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COMPUTER BITS BY DARREN YATES The Electronics Workbench revisited: new version has optional modules A couple of years ago, we reviewed the first version of this PC-based circuit simulation software. Now with the release of Version 3, we take another look & see what improvements have been made. You only need to have had a quick look at a first year tech course to know that even the most basic electronic circuits need a whole range of mathematical equations to characterise their operation. The idea of circuit analysis or “modelling” is not a new one and was probably thought of as soon as computers came on the scene. But as circuits increase in complexity, so do the number and size of the equations. As the PC (and the Macintosh) increases in computing power, the availability of maths/simulation packages has increased enormously. However, because of the complexity of the pro­gramming required, the cost of these packages has kept them firmly in university and design laboratories. The Electronics Workbench attempts to bridge this gap with a reasonably priced package which enables users to create, simu­late and analyse analog and digital circuits. The package As you would expect, there are no wires, signal generators or breadboards to be found in the Electronics Workbench package – just a 300-odd page manual and the floppy discs. Most common analog circuits can be handled by the Electronics Workbench. This LC oscillator circuit has the oscilloscope tool attached to it to show a reasonably accurate waveform. 42  Silicon Chip Installation is fairly straightforward but make sure that you read all of the loose sheets that come with the package before you install it. The reason for this is that Interactive Image Technologies Ltd, the makers of the Electronics Workbench, has used some frustrat­ing techniques to ensure that you don’t copy the discs. In fact, you can’t even make backup copies of them. Bad sectors have been introduced into the floppy discs to ensure that any copies made will not work. They’ve also made it quite clear that you can only use these discs to have one copy of the soft­ware in a machine at a time. Now while we in no way support software pirating, this system is not only cumbersome and frus­trating, it also can leave legitimate users in real difficulties. If for some reason you need to remove the Electronics Workbench from your PC, you must insert the first This 3-stage amplifier is fed using the function generator which can produce signals from a Hz to MHz. The CRO looks at both the input & output signals & these are colour-coded to make them easy to distinguish on-screen. EWB also has the ability to create “repeatable errors” by allowing any one or a number of components to be either open or short-circuit. Students can then try to diagnose the fault using standard fault-finding techniques. floppy disc and run the “Uninstall” program. If you simply erase or move the program without running this Uninstall program from the floppy, these discs are programmed to not allow installation again and are effectively useless. Interactive Image Technologies is not the only company to persist with this form of copy protection. A number of other well-known software packages, including the accounting package “Attache5”, also include this style of once-only no-backup in­ stallation. It’s worth noting that most of the larg­er software manufacturers, such as Micro­ soft, abandoned this some time ago. During the installation, you are asked whether you wish to use ANSI or DIN component symbols. In the circuit diagrams for SILICON CHIP, we use the ANSI standard which are clearly much easier to understand if a little harder to draw. The European DIN standard replaces zigzag resistor symbols with blocks, the familiar logic symbols with blocks, and the triangular op amp symbols with blocks; in fact, anything which isn’t a circle becomes a block in the DIN standard ... well, almost. Descriptions can be added to each circuit, which is helpful when producing “faulty” circuits. Normally, the faulty component is hidden by a password to prevent easy discovery by the student. • • • a Microsoft-compatible mouse; EGA or VGA display; and DOS 3.0 or later. After using the package, we further recommend that you have a 386 with a co-processor to help speed up calculations, particu­larly during analog circuit simulation. A VGA display is also recommended for visual clarity. If your hard drive is running DoubleSpace or Stacker, then you’ll need to have around 7Mb of space available. What can it do? The Electronics Workbench is designed to simulate and analyse both analog and digital circuits. Creating Requirements As with most software these days, your computer needs to have at least the following: • a 286 processor; • a hard disc drive with at least 4Mb free; • 1Mb RAM; The Electronics Workbench comes with a comprehensive 300-page manual. A range of optional modules is also available. the circuits is quite easy. You have a “parts bin” from which you can pull an unlimited number of components and you connect between them by clicking and dragging lines with the mouse. The selection of components has been expanded and now includes JFETs and MOSFETs. One of the drawbacks of version 1 was its inability to combine both analog and digital components together in the one circuit, which is very common these days. This makes it diffi­cult, if not impossible, to