Electronics Design for Green Manufacture?

Posted on December 7, 2009 by Ray Keefe

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.

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

Enocean

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

Posted on November 30, 2009 by Ray Keefe

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

Posted on November 23, 2009 by Ray Keefe

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 beginning.

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’t be 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 your 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.

Green Electronics Strategies – Reducing Power Consumption

Posted on November 18, 2009 by Ray Keefe

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 its 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.

Improving Product Development Outcomes

Posted on October 27, 2009 by Ray Keefe

In this post we will look at the Product Development Process and how to get improved outcomes. But first here is a fun graphic made from our logo.

Successful Endeavours – Making Electronics and Embedded Software Work

Product Development Process

The Product Development Process is intended to reliably deliver new products for manufacture or distribution. This is a critical component of a Product Strategy where you are creating the product rather than sourcing it from a supplier. So you would think that it should be a highly optimised, well oiled machine that reliably delivers successful products. Alas that is not always the case. With 30 years of experience in Developing Products for a wide range of industries I have seen my share of projects handled well and not so well. Here are some general principles I have gleaned from my experience in Successful Product Development Projects:

Risks must be identified and managed. Track them and eliminate them as soon as possible.
Anything clever or tricky needs to be checked by someone else.
Everything else also gets checked. Design reviews, code walk-throughs and prototypes save time, money and heart ache later on.
Hold the timeline. Foster an attitude that slippage is not acceptable.
Test and check everything.
It’s not finished until no-one has to do another thing to it.

So six core principles. They are inter related of cousre. Let’s look at how these work out in practice.

Successful Product Development Principles

Lets look at how each of these priciples can be used to improve the likelihood of a Successful Product Development Project.

Risk Management

Risk Management is an old idea. Not surprising since risks have always existed. Did you know that during the Manhattan Project it was determined that there was a chance that a fission bomb could ignite the whole atmosphere ? Having got contradictory reports the argument was eventually settled by a report showing that although it was possible, it was unlikely. How comfortable would you feel running that risk ? Fortunately the average Development Project is dealing with much more mundane risks such as achieving Technical Requirements such as:

Power Consumption
Unit Manufacturing Cost
Performance Criteria

But the approach is still the same:

Identify the risk
Work out how to ameliorate the risk – reduce it – or eliminate it
Do tests to confirm the risk has been dealt with
Iterate until it is no longer a risk

Review the clever bits

Test Everything – Clever Design Needs Test

Where possible, any particularly clever or tricky areas of the project need to be reviewed by someone not involved in the everyday work of the project. This is primarily to ensure that assumptions are challenged. If you can’t get an outsider to do the review, use a process like Six Thinking Hats by Edward De Bono which can allow team members to step outside their emotional and assumptive predispositions. Unchallenged assumptions are unmanaged risks.

Review the rest of the project

Review Everything

The astute amongst would have noticed that I am proposing everything gets reviewed. But the tricky bits get extra review. This section is for the regular bits. Reviews are an essential tool to find mistakes early and eliminate problems down the track. You don’t have to solve a problem you don’t have. Or as Jack Ganssle famously quipped “Skip Bugging To Speed Delivery”. That article refers to using Code Review and Design Review to find problems early and fix them so they don’t become much bigger problems later on. Imagine a scenario where a Software Bug causes an electric motor to try and spin backward every now and again and then corrected itself almost immediately. You would get a momentary shudder or jerk followed by correct motion and it would only happen every now and again. How would you determine that this was a software fault and where the fault lay? It could be symptomatic of any number of issues including Mechanical Design and Electrical Design. How about this similar real world case. I won’t mention the company, but their elevators had an Integer Overflow problem in the motor controller that caused the elevator to go in the wrong direction, about once a month, for half a floor. Very disconcerting to the passengers if they pressed up, and promptly dropped half a floor before then going up. Fortunately they found it and fixed it before it happened to someone at the top or bottom floor. All the Software Industry Metrics show for that for Software Development; Design Review, Code Review, Unit Tests and System Simulation save money and time. And yet in many projects they don’t happen enough or are done after the event as a Quality Assurance box ticking activity where they add mostly cost and little in the way of value. Lean Coding argues that you can reduce your Software Development Budget in particular by doing Code Inspections during the project as part of the Risk Management and Quality Management process. By reducing the bugging, you can reduce the debugging.

Stick to the Timeline

Project Development Timeline

An attitude that the schedule slipping is normal can be very costly. Some examples of how to avoid this are:

Develop and Simulate the Software before the Hardware is ready
Prototype early and thoroughly
buy in IP where it makes financial sense – this can also reduce risk
get expert assistance with areas outside your competence
review regularly and honestly

As someone who has done a lot of team leading and project management, I have learned to ask about progress in more than one way. I find the following to be very common: Manager: “This module is estimated as 10 days of work to complete. How complete is it”? Developer: “About 80%”. Manager: “How many more days of work are required to fully finish everything”? Developer: “To fully finish everything, I would think 6 more days would cover it all”. The discrepancy is easy to spot. People estimate high on progress because they want to please. They also like to finish well so they tend to estimate conservatively on required effort. In practice the real answer lies somewhere between the 2 extremes. If the task had already consumed 6 days of effort then it is likely to run late. If you have ever built a house you might have experienced the knock on effect it has when one trades person doesn’t turn up and everyone else misses their scheduled action time because they are now waiting on a predecessor task, the trades person who has to come back again, before they can start their task. The same thing happens on projects. So fight hard to hold to the schedule. It is better to over resource a task (according to the plan) and get it done than to let everything and everyone slip which usually costs a lot more. Additionally, it is quite common that the later you are in the market, the lower the overall profit. So it is worth holding the schedule for this reason as well.

Test and Check Everything

Test Everything

This is another Risk Management related principle. Don’t assume it will be OK. Even if you have done it 100 times before, test it again this time. Make sure it really is OK. This ensures it really is 100% complete. This also implies that you are going to design things so they can be tested. Another principle. Design For Testability or sometimes called Design For Test. Do it. It will save you time, effort, money and sleep. Test Driven Development is another example of a Modern Development Methodology where you set up the test first then develop the product so it passes the test. If the Product Requirements change, you change the tests first, show that the old Product Design fails the test, then update the Product Design until it now passes the test.

It is not finished until no-one has to do anything else to it

Many tasks are called complete but they aren’t. The documents might be checked into the Revision Control System, also known as a Version Control System or Version Management System, but it isn’t complete until it is 100% tested, 100% integrated, 100% reviewed and 100% signed off and no-one has to do another thing. This also means that when tasks are identified that weren’t thought of in the original Project Plan, you then add them and don’t try and fiddle them into existing tasks. This is different to working out the fine detail of a task and realising it is under resourced or over resourced on the Project Plan. You also want the extra tasks visible on the Project Management Plan so when you do the next project you have evidence that they were required last time and can make allowances for them.

Trip Assurance for Developers

Satisfaction Guaranteed

In marketing, the term Trip Assurance refers to the client having a clear expectation of this transaction or experience being a good one, just like every other one has been. I think we can begin to develop some of the same as developers whereby projects can be routinely good experiences and likely to be so each time.

This post is also available as an eZine article with Expert Author classification.

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