Basic Electronics

• Active Filters Demo
• Analogue Circuit Simulator – DC
• Analogue Circuit Simulator – AC
• Audio Network Analyser
• Bode Plots
• Digital Logic Simulator
• Fourier Square Waves Demo
• Karnaugh Map Demo
• Lissajous Figures Demo
• Log and Linear Graphing Demo
• Quiz on Basic Electronics
• Oscilloscope Demo
• Transmission Line Demo
• Resistor Colour Codes Game
• Veroboard Layout Game

Active Filters Demo

This one is used in a talk at the beginning of a lab session where students build up a voltage-controlled voltage-source (VCVS) active filter, and investigate stability and Q-factors. Most controls should be intuitive, but note if you double-click on the resistors and capacitors you can input a new value, it accepts inputs of the form “3u3” for 3.3 microFarads; and click on a junction to get the voltage at that point on the scope-like display. The “Auto” checkbox makes the scope-like display update its timebase automatically to reflect the input frequency.

Analogue Circuit Simulator – DC

Another rather complex one, with a lot going on behind the scenes. It just does DC operating points at the moment – no transient responses or frequency responses yet, but I do have plans for both these features in the future. Saving and loading designs is done using the clipboard (Silverlight programs can’t directly access the local hard drive); they are just text files, so can be saved using any text editor. There are a few preset designs; if anyone has any presets they would like adding in, let me know.

Analogue Circuit Simulator – AC

I said I’d put up one demo per month and I’m running behind this year, so while this might be cheating a bit (it’s really a different build of the analogue simulator), it is, I think, perhaps more useful and worthy of inclusion in its own right. It adds capacitors and inductors, a phasor diagram, scope-like output screen and frequency and phase response plots. It was developed for use in a lab teaching phasor techniques here.

Like the previous demo, saving and loading designs is done using the clipboard. In the meantime, if anyone has any presets they would like adding in, let me know.

Audio Network Analyser

Strictly speaking this one should not be here, since it’s not a Silverlight demo. You’ll have to download the executable file as it’s a standalone Windows program. It’s based on the Bode Plots demo, but it measures the response of real circuits in the lab. Just connect the circuit to be measured between the left channel output and left channel input of a soundcard. The right channel should be connected directly from the output to the input, it acts as a phase and amplitude reference.

The game to play in the lab is to try and match the theory (the blue and green lines) to the actual measurements (the red and orange dots) by moving the positions of the poles and zeros, and then relate the poles and zeros frequencies to an analysis of the circuits.

Bode Plot Demo

Double-click somewhere on the magnitude graph (the upper one) to add a pole; double-click on an existing pole to turn it into a zero; either treble-click on a pole or zero or drag it off the graph to get rid of it. (You can pick up the poles and zeros and drag them around.)

That’s about it – with luck everything else is self-explanatory. Another very simple one, but I hope it will prove useful.

Digital Logic Simulator

Rather a complex one this – it’s a full digital logic simulator. Rather unusually, it can also simulate what happens when the clock speed is so fast that the wire speed has a significant impact on the circuit behaviour, which leads to some interesting results. Saving and loading desigs is done via the clipboard, they’re just lines of text, so can be saved using any text editor; to load a design, copy the relevant lines on the clipboard and press the Load button. There are a few designs built-in; if anyone has any presets they would like adding in, please let me know.

Making and Filtering Square Waves

This one is used at the start of a first-year lab where students are asked to take the frequency response of a circuit (a simple low-pass filter), then put in a square-wave, note the rounding of the edges, and attempt to explain the relationship between the two results. That’s rather a difficult task for a first-year who hasn’t come across Fourier before, so this demo was written to let me illustrate the basic idea.

Karnaugh Map Demo

I hope the operation of this one is intuitive. You can enter loops either by clicking and dragging the mouse, or by typing in the box at the top right (use “!A” to mean “not A”). Double-clicking on a loop will remove it; and putting the mouse over a loop will highlight the included terms in the list on the left. Click on the cells in the list on the left once to change their state; you can also do this on the Karnaugh map itself, but you have to click twice here.

Lissajous Figures Demo

Yet another Lissajous figure simulator. This one was written for a lab session in which the figures were used to measure the phase offset of two oscillators, so there is a “measurement” checkbox that takes the relevant measurements (note that this only works if the oscillators are at the same frequency).

Logarithmic and Linear Graphing Demo

Very simple one this, just to make teaching the use of linear and logarithmic scaled graph paper a bit more entertaining. Set-up the axes scales as desired, then double-click on the graph to add a point, you can then drag it around. Alternatively, select a graph type (lowpass, highpass etc) enter a frequency and the program will give you a reading which you can then plot.

Basic Electronics Quiz Demo

This one is part of an experiment to see what effect computer-moderated assessments and games have on student learning and retention. It runs quizzes of eight questions each on a variety of subjects in basic circuit theory, with (almost) instant feedback.

Resistor Colour Codes Game

You can use this as a quiz (revealing the answers), or as a tool for identifying resistors: click on any rectangle of colour and drag it to a suitable location on the resistor and the value will change. Double-clicking on a resistor colour band will remove the band. Note that the quiz includes numerical codes for resistors as well, and the app recognises resistors either way round.

Oscilloscope Demo

Very basic oscilloscope, used in lectures to illustrate the basic of how oscilloscopes work before letting the students loose on a real one with many more facilities. There’s a few things I want to add to this, but rather embarrassingly I’ve lost the final source code (no idea how that happened – all my backups were corrupted in the same way). So this one will have to stay this way for now.

Transmission Line Demo

It’s a bit basic this one at the moment. Controls not very well labelled, but if you play around with them you should get the idea. The little button by the side of the combo box sends more pulses in pulse mode, or turns the step on or off in step mode. The slider replays through the first bit of history; this is intended to make it easier to talk about what’s going on.

Veroboard Layout Game

Designed to be a fun game for students on their first week studying electronics. When the layout reflects the circuit diagram, the big red cross turns into a big green tick, so the students get some reassurance that their design is correct before they start to build. There are two circuits programmed in – a basic circuit that I use to demonstrate the operation, and the astable multivibrator that they build. You select between them by adding “?circuit=demo” or “?circuit=astable” to the end of the URL.