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computer analysis of circuit networks

Discussion in 'Electronic Basics' started by [email protected], Jan 8, 2006.

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  1. Guest

    Hi there

    I am wanting to write a program that, given a network, can calculate
    current, voltage, etc over all components and branches in the network.
    At the moment, I am just concentrating on linear DC networks that have
    nothing but voltage and/or current sources, and resistors. I'm
    ignoring capacitive and inductive components for the time being

    In a circuit analysis textbook I've got, it says that branch current
    analysis can solve any linear DC network, so this is the algorithm I
    have chosen for the program. With voltage sources and resistors this
    seems to be no problem, as you are using KVL around each independant
    loop of the circuit, plus a couple of KCL equations, then you solve
    them simulataneously.

    I get stuck with current sources though. for example the following:

    | | |
    | | |
    V C R2
    | | |
    | | |

    Lets say V is a 6V battery, R1 is 2 ohms, C is a 2A current source and
    R2 is a 5 ohm resistor

    With branch analysis, there should be two KVL eqns and one KCL eqn.
    But how can you do KVL around a loop with current sources in? I know
    that you could convert C into a voltage source through source
    conversion, but what if you cannot do a source conversion, such as when
    there is not a convenient parallel resistor. i suppose what im asking
    for is a surefire algorithm that can be used in a computer program (ie
    generic and doesn't rely on human intuition) that will solve any
    network. Any hints or open source programs that can be of help are

  2. Guest

    The following two pages have some good tips:
  3. Its SPICE...

    Why do you want to reinvent the wheel? Its all been done for 30 years.

    The soucce code can be obtained from many sources, e.g. ngspice

    Even the my windows version XSpice engine can be ran standalone to do
    this if that's all you are after.

    Kevin Aylward
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
  4. Michael, use nodal analysis if you want to tackle this yourself.

    Better yet, download LT spice (it's free ... give it a Google) and learn how
    to use it.
  5. Guest

    I know Kevin, I used Spice at uni. That's not the point.

    Call me unhinged, but sometimes I like to understand how things work,
    especially algorithms. I am after all a programmer by trade...

    Anyhow, I found out what Spice uses, an algorithm called modified nodal
    analysis (MNA). Right now, I don't completely understand the
    mathematics behind it, but I know enough to implement it in software.

    Thanks all for your help

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