Tuesday, June 10, 2008

Leaving the lights on

DVD player standby buttonI am an advocate of making sure that every device consumes as little power as possible at all times. Indicator lights should be off, processors should be sleeping as much as possible, and generally the device should just be optimised to use as little power as possible.

I may have to rethink that....at least a little bit.

Dan Lockton has a brilliant blog, Architectures of Control, where he discusses how things are designed to result in a certain action (or lack of action) – or as he calls it, design with intent.

There are two devices in my home which have helped me to reconsider turning off all the lights, my DVD player and my laptop. Each has its own subtle "architecture of control" whether intentional or not.

Our DVD player has (to me) the most irritating standby light that I have ever seen on any device. When on, the light is constantly illuminated, but when in standby the light flashes continuously (at a slow rate). This drives me mad, but results in an interesting action – it causes me to turn it off at the plug when I am not using it (which is most of the time). Suddenly one little flashing light has resulted in more energy saving than having no light.

laptop power indicatorsMy laptop has a similar "feature." When it is powered down the battery indicator remains on (green if full, flashing yellow if charging). This used to bother me, and I thought, "Why not just leave the light off when the battery is charged?" My wife's laptop is like that, the battery indicator only flashes if it is charging, once charged it turns off.

That is all good, except my laptop communicates to me that it is plugged in and consuming standby power when it is not in use. When I unplug it from the wall socket, then the battery indicator goes off – I save the standby power of both the power brick and the laptop.

There is one problem with this, it only works on people who care. If I did not care about saving energy, then I would just leave the laptop plugged in and the DVD player on. That means that you have to consider how your users will handle this kind of subtle feedback and determine whether turning the light off, or encouraging unplugging results in more energy savings.

Sometimes the most obvious design decisions may not be the ones which result in the greatest energy saving. Keep designing for low energy consumption and also keep your mind open to new possibilities.


11 comments:

Pieter said...

I've read a similar article before and agree that standby power should be minimised. I know, e.g., that my audio amplifier consumes about 2W of power when on standby. Basically, this standby feature enables me to use my remote to switch it on and to otherwise power the blue LED. We all have numerous appliances that consumes standby power most of the time. How much of this is really needed? I've read somewhere about a guy that has this timer attached to his home circuit to basically cut power to certain plugs in order to save standby power when he's not there (e.g. at work or at night when sleeping).

Duncan Drennan said...

There is a lot that we as engineers can do. For example, I brought the idle power consumption of a device I am working on at the moment down from 130mW to 30mW with just a few minor changes to the firmware (turned off the PLL and used a slower clock, and put the micro to sleep while waiting for comms). I still think that 30mW is too much for doing nothing though...

We have to constantly be looking for ways to reduce power consumption through clever engineering. We also need to be open to designing in a way that encourages power saving (the above may be examples of that).

Thanks for your comments, they are always appreciated.

Stefan said...

When it comes to standby power, I often wonder whether we aren't penny wise and pound foolish. If I boil my kettle once fewer, I can leave my notebook on standby for a month (a year?). With all the best intentions, I switch off the (energy saving) lamps in my house whenever I can. But a single mine in South Africa forgets a generator on, and it takes up a million times the power I saved. On the other hand, if I recall correctly, home users still account for more energy use than the industry. My question remains: where should we save electricity to have the biggest impact?

Duncan Drennan said...

Maybe this is too broad an answer, but why not save it everywhere we can?

If I am designing warehouse floor systems I am making sure that their power consumption is as low as possible (especially if there are going to be 10000 units in a warehouse). At the same time an engineer designing fridges should also be keeping energy consumption as low as possible. We should all be doing it.

I think that we also have to look at our inputs and question the amount of energy used to make an aluminium housing and evaluate that too.

There is also a question of engineering effort versus quantity and total energy saving. Each project needs to evaluate that. Often the effort is relatively small (like putting processors to sleep while idle).

I feel that as engineers we should be driving these kind of issues as a matter of ethics and good - no wait - great design.

