Because our work depends so much on the technologies we utilize, one of our year-end reviews covers a post-mortem summary of all failures related to our equipment use. The summary includes system failures, which are thankfully rare, and also encompasses use-model failures such as our discovery that the RF data-link receivers we use on location don’t work reliably with 4G mobile handsets nearer than about a half meter. Good to know; easy to avoid.
Beyond the gear itself, we track and review failures of associated accessories including power sources, small signal adapters and converters, and interface cabling. For good or for ill, it’s this last item that seems to dominate our attention this time of year:
For the fourth year in a row, the number-one source of malfunction we’ve experienced was due to connector failures. The one-and-only problematic connector was the micro-USB.
We’re not particularly hard on cables here. On the contrary, we’re quite careful with interconnects: We have XLR audio cables that have entered their third decade of field service and are hardly distinguishable from their nearly-new brethren. By contrast, we’re still looking for a common USB type-A to micro-USB type-B cable that can last through more than six months of normal use despite the fact that the form factors have been in heavy use for years.
As far as we’ve been able to determine, the problem with USB type-B connectors is a combination of mechanical design and material choice that results in connectors quickly losing their retention ability. Eventually, cables simply fall out of the devices they’re connected to because of the weight of the wire between the two connector ends. That’s not a reliable interconnect.
The micro-USB type-B is now one of the most common connectors in use to recharge handheld portable devices. WiFi has taken over the task of data connectivity for mobile phones, pad computers, and many other portables. But battery charging for a huge population of devices still depends on the USB port. Indeed, USB appears to be the top electromechanical interface for portable device charging so, at this point, it is the source of an industry-level reliability problem.
The underside of the micro-USB type-B plug features a pair of protruding fingers that grip the interior of the mating jack. The sample shown here is among the most robust of those we’ve found. Unfortunately, it is rare indeed to be able to see how a particular manufacturer chose to design and form this part of the mechanism. And it’s uncommon, in our experience, for equipment manufacturers to pay much attention to it when sourcing accessories to be included with their products.
All product designs are under constant pressure to miniaturize. Without careful attention to the mechanical and electromechanical design, however, miniaturization can degrade product robustness and reliability. We recommend a few habits for electronic design engineers in this area:
• Your product’s user interface is more than software, a screen, and some buttons. Treat every connector, no matter how common, as an integral and critical part of a user’s access to your product.
• Take your local mechanical engineer out to lunch. Better still, make them your best friend. They can offer insights and evaluate electromechanical options that will have as much or more affect on the customer experience of your product than any whiz-bang feature you can add. Plus they have great stories.
• Unless you’re in a sector that has already locked into a particular electromechanical interface, determine whether there are more robust options available. This is one area in which Apple’s penchant for proprietary connectors has actually served its customer base with more than just higher prices. Proprietary connectors, however, are not the only solutions to the problem. USB is a valuable and ubiquitous interface standard that has kept pace with performance demands. Its mini version appears vastly more robust than does the micro version.