ElectroSim 2.0
Interactive Simulations of Basic Electronic and Operational Amplifier Circuits

Tom O'Haver
Department of Chemistry and Biochemistry
The University of Maryland at College Park

Last updated September, 2006
A Links2Go Key Resource Award in the Simulation Models topic.
A StudyWeb 4-star site.

This is a collection of real-time, theory-based interactive simulations of some simple electronic circuits for use by students in my course in "Electronics for Chemists", basically a course in elementary practical instrumentation electronics. I use them after the students have constructed and studied these circuits in the laboratory, in an effort to deepen their conceptual understanding.

One of the problems in teaching electronics is the difficulty students have in moving back and forth between the static, two-dimensional symbolic representations of traditional schematic diagrams and the real, 3-dimensional circuits in the laboratory. My simulations help to bridge this gap by allowing the student to work with representations that look just like the schematic diagrams in their textbooks, yet actually work and respond to changes just like the real circuits. Using the mouse, you can drag sliders to control voltages and resistances, open and close switches, and type in the values of various components. Changes to voltages and currents throughout the circuit are displayed dynamically in real time as the sliders are moved.

Another problem is that so much is invisible. The actual laboratory experiments show only the outer, macro-level effects, leaving the student to imagine the inner workings such as current flows and voltages changing at multiple points in a circuit. Computer simulations can sometimes show these inner workings in a way that real experiments can not. Still, these computer simulations were not intended to replace laboratory experiments and real-world experience, but rather to extend and augment textbook treatments.

next Click to view a screen shot of the first simulation.

These simulations do not run on the Web; they are self-contained programs that can be downloaded and run on stand-alone machines. They were developed in HyperCard for the Macintosh, but there are also versions for PCs and Unix macnines.

If you have a Macintosh, you can download and run the original Hypercard stacks. They are very small and require little computer power or screen space; you can have several of the simulations open at the same time in separate windows. They'll even run on the old monochrome "toaster" Macs such as the SE or Classic. Click here to download the complete set of ElectroSim 2.0 modules in ".sit" compressed format (570 KBytes), including the Hypercard Player application. Stuffit Expander will automatically decode and decompress the downloaded file into a folder containing the full set of ElectroSim modules. Double-click on a module to launch it, or drag and drop it onto the Hypercard Player.

PC users and others can run these simulations via the free downloadable Revolution Dreamcard Player, which is available for several platforms. To download the complete set of ElectroSim modules for a Windows PC, right-click on this link and select "Save Link As..." to begin the download (5.5 MBytes) to your PC. Then right-click on the ElectrosimRevolution.zip file and select "Extract All...". Open the resulting ElectrosimRevolution folder and install the Dreamcard Player by double-clicking on "dreamcardplayersetup.exe" and following the on-screen instructions. Thanks to Phil Oror (jpodor@f2s.com) for his excellent work in converting my Hypercard stacks to Revolution Dreamcard format.

On the left side of each simulation module is a panel with several icons: click on "What do I do?" for quick instruction for that module; click on "Explain" to pop up a series of text boxes that explain the circuit operation (click again to hide the boxes); click on "Show current flow" to see an animation of current flowing; click on "Show specs" to inspect and edit the transistor's characteristics.

Ohm's Law

Series resistors

Parallel resistors

Wheatstone bridge

Half-wave DC power supply

Full-wave DC power supply

Simple Zener-regulated power supply

Transistor switch driving a relay

Common Emitter AC Amplifier

Operational amplifier without feedback

Voltage Follower

Non-inverting amplifier

Inverting amplifier

Signal current flow in inverting amplifier

Effect of open-loop gain

Input resistance of a non-inverting amplifier

Adder (summing amplifier)

Subtractor (Difference amplifier)

Photodiode photometer



Voltage follower with transistor
output current booster

Programmable current driver with
transistor output current booster

Homework assignment for the operational amplifier simulations

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Links2Go Key Resource Award in the Simulation Models topic This page was created by Prof. T. C. O'Haver , Department of Chemistry and Biochemistry, The University of Maryland at College Park. Comments, suggestions and questions should be directed to Prof. O'Haver at toh@umd.edu. Last updated September, 2006.
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