Every electrical engineer who does DIY projects knows that dozens of free resistor calculators are out there that can save quite a bit of tedious work. Other simple tools can be found, but traditionally the free tool arsenal would stop there. Sure, there are base platforms such as SolidWorks and Autodesk, but what happens when they are missing a feature needed at that exact moment?
Now we're seeing a relative explosion in free tools for engineering electronics. It is easy just to hit the Net and use the myriad resources available. Some of those online tools prove to be worthless, and it's back to blind searching or some paid tool. But free software extends far beyond the functionality of a simple calculator.
To help sort out the nonsense from the useful online tools, check out the following list.
This article was originally published on EBN's sister publication EE Times .
Calculatoredge: when one calculator isn't enough
One of the more useful tools in an engineer's toolbox is a physical calculator. Why does it seem to get lost when it's truly needed? Workstations usually save the day. Those included in your OS of choice (Windows, iOS, Linux, etc.) are good for simple tasks but not so great for other things, even in scientific mode.
Searching for the right one online will net you roughly 131 million choices. Which one are you to choose when there are so many? Why not choose them all?
Almost all calculator versions known to humankind are located in one convenient site, Calculatoredge. It boasts no fewer than a few hundred calculators for just about every field imaginable (and perhaps some that are unimaginable), including electrical, mechanical, civil, chemical, and even math. There's no need to search aimlessly for that obscure number cruncher ever again. Some of the more complex calculators even come with some rudimentary instructions.
SourceForge's Cedar Logic Simulator
When it's time to test simple digital logic gates and registers or even some high-level components, you can turn to SourceForge for some free online simulations with its Cedar Logic Simulator (still in beta edition). Designing circuits is great and all, but will they function correctly and perform when it counts? The Cedar Logic Simulator allows users to perform test simulations at the transistor, register/transfer, gate, and other levels.
The software also can be used as an introductory tool for teaching logic design and an entry platform for circuit design by allowing users to drag and drop gates, inversions, and connections. There are also options for undo/redo and copy/paste functions. Projects can even be exported to monochrome or color bitmap files for project integration. SourceForge's main application window allows users to move back and forth through 10 different pages for multiple projects, making it one of the better free applications on the web.
Logisim 2.7.0, an alternative to Cedar Logic Simulator
SourceForge's Logic Simulator isn't the only free simulation tool available on the Internet. Tools that rival its design and simulation applications include Carl Burch's Logisim logic simulator. Students of the computer sciences often use the app as an introductory circuit design/learning tool, but it's practical for use outside the classroom, as well.
Logisim incorporates some of the same features as Cedar, including design and simulation platforms with preconfigured elements: AND, OR, NOT, etc. However, the software provides more in-depth functionality, including a tool for drawing color-coded wiring connections that make programming and debugging a little easier. One of the more interesting aspects of Logisim is that it's portable and can be stored on removable storage media. It also can be used on any Windows-based PC, and it runs immediately after you click on the program. That's a luxury in today's install-but-with-malware world.
Qucs: Quite universal circuit simulator
Sometimes simple simulation is all that is called for after the design has been created. There are more design simulators on the Internet than there are particles of sand on a beach (not really, but you get the idea). Traversing all the offering would take forever, but there are a few that stand out in terms of functionality, like Michael Magraf's Qucs (Quite universal circuit simulator).
The open-source circuit simulator provides feedback for analog and digital components, including S-parameter, AC/DC, transient, harmonic balance, Digital sim, and Parameter sweeps. The initial interface is presented in GUI format. Analysis testing and diagrams can viewed in myriad platforms, including Smith-Chart, Cartesian and totally Tabular (for those who love the 1980s). Simple and to the point (with a host of options) is what Qucs is all about.
SmartSim running on the Raspberry Pi SBC
Simple is one aspect that truly is functional when it comes to design and simulation, but what if your skills are more advanced? Then perhaps Ashley Newson's SmartSim is what you seek. The beauty of it is that it can be used by students and professionals with different skill levels. Yes, SmartSim is a digital circuit design and simulation application, but it is more in-depth than the ones mentioned earlier.
SmartSim allows users to create complex circuits using custom components and drop them into other projects as if they were any other component. The final circuit design can be used in any number of projects and subprojects without extended modifications. Completed circuits can be tested utilizing the software's interactive feature, which allows exploration of the design down to the hierarchical subcomponents while the circuit is in operation. One of the more notable features of the application is that it's cross-platform capable, meaning that it can run on Windows and Linux-based systems, including the Raspberry Pi.
Static Free Software's Electric VLSI design and testing software
Who needs new school when we still have old school — really, really old school?
That's right. What would this roundup be without Steven Rubin's Electric VLSI Design System, which was released a whopping 34 years ago? Yes, the initial software has changed hands over the years and has undergone multiple revisions, but the core remains practically the same.
The design and simulation software is unique. It understands a host of analog and digital technologies, including MOS (nMOS/CMOS), Bipolar, and even PCB. It can also utilize graphical forms, as well, including schematics, artwork, and FPGA architectures. Simulation tools include design/electrical rule checking, routing, Logical Effort, and LVS, making it a great choice for old-school analog IC.
CoolCAD is synonymous with semiconductor design and fabrication in the world of photodetectors. However, the company also specializes in design and prototyping. To top it off, it offers a host of free Spice (simulation program with integrated circuit emphasis) tools for niche applications.
CoolSpice is an analog circuit simulator catering to CMOS designs and includes ngSpice (a GUI-based schematics editor), a plotter application, and a text editor for netlists. Actually, ngSpice is a software conglomerate of sorts. It incorporates three simulators for analog and digital designs, including Spice3 (still going strong after 30 years), Cider (a marriage between Spice3f5 and DISM) and Xspice (code modeling support and simulation of digital components). NASA first used the software suite to simulate cryogenic environments for CMOS-based electronics. The software is now used for silicon-carbide device models in power electronics simulations.