analyse most of the circuits pub­lished in SILICON CHIP and many “real world” circuits. Unfor­ tunately, this latest version still has the same problem. We would really like to see it able to handle digital and analog components together. Still, at a price of only $495 for the DOS, Windows and Apple Mac versions, it certainly wasn’t meant to be equivalent to circuit analysis packages which cost thousands of dollars. What it does do is allow students of electronics to get a feel for how components fit together to form recognisable circuits, as well as being able to perform some reasonably simple analysis of the results. There have been some media claims that it can be used to replace the workbench and allow students to work straight from the PC or Mac instead. This is simply nonsense as it could never be used to replace “hands-on” practical circuit design. Problems such as earth-loops or thermal runaway in audio amplifiers cannot be simulated December 1994  43 The digital section of EWB allows you to mix any of the normal logic functions into a circuit. These functions are available from the toolbox on the right hand column & are selected by dragging them across to the work area. using a computer. However, as a means of introducing students to electronic circuits, particularly the simpler cir­ cuits such as RC networks, rectifiers and filters, single stage amplifiers and the like, it is very effective and probably a good deal more efficient than using breadboards and actual components. When combined with practical laboratory work, the Electronics Workbench would become a powerful teaching tool. This is especially so in the digital side of things where it includes a “word generator” to produce streams of 16 8-bit words which can be fed to circuits one bit at a time, in bursts or cycled through continuously. It also includes an 8-channel logic analyser and again, the efficiency of teaching logic prin­ciples on a simulator would be difficult to overestimate. Manual On the other hand, it could be made somewhat easier to use. If anything, at 300 pages, the manual could have been a little more comprehensive. Some things, such as how to hook up the in­struments correctly, are not clearly explained and you have to look at the examples to see how it’s done. There are quite a few examples supplied with the software which will give you food for thought and you can modify them as you wish and save them for later use. As one of the options, you can obtain a set of models which contain the parameters for over 300 active components. These include BC548 44  Silicon Chip The Word generator allows you to feed specific digital signals to a circuit to observe the results, which can be seen on the Logic Analyser. This circuit is a simple 7-segment decoder. and BC558 transistors, op amps such as the 741 and LM324, and audio amplifiers such as the LM1875 which we featured in our 25W amplifier module in the December 1993 issue of SILICON CHIP. This package is an extra $89. Fault Finding Probably the best feature as far as students are concerned is EWB’s ability to give them experience in fault-finding. Once a circuit has been loaded, the teacher can select any number of components to be faulty –either short or open circuit. This fault is noted by the software and can be held under password protection. The students can then try to find out what the fault is and where it has occurred by observing the circuit’s behaviour on the instruments provided. Fault finding is one of those areas that you can’t teach all that well unless you have a specific, “re­peat­able” fault which all students can try to find. Fault finding is really only taught by experience but the Electronics Workbench goes quite a way to giving students a head start. This feature alone makes it a worthwhile addition to the electronics teaching laboratory. Another optional package is called the Troubleshooting Circuit Set and contains a number of circuits with predefined faults for analysis. This package retails for $49.95. Other extras Other optional extras include a package called “Practical Teaching Ideas” which was written by a Canadian lecturer and designed for teachers as an aid to implementing EWB as part of a basic electronics course. Included with the disc/manual set are example assignments and exam papers which could be used as the basis for a course. For those who don’t want to spend time laying out circuits, a 150-circuit package is also available. This contains 150 common circuits laid out with the appropriate instruments for immediate use with the software. This is well thought out and well worth the price of $49.95. Since it is most suited for teaching applications, network versions of EWB catering for small (10 users) and large (25 users) labs are also available. Conclusion Overall, the Electronics Workbench is suitable as a teacher or lecturer’s aid, enabling students to have a good introduction to the practical use of components and how they join together as circuits. While it shouldn’t be suggested as a replacement for the breadboard, it will give students a controlled introduction into the sometimes difficult world of circuit design. At $495, it is quite reasonable value for money and, if purchased, we can recommend the optional add-on packages listed above. For further information on Electronics Workbench and its optional packages, contact Emona Instruments, PO Box 15, Camperdown, NSW 2050. SC Phone (02) 519 3933.