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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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2 questions about a fully DC Sine Wave....let's suppose you have a DC
Sine wave which varies from +5V to +15V peak-to-peak going into a load with R, L, and C components..... Question #1: Is the load's impedance a function of R, L, and C (and wave frequency) or is it simply just R (i.e. Z=R)? In other words does non-resistive impedance (L + C) really only matter with an AC signal OR anytime voltage varies periodically (even if it is all DC)? Question #2: Would a "regular" negative peak detector ciruit, like shown he http://www.elektroda.net/cir/index/D...CTOR.htmgative work for the DC Wave described? Will it output +5V or do negative peak detectors only work for AC signals? Thank you. |
#2
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![]() wrote in message ups.com... 2 questions about a fully DC Sine Wave One answer. Sine waves aren't DC. N |
#3
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How come? Do you object to the term "DC" - is monophasic acceptable to
you? See also: http://64.233.161.104/search?q=cache...n&lr=lang_ en |
#4
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![]() wrote in message ups.com... 2 questions about a fully DC Sine Wave....let's suppose you have a DC Sine wave which varies from +5V to +15V peak-to-peak going into a load with R, L, and C components..... Question #1: Is the load's impedance a function of R, L, and C (and wave frequency) or is it simply just R (i.e. Z=R)? In other words does non-resistive impedance (L + C) really only matter with an AC signal OR anytime voltage varies periodically (even if it is all DC)? Question #2: Would a "regular" negative peak detector ciruit, like shown he http://www.elektroda.net/cir/index/D...CTOR.htmgative work for the DC Wave described? Will it output +5V or do negative peak detectors only work for AC signals? Thank you. Impedance varies with frequency if there are reactive components, L's and C's. Since you haven't told us whether this is a series or parallel circuit of L's, R's and C's, We don't know what the impedance is at DC, zero frequency or any other frequency for that matter. If it's a parallel circuit the DC impedance is zero unless there is resistance in series with the L as is the usual case. In that case, the impedance is R at DC. If it is a series circuit, the DC impedance is infinite. SO, you have three choices, Zero ohms, Infinite ohms or R ohms depending on the connection. A peak detector will have to work on the range of voltages expected on it's input. I can't get to the URL, sorry. Bob |
#5
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Bob Eldred wrote:
Impedance varies with frequency if there are reactive components, L's and C's. That is not always true. Take 1) A resistor of resistance R in series with a capacitor of capacitance C. 2) Another identical resistor of resistance R, but in series with an inductor L. Make R=sqrt(L/C) and put 1 and 2 in parallel and measure the impedance across that combination. The impedance is always R, and is independent of frequency. A useless fact I would admit!! |
#6
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![]() wrote in message oups.com... How come? Do you object to the term "DC" - is monophasic acceptable to you? Varying DC? i.e. DC varying in amplitude a manner similar to an AC sine wave. If it goes into plus and minus regions I guess we are getting pretty close to an AC waveform? |
#8
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Since you haven't told us whether this is a series or parallel circuit
of L's, R's and C's, O.K. here's the combinatrics: Combo 1: DC Sine Wave + (R+L in series with C parallel) Combo 2: DC Sine Wave + (R+C in series with L parallel) Combo 3: DC Sine Wave + (L+C in series with R parallel) Combo 4: DC Sine Wave + (R, L, and C all in parallel with each other) Combo 5: DC Sine Wave + (R, L and C all in series) A peak detector will have to work on the range of voltages expected on it's input. O.K., so can I correctly infer from your response that a negative peak detector will yield a value of +5V for a sine wave which varies from +5V to +15V? |
#9
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There is no such thing as a "DC sine wave." I suspect you mean what would more
