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Discussion in 'General Electronics Discussion' started by Steven Tyson, Aug 30, 2016.

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  1. Steven Tyson

    Steven Tyson

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    Aug 30, 2016
    can anyone tell is ltspice accurate...would you recommend it?
     
  2. duke37

    duke37

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    I have used ltspice very little. The accuracy will depend on the models you employ, the components are only approximations to the real world.

    What do you mean by accuracy?

    I have used 5spice as the circuit seems to be easier to enter but the free version is limited.
     
  3. Steven Tyson

    Steven Tyson

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    Aug 30, 2016
    ACCURACY LIKE WAVEFORMS OR JUST ANYTHING I CAN MEASURE IN THAT SOFTWARE...I'M NEW TO THAT SOFTWARE, DAVE JONES FROM E.E. BLOG ON YOUTUBE RECOMMENDS IT..I'M ALSO TRYING TO ADD MODELS TO MY LIBRARY, BOY I'M TO BUSY TRYING TO FIGURE THIS STUFF OUT...OH WELL I'M PATIENT UNTILL I'M ALL SET....HEY THANKS FOR THE INFO
     
    Last edited by a moderator: Sep 7, 2016
  4. Alec_t

    Alec_t

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    I can definitely recommend LTspice. A fairly steep learning curve, but worth it.
     
    Steven Tyson likes this.
  5. Steven Tyson

    Steven Tyson

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    hey thanks alect_t and duke37....i'm new to this forum and i'll bet i'll learn a great great deal in the future
     
  6. OBW0549

    OBW0549

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    Yes, I'd certainly recommend it; Spice can be a huge time-saver (it can also be a huge time-waster, but that's another matter) and it can be a valuable tool for gaining confidence that a design will probably do what you actually intended it to do, and for catching major design blunders. It is also often good for playing "What if...?" and seeing what effect changing component values or circuit configuration might have on a design. It can also drastically speed up the process of troubleshooting a design to see why it isn't behaving as intended, and evaluating the probable effectiveness of various corrective measures.

    But note the "weasel words" in the above paragraph-- "can be," "probably," "often," "might have," "can also," and "probable." Because Spice is NOT dead-accurate; after all, it is only a simulation, and is therefore subject to all manner of errors and inadequacies. The similarity of Spice results to actual circuit performance can range all the way from "just plain flat-out WRONG" to "kinda-sorta like" to "very much like" all the way up to "creepy accurate."

    Most of the time, when used judiciously with experience and skill, and with realistic expectations, Spice results will pretty closely approximate the actual behavior of real-life circuits. But they will not be exact.

    And finally, as Alec_t noted, there is a pretty steep learning curve involved; it takes quite a bit of experience and practice to reach a point where Spice becomes a valuable tool to keep in your "engineering toolbox."
     
  7. Steven Tyson

    Steven Tyson

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    Aug 30, 2016
    hey thanks alect_t and duke37....i'm new to this forum and i'll bet i'll learn a great great deal in the future
    hey thanks i appreciate the info...wow this forum is very useful....i'll bet i'll have more ltspice questions in the future...ENJOY YOUR LABOR DAY WEEKEND...THANKS
     
    OBW0549 likes this.
  8. OBW0549

    OBW0549

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    Thank you. Best of luck in your adventure, and enjoy the holiday!
     
    Steven Tyson likes this.
  9. HellasTechn

    HellasTechn

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    Welcome,
    I am sure you will. I have :)
     
    Steven Tyson likes this.
  10. chopnhack

    chopnhack

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    Hi Steve, LTSpice is very useful, but you have to take results with a grain of salt - they are just models - an imperfect approximation of what is really going on. Operating parts outside of their parameters or expecting ideal functions of parts will get you into trouble. Also, as was mentioned earlier that there is a long learning curve to it - to go further on that, not knowing enough about the program and individual settings can cause you to end up with faulty results. There have been a few times that has happened to me. Post your waveforms here with schematics and the awesome forum members can probably light your way.

    Welcome to the forum!
     
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  11. Steven Tyson

    Steven Tyson

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    Aug 30, 2016
    THANK YOU
     
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  12. OBW0549

    OBW0549

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    Yup. Been there, done that.

    Another nasty little trick Spice is fond of pulling comes from the fact that in Spice, two or more transistors of the same type (2N3904, BC550 or whatever) are not merely similar to one another like they would be in real life, nor are they very similar to one another like they would be if they were alongside each another on an integrated circuit die; they are EXACTLY the same, identical clones of one another in every respect.

