Seeking advice on modifying a battery experiment.

Discussion in 'The Projects Forum' started by Yusif Nurizade, Jan 12, 2012.

  1. Yusif Nurizade

    Thread Starter New Member

    Jul 4, 2011
    21
    0
    Hello,

    I am hoping to get some help on a project I am planning out.

    A couple of weeks ago we arranged an experiment where we put together an LRC circuit. To be more specific, we actually placed the inductor and capacitor while being content enough with the internal resistance not to add a resistor. This was connected to an DC power supply and an oscilloscope which monitored either the capacitor and inductor or just the capacitor (my memory of this detail is murky). Once the power source was instructed to go to a certain voltage, we could watch the same occur on the oscilloscope screen and see how long it took, whether it overshot, etc.

    Now I am trying to make a similar experiment except using a battery. My idea is to use an E-load and power source to take it back to back in cycles and monitor factors like the time it takes, the overshoot, oscillations etc. I'd gather this information using an oscilloscope or DAQ board and record it with a computer program.

    My question is with regard to the circuit. If I were to do this using an E-load and a DC power source, would I have any need for a circuit like the one we used in the first experiment? Would using the devices I mentioned make it more artificial and less reliable? I know the last part might sound silly but I would like to get the best results out of this experiment so the details matter. Futhermore, is there any specific reason we were told to use the LRC as opposed to say, just a resistor? One advantage I see to creating a circuit is that I could model it in something like PSPICE to have something to compare to. In such a case, I am curious as to how an E-load would factor in or whether I should abandon it as an element in the experiment.

    Any advice is greatly appreciated, I learned a lot on these forums and hope to continue to do so.

    Thanks,
    Yusif Nurizade
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,145
    3,055
    I think anyone will have trouble offering advice without a schematic. The more detail you can provide, the better help you'll get.
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,027
    3,236
    If you are just want to see the battery characteristics then you would want a simple resistive load. LC components add a resonant circuit which will oscillate and ring when you apply a step voltage. Have you not studied resonant circuits?:confused:
     
  4. Yusif Nurizade

    Thread Starter New Member

    Jul 4, 2011
    21
    0
    Thank you for the replies fellas,

    wayneh: The circuit we had for the first experiment was a simple LRC. Do you mean I should provide a schematic for an LRC or specific values? I assumed everyone would be familiar with an LRC and my question was whether I should have a circuit or simply use an E-Load when testing a battery. To me the benefit of a circuit was that I could model this in say PSPICE and then compare.


    crutschow: We touched on resonant circuits but the class that delves deeper is still on the horizon (the semester starts in two weeks). This experiment is, among other things, my attempt to gain practical versus theoretical knowledge of the subject. Again, I know what the circuit would do; my question is whether or not this would be preferential to an E-load or a resistor because as far as I could see it offers for a better virtual model.

    I apologize if I did not articulate myself well enough initially.

    Yusif Nurizade
     
  5. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    There is more than one way of using a power supply, a switch and an LC(R) circuit. One of the most standard involves charging the capacitor initially from the supply, then using a change-over switch to disconnect the capacitor from the supply, then put it in parallel with the inductor, when the decaying oscillation will be seen. Otherwise, the coil and capacitor may both be put in parallel with a power supply, the latter most likely current limited, and left connected until a steady current is passing, then switched out.

    Electronic loads (if that is what you mean) generally contain control systems to produce a range of different load characteristics. They are designed to offer stable operation as far as possible, but connecting one with an LC circuit might possibly lead to oscillation.

    A schematic of what you have in mind would help a lot.
     
  6. Yusif Nurizade

    Thread Starter New Member

    Jul 4, 2011
    21
    0
    Thank you for all the responses I will post a schematic tomorrow.
     
  7. Yusif Nurizade

    Thread Starter New Member

    Jul 4, 2011
    21
    0
    I want to apologize in advance for any mistakes I make in positing the problem; I am still new to this and trying to learn which is why I turned to the forum.

    I was able to speak to someone who was better able to explain what we did initially an created a schematic as was requested. To clarify the drawing; the probe is on the capacitor, not the whole circuit.

    I have included a resistor in the schematic but the circuit was laid out on a breadboard with some internal resistance assumed and therefore no actual resistor. We had an Agilent DC Power Supply set to some nominal voltage which was incremented producing a step voltage that produced a jump on the oscilloscope with oscillations that eventually settled. The nature of this jump is what we were interested in.

    Now, my project involves testing a rechargeable battery. The most obvious way I could think of to do this is to connect it to an E-Load for discharge and a power supply for charging but I would like to see more and was curious if I could apply the same circuit using my battery as a power source. The difficulty I am looking for help with is that I can't increment the voltage of the battery as I did with the DC power supply and was hoping there was some way to get around that.

    Thank you for taking the time to read and offer advice.

    Yusif Nurizade
     
    Last edited: Jan 13, 2012
  8. wayneh

    Expert

    Sep 9, 2010
    12,145
    3,055
    You can increment from full off to full on. You can toggle a series of different loads on and off, or even an external charger could be toggled to incremental charging current levels.

    Perhaps if you describe the data you want, someone will think of a clever way to accomplish the experiment.
     
  9. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,792
    948
    [​IMG]

    The switches are to simple to actually be useful when using this for signal generation viewable on an oscilloscope.

    You need to replace the switches with transistor or mos devices and use them as switches. A simple 555 timer can be set up to drive the switches on and off and also provide a trigger signal for the o'scope.

    ???
     
    Yusif Nurizade likes this.
  10. Yusif Nurizade

    Thread Starter New Member

    Jul 4, 2011
    21
    0
    I apologize for the late response; I was a bit distracted by the move and the beginning of the semester.

    Thank you for your responses, I've been looking into MOSFETs and they seem like a great idea! My current electronics class covers them extensively and my signals class goes heavily into filters so I think I should be in good shape to implement the project over the summer.

    Hopefully I can just resurrect the thread then if there are still things I am murky on.

    Thanks again,
    Yusif
     
Loading...