Eaglesp3 Help

Tutorial 1: DC Analysis


After completing the installation, you can start the whole thing from your eagle working directory:
   ./starteagle
The eagle control panel will appear.

From the eagle control panel, double click onto the "dc" schematic symbol. The schematic editor will rise, containing a schematic with a voltage source V1, a resistor R1, a diode D1 and a voltmeter P1. The voltage source has an DC value of 10V:

So far there is nothing special with the circuit.

The first special thing is the green textline which begins with a dot, ".DC V1 0 5 0.1". It is handled as a special command string for spice3. Its meaning is to perform a DC sweep using V1, overriding the original attached DC value of 10V and ramping it up from 0V to 5V with a stepwidth of 0.1V.
Before doing so, spice3 will remove all capacitances, and shorten all inductors in the circuit (if present).

The second special thing is the ground symbol, which has the meaning to attach the label "0" to the spice3 net (in eagle it is the net "ground"). Spice3 needs this net to calculate the circuit.

To run the simulation, just press the F12 function key (with the cursor in the schematics window). Two spice3 windows will rise, one with a prompt, and one with a graph that shows the voltage associated with the voltmeter (if not, go back to the installation troubleshooting section). In the command window, just type "q" to quit the simulation session.

You may now experiment with the circuit, varying its values and/or structure.
To compare the variations with the original circuit, press F12 again to see the previous simulation. Then you may "change text"  of the sweep command to get a finer sweep (".DC V1 0 5 0.01"), or  "change value"  of the resistor to 2K. Press F12 again to get a new independent simulation to see the changes.
To "measure" a value in a graph, you can easily click onto any point or click-hold drag-release the cursor to measure a difference. But it is not possible to combine the results of both simulations into one window. To get this done, you have to combine the two circuits into one schematic:

Zoom out  to get more free space, click on group  and select the whole circuit by click-dragging. Click on the group midpoint, Cut  it and paste   it to another place just below the original circuit. Because there is only one sweep source allowed, you will have to delete  the second voltage source and feed the second circuit from the first source, too. Do this with net , drawing a wire for the connection. If you are done, click two times on the wire end point to finish. To get the graphs combined, we have to delete  the two VMETERS, add   a VMETER2 and connect the right nets to it. Finally change the R1 value back to 1K and press F12 to see the simulation differences.

If you want to play with a completely new spice3 command string, you will have to write it onto the spice layer. That is, "change layer"  to spice, and input text  to generate the new spice command.

In the any eagle window, you can access help about the spice3 simulation interface and library via the "help/contents" menu. In the rising index page, you will find the simulation topics at the bottom.
 


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