Custom Electronics Design or Commercial Off The Shelf (COTS)?

SUMMARY

Making a custom electronics system is a complex task and unless you have the right experience and tools can present many pitfalls.

Once you have identified that you require some electronics, you need to search for the best way to achieve your goals. To start with, it is necessary to properly define your functional requirements and to interpret them into the electronic functional blocks required, which we can help you with if you would like.

There might be something already designed and available to buy from somewhere – something known as Commercial Off the Shelf or COTS. It may be that some parts of your system can be COTS, but probably not all of it – otherwise your system has already been made by someone else.

Systems that can be made using programmable electronic hardware, with a processor or maybe a Field Programmable Gate Array ( FPGA ), might be able to use a COTS board that has that programmable element. Then your system might just need some custom software to make it perform the functions that you require but often such a system will also need some custom electronics to join it to the outside world.

The engineers at Dotstar have the expertise and experience to search out all of the options that can achieve your aims – giving you the information you need to be able to make the correct choices, and if you would like, some recommendations based on past projects. They can also help you with the custom parts of your electronics system whether it is hardware or software.

Even if there is a board that you can buy in for your project, you must consider if that will actually be the best solution for you in the longer term. For the first few systems, buying in your electronics pre-assembled can help to accelerate your software development and time to market, but whether you continue with that electronics or have a custom design is a difficult decision with a lot of factors coming into play.

If your volume requirements will remain low it is difficult to justify the cost of a full custom board development but things other than the initial cost must be considered. Many electronic components and sub-assemblies are available for only a short time, and the costs involved in changing your system design to accept replacement parts can be disruptive and costly. If you need to be able to obtain the parts to build your systems for any significant length of time, you must carefully select your suppliers and even the components contained within those products to minimise the likelihood of disruption.

It might be better to own and be in control of the manufacturing of your own electronics that has been custom designed from the outset so that you can make these selections from the early stages.

If you will need a high number of your electronic systems, then it will almost always be cheaper for you to develop your own custom electronics.

If a COTS solution cannot be found, or for one of the reasons above you need a custom design for your electronics you need access to many areas of expertise to be successful. You might have some or all of that expertise yourself, but more likely you would like someone to take care of it all for you.

The first step of your custom design is to capture the requirements into a document that clearly defines your needs, and to have that fully agreed before proceeding. Then a block diagram of your system can be drawn up, breaking the problem down into separate parts that can each be designed in turn.

Each of these parts of your custom design needs to be considered, and components selected that can meet all of the requirements. Then a circuit diagram ( schematic ) can be generated, where the small details of how to connect each component together must be finalised and entered. This is the first time that Signal Integrity (SI) must be considered, with signal terminations connected and their initial values and positions chosen. Some pre-layout IBIS simulations (using IBIS models provided by the manufacturers of the components) can help with this process.

Custom Electronics Design (Schematic & Layout)

Selecting the right components for a custom system must include several factors over and above the function of those parts. Cost and availability from a reliable source are important factors to consider, as well as minimum order quantities. Information regarding RoHS and REACH must also be available to be able to comply with the directives from the EU. Here each manufacturer and supplier must also be assessed for their performance of continuing supply in the future – a redesign of your custom system to replace a part that is no longer available is entirely possible, but it is not a cost or delay that you want if it can be avoided. Other factors like size and power consumption are also important in many designs.

Your design also needs to provide for the Power supplies and connector choices in order to complete your system.

Once that initial schematic design is finalised and captured into the CAD system, the physical Printed Circuit Board ( PCB ) can be designed. The number of layers and selection of Power and Ground layers is important to allow the routing of the signals, but also to provide good Signal Integrity for the custom board. Components must be positioned for best routing of the connections but also making sure that the production and test is possible. During and after the routing of the PCB, more IBIS simulations can be made to check the SI goals are achieved.

When the custom PCB design is completed, the CAD system is used to generate the manufacturing files to be sent out to the PCB fabricators. These specialised companies use large machinery with many types of chemicals to produce your custom PCB to very fine tolerances.

When your custom PCB is received you need to have the components ready to assemble into a prototype. This alone takes some considerable effort to manage, but Dotstar can do that part for you too.

It can often be useful to assemble the first board or two with only some of the components – maybe starting with the Power Supplies and some simple control circuitry. Only when those sections are fully debugged and finalised are expensive items added to another prototype. Here it can be useful if your assembly machinery is close by and available at short notice. At Dotstar we have the equipment ourselves making it simple to arrange and schedule the various stages of prototype production.

As the prototypes are tested it will be necessary to develop firmware for any microcontroller, processor or FPGA to exercise the custom circuitry fully and prove that the design is working as intended. At Dotstar the same design engineers that have designed your custom hardware are able to develop this firmware, and finally to develop that into production test software. If we are also developing the firmware for your final project, the engineers will already have a head start on that too.

In addition to designing your custom electronics, Dotstar can produce small to medium numbers using our vapour phase and other assembly equipment to achieve high quality results. For larger numbers we can help to hand the production over to a larger assembly house, and can even manage that process for you if you would like us to.

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