Electronic Design

Going Green, Or Just Using Old-Fashioned Design Practices?

Going green is all about cost, value, and tradeoffs. The big difference in designs from a decade ago is that more of the real costs are starting to surface. This ranges from the cost of recycling devices to how much power a system consumes. Power consumption has become the focus for hardware designers for a range of reasons, from portability where batteries are required to cooling limitations.

Designing a green system is really a matter of checking out options instead of following the usual road. In many cases, this means you can’t cut design corners anymore when it comes to aspects of the system that aren’t the primary part of the architecture. For example, providing power is no longer a matter of popping a pair of AAs into a design.

More options are available on both sides of the equation, such as very low-power microcontrollers for wireless devices that run ZigBee, Zwave, or Bluetooth and operate intermittently instead of continuously. Design gets more interesting as power from scavenging sources become more prevalent.

Texas Instruments teamed with Cymbet to create the $149 eZ430-RF2500-SEH (Fig. 1). This selfcontained solar-powered wireless development platform comes with a pair of eZ430-RF2500 modules and a USB programmer. One module plugs into the Cymbet demo platform, which consists of a solar cell and the Cymbet EnerChip-based power module.

The EnerChip is a thin-film battery in a surfacemount chip. Multiple chips can be used if more power is required. The EnerChip contains circuitry to handle incoming power and deliver regulated output, eliminating system design complexity in addition to fitting everything on a single circuit board.

Thin-film on-chip batteries are neat, but developers need to keep an eye on battery technology as well. New batteries like Energizer’s rectangular, zinc-air Prismatic may be the right choice (Fig. 2). The Prismatic line is a primary, non-rechargeable technology.

Zinc-air technology isn’t new, but it does deliver three times the power capacity of existing devices since it uses air as part of the chemical reaction to generate power. These batteries are designed for devices like portable audio players and noise-cancelling headsets.

The Prismatic is only 5 mm thick versus 8 mm for AAAA batteries, so it works with compact devices. It requires air circulation, though. The battery placement and ventilation are key to battery life. This is why Energizer is working with designers on the best way to use the technology.

Think wireless but not mobile when it comes to Powerbeam’s power transmission system. The transmitter uses infrared laser diodes to beam heat to the receiver. Like the Cymbet module, it contains a battery because transmission is designed for intermittent use. Consider continuous versus peak use for applications like wireless speakers that might be used for a few hours per day.

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