# Help and Documentation

How to use the equations panel

Constructing and simulating circuits on DoCircuits is as easy as pie, but what if you want to calculate circuit parameters which have certain mathematical relation with each other. Let me give you an example, for a half-wave rectifier how to calculate ripple factor or efficiency? The answer to this question is writing custom equations.

Equations panel allows users to write custom equations and process the simulation data. This is a very handy tool for those who want to analyze the circuits in detail and inspect circuit parameters. You can play around with the data acquired by measuring devices such as ammeters, voltmeters,Labels and oscilloscope channels etc.

Writing Equations:

Let us understand various steps involved in writing equations and simulating them. Assume that for the following circuit we want to calculate ripple factor.

1. Rig up a half-wave rectifier circuit as shown below

2. Click on “Equations” button which is just besides components panel

3. Equations editor panel looks like this, the panel provides you a list of available measuring devices in the circuit

4. To calculate ripple factor, we have,

Ripple factor(%) = (Vrms / Vdc) *100

Vdc =0.318*Vout and Vrms =0.385*Vout

By taking a look at our circuit, it is obvious that circuit output Vout is connected to oscilloscope channel 2.

Let us start writing equations for Vdc by providing a suitable name for the equation, use virtual on-screen keypad to write the     equations.

5. Click on "Add" button after writing the equation correctly. Similarly, add other equations as well.

6. Run the simulation and on the data analyzer you should be able to view Vdc, Vrms, ripple factor values along with sinusoidal input and rectified output as shown below

Modifying an existing equation:

If you want to modify an existing equation, go ahead and hit “Equations” button, this opens “Equations Summary” which displays existing equations.

Equations summary panel allows you to choose equations for simulation. Click on the equation to be modified. Make changes to the equations as shown

Click on “Update” button, close the panel and run the simulation again