LTspice
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Posted by John Larkin on October 4, 2007, 11:38 pm
Please log in for more thread options analysis sweeps, as a function of pot rotation. I can't find this. Any other way to simulate the function? I really need the varying resistances, so I can't just use a multiplier. John | |||||||||||||||||||||||||||||||||||||
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Posted by John Popelish on October 4, 2007, 11:53 pm
Please log in for more thread options For a resistance value, use a variable name enclosed in curly braces (to solve the variable before each run), e.g. . Then add a parameter step command to the schematic, e.g. .step param RV 1 10k 1k using the Edit, Spice directive menus. To make a potentiometer, define the values the two halves of the pot (on each side of the wiper) with a position formula in curly braces), e.g. and . Then add a parameter to define Rtotal, .param Rtotal=10k and a step command for the position, .step param position 0 1 .1 The extra ohm in the formulas prevents the section resistance from reaching zero ohms which blows the math up, and sort of represents the wiper resistance. If you want to run single position runs, add a position parameter definition .param position=.5 and comment out the step position by right clicking on the command and clicking the comment button. Later you can comment out the position parameter and uncomment the position step command, if needed. | |||||||||||||||||||||||||||||||||||||
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Posted by Tam/WB2TT on October 4, 2007, 11:54 pm
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> Does LTspice have a potentiometer component? I'd like to do transient
Interesting you should ask. I was 100% certain that there was a
> analysis sweeps, as a function of pot rotation. > > I can't find this. Any other way to simulate the function? I really > need the varying resistances, so I can't just use a multiplier. > > > John > potentiometer. But, using the latest version, like you, I could not find it. Tam | |||||||||||||||||||||||||||||||||||||
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Posted by Jim Thompson on October 5, 2007, 10:37 am
Please log in for more thread options On Thu, 04 Oct 2007 20:38:57 -0700, John Larkin
>Does LTspice have a potentiometer component? I'd like to do transient
>analysis sweeps, as a function of pot rotation. > >I can't find this. Any other way to simulate the function? I really >need the varying resistances, so I can't just use a multiplier. > > >John Posted many moons ago... http://analog-innovations.com/SED/PotentiometerForSpice.pdf ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | America: Land of the Free, Because of the Brave | |||||||||||||||||||||||||||||||||||||
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Posted by Joel Kolstad on October 5, 2007, 12:49 pm
Please log in for more thread options > Does LTspice have a potentiometer component?
Nope! From hearing Mike Engelhardt (the author) answer the question, I'm pretty sure it's that way on purpose -- he really does prefer two resistors, with one set to, e.g., and the other set to . (And then you use a .param statement to have LTspice step through the various values of x you're interested in.) I'm told that someone has posted (presumably on the Yahoo! group) a potentiometer just bundling up the two resistors into a single package (as Jim's .pdf demonstrates) in case you want something that looks "nicer." It's interesting that Mike seems to feel so strongly about pots one way whereas John Warner of SIMetrix fame seems to like pots so much he added the ability to use the cursor keys to "turn" the pot and automatically re-run simulation each time! ---Joel | |||||||||||||||||||||||||||||||||||||
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> analysis sweeps, as a function of pot rotation.
>
> I can't find this. Any other way to simulate the function? I really
> need the varying resistances, so I can't just use a multiplier.