 60Hz square wave and wound up with a 60Hz sine
wave, what happened to all the energy in the harmonics if it's not
wasted?
---
>For better options you'll need to do some study on different class
>amplifiers. Try this for starters ->
>
>http://www.bcae1.com/ampclass.htm
>
>I would stay away from class A amplifiers since they generate dc
>current. Therefore it would be difficult to filter out the unwanted
>frequencies, including dc, without corrupting the amplifier.
---
Since your filter has a series capacitor (7000µF, remember?) won't
that block DC?
---
>Class B
>would work but are generally not used for high quality because of
>crossover, which generates some unwanted high frequency. Class AB is
>more efficient.
---
No, it isn't, since both stages are continuously biased into
conduction in order to eliminate crossover distortion. That bias
doesn't exist in class B, so that quiescent power is never dissipated,
making class B more efficient than class AB.
---
>Class D is extremely efficient. Class E is even more
>efficient. Class G & H are less efficient than E. Here's a brief
>explanation of some different class amplifiers ->
>
>http://www.absoluteastronomy.com/encyclopedia/e/el/electronic_amplifier.htm
--
curiou...@yahoo.com
> But remember that the EM field, or rather magnetic field you use,
> decreases at the third power of the distance!
I don't think you should have included EM in that statement because the
magnetic and electric field from EM falls as 1/r. A closed loop dc
current causes magnetic field that falls as 1/r^3-- of the equation is
not linear at close distances and in such a case there are more complex
equations. Magnetic field from a current segment falls of at 1/r^2
curiou...@yahoo.com
> The equation is f = 1 / [ 2pi *
> >(LC)^2 ]
>
> ---
> No, the equation is:
>
> 1
> f = --------------
> 2pi sqrt(LC)
> ---
Thanks! That was just a typo on my part, ^2 should have been ^1/2 You
can see that I used the correct equation in my numbers; i.e., 7000uF &
1mH ~= 60Hz resonance frequency -- 1/[2pi * (7000uF * 1mH)^1/2] = 1/60
Hz.
> >Also, such a dirty method would not waist that much energy
> >because the LC circuit resists all current outside 60Hz, but it's
> >reactive resistance. Pure reactive resistance will not consume energy.
>
> ---
> If you started with a 60Hz square wave and wound up with a 60Hz sine
> wave, what happened to all the energy in the harmonics if it's not
> wasted?
> ---
There was no energy because it was just a voltage penitential generated
by the amplifier. As mentioned, it is a dirty method mostly to
demonstrate what is happening since you can't perfectly filter out all
unwanted frequencies.
> >For better options you'll need to do some study on different class
> >amplifiers. Try this for starters ->
> >
> >http://www.bcae1.com/ampclass.htm
> >
> >I would stay away from class A amplifiers since they generate dc
> >current. Therefore it would be difficult to filter out the unwanted
> >frequencies, including dc, without corrupting the amplifier.
>
> ---
> Since your filter has a series capacitor (7000µF, remember?) won't
> that block DC?
> ---
Yes, which is why I clearly said no Class A amplifiers :-)
Thomas Magma
distortions there are variations in amplitude, phase and frequency. But
because of the low pass nature of power lines and other components, the
spectrum of the AC is somewhat cleaned up.
In fact, it is debatable whether pure sine waves even exist in our physical
world.
Thomas
"emma" <mrandmrsr...@yahoo.com> wrote in message
news:1120042632.4...@z14g2000cwz.googlegroups.com...
>
>
> Jan Panteltje wrote:
>> On a sunny day (28 Jun 2005 18:37:11 -0700) it happened "emma"
>> <mrandmrsr...@yahoo.com> wrote in
>> <1120009031.5...@g43g2000cwa.googlegroups.com>:
>>
>> >Hi,
>> >
>> >I learnt that square waves for examples produced by power
>> >interver has high frequency components.
>> Any square wave can be thought of as an infinite amount of sine waves.
>> In practice you will have some harmonics, f, 2f, 3f, 4f etc.
>> Look up Fourier analysis.
>>
>> Some inverters make a near square wave, some a modulated pulse width
>> that is filtered into an approximate sine wave, some just combine some
>> smaller square waves to make something that looks a bit like a sine.
>> Some make really good sine waves.
>>
>>
>> >What's the typical
>> >value of the frequency supposed the source is 110 volts,
>> >60 hertz.
>> 120, 180, 240, 300, etc, with varying amplitude.
>>
>> >Is there no way to remove the high frequency
>> >components? How does it affect the load?
>> Yes, LC filter, but you will lose some power.
>
> So the high frequency can be removed. I thought they can't.
