Creation of a device or instrument involves many stages, right from inception of the idea to getting the final product in hand. Many of these devices have been made simpler by using the free or licensed electronics design and automation (EDA) tools available. Let us take a look at the different processes involved in an electronics design and the software used to automate these processes.
Normally, the steps that need to be taken for designing an electronic product are:
1. Capturing of product idea as schematic
2. Synchronising with printed circuit board (PCB) layout tool
3. Performing the layout (placement and routing)
4. Creating the manufacturing outputs
Circuit design and schematic entry
The process of designing standard circuit diagrams with related symbols and parameters is known as schematic capture or schematic entry. This is achieved with the help of an EDA software known as schematic editor. Present-day schematic editors also have some or all of the following features:
1. Extensive component libraries
2. Options to create and define your own components
3. Capabilities for hierarchical designing
4. Automatic detection of unfeasible connections and other errors
5. Documentation of circuit details and calculation of bill of materials
6. Creation of netlists and other commom formats for storing and transferring data related to the circuits
Creating a layout and printing it on board used to be a fully manual procedure but, thanks to the numerous PCB layout tools available these days, most of the steps in PCB layout creation and editing are automatic now.
For instance, the tools for signal integrity (SI) measure a set of parameters to check the quality of a PCB. Issues like transmission losses, cross-talk, impedance mismatch, thermal stress and strain etc are identified and steps taken to solve these before sending the product for manufacture. This reduces the failure rate of PCBs, thereby reducing time, effort, material and cost.
There are several design rules for minimum spacing between pads and traces, acute angle, minimum annular ring, drill-to-drill clearance etc, which determine whether a product can actually be manufactured properly. The computer-aided design (CAD) and computer-aided manufacturing (CAM) validation ensures that the design created is compatible with all these criteria and lets you create an optimised model. A netlist is generated from this software and sent to a manufacturer for PCB validation.
The right tool for you
So now you have an idea of the different steps of software-enabled circuit designing. The next question is how to select the right tool for your application? What all parameters are to be considered before going to the vendors?
Design complexity. The first and foremost parameter to consider is the kind of boards/products you want to design. If all the designs you expect to create are of less to medium complexity, you can go for relatively simpler, low-performance tools/suites like OrCAD, PADS or Proteus.
What your target customers use. It is necessary to understand the EDA products used by the service providers to whom you are delivering the design. If the customer uses one tool and you give them a design that cannot be compatible with that tool, you may lose the customer. Of course, there are other tools available online that can convert the output design file to a different format. But that requires more effort and time. So it is best to use the tools that are compatible with those used by your customers.
Product design. Some of the products put more emphasis on the electronics and electrical part; the physical form of the product is less important. Some other products have a prominent mechanical form and the electronics part is limited to a PCB and a couple of wires. Tools like Altium Designer and CR-8000 provide better integration or co-design of electronic CAD (ECAD) and mechanical CAD (MCAD) elements for designing the final product.
Cost. Price of the software tool(s) can be a constraint for start-ups, small and medium enterprises (SMEs) and academia. If the design complexity is less, one can always go for free and open source tools. Generally, paid-for tools offer more and better features besides the support required for complex designs. Tools like Allegro can be very expensive but price of CADSTAR is a bit on the lower side. The cost of Altium Designer is in between these two.
Some EDA firms offer flexible purchasing schemes. The customer can buy licence for only certain modules of the suite instead of buying the entire package. More tools from the package can be purchased later, when required. There is also a feature called floating licence which allows the use of the same licence on multiple machines so that the user does not have to buy separate licences for multiple systems. Almost all vendors provide the evaluation version of their software for usually one month.
Support from the vendors. Many of the EDA tool vendors work closely with the customers and help them throughout the designing process, and provide online and on-site technical support. The support available from some of the vendors is better in certain regions than in the others. So it is better to go for a vendor that has good reputation and history, introduces occasional updates and bug fixes, provides training courses and offers support in your region.
Integration. Flexibility or integration with other tools is an important factor to be considered. Make sure the software you select has functions to import and export files from and to formats supported by your target customers.
Interface. OrCAD, Eagle PCB and most open source software have easy-to-understand graphical user interface (GUI), which makes it easier for beginners and intermediates in the designing field. Some tools like XPedition use command-line interface, which can be a bit difficult for first-timers.
Free and open source tools
There are several free tools available online, individual software as well as design suites, that serve the purpose of circuit and embedded designing at different stages. Though these are quite popular among academia and hobbyists in electronics, the industry penetration of these software is very less; perhaps less that 5%.
One of the main reasons for the lesser popularity of free tools among professional designers is the limitation they provide in the number of pins, components, layers, multiple boards and so on. Hence these can be used only for low-end and mid-range schematic and PCB designing.
According to Rizwan Hirani of eInfoChips, compatibility with other layout tools is lesser for the free open source tools. The time taken for designing is usually more for such free tools. Performance, precision, training, support and documentation offered by licensed tools are also generally better than that available with the free tools. But in case of open source tools the users usually form a community to support and learn from each other.
The author is a dancer, karaoke aficionado, and a technical correspondent at EFY. Find her on Twitter @AnuBomb.