Recent content by BackEMF

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    InfraRed Detector Mystery (but not Elementary....)

    I managed to get an OS-1838B IR detector, so no longer need to figure out what the mystery device is exactly. But I still want to! I compared the output waveform of the 1838B IR detector with that of the unknown element, when they are excited with a TV remote control signal. I get the...
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    InfraRed Detector Mystery (but not Elementary....)

    Thanks, fellow sleuths. A photodiode seems likely, although the pinout still confuses me. Perhaps a phototransistor, where the base should be left floating? An excellent rule! I think I'll adopt this. This should have been my approach from the beginning, but since I can't just buy components...
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    InfraRed Detector Mystery (but not Elementary....)

    Hello! I found this circuit element below in a drawer marked "IR detectors" (which I must have written on it myself, a long time ago...although I must admit don't remember doing so #OldAge). First of all, I'm trying to figure out what, exactly, it is. My initial assumption was that it looks...
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    Programs Is pursuing a second undergraduate degree after completing a PhD a good idea?

    I have looked into this. It doesn't seem like a possibility anywhere near where I live. There's no evening universtiy classes in mathematics for the purpose of obtaining a degree in the country, as far as I can tell! Thanks for the advice. I am considering a one-year postdoc position at the...
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    Programs Is pursuing a second undergraduate degree after completing a PhD a good idea?

    So, as the title says, I'm considering doing a second undergraduate degree having recently completed my PhD. I've searched for advice on this online and I can't see anyone else who has asked this before, which hasn't made my decision any easier. My educational background is an undergraduate...
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    Non-homogenous secx ODE's and Euler eq's

    Non-homogeneous secx eh? :P You could always try a Power Series solution if you expand the sec(x) in a power series: http://en.wikipedia.org/wiki/Power_series_solution_of_differential_equations
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    What is the Minimum Sampling Frequency for a Sinusoidal Signal?

    Yes, I suspect this may the approach the question is designed to test. But, of course, Carnson's Rule only gives about 98% of the bandwidth - there's no indication in the question that this is enough. That's actually the instantaneous phase, not the frequency. To get the instantaneous...
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    Doubting Ohm's Law: LED & 220Ω Resistor

    Can we verify the battery's voltage?
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    Doubting Ohm's Law: LED & 220Ω Resistor

    1) Measure the actual resistance of the "220 ohm" resistor. 2) Check the accuracy of the meter (use another meter - digital might be better as it would probably change the circuit less than and analgoue one)
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    What is the Minimum Sampling Frequency for a Sinusoidal Signal?

    The question is really weird! First of all, sampling is generally defined for signals that exist for all time, yet you're told you only care about signals between t_o and t_f . Also, sampling is usually based on Fourier theory, but this signal doesn't have a Fourier transform if you're...
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    Fermi Energy and Fermi Level in Semiconductors

    Yep, that's it - as the energy of the electrons increases the probability of finding some at higher energy also increases, and in particular the energy level at which the probabilty of find an electron is 0.5 i.e. the Fermi level, will rise up from somewhere near the middle of the bandgap in an...
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    Fermi Energy and Fermi Level in Semiconductors

    The Fermi-Dirac distribution gives us the probabilty that, should there exist a quantum state at a particular energy level, we find an electron occupying that state. It is the "probabilty of occupation" of an available energy level. To get the total number of electrons per unit volume, in a...
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    Would this class be useful for an EE? Advanced Engineering Calc.

    Seems useful to me. It'd be hard to have enough applied maths courses. Pertubation theory appears in many areas, if you get into the quantum side things it would be quite useful there. Hamiltonian stuff is useful for quantum too, and Laplace, special functions and Sturm-Liouville theory is...
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    Decomposition of a Rotation Matrix

    A good book by all accounts (I haven't read it yet myself) is this: Quaternions and Rotation Sequences. It may be a bit too advanced at the moment. Keep it for later reference maybe, something to work toward!
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    MATLAB precision for variables

    Hi Sara, I came across this article on computing pi recently. It might be of use in general for implementing variable precision commands in matlab. http://www.mathworks.co.uk/company/newsletters/articles/clevescorner-computing-pi.html
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