    The consequences of this can easily drive one head-bangingly insane.

    On the one hand, if you're not careful you can design a circuit which depends on two or more devices being perfectly matched; it will appear to work just fine and dandy in Spice, but when you build it with real-world devices it doesn't work worth a hoot.

    The opposite situation happens, too: you can have a circuit which depends for its proper operation on devices not being precisely identical and which works fine when built with real components, but Spice simply cannot be coaxed into simulating it properly, nohow.

    Spice is such fun...
     
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  13. Steven Tyson

    Steven Tyson

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    Aug 30, 2016
    COOL THANKS FOR THE HEADS UPM JUST THE INFO I NEED BEFORE GOING INTO BATTLE, CAUSE GOOD INFO TAKES THE EDGE OFF OF HEAD BANGING INSANITY...HONESTLY THIS IS THE BEST FORUM I EVER CAME ACROSS... I'M TRYING TO ADD REAL COMPONENTS TO MY PARTS LIBRARY...WIN LOSE OR DRAW I WILL LATER POST MY SCHEMATICS TO THIS FORUM...BECAUSE I BET MY LAST DOLLAR THIS FORUM WILL HELP ME A GRAET DEAL...AND YES SAVE ME THE HEAD BANGING INSANITY...THANKS GUYS AND AGAIN HAVE A LOVELY LABOR DAY WEEKEND
     
  14. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Actually, components of the same part number don't have to be identical. I don't use LTSpice much but I do use Tina. With Tina I can easily change the value of just about any component parameter in its properties panel. Though this fact doesn't diminish the comments made regarding the pitfalls of spice. After all, Spice doesn't know that the user is going to build the UHF amplifier he just simulated. It also doesn't know that node6 that connects directly to node14 is going to look more like an antenna than a wire connection. On the same note, spice doesn't know that the users soldering skills are akin to "The bigger the blob the better the job" philosophy. :p

    The same can be said of bench testing a design vs field testing it. It's two different worlds. Bench testing is a controlled environment. While field testing requires time in grade, where man made and natural elements kick you in the a$$, either immediately or over time.

    Chris
     
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  15. OBW0549

    OBW0549

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    Very true, but the user needs to be aware that they will be identical unless he takes specific steps to make them different. 99% of the time this is not important; but it's the 1% of the time that bites you in the kiester.

    Yes, that's another VERY important point. Spice won't model parasitics (inductance, capacitance, resistance, transmission line effects, etc.) unless you specifically include them as circuit elements.

    I knew a guy once who built stuff like that. Ugly!

    Agreed.

    When it comes to design verification, I think there's a natural progression for most products:
    1. Gut feel and "guesstimation"
    2. Back-of-the-envelope calculations
    3. Traditional circuit analysis done with rigorous attention to detail
    4. Modeling (simulation) either with Spice or via spreadsheet or some other tool
    5. Bench testing and comparison with modeling data
    6. Environmental testing (temperature, humidity, etc.)
    7. Trial run testing with extensive data collection on multiple units
    8. Field testing
     
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  16. Steven Tyson

    Steven Tyson

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    Aug 30, 2016
    wow i never heard of tina (i'll look her up, i mean the software up(lol pun intended) tina sounds more user friendly.
    lol bigger the blob better the job?.lol thats a first for me also
     
    Arouse1973 likes this.
  17. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Steven, my first version of Tina was 'Tina-TI' which I downloaded free from the Texas Instruments website. That was many years ago and have been using Tina 'Classic' (not free) since then. I find I can build a schematic in 1/10th the time it takes me in LT Spice but that could be because I'm so familiar with the Tina GUI.

    LT Spice is very popular here on EP and has proven itself to be an excellent tool. LT Spice was Kris Blue's Schematic Editor / Spice Simulator of choice before he passed away. For many of us here, Kris' use of it could be considered an endorsement because he was and (I believe) will always be EP's most valuable member.

    In either case they're both free to download, so you have nothing to loose having both of them on your hard drive.

    Chris
     
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  18. OBW0549

    OBW0549

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    Jul 5, 2016
    Another thing to consider is that when you do a simulation and run into difficulties, with LTSpice you'll be able to post the simulation files here and get help from a large number of other people who use LTSpice; the same may not be true with other simulators that aren't as widely used.
     
    Steven Tyson likes this.
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