If you’re working in a large, dedicated PCB-making facility,
you’re
probably using one of the major Electronics Design
Automation (EDA) systems such as OrCAD (www.orcad.com), Protel (www.protel.com),
PADS (www.pads-pcb.co.uk) or CADSTAR (www.cadstarworld.com). These
are highly sophisticated software systems, costing many thousands
of pounds, aimed at enterprises that produce boards and chips by
the millions.
Then there’s the rest
of us. If you’re designing the
occasional board as part of a product you manufacture, or building an electronic system, you’re unlikely to have the budget, or the
need, for such top-end software. But the various freeware and shareware offerings that abound are really for hobbyists: as a professional designer, you need something rather more capable.
You could try
one of the rather basic data capture and layout products issued freely by board manufacturers, such as PCB123 (www.pcb123.com) or ExpressPCB (www.expresspcb.com). You can design a reasonable board with these packages, but the snag is
that to get them built, you have to go to those companies. If your needs are basic and you don’t mind being tied to a US-based manufacturer, this could be a solution.
Of the mid-range (sub-£1000) PCB
design packages, the most popular today are Eagle and Easy-PC, both with impressive capabilities for schematic capture and PCB layout. Eagle is developed in Germany, where it is
the market leader in its price range (between £375 and £750
depending on configuration, with an auto-routing package included). Easy-PC (http://easypc.adeptscience.co.uk) is the UK market-leader in this sector, and is available in 500, 1000, 2000 and unlimited pin versions at prices ranging between £97 and £397. All versions,
apart from the 500-pin edition, include an auto-router.
Both offer design rule
checking (DRC), essential if you’re producing boards professionally. Any board layout has manufacturing design rules governing the layout geometry to ensure a high yield. Most PCB software checks the whole board design, but Easy-PC boasts online DRC, which warns you of rule violations while you’re actually editing tracks. Easy-PC also produces a full report after testing the design spacing rules, a standard requirement in many organisations.
Most PCB design packages output to standard manufacturing formats such as Gerber and Excellon NC Drill, and sometimes also
to mechanical data formats such as DXF (AutoCAD) and IDF. Easy-PC supports all these (though IDF export is an option you’ll pay
extra for), and will also import Gerber and DXF files for modification.
Eagle incorporates a CAM Processor, which allows you to create the data you need to manufacture your PCB. It can produce data for drill stations, photo-plotters, postscript machines and pen plotters.
The latest version of Easy-PC also exports to ODB++, an open, intelligent CAD/CAM data exchange which many predict will become the industry standard for transferring PCB data into manufacturing
- some board manufacturers are already offering attractive fabrication prices for design data delivered in this format.
Once you’ve
designed a board, it’s useful to simulate
the electronic function and performance of its circuits before going
to manufacture. SPICE is still the standard for verifying circuit
designs and predicting the circuit’s behaviour, and modern SPICE programs are capable of mixed-mode (analogue and digital) simulation. Easy- Spice is a £295 add-on for Easy-PC. Eagle doesn’t offer
a SPICE simulation option, but B2 Spice (www.beigebag.com), which costs around £230, supports Eagle and includes a 15,000 parts model library.
There are dozens of other software products around. AutoTRAX (www.autotraxeda.com) delivers schematic entry, layout, simulation, auto-routing and CAM tools for under £100. It also offers (as
does Easy-PC) 3D visualisation of the finished design, which can be
very useful: but it lacks professional features such as design rule
checking. Feedback on the AutoTRAX user discussion forum indicates that there are currently a number of unresolved bugs in the software. More expensive (well over £1000 for professional versions)
are Vutrax (www.vutrax.co.uk), which has been around for a long time and still has a DOS-in-a-window feel to it; and Electronics Workbench (www.electronicsworkbench.com), which is especially popular in education. A Google search will reveal many others.
Prices quoted
in this article were taken from the respective suppliers’ Web
sites and are given exclusive of VAT.
Dr Know's recommended download is the Easy-PC Demo - download yours today.