The stackable connector systems have an array of male pins on one surface and a complementary array of female sockets on the opposite surface. This allows stacking of multiple units.
Factors to consider for selecting the best connector
Connectors for embedded systems can be of two types based on the application or the type of transmission they allow—power or data. You have to know whether they would be used on a printed circuit board (PCB) or in a harness assembly. Another typical division is based on whether they are input connectors, on-board connectors or output connectors. The main consideration for choosing a connector would be the end application of the embedded computer.
There are multiple criteria based on which a connector can be chosen depending upon its application.
In case of the input and output (I/O) connectors, the main parameters to look at are size and number of I/O signals required for your design, amongst other things.
For coaxial radio frequency (RF) connectors, the frequency range and attenuation levels are what matter the most.
For power connectors, the factors that have more emphasis are voltage ranges, current ranges and operating temperatures the connector can withstand.
The connectors used in aerospace and defence industries require safety, security and ability to withstand harsh environments. More rugged types of connectors, which cannot be easily bypassed, are the kind required here. Other properties, such as material science, also vary depending upon several technical and commercial factors.
Compactness and portability. The size and weight of a device can be an important factor in certain application fields. If the dimensions of the product forbid the designers to use a particular type of connector, they might have to go for a non-standard way of using different interfaces on it.
Miniaturisation and portability requirements are very high on consumer electronics end. The size of PCB is becoming smaller and the design of connector is also changing accordingly.
Another area where compactness and portability issues come up is the avionics sector. On devices such as unmanned aerial vehicles (UAVs), vibration form factor, the size, height and weight are very important criteria. The overall electronics used in UAVs are bound to be very small in size, and that is when portability of connector becomes a key aspect.
The industrial requirement for embedded systems would not maintain so much of miniaturisation or portability issues. In that case, the designer can afford to use bigger connectors since there are no major constraints in terms of compactness.
Significance of interoperability/compatibility. Another important aspect for designers is whether the connector supports interoperability and, if yes, with how many components or devices. If the given connector is compatible with products from three or four different vendors, the user can buy a connector made for the device for one brand and match it with the device of another brand. But a user needs to look into such prospects under worst-case scenarios.
When it comes to the manufacturing side, there are a lot of lead time and production issues. So the manufacturers have to look at the possibilities for replacements that can be used for a product in manufacturing.
Previously mentioned industry standards, such as USB and HDMI, help ensure intermateability of connectors.
Longevity. Longevity of a connector is generally defined by its insertion (and removal) cycles and gives an idea of how long it is expected to work properly. Insertion cycles are defined in the datasheet of each connector. Consider a connector with an insertion cycle of 200. Under normal conditions, you can insert and remove the connector approximately 200 times and still expect reliable performance. After that, the behaviour is not predictable.
For devices such as cellular phones, where we plug in the connector once or twice daily, the insertion cycle and longevity are expected to be greater.
Longevity depends on vibration aspects too; what wear and tear the product faces throughout its life cycle.
Environmental factors. The designer should keep in mind all the possible environmental conditions under which the device could be operated by the user, and accordingly ensure that the connectors and cables can withstand these. For example, in case of fire or heat exposure, one should ensure that the connectors are of proper fire retardant (FR) grade. Sealed connectors are commonly used in such rugged environmental conditions.
Availability and serviceability. “Use of expensive or out of the ordinary connectors makes it difficult to service and satisfy customers,” says T. Anand. But according to Gagan Shah, the product specialist of Phoenix Contact, “The selection criteria for connectors should not be based on the price. It is important to understand the need and application area of the customer before providing the right connector solution. Sometimes with additional cost the customer can get more benefits which cannot be achieved with low cost solutions.”