standby power

[KenB]

Supercapacitors could well provide a solution.

One design I worked on used a 0.22F supercap which we were buying in volume for just $0.32.

If the mains power switch was a latching power relay, with a mechanical button on it, even if the supercap was flat, the user would just have to push the button for a couple of seconds to restore the power.

The reason why manufacturers don't like real mains switches, is the inconvenience of the additional mains carrying wires or pcb tracks brought to the front fascia of the device/appliance.  Most set top devices have evolved to have the mains circuitry and power supply confined to one corner at the rear of the product - this makes manufacture  simpler and cheaper.

So to get around the problem of not having a real power switch on the front, they devised the standby button, which means that a proportion of the circuitry has to remained powered - and this normally means the power losses associated in keeping the switch-mode power supply powered up.

Increasingly there has been discussion about running a low voltage 12V ring main. This would be ideal for devices such as routers and laptops that can run from 12V power.  Again the manufacturers have to come up with standard connectors for it to catch on.  Additionally, you are limited to only a few amps (<5A) otherwise cable losses become significant, so you might not be able to power a 19" flatscreen monitor, or an inkjet printer or other watty devices.   A 12V powered hub, that provides 4 or 5 ports with 12V power, and has a single high efficiency switched mode supply might be a solution for the average home-office.

My office power requirements are close to a constant 50W, when using the laptop, and wireless router.  21W of that is the permanently plugged in devices, and 30W is the laptop.

The linear  12V 1000mA transformer based plugtop supply on the router draws 3W before the router is even turned on. This is not losses in the transformer - it draws 0W when not plugged into the router.  It's 3W of power just keeping the router powered, even though the front panel power switch is off!  This climbs to about 10W with the router active.

So a permanently powered wireless router costs me 87.6kWh a year or about  £12.30 a year (Southern Electric £0.1403/kWh).

So I think its about time to get my 90W solar panels on the roof and run a 12V dc feed to the router.  The laptop needs about 30W, so nearly 3A at 12V.  The power supply says 15V on it but I will try it on 13.8V and see how it fairs.

I had a whip-round and unplugged all unnecessary plugtops, and got the laptop and router to below 45W.  The 1A 12V linear supply runs quite warm, so I might swap this out for a switcher and see what I can save.

Flamethrower - might be worth some net-research to see who Virgin cable uses for their broadband router.  A 10Mb datarate is likely to require more power than 2Mb, but as it is a fairly new design, it might be lower power than the previous generation of 2MB kit.

I see they are using Netgear WGR614 which works from a 12Vdc 1000mA adaptor.  This is a cable modem and wireless router combined.

http://www.netgear.co.uk/pdfs/WGR614.pdf

http://allyours.virginmedia.com/html/internet/wireless.html#grouter




Ken

[KenB]

Flamethrower

- might be worth some net-research to see who Virgin cable uses for their broadband router.  A 10Mb datarate is likely to require marginally more power than 2Mb, but as it is a fairly new design, it might be lower power than the previous generation of 2MB kit.

I see they are using Netgear WGR614 which is a cable modem and wireless router combined. It works from a 12Vdc 1000mA adaptor - so 12W maximum.

http://www.netgear.co.uk/pdfs/WGR614.pdf

http://allyours.virginmedia.com/html/internet/wireless.html#grouter




Ken

[KenB]

The 1A 12V linear supply runs quite warm, so I might swap this out for a switcher and see what I can save.

Fortunately I had a 12V 1600mA universal switcher lying around from a previous project.  It has interchangeable tips - so I just had to match the voltage and polarity.

The router now uses 8W rather than 10W - as a result of 2W of losses saved in its plugtop power supply - so over the course of the year this would save me  17.5kWh or about the cost of a pint of beer.

This just goes to show that the old 50Hz transformer based linear power supplies are considerably less efficient than a more modern switcher.  The irony (no-pun intended) is that the switchers are now cheaper to make as they contain considerably less iron and copper,  and this saves a lot in weight on global shipping costs, as well as reducing the need for costly raw materials.

The laptop and router now hover around the 35-36W combined power consumption - which is acceptable - bearing in mind this is a 5 year old Toshiba notebook with a 12" screen.   Sure I could lower my computing power requirements by going for a Asus eee, but that would involve cash-flow.

As a passing thought, if manufacturer's equipment defaulted to a low power "sleep" mode, when mains power is re-applied, and from this sleep mode, they could be woken up either by remote control or by pressing a front panel button - then that would be a first step in making less power hungry devices.   If in this suspend mode, all previous settings were maintained (eg TV remembers channel it was on, VCR has non volatile clock etc), then this would greatly improve the user experience of a ByeBye Standby device.  One click on any IR remote control and everything is back up running and ready for use.

It would also be easier if devices could make more sharing of remote controls - we have at least 4 lying around the sofa, and some of the machinations of the remotes to record one programme whilst watching another seriously tax the brainpower of the average 40 something year old.




Ken

[RichardKB]

Sorry KenB but that is only a broadband router which requires a cable internet connection and modem.

My origional modem supplied by Telewest was a Motorola SB3100 when I was upgraded to 10M I had a Motorola SB5100 as a replacement both of these units have a 9W nominal consumption.

This is a list of some of the modems used by the cable companies in the UK.


http://www.chetnet.co.uk/articles/index.php?page=index_v2&id=91&c=4

Rich

[KenB]

Rich,

I first thought that a cable modem would be needed with the WGR614 - and that's what I originally wrote in my first post.

After subsequent reading of the spec-sheet, I got the impression that the cable modem was combined with the router - so I edited my post.

I am now not sure if the WGR614 is a combined product or not.


Ken

[KenB]

OK- I stand corrected.

The cable modem is a separate entity, usually provided by the service provider.  So you will have the combined power requirements of the cable modem and the wireless broadband router.

In this day and age I would have thought that they would be putting the cable modem and the broadband router in the same box - sharing much of the functionality and power supply. Perhaps they are - but since I am a DSL/landline broadband customer - I have never have had to give thought to those with a cable service.

In a few years it will all be optical...judging by the latest Virgin adverts.  (The Virgin optical marketing is a real con -  there is no intention to have anything other than copper coax from the street cabinet into the house).

I remember a lecture at school in 1979 when a nice chap from BT labs at Martlesham Heath came to talk to us about optical fibre communications and showed me my first laser diode - that was thirty years ago.  It'll probably be another decade before we have a fibre connection into the home.

As a cautionary tale we have IP phones at work.  When you log in to them they take a minute to reboot with your number - doh!  The company server went down last week and we lost all the phones.  There is still something very comforting about an old analogue phone and the pleasant purr of the dial tone as soon as you lift the handset.

Now that's progress for you!


Ken

[tony.]

didnt wyleu speak about a dedicated extra low voltage circuit a few years ago?

tony