Circuit simulation in LTspiceIV

by JGJ Veken

1. Introduction.

LTspiceIV is a Spice III simulator, it includes schematic entry and
waveform viewer , it is a free design tool from Linear - Technology and has a huge user community. LTspiceIV is used to setup a simulated jeeNode I/O port using a switch. As an example the LED discharge circuit is used. see this link

jeenode LTSpiceIV&\#95;small

                Jeenode                             LTspiceIV (astable.asc)

2. Installing LTspiceIV.

System requirements.

Windows ,7, Vista, XP, 2000,98,ME,NT4.0
LTspiceIV works fine under linux (wine).

Download and installing LTspiceIV

Download LTspiceIV with this link
The LTspiceIV.exe is approximately 9.6Mb and is self-installing.


LTspice 4.10s December 20 2010

3. Setup the simulation.


This is the circuit wich will be simulated. JP1 is connected to a Jeenode I/O pin.

The circuit diagram in LTspice format and analysis data can be loaded.

Startup LTspiceIV and you will get an empty canvas.
Left-click File > Open Schematic to load the file from your download location,you will get the screen below.


3. Startup the simulation.

Left-click Simulate > Run and you will get the graph below.

LTspice Graph
LTspice Graph

Right-click on the value text of the components to change its value.

With LTspice you can simply probe the schematic. You simply point and click at a wire to plot the voltage on that wire. You can plot the current through any component with two connections(like a resistor, capacitor or an inductor) by clicking on the body of the component.

On the graph below the current through the LED is displayed at the right side.(ID1)

LTspice Graph
LTspice Graph

4. Important settings

How is the input pulsstream made .

Right-click on the V1 voltage sourcesymbol

    .Vinitial[v]   0
    .Von[v]        3.3    red graph value 
    .Tdelay[s]     1 to give a nicer picture
    .Trise time[s] 500nS  component specific variable rise time L to H puls
    .Tfall time[s] 500ns  component specific variable rise time H to L puls
    .Ton[s]        1 puls width high level 
    .Tperiod[s]    6 the low level will be 6-1 = 5s  
    .N cycles      0 when free run

How is the switch setup .

Right-click on the MYSW SPICE directive (text above circuit) .

    . Ron   1 resistance 1 ohm
    . Roff  100Mohm resistance
    . Vt    threshold voltage 
    . Vh    hysteresys voltage          

How is the Time-frame setup (15s).

     Left-click the Simulate tab > Edit Simulation Cmd

5. Tutorials

These links: