For a specific frequency, with a DC pulse generated using Arduino, can we expect the same potential difference across resistors and inductors every time in a RL circuit?
( a little bit new info)
By continuous dc pulse I meant square wave not sine wave, and no issue with the basic time needed to take the reading. Also can manipulate time constant and frequency accordingly.
I am trying to measure unknown inductance using arduino and series RL circuit. So they are normally done by finding frequency where the potential difference across resistor and unknown inductance are equal Or by varying resistance until they are equal. Am I right? So I am confused if I keep the same frequency and resistance constant, there will some potential difference across inductor irrespective of its value, is I intend to use that potential difference (irrespective of the circuit is resonating or not) to find the value of inductor, will that inductance and potential difference across it vary linearly? how precise can the values be, can it vary by some factor I am not taking into consideration due to which I won't be able to calculate the inductance? Is there any other way using RL circuit to measure unknown inductance?
Also sorry for the prior confusing question.
(a small addition)
I have not drawn out a circuit out till now, I am trying to find a better way to measure inductance of a unknown value as precisely as possible using arduino,
The most widely used way I found was using a LC circuit, but I am trying to find it using RL circuit which I feel can be more promising,
So the ways to measure are 1) regulate frequency so that we potential difference across resistor should be equal to potential difference across inductor so the circuit resonates and we find precise time constant
2) the second was to regulate resistance to find the circuit resonating
So, if we keep both of them constant, will inductance and potential difference across it vary linearly?
there is one more way of passing a constant high and measuring time constant directly using hall sensor, but I am not sure if that can work either?
kishoraditya:
For a specific frequency, with a DC pulse generated using Arduino, can we expect the same potential difference across resistors and inductors every time in a RL circuit?
You are going to have to explain the question a lot better than that. Please post a schematic (hand drawn and photographed is fine) illustrating what you are asking about.
For a specific frequency, with a DC pulse generated using Arduino, can we expect the same potential difference across resistors and inductors every time in a RL circuit?
Sounds like you could use a crash course in Ohm's Law.
If the arduino is only capable of outputting a 5V pulse, is it going to change the potential difference from
the output pin if you vary the resistance to ground ? Think about it. Look at ohm's law. No amount of
resistance or inductance placed between an output pin and ground is going to change the potential difference
from the output pin to ground. That's electronics 101. It would only change the current.
kishoraditya:
For a specific frequency, with a DC pulse generated using Arduino, can we expect the same potential difference across resistors and inductors every time in a RL circuit?
One possible answer is "No, as the inductor will damage the Arduino pin at the end of the first pulse due to inductive kick-back voltage."
Another answer: "No, there may still be currents circulating from the last pulse so that second and subsequent pulses see different circuit conditions from the first pulse"
Please be much more specific with your question, provide the circuit and code if at all possible.
In a word no but there is much more to it. How much current can your Arduino source? If I even remember Lenz law figures in along with Ohms law and let's not forget Kirchhoff's law. Then as mentioned how will your Arduino feel about things when the first pulse transitions high to low and the inductor field collapses? That may get ugly.
You really need to draw your circuit and assign values to L and R.
The question was not whether or not a dc
pulse through an RL circuit driven by an arduino output would ring or damage the pin. The question was very clearly whether the potential difference
across the resistor and inductor would be the same for the same pulse. Granted , it is difficult if not impossible to tell from the wording if he meant
the across the individual components or the
same across the series (assumedly) combination
of the two (also assumed to be one each).
It says "for a specific frequency", and unless you can show how the potential across a resistor or inductor would differ
from one cycle to the next , and assuming the
arduino hasn't self destructed from
inductive kickback (which , personnaly I think the
the internal diodes can handle) , I
don't see , or , have yet to see,
proof that the potential difference
would not remain the SAME as long as the frequency
doesn't change. If there IS inductive kickback and
you view it on a scope, it should be CONSISTENT
as long as the frequency is consistent and at no time did the OP ask if there would be kickback and
even if there was it would be consistent. so
YES we can expect the same potential difference
across the SAME components and NO if you
CHANGE the components but YES across ALL the
components (from output pinto GND).
