Circuit simulator?? Not sure its 100% correct

Discussion in 'General Electronics Chat' started by wannaBinventor, Apr 26, 2010.

  1. wannaBinventor

    Thread Starter Active Member

    Apr 8, 2010
    I'm using the circuit simulator found here:

    I started using it because it was simple and had plenty of examples. I'm now questioning the accuracy of it a bit. I'm far from an expert, heck, I'm barely a novice, but I feel like some of the simulation just doesn't match theory.

    Does anyone here have any experience using that simulator? Can you
    vouch for its accuracy?

  2. count_volta

    Active Member

    Feb 4, 2009
    I use this sim a lot. Its very cool. Its accurate most of the time, but I did notice that for very complicated analysis it can be inaccurate.

    I say use it for simple stuff and to get an idea of how stuff works, but if you want accuracy use pspice.

    Can you give an example of where you say its inaccurate?
  3. Wendy


    Mar 24, 2008
    It is pretty close. It is meant to show graphically what is usually explained with math, so some allowences are made.

    There are other simulators (some that are available for free downloads) call SPICE (Simulation Program with Integrated Circuit Emphasis) that are powerful tools for beginners. If you make a mistake only the display electrons are inconvenienced, no magic smoke escapes nor parts destroyed. There are quite a few versions, each with its own advantages and disadvantages. They can be quite good, but sometimes they are also a bit off.

    Speaking for myself I learned electronics long before these tools were available, so I tend to trust the one between my ears more. This doesn't make be better than these tools, just hard headed.
  4. kkazem

    Active Member

    Jul 23, 2009
    Hi all,
    For circuit simulation, I highly recommend LTSPICE, which is free of charge at Linear Technologies website at: You can use most any SPICE models from various IC, semiconductor, and even magnetics manufacturers for their various components. There are also models for various kinds of circuits all over the web made for SPICE that are mostly free and can be found with a google search or similar. Linear Tech has their own extensive library that comes free with the LTSPICE, as well as free updates, well written user manuals, and other training aids and help files. Finally, there is a Yahoo user group for LTSPICE users and and all are welcome. Not only is this a fantastic database of problems and solutions for LTSPICE and SPICE in general, if you have a specific problem and post it, it will get answered quickly in most cases. The only stipulation is that you have to register, but they don't give out user contact data. I've used several SPICE simulators including the most popular one called PSPICE, and I can say without reservation that LTSPICE is better. PSPICE is still out there and there is a free student version with a limitation of something like 25 nodes, and it costs in the low thousands the last time I checked from ORCAD.

    LTSPICE, like all other good simulators has a schematic capture input and a great post-simulation graphics processor that you can display not only circuit waveforms, but you can do math on waveforms and see the results graphically, like multiplying a current and a voltage waveform to get the true instantaneous power waveform and much, much more.

    Good luck.
    Kamran Kazem
  5. andreapg

    Active Member

    Feb 2, 2010
    I think that happens with all simulators.
    Recently I built and tested a roll shutter circuit. If I press a button for 4 or more seconds the relay keeps the high level, so the door works automatically until the limit switch is activated (or until the opposite direction button is pressed).
    When I simulated it (microcap9) I got the same delay using 4700uF instead of 220uF...
    I think there is always a difference between virtual and real components...