Circuit Virtual Laboratory's Electronic and Electric Circuit Simulation
There's specific knowledge base simulation, and then there's overkill for those electronic circuit design and simulations, which can be found at Circuit Virtual Laboratory.
That's not necessarily a bad thing, since its site offers tutorials, explanations for electronics and circuit design, and simulation tools for novices and advanced users alike. It offers tutorials for everything from fuzzy logic to complex number phasor linear calculus and every conceivable thing in between. Simulation is also extensive, with free online tools and calculators for bipolar transistor simulation, diode simulation, JFET/MOSFET transistor simulation, and a host of electric simulations. Though the site does not feature a calculator base like CalculatorEdge, it does cater to those with specific circuit design parameters in mind.
TinyCAD does one thing and nothing else — well, actually, it does two things, but why get technical? The main purpose of the application is to let users design basic or complex electronic or electric circuits. And it boats a massive 755 symbols under 42 libraries to help get those designs created.
Everything users could possibly need is listed in those libraries, including drop-ins for logic gates, connectors, analog circuits, microcontrollers, power sources, and mechanical symbols. Every symbol can be edited to suit project needs, and users can even incorporate their own customized symbols. Finished designs can be exported to a clipboard for printing. The software even sports a feature that exports the user's circuit netlist in order to manufacture the PCB. That's the software's second feature, and though it doesn't pack everything under the sun (such as simulation), it does what it's meant to do extremely well.
What's circuit design without the PCB design into which it will be embedded? That's like peanut butter without chocolate — good separately but great when paired together. That's precisely what DesignSpark PCB does. It's a free-to-use schematic capture and PCB layout tool for electronic design automation.
The Windows-only software packs a schematic editor that allows users to draw up their designs using multiple sheets and myriad component libraries for symbol drop-ins. Don't have the symbol you need? No problem. There are myriad third-party tools that can be added, and customized symbols can be used. Once the circuit design is finished, users can incorporate them into a PCB layout schematic using the PCB Wizard.
One of the more interesting facets of the software is the auto placement of components and routing tracks, which can save users a considerable amount of time in the design phase. A cautionary note on auto placement: Unrouting a track can sometimes lead to inadvertently deleting a component if you're not careful. Also, make sure you have the minimum hardware requirements before using DSPCB. It can be a resource hog, depending on how many libraries are open at any given time.
Though DesignSpark PCB favors a Windows OS to run its software, gplEDA prefers Linux systems to lay down the schematic designs. Just like DesignSpark, gplEDA lets users create circuit designs using symbol drop-ins from multiple libraries and place their finished products into a PCB layout for circuit integration.
Tools incorporated into gplEDA include Fritzing (created circuits can be incorporated on to a virtual breadboard for editing), gEDA (circuit design, capture, simulation, prototyping, and production), KiCAD (for circuit conversion to PCBs), Qucs (circuit simulation, complete with GUI interface), and XCircuit (schematic conversion for publishing and manufacturing). The software suite runs natively on Linux-based systems, but it will function on Windows systems with an X-Server running in conjunction.
Yes, it's CAD-based design software. Yes, it's used to create, edit, and view the .dwg files used to create project parts, but Dassault Systemes' DraftSight 2D CAD software app can be used to design and export PCB layouts to the .DXF file format for manufacturing.
The interface is reminiscent of AutoCAD and has a similar collection of tools to get designs ready for product incorporation or transfer to 3D representations. DraftSight is perfect for those who want a sense of what the final turnout will be for project parts or designs that incorporate their circuit and PCB designs. In some rare occasions, even circuits need to be drawn in a simple 2D CAD application. There is always a need to sketch something up in CAD. This is an absolutely essential part of the electrical engineer's arsenal.
If you're trying to get a feel for what the end project or part will look like, eDrawings may be just what you need. The software allows users to see what their designs look like from any number of CAD platforms, such as SolidWorks and Autodesk. It even supports project animation with intelligent interpretation tools, including a 3D pointer, virtual folding, and animation drawing views.
When it comes time to manufacture your project, there are two ways to go about it: Do it yourself or get someone else to do it for you. For the DIY crowd, there are many CNC software options. Most come at a price. Some are free, though with limitations.
On the free (or trial) end, Newfangled Solutions offers a trial version of its Mach3 platform, which lets users input up to 500 lines of Gcode before requiring an upgrade. Essentially, Mach3 turns the user's PC into a six-axis CNC control center (provided the user has the CNC hardware). It allows for direct file (.DXF, .BMP, .JPG, etc.) imports, auto generates Gcode (via Wizards or LazyCam) with interactive Gcode display, and has customizable macros and M-codes. Best of all, the software is fully functional with lathes, mills, routers, lasers, and even engravers, so incompatibility is slim to none.
Unfortunately, the software is currently for Windows only, so Linux users will have to beg, borrow, or steal a machine outfitted with the OS until it's been converted.
Of course, if you have no manufacturing hardware, or if cost isn't a factor, outsourcing your project manufacturing needs is the way to go, and CustomPartNet has you covered.
The site contains cost estimation tools for materials, capacities, part lots, processes, and everything in between. There's no need to worry about the material your project uses; the site has manufacturing processes for everything, including polymers, metals, and even adhesives, along with time estimates for each. It also provides case studies for cost analysis, part redesigns, and product development. It also has an extensive list of suppliers for everything from parts to manufacturers, so you can go with who you want with what you want, as long as you can afford it.
Keep in mind: A resource is a tool, too.