I would be curious to see someone make a case
for how the voltage (standard nomenclature for
"potential difference" (a term LITERALLY used
ONLY in CLASSROOMs , indicating the OP's
probably a student (really, where else would he
hear such a cumbersome term for 'voltage' ?)
While I agree the question is pretty much nonsense with nothing defined. Less any values what is the RL time constant? What is the Pulse Repletion Time and Pulse Width? Like an RC time constant if I remember any of this stuff correctly it will take 5 time constants to get the voltage up to the applied voltage. Maybe it is homework and if that is the case the thread starter should do his homework. Anyway, my answer is no and remains no to his question if all he or she wants a yes or no a one or zero.
Ron_Blain:
Like an RC time constant if I remember any of this stuff correctly it will take 5 time constants to get the voltage up to the applied voltage.
By then it reaches about 98% of the full voltage, it's a limit approach and the math will tell you it never quite gets there. But for all practical purposes an RC circuit on a DC source reaches full voltage after about 5x RC time.
However the OP is not applying a constant voltage, they're applying a block wave, and that complicates the whole thing.
I don't see inductive kick-back happening as the current is not stopped (the circuit is not broken, just one point of the circuit changes potential). But I may be wrong here, as OP didn't clarify their complete intended circuit.
The 'kickback' only occurs when the magnetic field collapses at whichtime the charge stored in an inductor reverses polarity. In the case of a pulse,
this cannot occur because the falling edge of the
pulse drains the charge through the resistor ,
rather than a sudden drop. The current, and therefore the kickback is impeded by the resistor.
To generate a kickback, you need a switch that closes before charging the inductor and then opens
when it is charged to maximum voltage (5V in this case). Look at a switchmode power supply .
I believe that's why the diode is there, to prevent that.
PerryBebbington:
You are going to have to explain the question a lot better than that. Please post a schematic (hand drawn and photographed is fine) illustrating what you are asking about.
raschemmel:
Sounds like you could use a crash course in Ohm's Law.
If the arduino is only capable of outputting a 5V pulse, is it going to change the potential difference from
the output pin if you vary the resistance to ground ? Think about it. Look at ohm's law. No amount of
resistance or inductance placed between an output pin and ground is going to change the potential difference
from the output pin to ground. That's electronics 101. It would only change the current.
The potential difference across the resistor and across inductor which are connected in series, those individual may vary, right?
MarkT:
One possible answer is "No, as the inductor will damage the Arduino pin at the end of the first pulse due to inductive kick-back voltage."
Another answer: "No, there may still be currents circulating from the last pulse so that second and subsequent pulses see different circuit conditions from the first pulse"
Please be much more specific with your question, provide the circuit and code if at all possible.
I have not drawn out a circuit out till now, I am trying to find a better way to measure inductance of a unknown value as precisely as possible using arduino,
The most widely used way I found was using a LC circuit, but I am trying to find it using RL circuit which I feel can be more promising,
So the ways to measure are 1) regulate frequency so that we potential difference across resistor should be equal to potential difference across inductor so the circuit resonates and we find precise time constant
2) the second was to regulate resistance to find the circuit resonating
So, if we keep both of them constant, will inductance and potential difference across it vary linearly?
there is one more way of passing a constant high and measuring time constant directly using hall sensor, but I am not sure if that can work either?
raschemmel:
The question was not whether or not a dc
pulse through an RL circuit driven by an arduino output would ring or damage the pin. The question was very clearly whether the potential difference
across the resistor and inductor would be the same for the same pulse. Granted , it is difficult if not impossible to tell from the wording if he meant
the across the individual components or the
same across the series (assumedly) combination
of the two (also assumed to be one each).