correctly be described as a 10 volt peak- to-peak sine wave with a +10 volt DC offset. Not that it's that important, but I don't see why a "DC sine wave" is an impossible concept, considering the definition of DC as a current which flows in one direction: http://www.answers.com/topic/direct-current A "DC Sine wave" doesn't say that current reverses direction, only that the current flow wanes and waxes.....like a river is still a river even though its flow varies with rainfall... The principle of superposition applies: the currents and voltages in the circuit will be the sum of those that would result if the DC voltage and the AC sine wave were applied to it seperately. O.K. - now we're getting somewhere......you're saying the current and voltage (and the implied impedance Z = V/I) of the "DC sine wave" is the sum of the respective current and voltage of a +10V DC signal and a -5V/+5V AC signal going into the same load. Example: DC +10V into load produces 1 Amp, therefore implied resistance = 10 ohm. and AC -5V/+5V (and given frequency) into load produces 0.5 amps, therefore implied impedance = 20 ohms, then what would the superposition prinicple predict as the resulting combined current and impednace? |
#10
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read the original post - talking about a sine wave bouncing between +5V
and +15V - no where near negative |
#11
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![]() wrote in message oups.com... read the original post - talking about a sine wave bouncing between +5V and +15V - no where near negative That's an AC wave with a DC offset. N |
#12
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#13
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On 6/10/05 3:13 PM, in article
, " wrote: How come? Do you object to the term "DC" - is monophasic acceptable to you? See also: http://64.233.161.104/search?q=cache...com/global/our _product/sp_Inverter/3_techno.html+%2B%22dc+sine+wave%22&hl=en&lr=lang_ en Your posts have all the characteristics that indicate you are a troll. If you aren't I suggest you quit being combative and learn from what the posters are saying. And re the link; that refers to an inverter that uses a DC input and outputs a sinewave. You must be troll. |
#15
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wrote:
2 questions about a fully DC Sine Wave....let's suppose you have a DC Sine wave which varies from +5V to +15V peak-to-peak going into a load with R, L, and C components..... Question #1: Is the load's impedance a function of R, L, and C (and wave frequency) or is it simply just R (i.e. Z=R)? In other words does non-resistive impedance (L + C) really only matter with an AC signal OR anytime voltage varies periodically (even if it is all DC)? Question #2: Would a "regular" negative peak detector ciruit, like shown he http://www.elektroda.net/cir/index/D...CTOR.htmgative work for the DC Wave described? Will it output +5V or do negative peak detectors only work for AC signals? Thank you. Question 1: A capacitor "capacitates" whether it sees AC or DC. An inductor "inducts" whether it sees AC or DC. A resistor resists whether it sees AC or DC. You might find it beneficial to think of what happens to each component on a component level rather than thinking of total impedance. Understand what each component does, and circuit impedance will make more sense. Question 2: 404 file not found error That said, you can peak detect on a varying DC sine. As someone else said, its AC with a DC offset. Ed |
#16
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wrote:
2 questions about a fully DC Sine Wave....let's suppose you have a DC Sine wave which varies from +5V to +15V peak-to-peak going into a load with R, L, and C components..... Question #1: Is the load's impedance a function of R, L, and C (and wave frequency) or is it simply just R (i.e. Z=R)? In other words does non-resistive impedance (L + C) really only matter with an AC signal OR anytime voltage varies periodically (even if it is all DC)? The impedance of a set of passive devices is independent of the voltage across them. It only depends on R, L, C, and f. The fact that there is a DC component makes no difference. An inductor will pass DC current as if it were a wire. Only differences in current cause a voltage across it. A capacitor will not pass DC, so the DC does not matter. Obviously, a resistor is a resistor, and cares nothing for ac vs dc. This is only true for ideal components. In the real world, inductors, caps and resistors have voltage limitatations. They are usually well beyond 15V, though. Question #2: Would a "regular" negative peak detector ciruit, like shown he http://www.elektroda.net/cir/index/D...CTOR.htmgative work for the DC Wave described? Will it output +5V or do negative peak detectors only work for AC signals? Thank you. Your link has crap on the end. Here it is without the crap: http://www.elektroda.net/cir/index/D...20DETECTOR.htm With this circuit, the input at V+ will always be outside the power rails. Thus, it will not work. NOTE: I changed the followup-to field to sci.electronics.basics, because that is where this thread belongs. I hope you don't mind. --- Regards, Bob Monsen |
#17
