Many electronics products developed are inherently mobile and require a small and portable energy source. When coupled with design requirements for long battery life and for practically zero maintenance, an opportunity to implement several well-practised design strategies presents itself.
In the interest of carbon-footprint reduction, these practices also need to be considered and implemented in applications where a fixed energy source is available. Truly smart electrical and whitegoods products within which the quiescent or standby energy draw is practically zero is a realistic design target.
Both these development scenarios are becoming increasingly simple and achievable, as many manufacturers of integrated circuits market the values of miniaturisation and excellent energy efficiencies.
In this article, several approaches for energy-wise applications are considered and include energy-saving algorithms, discrete electronics versus microprocessor, processing speeds, operating voltage and energy-saving sleep mode. We will also take a quick look at the exciting new series of energy-harvesting products, which may deprecate battery life considerations altogether!
O(n) Task? Energy-saving Algorithms
During the firmware development phase of an electronics product, a high level of the effectiveness of the algorithm or program is warranted. The processing complexity of algorithms is often written in O(n) format. This nerdy expression assists designers to determine how much processing power a given algorithm requires and, consequently, how much electrical energy is required.
In order to determine this parameter, there are several tools available to the designer, including mathematical modelling tools, CPU simulators, and custom test benches often implemented in software for proofing and subsequent porting to actual device firmware. An experienced electronic design engineer will employ these tools during the prototyping stage to find the best power-saving solution.
As an example of this process, consider the following theoretical scenario. In this instance, the energy-wise battery-powered electronics LX Group Hardware Development is developed and built to the prototype stage. Next, firmware is developed as a “best-guess” algorithm for field testing. In parallel, a data-logging process which collects real-time fine-grained date is implemented for power consumption justification. This phase of field testing and data logging drives the adoption of a proven algorithm in which minimal energy is expended to achieve the correct functional result.
We’ve Learnt to be Discreet: Discrete Electronics vs. Microprocessor
Experienced electronics designers often consider the deployment of a simple discreet component solution. With the advancement of low-power microprocessors and microcontrollers, however, often a design employing discreet components will require significant complexity to achieve temperature stability, low quiescent and operating currents and, ultimately, is not a flexible option.
Whereas inexperienced designers will reflexively “whack down a micro”, there are significant design, cost and flexibility bonuses involved with this approach. The “discreet” choice has become a low-power microprocessor
Watch Your Speed: Processing Speeds
Newer micro-controller and microprocessor products offer much flexibility in the choice of operating speeds available to the designer. Frequently, robust watch-style crystals are supported, and when used appropriately, designs can run for years on a small cell without requiring manual intervention.
How Low Can You Go? Operating Voltage
Modern microcontrollers continue to push the minimum operating voltage boundary down. Some readily-available commercial-type devices are now operating down to 1.8V and less, and this at breathtaking operating speeds.
There are often other benefits derived from low-operating voltages. This often includes the omission of the inefficient voltage regulator from the circuit, providing energy and space savings. In addition, only a single cell may be required to operate the controller, potentially halving the physical volume occupied by batteries.
Rest Up: Sleep Mode
For some years, sleep modes have been offered with microcontrollers. The sleep mode assists energy saving by reducing the operating current drawn in parts of the controller’s circuitry that are not required. Typically, a processor is programmed to periodically awake, perform some small piece of calculation, and then to go back to sleep. The sleep/wake proportion directly affects the energy consumption bottom line. More recently, the sleep modes have become increasingly flexible, with choices over which chip sub-systems remain in a powered state.
Assisting the duration of the rest periods are multitudinous CPU peripherals inside modern microcontrollers that allow the CPU to remain asleep while peripheral tasks are performed automatically. There are sophisticated Direct Memory Access (DMA) controllers, UART’s with programmable wake-up on data received sequences, analogue to digital converters with their own sample-rate clocks, and the list goes on. In some cases, the CPU could literally setup the on-chip peripherals and then effectively self-euthanize!
The default state for these on-chip power-saving features is, naturally enough, ‘off.’ The designer leaves these items off unless they’re required by the application, and even then, the designer considers to what extent power to the peripheral is modulated. The modern microcontroller has certainly evolved to save energy.
Lean & Green: Energy Harvesting
The most recent advancements into the consumer and designer market, in terms of green products, comes from the field of energy harvesting.
Energy harvesting can power smart wireless sensor networks used to monitor and optimise complex industrial processes, remote field installations, and building systems. In addition, otherwise wasted energy from industrial processes, solar panels, or internal combustion engines can be harvested for useful purposes. Typical energy-harvesting inputs include solar power, thermal energy, wind energy, salinity gradients, and kinetic energy.
Critical to success of harvesting these minute energy sources, is the expenditure of minimum electrical energy in the application, some techniques for which have been discussed.
Thoughtful Design: LX Group
At LX Group, specific design and development effort in consideration of energy saving is assured, as the technologies preferred by our internal developers are market leaders in efficiency. Additional development costs for this design phase are minimal, as the design ramifications for energy-wise products are increasingly becoming de-facto performance standards in the industry, and are well documented.
Designers at LX Group believe that the development of a superior green-product is well within reach for clients. The additional development effort previously required for such a functional requirement is no longer a significant risk consideration or cost barrier. The approaches discussed in this article are a sampling of technologies and techniques available to LX Group designers to rapidly prototype your killer low-power concept
Published by LX Group for itself and the LX Group of companies, including LX Design House, LX Solutions and LX Consulting, LX Innovations..
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