> How complicated is the LC filter design to remove 100% of
> the high frequency component in the square wave?
>
>>
>> If you for some reason need a pure sine wave, get a converter that does
>> that.
>>
>> Many applications / appliances do not need a real good sine wave, as
>> these
>> have their own power processing / power supplies - those could handle
>> square
>> waves even.
>> In fact in some cases square wave could be beneficial.
>
> In pure line Alternating Current (sine wave) from power companies.
> Is there any high frequency component in the sine wave or is it
> pure 100% 60 Hz AC??
>
> emma
>
John Fields
>> >I would stay away from class A amplifiers since they generate dc
>> >current. Therefore it would be difficult to filter out the unwanted
>> >frequencies, including dc, without corrupting the amplifier.
>>
>> ---
>> Since your filter has a series capacitor (7000湩, remember?) won't
>> that block DC?
>> ---
>
>Yes, which is why I clearly said no Class A amplifiers :-)
---
You missed the point, which was that since the capacitor will block DC
it doesn't matter whether the filter's being driven by a class A
amplifier or not, no DC will get into the load since it's being
"filtered" out by the cap.
emma
Jan Panteltje wrote:
> On a sunny day (30 Jun 2005 07:50:11 -0700) it happened "emma"
> <mrandmrsr...@yahoo.com> wrote in
> <1120143011.8...@g44g2000cwa.googlegroups.com>:
>
> >I didn't say I'm gonna power a convensional radio. But something
> >nanotech like molecular circuitry (which I'm still exploring). For
> >now I just want to master the different magnetic field variations
> >produced by different current and voltage waveforms.
> OK
>
> >I can't find any 3 ohm 75 Watts at any electronics stores in my
> >place. The most they have is 1 watt. If I'm gonna use a load such
> >as bulb or heater. Are you aware of anything that is only 3 ohms??
> Using light bulbs as load works, but light bulbs have this peculiar
> thing that if cold, the resistance is about 1/10 of when hot.
> Say you have a 35 W car headlight (available form any garage), 12 V
> So (12 x 12) / R = 35, so R = 144 / 35 = 4.11 Ohm.
> However when cold it is more like 0.4 Ohm.
> It will perfectly protect your power amp though, light bulbs (with a
> filament) act as a constant current source.
> Most transistor amps have output power limiting.
> You can increase resistance by 2 by using the dim and main light connections
> only (series), divide by 2 by using both in parallel.
I've got other idea. I'll get meters of high gauge wires and measure
3 ohms and use it as resistor. How do I calculate how much will it
heat up? I've got Resnick and Holliday 800 page book on
Electromagnetisms and still slowly going thru it but need the
information asap. Thanks.
Say. Is there a difference in performance if I have say a 20 meter
thin cooper wire measuring 3 ohms versus a thick 5 meter cooper
wire measuring 3 ohms also?
Thanks. It explains why I fried my power transistors 2 times
already. Well if I never go below 60 Hz but go higher to 10Khz.
Would it also fry the circuit?? I notice a high pitch sound in
the circuit when the frequency is increased linearly from 60 hz
to 10 Khz.
>
> >I thank you so very much for the replies and all the information,
> >Jan. I've gained the necessary information I needed in my project.
> You are welcome.
>
> >> And what sensor do you use for detecting the magnetic fields?
> >
> >My friend has a very sensitive 3D sensor where he can image the
> >entire magnetic field intensity and harmonics. I don't fully
> >understand it well yet.
> Neither do I, what is a 3D sensor?
> Ask him some time, I'd like to know.
Some kind of non-linear detection system that is based on the
quantum potentials of the vectors. I can't explain it. I'll ask.
emma
Vidar Løkken
>
> I've got other idea. I'll get meters of high gauge wires and measure
> 3 ohms and use it as resistor. How do I calculate how much will it
> heat up? I've got Resnick and Holliday 800 page book on
> Electromagnetisms and still slowly going thru it but need the
> information asap. Thanks.
>
> Say. Is there a difference in performance if I have say a 20 meter
> thin cooper wire measuring 3 ohms versus a thick 5 meter cooper
> wire measuring 3 ohms also?
Go read that book. Thicker wire == less resistance pr m cable, since
there's far more copper to conduct the current.
Think of it as water. Bigger pipe equals lower resistance equals more water.
Higher pressure equals more water trough the same pipe.
--
MVH,
Vidar
Jan Panteltje
<mrandmrsr...@yahoo.com> wrote in
<1120162659.0...@g47g2000cwa.googlegroups.com>:
>I've got other idea. I'll get meters of high gauge wires and measure
>3 ohms and use it as resistor. How do I calculate how much will it
>heat up?
