(→Simulating the Circuit)
Revision as of 17:28, 13 July 2006
CircuitMaker is a program that can be used to simulate circuits on a computer. The following tutorials explain some of Circuitmaker's basic functions.
For the first part, we will create a simple voltage divider circuit.
Start CircuitMaker. It should open up with a blank canvas. To add components you can either browse through CircuitMaker's catalogue, or search the the part's name, number, or description. The buttons for these tasks are found at the toolbar at the top:
Click on the button on the left to open up the Device Selection window. The components are organized in a hiearchy:
Major Device Class > Minor Device Class > Device Symbol.
We now add a voltage source to our circuit: Source > Linear > VSource. Note that you can specify values and hot keys in this window. Checking the return box will cause this part selection window to automatically re-open after you've placed the part on the canvas.
Enter 10V into the Label-Value field and click Place. The window should disappear and your mouse cursor should become the voltage source symbol. To rotate the part, right-click. To cancel the part placement and get your mouse cursor back, press Esc on your keyboard. After you've placed the component, you can right-click it to edit its attributes. (Note that right-clicking on the empty canvas will also bring up a useful context menu.)
Now, we are going to change the voltage source from 10V to 5V. Double-click on the symbol (or right-click > Edit Device Data...) to open up a new menu. In the Label-Value field, change 10V to 5V.
To add a resistor to our circuit, open up the device selection window again, and select Resistors > Resistors > Resistor. Enter 100 for its value.
Add a second resistors, and give it a value of 200 (Ohms).
Our circuit should look like this:
To connet our circuit, use the wire tool to connect the pins. We also must add a ground (Source > Linear > Ground in device selection window), so CircuitMaker will know what to use as a reference when calculating voltages. Hook up the circuit like this:
Simulating the Circuit
Then, go to the Simulation menu and select Analyses Setup. Make sure only Always set defaults for transient and operating point analyses is selected.
Exit the Analyses Setup window, and click the run button in the toolbar (or press F10). The run button will turn into the stop button with a stop sign icon. (Note that while the simulation is running, you will not be able to access many settings or edit the circuit. Stop the simulation to make the changes.)
A multimeter window should appear. If it doesn't, go to Window > Multimeter to bring out the multimeter.
Select the probe tool , click on the multimeter window, and click on one of the wires in the circuit to view the voltage of the wire. If you click on a component's pin, you can view the current flowing into the pin, and if you click on a component, you can view the power dissipated by the component.
Viewing Transient States
You can use CircuitMaker to view the transient state of circuits, and make it plot traces like those you would see on an oscilloscope.
This section will show how to simulate the transient state and create plots like those found in the RC and RL Exponential Responses page.
Use the methods above to create the following circuit:
Make sure you are running in analog mode, then go to Simulation > Analyses Setup in the menu bar. Uncheck Always set defaults for transient and operating point analyses, and check the Transient/Fourier checkbox. Then click on the Transient/Fourier button itself to open a new menu.
Here, we set how long we want the simulation to run, and what our time step should be. CircuitMaker will acutally vary the time steps to help make the plots converge correctly, and we can specify the maximum allowable time step if we wish. Usually we should just set Step Time and Max. Step equal to each other. For our simulation, set Start Time to 0, Stop Time to 10 ms, and Step Time/Max. Step to 10 uS. This should give us 1000 data points, which is plenty. Check the UIC (Use Initial Conditions) box.
Warning: If your time step is too small, it will take a long time to simulate. If your time step is too big, you may have problems with accuracy.