Switches get smarter and smallerSwitches get smarter and smaller

"Switches are not limited to turning things on and off anymore. They can now sense, measure, record, trigger, and activate systems remotely," says Mike Fasano, vice president, advanced technology at Carling Technologies Inc. (Plainville, CT), formerly Carlingswitch Inc.

The trend is also away from discrete components for each function. Universal, intelligent switches will not only activate systems, but can be installed in many places because plug-and-play intelligence built into them will tell them what circuit they are in and what to do with the information they are processing. Such sensing capabilities can, for instance, allow drivers of trucks and agricultural equipment to operate them with greater safety.

In fact, Carling plans to introduce a Hall effect truck brake pedal sensor soon. The electromechanical switches currently being used in this application must be adjusted every six months or so, due to rough treatment truckers dish out. Add to that the fact that the life of a truck is about an order of magnitude longer than that of a car, and the expense of repeated brake adjustments adds up. The Hall effect system positions itself precisely and needs no adjustment.

While all-electronic switches are not yet commonplace, they are popping up in other vehicle applications. According to Senior Vice President Mike Bhojwani, current applications include engine functions (fuel and emission sensing), and cruise control-with dash-mounted controls on multiplexed systems a coming innovation.

Despite the trend toward all-electronic systems, there's still plenty of steam left in products that combine electronic and mechanical technologies. One such example is Carling's Remote Operated Circuit Breaker (ROCB), which allows off-site control of breaker functions, such as on/off for resetting, service, and diagnostics, via phone or the Internet. Software in a customer's system sends a signal to the breakers. A technician needn't take the time and go to a remote site, such as a cellular base station or an ATM, to reset breakers.

The latest twist to the ROCB is a voice-mail-like cueing system that allows a factory-automation or telecom-equipment manager, or even a boat owner, to dial-up and be walked through a menu of system options. The system reports breaker status as "open," "closed," or "tripped." Thus functions, such as air conditioning, can be turned on, off, or reset prior to personnel arriving at a site.

Keys to the device are algorithms integrating electro- mechanical and electronic-sensing functions, as well as communications interfaces. Another enabler is packing the small, high-torque electric motor (run off line current or battery backup) and drive mechanism, along with the control electronics, into a standard circuit-breaker housing. This unit is then gang mounted in a panel with up to three poles of breakers.

Switches get small, too. Bill Agnatovech, director of design engineering at C & K Components (Watertown, MA), says that the drive to smaller products is aided by over molding, which involves stamping small inserts from a metal strip. The pieces are retained in the strip format, which is over molded by a plastic shape, and the resulting strip reeled up to use in production-no muss, no fuss, no lost or misoriented parts. This method is used in all types of switches, including DIPs, push button, and tactile.

Agnatovech says increased miniaturization is also affecting materials selection. "Smaller feature sizes mean smaller wall thicknesses, so plastics have to fill more confined walls and still withstand high surface-mount soldering temperatures," he notes. But, he adds, newer liquid crystal plastics and 4/6 nylon can allow this and maintain dielectric strength for electrical isolation. The latter, unless in power applications, is not usually a problem.

While market acceptance of new technologies appears to be good, Bhojwani concludes the transition from traditional switches and wiring to intelligent switches is not always as easy for the engineers who apply them as it is to the engineers who design them. "It's great to be on the cutting edge, but that's not useful if nobody is there with you. We have to be a partner to the customer in developing products."

As these types of partnerships mature, suppliers like Carling are seeing more capabilities outsourced to them from customers. In the past Carling would supply circuit breakers to telecom customers for their power distribution center enclosures. Now these customers are concentrating more on their core capabilities in software-based developments and asking Carling to fabricate the entire distribution box.