Re: Basic queries on using LT Spice

From: Terry Pinnell (terrypinDELETE_at_THESEdial.pipex.com)
Date: 11/30/04 

Date: Tue, 30 Nov 2004 20:34:55 +0000

"John Smith" <kd5yikes@mindspring.com> wrote:

>----- Original Message -----
>From: "Terry Pinnell" <terrypinDELETE@THESEdial.pipex.com>
>Newsgroups: sci.electronics.cad,sci.electronics.design
>Sent: Tuesday, November 30, 2004 3:42 AM
>Subject: Basic queries on using LT Spice
>
>
>> These are very basic questions, some no doubt in the Duh! category.
>> FWIW I've read the tutorial, albeit quickly. But a few quick pointers
>> from the established LT Spice users could save me hours please! Or
>> maybe there is an existing source for learning practical details which
>> I've not yet found? I'm so familiar with CM that getting comfortable
>> with LT Spice may take me a while, but I'd like to master it as its
>> simulation facilities are plainly superior.
>

>A dedicated LT Spice newsgroup:
>http://groups.yahoo.com/group/LTspice/?yguid=161100399
>
>
>> 1. What's the difference between Move and Drag? (Both appear to move a
>> selected part or group of parts around, until left click fixes them in
>> new position.)
>
>
>If the component is connected in the schematic, using drag will pull the
>wires along with the component when you move it. Move moves the component
>without stretching the wires. Note that you can draw a rectangle with drag
>or move to select an entire area to move or drag.
>
>See Help/Schematic Editing.
>
>> 2. With a circuit drawn, I click Run and get the 'Select Visible
>> Waveforms' dialogue, with choices like V(n001),V(n002),etc. But how do
>> I know what those nodes are? IOW how do I first ensure the nodes are
>> displayed on the schematic.
>
>
>I believe this question has been answered. If you don't want to pass the
>crosshairs over the wire to read the node ID below, you can label the wire.
>See Help/Trace Selection.
>
>> 3. In the absence of such indicators, suppose I just choose the first
>> and get a plot headed
>> 'V(n001)'. Can I *now* get the schematic to show that choice? Is there
>> any other way of finding what voltage or current I'm seeing, apart
>> from clicking each node with the cursor and observing the result?
>
>
>No. Not that I aware of. Note that you single click a node to plot it.
>Clicking the same node twice in succession discards all plots but that node.
>This is not what you asked, but it is handy to know.
>
>
>> 4. If I decide to take the Help's advice "The easiest method is to
>> simply probe the schematic. You simply point and click at a wire to
>> plot the voltage on that wire," how do I by-pass that initial
>> dialogue? Even with none of its choices selected, if I click Cancel,
>> it still plots V(n001). I could of course then close that, to get a
>> clean slate ... if I knew which node to click!
>
>
>On a new schematic, or when you have closed the plot window, LT Spice
>doesn't know which node you want plotted, so it asks. You must either tell
>it which node to plot or it will plot node 001. After the initial run, it
>will continue to display the node or nodes previously selected until you
>close the plot window again. If you have a display which you like, you can
>click on the plot window somewhere to make it the focus, then save the plot.
>Save the plot with the same name as the schematic. The next time you do a
>run after closing the plot window (or after closing LT Spice and then
>reloading), LT Spice will look for a plot file and use it to display your
>plots as selected previously.
>
>See Help/Save Plot Configurations
>
>> 5. With several voltages plotted, how do I separate them into
>> individual windows?
>
>
>I think this has been answered, but, right click the plot pane. Select Add
>Plot Pane. Click the node of interest.
>
>
>> 6. To edit the schematic, I take it you must first close all plots?
>
>
>No.
>
>
>>
>> 7. In CM I can select a 'component' called '.IC' and connect it at a
>> node. In LTS I see I add this as a Spice Directive. But how do I
>> connect it?
>
>> 8. Is there any way to re-assign shortcuts? For example, I have ctrl-z
>> ingrained for Undo, and Ctrl-c for Copy, not F9 and F6.
>
>
>I've never used this, but look under Help in Shortcuts.
>
>
>> 9. Where can I find step by step examples of adding/importing new
>> models?
>
>
>Look in Help/FAQs/Adding Third Party Models
>
>
>> 10. For a Transient Analysis, with whatever defaults running, what are
>> the steps for changing the key parameters: Start Time, Stop Time, Step
>> Time, Max Step Time. Are these all entered as Spice Directives? If so,
>> is there a succinct summary of the main directives and their syntax
>> please? (In CM, I use only the GUI.)
>
>
>With focus on the schematic, click Simulate/Edit Simulation Command. A
>dialog box opens for you to insert the values without resorting to
>directives. Otherwise, see Help/Dot Commands.
>
>Note that my answers here are based on my experience and there may be other
>and better answers.
>
>LT Spice comes with example programs and pretty good help, especially for a
>free, powerful program. I strongly recommend you read the Help and run the
>examples. I should do this, too.
>
>Good luck.
>
>John
>
Thanks for that very thorough and helpful reply, John. Much
appreciated. Have now joined the Yahoo Forum. 

-- 
Terry Pinnell
Hobbyist, West Sussex, UK
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