That depends on a lot of factors, for example when you wind it like a coil
it will heat up a lot more then when you leave it laying about.
>I've got Resnick and Holliday 800 page book on
>Electromagnetisms and still slowly going thru it but need the
>information asap. Thanks.
Try it!
There is special resistance wire, that you can use to make your own
resistance. Google:
http://www.surplussales.com/Wire-Cable/Resistance.html
Then you can use shorter length.
>Say. Is there a difference in performance if I have say a 20 meter
>thin cooper wire measuring 3 ohms versus a thick 5 meter cooper
>wire measuring 3 ohms also?
Well, since you want to measure magnetic fields, I would use a light bulb,
because that wire (especially when the 20 meter is wound) will be a coil
of its own, with its own magnetic field, interfering with your setup!
I presume you meant 20 meter thick versus 5 meter thin.
>Thanks. It explains why I fried my power transistors 2 times
>already. Well if I never go below 60 Hz but go higher to 10Khz.
>Would it also fry the circuit?? I notice a high pitch sound in
>the circuit when the frequency is increased linearly from 60 Hz,
>to 10 kHz.
At higher [switching] frequencies the switch time of the transistors
becomes important (they will dissipate heat while not 100% on or off),
and also the losses in the core of the transform will increase.
Then there is 'skin effect' in the wire (electricity only flows in outside).
For this reason above say 3 kHz you will often see ferroxcube (ferrite)
cores.
And possibly litze wire (wire made up of many strands).
>Some kind of non-linear detection system that is based on the
>quantum potentials of the vectors. I can't explain it. I'll ask.
Squid!
Well that should be sensitive enough :-)
But what about the liquid cooling and the totally magnetically screened room?
Well ask anyways :-)
St. John Smythe
> On a sunny day (30 Jun 2005 13:17:39 -0700) it happened "emma"
> <mrandmrsr...@yahoo.com> wrote in
> <1120162659.0...@g47g2000cwa.googlegroups.com>:
>
>>I've got other idea. I'll get meters of high gauge wires and measure
>>3 ohms and use it as resistor. How do I calculate how much will it
>>heat up?
>
> That depends on a lot of factors, for example when you wind it like a coil
> it will heat up a lot more then when you leave it laying about.
You fellows are being trolled big-time. Can't you see it?
--
St. John
curiou...@yahoo.com
> >Yes, which is why I clearly said no Class A amplifiers :-)
>
Perhaps.
Do you know much about low temperature electronics? I am looking at an
ADC chip, which has a temperature range of -30 to 80 C. Why wouldn't
the chip work with say -50 C? I would like to work with low fields and
eliminate as much thermal noise as possible. Any ideas?
emma
Thanks for this crucial information. I know thicker tungsten means
lesser resistance because there are more spaces in the lattice where
the electrons can move or vibrate. So it is also valid in pure
wires. You save me the trouble of getting very thick wires and
more length required because of lower resistance. So I'll just
get thinner wire.
emma
emma
Many thanks for this important information. I'll attempt to
build my fried circuit for the third time and just use frequency
of 60 hz and above (to 20Khz). I hope it won't fry anymore.
So many thanks for all the information. I have enough to carry
on and read the Resnick book with perspective.
emma
emma
You thought that way because I asked too many questions. Well.
I have gotten the necessary and important information already
so I'll carry on myself with the help of Resnick thick book on
electromagnetism and not ask too many questions (that is starting
to irritate some folks).
Sorry and many thanks.
emma
Old Man
"John Fields" <jfi...@austininstruments.com> wrote in message
news:l738c1tspg5lbfunc...@4ax.com...
> On Wed, 29 Jun 2005 13:18:41 -0500, "Old Man" <nom...@nomail.net>
> wrote:
>
>>
>>"Tm" <smill...@nospamcast.net> wrote in message
>>news:DI6dnfn9gcj...@comcast.com...
>
>>> Low Pass will do it. But you will need more than a 110 volt square wave
>>> to
>>> start with if you expect to get a 110 volt sine.
>>
>>No loss in RMS power.
>>
>>In principle (R_ series = 0, R__parallel = infinite), an LC
>>low pass filter is lossless.
>
> ---
> 1. There is no such thing as "RMS power"
Semantics. Write the equation.
> 2. Since, for a square wave, RMS and peak voltage are the same and
> since for a sine wave they're not, a lowpass filtered 120V 60Hz
> square wave will yield a 120V _peak_ 60Hz sine wave. That's about
> an 85VRMS sine wave.
No. Simple addition doesn't cut it. In a series LC circuit,
voltages are added in quadrature. The voltages across L
and C (+ R_load) aren't in phase.
