[Flownez] sent in a tip that a port of the venerable Falstad circuit simulator is now available that doesn’t require Java (it uses HTML 5). This is a welcome port since some modern browsers (particularly Chrome) make it difficult to run Java applets and prevented the Falstad simulator’s execution.
Like the original simulator, this one is great to show a classroom circuits and encourage building or studying circuits in the browser. There’s no extra software to install, which is handy for an impromptu demo. Another cool feature is the visualization of current flow as animated dots. The dots move in the direction of the current flow and the speed of motion is proportional to the amount of current. Watching a capacitor charge with the moving dots is very illustrative. You can also view data in a scope format or hover the mouse over things to read their values.
You can open a blank circuit and add quite a few components (use the right click button on your mouse or the menu to add components and wires). However, you can also pick from a number of predefined circuits ranging from the simple (a voltage divider, for example) to the illustrative (a PLL frequency doubler comes to mind). There’s even an AM radio (see below) that you can tune to find several “stations” by varying the tuning capacitor’s value. Circuit elements include many types of analog and digital components.
The simulator probably won’t lure you away from LTSpice, and there are other Web-based alternatives like TINACloud and others, but the simplicity of the Falstad simulator (and the new HTML 5 port) along with its library of illustrative circuits makes this a site you’ll want to bookmark.