It says "for a specific frequency", and unless you can show how the potential across a resistor or inductor would differ
from one cycle to the next , and assuming the
arduino hasn't self destructed from
inductive kickback (which , personnaly I think the
the internal diodes can handle) , I
don't see , or , have yet to see,
proof that the potential difference
would not remain the SAME as long as the frequency
doesn't change. If there IS inductive kickback and
you view it on a scope, it should be CONSISTENT
as long as the frequency is consistent and at no time did the OP ask if there would be kickback and
even if there was it would be consistent. so
YES we can expect the same potential difference
across the SAME components and NO if you
CHANGE the components but YES across ALL the
components (from output pinto GND).
I would be curious to see someone make a case
for how the voltage (standard nomenclature for
"potential difference" (a term LITERALLY used
ONLY in CLASSROOMs , indicating the OP's
probably a student (really, where else would he
hear such a cumbersome term for 'voltage' ?)
THANK YOU, I was only looking for wether or not the values will change at the time I asked this question, which YOU have answered in this reply that it won't and also for explaining my confusing words to others.
Although I realized I should have asked whether or not that value will vary linearly with inductance value if we keep frequency and resistance constant.
Also for inductive kickback, that can be managed by the off cycle of the pulse right?
And YES I am still learning a lot of things, BUT I feel it is good to be precise and say potential difference rather than voltage level assuming the other end is grounded or maybe voltage drop across it can also be a term for what I meant there
Ron_Blain:
While I agree the question is pretty much nonsense with nothing defined. Less any values what is the RL time constant? What is the Pulse Repletion Time and Pulse Width? Like an RC time constant if I remember any of this stuff correctly it will take 5 time constants to get the voltage up to the applied voltage. Maybe it is homework and if that is the case the thread starter should do his homework. Anyway, my answer is no and remains no to his question if all he or she wants a yes or no a one or zero.
Ron
By 'specific' you could've assumed the obvious values and constants, but since you didn't get that and also the rest of the question was more confusing, I have added a little more part to it, you can take a look and help if you'd like.
Also, it isn't my homework I have done those already
And thank you for the answer to question I asked before, no satisfies and reasons it too.
wvmarle:
By then it reaches about 98% of the full voltage, it's a limit approach and the math will tell you it never quite gets there. But for all practical purposes an RC circuit on a DC source reaches full voltage after about 5x RC time.
However the OP is not applying a constant voltage, they're applying a block wave, and that complicates the whole thing.
I don't see inductive kick-back happening as the current is not stopped (the circuit is not broken, just one point of the circuit changes potential). But I may be wrong here, as OP didn't clarify their complete intended circuit.
Yes, I have updated the question a little more precisely, unfortunately I do not have a circuit design since I am just trying to experiment and understand the topic better.
Also inductive kickback can be a possibility, but can be managed through off period of pulse cycle.
Also yes, I was talking about the potential difference across resistor and inductor individually which may vary
So now we have to dig through previous mails to see what changed? No thanks.
You should just have added it to a new post.
You can still do.
Help us help you!
Let's be clear here , your signal is NOT steady
state voltage but a pulse, so while nobody has
stated the obvious we should state that the
voltage across both components is a function
of time , so when we say it doesn't change we mean the voltage at t= Vpeak(component-x)
(with respect to the pulse) will be consistent
from cycle to cycle just as the voltage at V(50%)
will be consistent , whereas the voltage before
and after V(peak) will not be the same V(25%|rising edge) would differ from V(25%|falling
edge ) due to the pulse shape (which, for a SERIES RL circuit is NOT a square wave) but the respective
values should be more or less consistent in liu
of component heating an ambient temp fluctuations. So the bottom line is that the people
who answered "NO" it would NOT change were
doing so because they were taking time into account and the fact that the voltage on the components will always be changing due to the
nature of the nonsteady state signal input and
the people who said "Yes" it would stay the same
assumed you meant the average peak and were
not trying to trick us with the time factor.
So depending on how you interpretted the question
the answer could be yes or no.
Does that help ?
Are you in fact a student ?