> 3. Of course there's a loss in power.
No. R_ series = 0, R__parallel = infinite. Give the equation.
All of the power goes into the resistive load. None elsewhere.
> Where do you think all the
> energy in the harmonics went, into the fundamental?
Exactly. Energy and power are conserved.
> John Fields
> Professional Circuit Designer
Professional ? Fields displays delusions of competence.
[[Old Man]
John Fields
wrote:
>
>"John Fields" <jfi...@austininstruments.com> wrote in message
>news:l738c1tspg5lbfunc...@4ax.com...
>> On Wed, 29 Jun 2005 13:18:41 -0500, "Old Man" <nom...@nomail.net>
>> wrote:
>>
>>>
>>>"Tm" <smill...@nospamcast.net> wrote in message
>>>news:DI6dnfn9gcj...@comcast.com...
>>
>>>> Low Pass will do it. But you will need more than a 110 volt square wave
>>>> to
>>>> start with if you expect to get a 110 volt sine.
>>>
>>>No loss in RMS power.
>>>
>>>In principle (R_ series = 0, R__parallel = infinite), an LC
>>>low pass filter is lossless.
>>
>> ---
>> 1. There is no such thing as "RMS power"
>
>Semantics. Write the equation.
---
What equation? There's RMS current and RMS voltage, and power is just
the product of current and voltage.
>> 2. Since, for a square wave, RMS and peak voltage are the same and
>> since for a sine wave they're not, a lowpass filtered 120V 60Hz
>> square wave will yield a 120V _peak_ 60Hz sine wave. That's about
>> an 85VRMS sine wave.
>
>No. Simple addition doesn't cut it. In a series LC circuit,
>voltages are added in quadrature. The voltages across L
>and C (+ R_load) aren't in phase.
---
You still don't get it, huh? Who said anything about a series LC
circuit? What we're talking about is using a lowpass filter to
eliminate/attenuate harmonics in a square wave in order to extract
the fundamenal. (That is, how to turn a square wave into a sinusoid
with the same period as the square wave) That means the filter is
going to look like this: (View in a non-proportional font.)
SQIN>--+--[L]--->>--+
| |
[C] [RL]
| |
GND>---+-------->>--+
Since the reactance of the capacitor will decrease, and the reactance
of the inductor will increase as frequency increases, the high
frequency components of the input square wave will be attenuated by
the inductor and shunted to ground by the capacitor, allowing the
desired low frequency(ies) to pass through the inductor and into the
load.
---
>> 3. Of course there's a loss in power.
>
>No. R_ series = 0, R__parallel = infinite. Give the equation.
>All of the power goes into the resistive load. None elsewhere.
---
No. We're not talking about a resonant circuit here, we're talking
about a lowpass filter.
---
>> Where do you think all the
>> energy in the harmonics went, into the fundamental?
>
>Exactly. Energy and power are conserved.
---
Of course they're "conserved", but that doesn't mean that the energy
in the harmonics will be magically converted into the fundamental.
What will happen is that it will be shunted to ground through the
capacitor and converted into heat. Wasted, in other words.
---
>> John Fields
>
>> Professional Circuit Designer
>
>Professional ? Fields displays delusions of competence.
>
>[[Old Man]
---
Still think so, ya goofy old fart?
--
Jan Panteltje
<jfi...@austininstruments.com> wrote in
<n5nic19sfc6iuskap...@4ax.com>:
>What we're talking about is using a lowpass filter to
>eliminate/attenuate harmonics in a square wave in order to extract
>the fundamenal. (That is, how to turn a square wave into a sinusoid
>with the same period as the square wave) That means the filter is
>going to look like this: (View in a non-proportional font.)
>
>SQIN>--+--[L]--->>--+
> | |
> [C] [RL]
> | |
>GND>---+-------->>--+
John, this is a bit dangerous if that thing really has low output impedance.
It will cause the switcher to current limit or blow up...
Enter it in spice, with square wave input, look at current in C.
It is set by the Ri of the source (and Rs cap).
in --L------- out
|
C RL
|
----------
is a bit safer I think, but without load can give very high voltages in
resonance.
John Fields
<pNaonSt...@yahoo.com> wrote:
>On a sunny day (Mon, 04 Jul 2005 11:53:08 -0500) it happened John Fields
><jfi...@austininstruments.com> wrote in
><n5nic19sfc6iuskap...@4ax.com>:
>
>>What we're talking about is using a lowpass filter to
>>eliminate/attenuate harmonics in a square wave in order to extract
>>the fundamenal. (That is, how to turn a square wave into a sinusoid
>>with the same period as the square wave) That means the filter is
>>going to look like this: (View in a non-proportional font.)
