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Thread: Practical Experiment in LRC circuits

  1. #1
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    Practical Experiment in LRC circuits

    Good evening gents,

    Do any of my established colleagues here have any classroom experiments that I can perform with my students regarding the use of inductors and capacitors? More in particular LC,RLC both series and parallel applications, circuits?

    I would like to show practical uses in everyday environments where these three electrical components work together. I can teach the numbers and calculations side of these but it doesn't really show how we use these components in everyday life. It would be good for my students to be able to put the calculations that I have taught them to use in a real life scenario and see how they work.

    Doing it on paper is one thing but being able to apply what we learn in putting it together is another. Like I tell my students, IMO, there are three types of people in the electrical field. Those that are book smart but can't build it, those that are "street smart" that can build anything with no book smarts and then those that can put both of the previous two together to engineer and build it at the same time. AKA - Nikola Tesla.

    Thanks and look forward to everyone's responses!!

  2. #2
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    Quote Originally Posted by Fishn sparky View Post
    Good evening gents,

    Do any of my established colleagues here have any classroom experiments that I can perform with my students regarding the use of inductors and capacitors? More in particular LC,RLC both series and parallel applications, circuits?

    I would like to show practical uses in everyday environments where these three electrical components work together. I can teach the numbers and calculations side of these but it doesn't really show how we use these components in everyday life. It would be good for my students to be able to put the calculations that I have taught them to use in a real life scenario and see how they work.

    Doing it on paper is one thing but being able to apply what we learn in putting it together is another. Like I tell my students, IMO, there are three types of people in the electrical field. Those that are book smart but can't build it, those that are "street smart" that can build anything with no book smarts and then those that can put both of the previous two together to engineer and build it at the same time. AKA - Nikola Tesla.

    Thanks and look forward to everyone's responses!!
    I don't know if you have a budget for classroom materials, but you might look into Snap Circuits. The level 500 kit has a ton of stuff. My oldest got the set when he was 10 and just kept going at it. It has all the components you are looking for and you can use lights and buzzers to see the outcome of your circuit. I would have used the Snap Circuit web site but it's not operating properly now.

  3. #3
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    you might look at a modelling program like matlab

    you can build any ckt and plot their response
    you can change parameters to see the impact
    use motors, xfmrs, contactors, etc
    do pf correction
    as simple or complex as you like
    I believe student versions are available
    The difference between genius and stupidity is that genius has its limits.

  4. #4
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    Quote Originally Posted by Ingenieur View Post
    you might look at a modelling program like matlab

    you can build any ckt and plot their response
    you can change parameters to see the impact
    use motors, xfmrs, contactors, etc
    do pf correction
    as simple or complex as you like
    I believe student versions are available
    Matlab can certainly get the job done, but even the student edition runs $99. They also restrict it to degree-granting institutions, so if the OP is at a trade school or doing a union-sponsored training course he may be out of luck. Individual copies are currently at $2,150. Yikes! I have an old copy I got back in the 1990's floating around somewhere. It might have been $99 or $199 back then. Wish I could make it run on my Vista machine.

  5. #5
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    There are a tremendous number of different possibilities. Broadly transient, steady-state, and transient on into its steady-state.

    You need an adequate scope, function generator, meters, loadcell, torque transducer (possibly rotary), pressure transducer, regulated voltage power supply, at least over a limited range a current source, a no-bounce switch, AC solid-state switch with turn on phase control, Ohmite power resistors, incandescent light bulbs, a true DC shunt wound motor with separate shunt excitation, current shunts for current measurement, capacitor start and run single phase motor, polypropylene capacitors, a transformer, a Variac, and an old automotive ignition coil and capacitor from early 1960s, a spark gap, possibly a 12 V drycell, and more.

    Somehow you need to simplify what you work with.

    I would start with a battery to a switch to an RC, RL, or RLC circuit. Do RL both turning on and off, and with and without a snubbing diode.

    Phase controlled turn on of a sine wave to an RLC circuit off resonance and at resonance.

    Phase controlled turn on of a voltage to an incandescent bulb. Same to a transformer.

    Half-wave rectifier to an RC load with and without a transformer. Same with a full-wave rectifier.

