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Electronics Design for Green Manufacture?

Ray Keefe — Mon, 07 Dec 2009 01:32:19 +0000

Electronics Design for Green Manufacture

This is not as straight forward a topic as it might at first seem to be. And this is because there isn’t yet a unified agreement on exactly what Green Manufacture means. And like most Design Issues, you cannot do Electronics Design without clear requirements. So what are the requirements?

Here are some Green Manufacture requirements or targets:

reduce product Power Consumption
reduce manufacturing Power Consumption
add Renewable Energy options to the product
add Renewable Energy options to the manufacture process
reduce pollution or waste in the manufacture process
reduce energy involved in upstream or downstream processes
reduce pollution or waste in the upstream or downstream processes
increase product life
increase product utility
increase manufacturing plant utilisation

I guess you can see the dilemma. It can be hard to know which target to aim for. Am I doing the Electronics Design with the product, process, life cycle or ecosystem issues as the primary concern? And how do I balance these concerns?

Here is one excellent article that also discusses this topic Green Supply Line.

Electronics Design can be Green

One major thing we can do is reduce the product Power Consumption. We are coming out of a phase where a mains plug pack power supply was considered an ideal way to avoid compliance costs when designing new products. This has led to a proliferation of low efficiency always on powered devices. A recent look under my desk reveals the problem we have as Product Developers where every device I use is either USB Powered or mains plug pack powered.

So a first step is to review this whole approach to supplying power to devices. We have made steady gains in the area of Power Consumption reduction for the devices themselves. Now it is time to do a similar thing on the Power Supply side.

Energy Harvesting

This is a new area that hasn’t yet reached mainstream development. The idea is that you can utilise the ambient environment to get power for free. Or at least you aren’t directly requiring extra Power Generation. Hence the name, Energy Harvesting.

How you do it and the Electronics Design and Electronics Technology required to make it work are still being defined but there has been some interesting new progress. Some key players are:

Linear Technology – new Energy Harvesting Integrated Circuit

Enocean – are front runners in bringing Self Powered Wireless devices to the market

What is Energy Harvesting?

This is where we use Electronics Design and Electronics Devices to generate power from the Ambient Environment. The result is a product that doesn’t need to be plugged in and recharges itself automatically. Some of the Energy Sources that are used are:

Light
Thermal differentials
Vibration
Chemistry
Pressure differentials
Air Flow

One example of a product that does this is the Enocean Light Switch where you can just put it where you want it. And if you change your mind, just move it. Now wiring required.

Right now the technology is still more expensive and so take up is slow. But as it develops and the price comes down that will change.

We are in for some interesting times.

Ray Keefe has been developing high quality and market leading electronics products in Australia for nearly 30 years. For more information go to his LinkedIn profile. This post is Copyright Successful Endeavours Pty Ltd.

Green Electronics Strategies – Reduce Power While Awake

Ray Keefe — Mon, 30 Nov 2009 03:14:00 +0000

Electronics Design To Save Energy

We have looked at how Low Power Electronics is a green strategy because it reduces the amount of power that has to be generated. And then we looked at a range of options for Reducing Electronics Power Consumption.

Now we are into specifics. The last post looked at Sleep Modes For Microcontrollers and how extending the Sleep Period and reducing the Sleep Current could dramatically Reduce Electronics Power Consumption.

Saving Electronics Power When Awake

The next logical step is to ensure that Power Consumption when awake is also reduced as much as possible. This can be a little tricky to get right as it can sometimes eliminate all the benefits you built up with you sleep strategy. The reasons for this are:

you can use Analogue Electronics to reduce software power requirements but it has to be turned off during Sleep Mode
if you do turn the power off to Analogue Electronics then there is a Settling Time after it is powered up
using Smart Electronics Chips can increase overall Quiescent Current
unless the Startup Time and Shutdown Time are quick, these can dominate the Power Consumption

Now there are some Software Architecture issues that affect these, especially the last one, but we will look at that in another post. For the last part of this post we will address the Electronics Design issues that have been raised here.

Electronics Design – To Save Power

Electronics Design can address these Power Consumption issues. Here is an example of a Power Consumption curve where an RC Time Constant must be taken into account to minimise average Power Consumption.

RC Time Constant affect Power Consumption

Here is a list of general strategies to select from to reduce Power Consumption:

using the lowest feasible Clock Rate so Clocked Devices use less power
using shorter Settling Times particularly by controlling RC Time Constants
select semiconductors for lowest overall Quiescent Current taking awake and sleep operation into account
ensure streamlined Startup and Shutdown operation

The overall Quiescent Current issues often gives the most difficulty. This can be addressed through Design Simulation either by SPICE, Software Modelling or a spreadsheet. For simpler systems the spreadsheet is often the easiest solution to implement. For very Software Intensive Systems the Software Modelling approach is the most reliable method. This will allow you to construct scenarios and be able to predict the Power Consumption implications for each of them.

For our Electronics Design and System Test methodology we often create a full system Software Model and so it is easy to use this same Software Model to accumulate the power consumption as it runs. This can also be automated and so simulate months of operation very quickly.

Next we will look at the role of Embedded Software in ensuring Power Consumption remains as low as possible.

Green Electronics Strategies – Sleep Saves Energy

Ray Keefe — Mon, 23 Nov 2009 02:28:14 +0000

How Does Sleep Save Energy?

For this post, we will look specifically at Embedded Software techniques to save power and energy. This is a well known Power Saving Strategy which doesn’t always get the recognition it deserves. It is also something you have to design into the Power Management Plan from the beggining.