Do we settle for something that is good enough, or strive for something which is great? I know which one I prefer.

Francois Cilliers said...

I agree. We SHOULD save energy everywhere we can.

It doesn't really help to compare sources of saving with sources of waste, because when we don't save even the smallest amount, that just adds to the total amount of waste.

The human race as a whole is wasteful by nature and way too lazy to bother with efficiency. So, since we as engineers are responsible for most of how society works, I also believe that we should take responsibility for creating products that are not wasteful. And, we need to consider the energy and materials cost in the development and manufacturing of any products.

Of course, we should also systematically identify and eliminate other existing sources of waste.

Duncan, I like the idea of devices that encourage you to save power without thinking about it. Although, I have always been under the impression that stand-by lights blink in order to save power (since they don't remain on all the time), rather than to irritate the user. Maybe it's a fortunate coincidental side-effect?

The concept of wasting a little in order to gain a little more, is more generally applicable too. For one example, just think about how much you gain in terms of well-being when you "waste" a little time on a holiday. ;)

In software development we also sometimes waste some CPU cycles in order to gain more design flexibility.

Stefan said...

We all have limited resources, and we must strive to apply those resources in the most focused and efficient way possible. In my mind, that means focusing on important power saving functions, instead of spending excessive time on tweaking components for minor (dare I say negligible) savings.

This scratches deeper than the surface. Do you use components from a responsible producer? Are you sure those Power Saving LEDs aren't manufactured by boiling innocent children?

I know people often say: "I can't solve these big problems, so I'd rather not bother with the small ones either." That is not what I am advocating. I'm simply saying: tackle the biggest problems you can first, and then move on to fry smaller fish.

Francois Cilliers said...

That's a good point Stefan. The bigger problems are more important and more urgent.

It is, however, much easier to tackle issues with which you have a direct involvement (eg. specific products you may be developing). So, I would recommend that you keep on hacking away at the "smaller fish" when they are within easy reach, but also explore ways of taking on the bigger ones at the same time.

Roy said...

My digital radio emits a highly irritating buzz when in standby and as the only place I can get reception is next to my bed, it kept me from reading in peace. I have now fitted a lightswitch to the power cord so I can power it down completely when not in use - thankfully it still remembers all my stations and settings, however the perverse feature is, in order to use it as an alarm, the thing must be in standby overnight in ordfer to switch itself on. So now I keep it powered down all day, and switch the power on just as I'm about to sleep just so that it can to be in standby all night to wake me up in the morning. This wouldn't bother me so much if that buzzing wasn't a constant reminder of how much energy it is frittering away!

The question of power and standby LEDs is interesting. My hard drive has a ridiciulously bright power light that illuminates the entire area under my desk, one which I'd rather nobody saw!

My digital camera battery charger has an LED that switches from red when charging to green when charged. Being red-green colourblind, along with a large proportion of the population, this feature is entirely redundant as the colours are at just the right saturation (suspiciously so) for the difference to be indiscernable to me. If you're going to add an LED of dubious benefit, at least make it benefit the widest population possible!

Graham Cliff said...

Energy conservation is, and will become, vital to future sustainability. We waste energy creating the 24 hour day. The 24 hour day with its LAN (light at night) is already destroying nocturnal habitats - they no longer exist. Bye Bye whip-poor-wills and night jars. Life no longer enjoys circadian control of its life cycles. LAN is killing bugs, birds and bats. What a future failure we face. Will kids today be happy adults in their future that we are creating today?

Duncan Drennan said...

Thanks for the thought provoking comment Graham - I had never really considered what the knock-on was of all the lights we have on at night.

amanation said...

Saving energy means save your nation and reduce your electricity bills.It tells the various features of laptop and when charging it shows diferent indicates.Most of the Laptop or Notebooks does not have he an option to manually turn off the LCD screen. Turning off the LCD screen will save power and it make sense to turn off monitor in case you are downloading files overnight. Windows has an option to turn off monitor when kept unused for some time, but this feature is not always good.This blog is knowledgeable.

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