    Auto ignition coil is a double tuned circuit with a spark discharge. Need a 30,000 V 1 MHz scope probe.

    What do you want to narrow it down to?

    Just some experiments:
    http://www.beta-a2.com/EE-photos.html
    http://www.beta-a2.com/cat-5e_photo.html

    .

  6. #6
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    he may only need the educational version
    matlab and simulink $1000 per yr

    just so flexible
    can be put on a projector
    can change freq and see the Z of an L change
    can do a LC and see the notch as freq sweeps
    make 2PiL = 2PiC = 1 and see total Z ~f
    nice simple graph

    with discrete components hard to 'see' responses
    need a scope, etc
    and difficult to make changes

    not sure what level of student he teaches
    just a thought
    Last edited by Ingenieur; 11-30-17 at 09:38 PM.
    The difference between genius and stupidity is that genius has its limits.

  7. #7
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    Ingenieur:

    What you suggest has some merit, but it is still a theoretical approach.

    I believe the intent of the original post was to do some experiments with real world components and real instrumentation.

    Thinking about my suggestion of an ignition coil, it is apparent that in one transient cycle one can simultaneously perform several experiments, and other tests can obtain other data.

    These would be --- (1) LR charging, (2) LRC on opening charging current, (3) Inductive coupling to a secondary, (4) Breakdown of an air gap, (5) Spark voltage drop, (6) Measurement of primary and secondary resistances, (7) Measurement of primary and secondary inductances, (8) Estimate of primary and secondary self resonant frequencies, and (9) Measurement of leakage inductance primary to secondary.

    In the real world I can measure the source voltage, and the transient current to a resistance in series with a real inductor. But I can not measure the voltage drop across either the resistive or inductive components. These I have to calculate from the current measurement.

    Change this to a high quality RC circuit and I can make the direct measurements.

    How to get valid measurements with a scope or other instrumentation takes real world components and equipment.

    .

  8. #8
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    Quote Originally Posted by gadfly56 View Post
    Matlab can certainly get the job done, but even the student edition runs $99. They also restrict it to degree-granting institutions, so if the OP is at a trade school or doing a union-sponsored training course he may be out of luck. Individual copies are currently at $2,150. Yikes! I have an old copy I got back in the 1990's floating around somewhere. It might have been $99 or $199 back then. Wish I could make it run on my Vista machine.
    Run a virtual machine which is running an earlier Windows OS. You can get a free open source VM environment called VirtualBox to do the job. Then all you need is a licensed copy of the old OS.

  9. #9
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    I used multisims in college, it is great.

    Hundreds of discrete parts, IC chips, meters, supplies, etc.

    You download a free demo and get a student version for 42 dollars.

    Well worth it.

    http://www.ni.com/multisim/
    "Electricity is really just organized lightning." George Carlin


    Derek

  10. #10
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    Quote Originally Posted by gar View Post
    171130-2353 EST

    Ingenieur:

    What you suggest has some merit, but it is still a theoretical approach.

    I believe the intent of the original post was to do some experiments with real world components and real instrumentation.

    Thinking about my suggestion of an ignition coil, it is apparent that in one transient cycle one can simultaneously perform several experiments, and other tests can obtain other data.

    These would be --- (1) LR charging, (2) LRC on opening charging current, (3) Inductive coupling to a secondary, (4) Breakdown of an air gap, (5) Spark voltage drop, (6) Measurement of primary and secondary resistances, (7) Measurement of primary and secondary inductances, (8) Estimate of primary and secondary self resonant frequencies, and (9) Measurement of leakage inductance primary to secondary.

    In the real world I can measure the source voltage, and the transient current to a resistance in series with a real inductor. But I can not measure the voltage drop across either the resistive or inductive components. These I have to calculate from the current measurement.

    Change this to a high quality RC circuit and I can make the direct measurements.

    How to get valid measurements with a scope or other instrumentation takes real world components and equipment.

    .
    Honestly, that is not really practical and it is difficult to see the results and impacts of changes and is very time consuming.
    Until we know the level of instruction it is hard to determine the best path forward.
    The difference between genius and stupidity is that genius has its limits.

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