For this example, we will use the MSP430 from TI which has some of the best Power Saving and Power Consumption figures in the industry. We have used them to create devices that run from a pair of AAA batteries for 2 years and which have time based control algorithms so that they can’tbe used in a purely event driven mode. Here is how it works:

Low Power Sleep Mode

This shows the power consumption versus time. In Low Power Sleep Mode the consumption is close to zero. Almost no power consumed. Then depending on what is happening it wakes up to varying degrees.

Get the best Electronic Sleep

So this is how you take advantage of this:

make the time between wake ups as long as possible
make the time awake as short as possible
only turn on the peripherals needs for a particular wake period

Now if you system only has to wake once every minute then you can get low power operation from a lot of different processors. If it wakes many times a second then you need a processor that gives you lots of ways to reduce power during wake, reduce the time awake, and increase the interval between wakes.

MSP430 Sleep

So back to the MSP430. It has Power Conservation features that allow it to do all three better than most. Here is the list:

Digitally Controlled Oscillator DCO allows it to wake and run quickly
Can run a Timer from a 32KHz crystal making interval timing very low power
Can use the DCO to set the run speed and so shorten the wake time
Lot’s of Power Down Modes so you can always find one that suits your application
Peripherals can be Shut Down when not in use
Can run down to 1.8V – more on that later but it can also help here

Low Power System Architecture

To take advantage of all this, you have to develop the System Architecture so that takes advantage of this. An example from a very long life application we did runs like this:

32Hz Oscillator runs a timer that generates a 1 second wake
User input keys set up to wake on change of state from high to low
Use DCO at 1MHz to quickly wake, execute & sleep again
Use State Machines to allow modules to execute predictably with eratic timing
Have early exit tests to prevent unnecessary Code Execution

The result is an application that runs a process with User Interaction, LED Indicators, and a 2 week cycle where the average Power Consumption is 20uA at 2.7V or 54uW. Of this, less than half is the processor executing the software and the single biggest energy use is the intermittently flashed LED Indicators.

To learn more, check out this more comprehensive article on “Low power MCU selection criteria and sleep mode implementation” from embedded.com which provides more examples.

Green Electronics Strategies – Reducing Power Consumption

Ray Keefe — Wed, 18 Nov 2009 03:36:31 +0000

What is so good about Low Power Electronics?

If you read my last post, you would have noticed that this has the potential to reduce overall Power Requirements. Up until now, only Battery Operated Devices have really cared about Power Consumption. If you could plug it into a wall outlet then all was OK unless you were consuming more power than a standard circuit allowed.

Today, things are different. Climate Change is a global concern and reducing the Carbon Footprint for a product is important, regardless of what sort of power it consumes.

If we can reduce the Power Consumption of an appliance by 50%, then provided it’s Electronics Manufacture does not add that back again, we have a net Carbon Footprint gain. In fact, if we can do this across all products then we will meet our Global Carbon Reduction target of 50% by 2050 with this strategy alone.

How to reduce Electronics Power Consumption

This is not a new topic, and much of what I present here represents the combined experience of the Electronics and Embedded Software industry. Here is the short list:

reduce the Supply Voltage for Microcontrollers, Microprocessors and CMOS Circuits in general
use Sleep Modes and keep the Wake Periods as short as possible
replace High Power Consumption Devices with Low Power Consumption Devices
replace high utilisation Digital Filters with Analogue Electronics equivalents
replace Polled Operating Modes with Event Driven Operating Modes
use Low Power Smart Peripherals that Wake the rest of the System only when required
reduce the Time To Wake and the Time To Sleep
optimise the Software Execution Flow
use Energy Harvesting
Remove power from sections of Electronics Circuitry when not in use

There is overlap and interdependency between these but that is a good starting point.

Next I will start look at specific examples.

Low Power Electronics

Ray Keefe — Fri, 13 Nov 2009 23:22:50 +0000

Low Power Electronics is a Green Strategy

There are 2 ways to reduce your Carbon Footprint. The first is to get the same power from a Green Power Source that reduces the Carbon Footprint at the power generation phase. This is where Wind Power, PV PhotoVoltaics, Wave Power, Geothermal Power and other such technologies come in.

Wind Power Generator

The second way is to use less power from the same source, which is a Power Reduction Strategy. This is a bit different to the concept outlined in Unlimited Wealth by Paul Zane Pilzer where he shows that we keep finding ways to meet the expansion needs of the future. That is also happening. The ‘use less power’ approach is about getting more from the existing. The great thing about this is that you can effect a reduction in you Carbon Footprint independent of the Power Generators and so this strategy can run ahead of large scale system changes.

First you have to have a baseline to measure from. This will become critical for businesses that must show Carbon Footprint reductions once legislation in this area is brought in around the world. The issue isn’t if, but when this happens, and what the specific details are. Carbon Trading is an interim measure that allows money to be made off the problem while not actually ensuring there is real progress. Eventually significant net reductions must happen.

Carbon Footprint Calculation

There is a Carbon Footprint Calculator available at IEEE. You can see what your Carbon Footprint looks like by clicking on the IEEE picture below

IEEE Carbon Footprint Calculator

How did you go? Some of the questions are not that easy are they? We often don’t know the source of some of our power or the real Carbon Cost of our lifestyle.

Carbon Footprint Reduction

So reducing the Electronic Power Requirements for Electronic Devices is a primary Green Strategy for reducing your Carbon Footprint. For a complete system the calculation is of course much more complicated. The survey above is aimed at households but the principle is the same. A true Carbon Reduction Strategy requires you to consider not only your own operation but upstream and downstream operations as well.

This is of course only one strategy and we will look at others in the near future. But for my next post I’ll concentrate on design techniques for Reducing Power Consumption in Electronic Appliances so that they become Low Power Electronics Appliances and help to reduce the overall Carbon Footprint.