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On Fri, 10 Jun 2005 14:55:02 -0700, jackbruce9999 wrote:
2 questions about a fully DC Sine Wave.. If you think that the term "fully DC Sine Wave" even means anything, then you have not understood the coursework. Either your teacher is incompetent, or you have been spending too much time partying and not enough time studying. Good Luck! Rich |
#18
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On Fri, 10 Jun 2005 16:51:10 -0700, Don Bowey wrote:
On 6/10/05 3:13 PM, in article , " wrote: How come? Do you object to the term "DC" - is monophasic acceptable to you? See also: http://64.233.161.104/search?q=cache...com/global/our _product/sp_Inverter/3_techno.html+%2B%22dc+sine+wave%22&hl=en&lr=lang_ en Your posts have all the characteristics that indicate you are a troll. Bull****. This kid is not a troll, by any means. He's just a student desperate to weasel answers to his final without having to learn the material he was supposed to have learned while partying and chasing tail. A troll is a much more serious matter. This is just a child who needs to fail the course, have Mom and Dad scold him, and next semester, pay attention in class. Cheers! Rich |
#19
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wrote:
2 questions about a fully DC Sine Wave....let's suppose you have a DC Sine wave which varies from +5V to +15V peak-to-peak going into a load with R, L, and C components..... Question #1: Is the load's impedance a function of R, L, and C (and wave frequency) or is it simply just R (i.e. Z=R)? In other words does non-resistive impedance (L + C) really only matter with an AC signal OR anytime voltage varies periodically (even if it is all DC)? Question #2: Would a "regular" negative peak detector ciruit, like shown he http://www.elektroda.net/cir/index/D...CTOR.htmgative work for the DC Wave described? Will it output +5V or do negative peak detectors only work for AC signals? Thank you. According to Fourier analysis, any repeating waveform can be decomposed into harmonically related and appropriately phase shifted sine waves and also a DC component. If all the components involved are linear, then they react to each of these components, independently, and the result is the linear sum of all those reactions. So the capacitors react to the DC component as open circuits, and the inductors as short circuits. At all frequencies, the resistances follow ohms law, and at each AC harmonic, the inductances and capacitances react in their normal frequency dependent ways. Throw in one nonlinear component, like a diode, and you have to do a completely different kind of analysis. |
#20
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![]() Question #2: Would a "regular" negative peak detector ciruit, like shown he http://www.elektroda.net/cir/index/D...CTOR.htmgative work for the DC Wave described? That is not a "regular" peak detector, it is a comparator used as an overcompensated opamp follower and exploits the open collector output characteristic of fast discharge and slow ( 10 second) charge of the capacitor. In concept it will work for a varying "DC sine wave" by replacing "-Vcc" with "GND" and all "GND"'s with "+15V" in that circuit diagram only. Then Vout= "Vpk,neg" =+5V. |
#21
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![]() wrote in message oups.com... There is no such thing as a "DC sine wave." I suspect you mean what would more correctly be described as a 10 volt peak- to-peak sine wave with a +10 volt DC offset. Not that it's that important, but I don't see why a "DC sine wave" is an impossible concept, considering the definition of DC as a current which flows in one direction: Maybe you shouldn't believe everything you read. DC has: 1. Constant amplitude (that's not to say you can't change it. 2. Frequency of 0 Hz. Also, a non 0 frequency does not imply polarity changes. Tam |
#22
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![]() "Dave" wrote in message ... Bob Eldred wrote: Impedance varies with frequency if there are reactive components, L's and C's. That is not always true. Take 1) A resistor of resistance R in series with a capacitor of capacitance C. 2) Another identical resistor of resistance R, but in series with an inductor L. Make R=sqrt(L/C) and put 1 and 2 in parallel and measure the impedance across that combination. The impedance is always R, and is independent of frequency. A useless fact I would admit!! Not exactly useless, you just described a Zobel network. It is used as crossover to feed two loudspeaker on HI range and LOW range presenting a constant resistive load to the Amp. It is used to compensate a shunt at higher freq. The transfer function is perfectly flat even with two reactances in the circuit. It is used to terminate a DC distribution line R+L with a R+C to avoid resonances, the line is perfectly damped, when the load current steps there are no oscillatory transients. MG MG |