>>
>>SQIN>--+--[L]--->>--+
>> | |
>> [C] [RL]
>> | |
>>GND>---+-------->>--+
>John, this is a bit dangerous if that thing really has low output impedance.
>It will cause the switcher to current limit or blow up...
---
I was just thinking of a way to get a lowpass circuit down for Old
man, but you're right. I didn't even think of that. Thanks! :-)
---
>Enter it in spice, with square wave input, look at current in C.
>It is set by the Ri of the source (and Rs cap).
>
>in --L------- out
> |
> C RL
> |
> ----------
>is a bit safer I think, but without load can give very high voltages in
>resonance.
---
Yes. Passive voltage gain!
Old Man
> On Fri, 1 Jul 2005 17:28:42 -0500, "Old Man" <nom...@nomail.net>
> wrote:
>>"John Fields" <jfi...@austininstruments.com> wrote in message
>>news:l738c1tspg5lbfunc...@4ax.com...
>>> On Wed, 29 Jun 2005 13:18:41 -0500, "Old Man" <nom...@nomail.net>
>>> wrote:
>>>>"Tm" <smill...@nospamcast.net> wrote in message
>>>>news:DI6dnfn9gcj...@comcast.com...
>>>
>>>>> Low Pass will do it. But you will need more than a 110 volt square
>>>>> wave
>>>>> to
>>>>> start with if you expect to get a 110 volt sine.
>>>>
>>>>No loss in RMS power.
>>>>
>>>>In principle (R_ series = 0, R__parallel = infinite), an LC
>>>>low pass filter is lossless.
>>>
>>> ---
>>> 1. There is no such thing as "RMS power"
>>
>>Semantics. Write the equation.
>
> ---
> What equation? There's RMS current and RMS voltage, and power is just
> the product of current and voltage.
Only for a resistor wherein current and voltage are in phase.
The voltage across C / L leads / lags the current by pi / 2.
Here's the equation that Fields should have written
Power = V * I * cos( phase)
for L or C phase = + pi / 2 or - pi / 2. In both cases,
Power = 0. Write the equation. Go figure.
>>> 2. Since, for a square wave, RMS and peak voltage are the same and
>>> since for a sine wave they're not, a lowpass filtered 120V 60Hz
>>> square wave will yield a 120V _peak_ 60Hz sine wave. That's about
>>> an 85VRMS sine wave.
>>
>>No. Simple addition doesn't cut it. In a series LC circuit,
>>voltages are added in quadrature. The voltages across L
>>and C (+ R_load) aren't in phase.
>
> ---
> You still don't get it, huh? Who said anything about a series LC
> circuit? What we're talking about is using a lowpass filter to
> eliminate/attenuate harmonics in a square wave in order to extract
> the fundamenal. (That is, how to turn a square wave into a sinusoid
> with the same period as the square wave) That means the filter is
> going to look like this: (View in a non-proportional font.)
>
> SQIN>--+--[L]--->>--+
> | |
> [C] [RL]
> | |
> GND>---+-------->>--+
No way. Cockeyed low pass filter. The capacitor is in parallel
with the load, not in parallel with the source. It is then a series
LC circuit with the load in parallel with the capacitor.
> Since the reactance of the capacitor will decrease, and the reactance
> of the inductor will increase as frequency increases, the high
> frequency components of the input square wave will be attenuated by
> the inductor and shunted to ground by the capacitor, allowing the
> desired low frequency(ies) to pass through the inductor and into the
> load.
The capacitor in fields cockeyed circuit dissipates no power.
Neither does the inductor.
> ---
>
>>> 3. Of course there's a loss in power.
>>
>>No. R_ series = 0, R__parallel = infinite. Give the equation.
>>All of the power goes into the resistive load. None elsewhere.
>
> ---
> No. We're not talking about a resonant circuit here, we're talking
> about a lowpass filter.
Resonant circuit is Fields straw man.
> ---
>
>>> Where do you think all the
>>> energy in the harmonics went, into the fundamental?
>>
>>Exactly. Energy and power are conserved.
>
> ---
> Of course they're "conserved", but that doesn't mean that the energy
> in the harmonics will be magically converted into the fundamental.
> What will happen is that it will be shunted to ground through the
> capacitor and converted into heat. Wasted, in other words.
Bullshit. Write the equation. "shunted to ground" is magic.
"ground" isn't a physical entity. The current flows back to
the source, pi / 2 out of phase with the source voltage. There
is no net power consumption. Go figure.
[Old Man]\