#23
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![]() "Don Bowey" wrote in message ... On 6/10/05 3:13 PM, in article , " wrote: How come? Do you object to the term "DC" - is monophasic acceptable to you? See also: http://64.233.161.104/search?q=cache...com/global/our _product/sp_Inverter/3_techno.html+%2B%22dc+sine+wave%22&hl=en&lr=lang_ en Your posts have all the characteristics that indicate you are a troll. If you aren't I suggest you quit being combative and learn from what the posters are saying. And re the link; that refers to an inverter that uses a DC input and outputs a sinewave. You must be troll. He's obviously not a troll, just not super knowledgeable about the subject at hand. If he were a troll he'd have crossposted to something like alt.vampires or alt.masturbation and alt.catholosism. |
#24
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Don Bowey wrote:
How come? Do you object to the term "DC" - is monophasic acceptable to you? See also: http://64.233.161.104/search?q=cache...com/global/our _product/sp_Inverter/3_techno.html+%2B%22dc+sine+wave%22&hl=en&lr=lang_ en Your posts have all the characteristics that indicate you are a troll. If you aren't I suggest you quit being combative and learn from what the posters are saying. The person I was replying to was being unnecessarily difficult and counter-productive....he knew what I meant (or should have known) as many other posters have graciously corrected....see also this previous thread where someone else uses the same terminology ("DC sine wave").... http://groups-beta.google.com/group/...a075188ea87d6b the replies were most considerate and productive and were not done in a childish and smug manner. I suggest the real trolls here are people who jump on the missue of conventional terminology (eventhough the message is otherwise clearly understood) to engage in mental masturbation with an "oh-so-witty"(not)8th grade, sophomoric "gotcha". P.S. I would challenge you to prove that the term "DC sine wave" is objectionable because it is fundamentally wrong as opposed to being at odds with conventional terminology and nomenclature.....Isn't a sine wave that operates as all positive voltages always yielding currents that operate in only one direction (i.e. "direct current")? Surely you wouldn't call this AC, would you? Isn't "DC sine wave" a more concise and readily (albeit only slightly more so) concept that an "AC sine wave that has been fully DC offset"? Is it conceivable that conventional terminology and nomenclature could have evolved such that "DC sine wave" was acceptable? If not, why not? How is it fundamentally wrong? (as opposed to being at odds with convention) |
#25
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Is that definition of "DC" written in stone (i.e. fundametnally true)
or as defined by convention? How is a sine wave operating as all postive voltages not yielding a current (albeit variable) of a single polarity, single direction that does not alternate? Isn't saying it is an "alternating current with a dc offset" a rather queer way of saying things since there actually is no (net) alternating (i.e. bi-directional) current flow? |
#26
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Again, is the term "DC Sine Wave" problematic because it is
fundametnally wrong OR is it problematic because it is at odds with conventional terminology and nomenclature.....if it is fundamentally wrong, then please show how.....however, if we're just talking about convention, then why break balls? (Wait, I'm sorry, I don't mean literally "breaking balls", that's just nomenclature).....if you were given a piece of paper a week ago with just the words "A Fully DC Sine Wave" on it and you were asked to come up with as many possible things it could realistically mean, how many things could you come up with? If you were being truthful I think you could only think of one thing (and think of it very quickly). If you think that the term "fully DC Sine Wave" even means anything, then you have not understood the coursework. |
#27
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#28
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#29
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Right...but your reply actually doesn't address the NET effect......if
the wave had a DC-component of +2 V and an AC-component of 10Vpp, then the wave would be NET AC (since its polarity changes pos/neg/pos/etc.)......however if the DC-component was +10V instead, then the wave would be NET DC (since its polarity never changes polarity - i.e. always positive).....that is why I argue a "fully DC sine wave" is a BETTER (albeit unconventional) and more concise way to describe what I'm talking about (without using actual values) than the conventional description you provided....your description is ambiguos...could be NET "AC" (biphasic) or "DC" (monophasic) |
#30
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If the low peak of the sine wave (and the rest of the the sine wave for
that matter) is "fully" above the "zero" reference point, then isn't it true that the current DOES NOT alternate? That is to say, that current only flows in one direction....i.e. "direct current"? Isn't it also true that if the low peak of the sine wave is -0.00001V then the sine wave results in current flowing in both direction (albeit for a nanosecond)....i.e. "alternating current".....I'm not arguing that my use of nomenclature is "pure" or conventional....but I don't see how it is fundamentally wrong, without merit, or lacking a reasonable basis..... |
#31
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![]() wrote in message oups.com... Again, is the term "DC Sine Wave" problematic because it is fundametnally wrong Yes. DC by definition is zero frequency. N |
#32
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#33
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On Sat, 11 Jun 2005 04:12:52 GMT, "NSM" wrote:
wrote in message roups.com... Again, is the term "DC Sine Wave" problematic because it is fundametnally wrong Yes. DC by definition is zero frequency. Um, no. DC is Direct Current, i.e., current that flows in one direction. For example, the output from a rectifier is DC but it certainly isn't "zero frequency." |
#34
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wrote in news:1118461679.394136.299150
@g14g2000cwa.googlegroups.com: Again, is the term "DC Sine Wave" problematic because it is fundametnally wrong OR is it problematic because it is at odds with conventional terminology and nomenclature.....if it is fundamentally wrong, then please show how..... Look jackass, AC means it is alternating in time. If it is DC it is constant. A sine wave alternates in time, thus is AC. Now shut up. ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#35
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I concede my terminology is anti-convention, and "wrong" (with respect
to convention) BUT I disagree with you he but do not try to communicate with anybody, because they will misunderstand you If you were given a sheet of paper a week ago, with only the phrase "a fully DC sine wave" on it, and you were asked to come up with as many realistic possible meanings, I have to believe that you could have only come up with one (and rather quickly) If true, then your statement: But because of the convention we keep up with the old definition to allow a communication with others. would hold true about "a fully DC sine wave" with respect to convention/"old definition" but not with respect to "communication" or ambiguity....while not "pure" or conventionally correct, is there really any other possible interpretation of "a fully DC sine wave" and therefore wouldn't you agree that being a "hyper-stickler" on this point is really not justifiable? Again, isn't there more ambiguity (poorer communication) in your description: The signal would be said to have a DC-component (of the average value) and an AC-component (of the rms value minus the DC) versus: a "fully DC sine wave" versus "a partially DC-offset AC sine wave" |
#36
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#37
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#38
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Let me try this:
would you object to "a sine wave which (net) results in a current that only flows in one direction" if you buy that, would you then accept it to be partially condensed into: "a sine wave which (net) results in a non-polarity-alternating current" if you buy that, would you then accept this: "a sine wave which (net) results in a direct current" and then "a (net) direct current sine wave" |
#39
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#40
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I will absolutely buy what you said, but understand the import of what
you're saying....you're saying that the language of "AC" and "DC" has essentially been somewhat *******ized from its original meanings to also mean zero-frequency and non-zero-frequency signals. Therefore, to describe a 10Vpp signal with a 10VDC offset as an "AC" signal is actually contrary to the original connation of "alternating current" since it (net) results in a signal which yields only a mono-directional (i.e. direct) current flow (albeit time variant). So in a sense, you could say I am holding "pure" to the original (circa 1890's) definition of AC/DC while its use has been "officially" corrupted to cover the concepts of "zero frequency" and "non-zero-freuency". Agree? |
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