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Black & Decker Power Monitor audits the digital home

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re: Black & Decker Power Monitor audits the digital home
NickJ2008   11/19/2008 7:59:25 PM
I definitely agree. When I see news articles claiming that the energy wasted by the wall warts in the average home can exceed 25 to 30% of the home's total energy use I am stunned that such a "preposterous misrepresentation" can get past the editors of any decent publication. None must have a drop of technical knowledge! (Or consult anyone who does when fact checking.) My "guess" of where such a ridiculous proposition originated is perhaps the fact that for a "given" very lower powered device it is quite possible that the energy wasted by the wall wart powering such a device while it is off or "perceived to be off" could easily be more than 25 to 30% of the total energy consumed "by that particular low powered device". Some technically inept writer may have assumed if that were true of a "given device" it could therefore be true for the whole house. Of course that is "not the case" and one HVAC unit or water heater in "one house" can use more energy than "all" the wall warts in "all the houses" in an entire small town like the one in which I grew up! (That's conservatively based on a population of 900 living in 350 houses with 20 wall warts per house or about 7000 wall warts creating a combined 5 Kw load to be equivalent to one HVAC unit or water heater in "one of those houses". As an example our company manufactures one of those "terrible products" whose wall wart "wastes" more energy while it is off (perceived to be off) than it uses while "ON" (perceived to be on). But guess what: It's total energy use (whether off or on) is less than a watt! (about 750 mw). As mentioned above it would take almost 7000 of these units to use as much energy as a 5 Kw load like a HVAC unit or water heater. Why does our product "waste" so much electricity? It uses less than 70 cents per year but perhaps the fact that 58 cents of that total cost is while it is "perceived to be OFF" is what has confused the non-technical folk who would have us unplug them when we leave the house. Would you unplug something and plug it back in 365 times to save 58 cents? The reason it seems wasteful is simple: Our product, the Felston DD740, is a remote controlled 4 input digital audio delay for lip-sync correction in home theater systems. It switches between 4 s/pdif digital audio inputs(both coax and optical) and delays the s/pdif bitstream by up to 680 ms controlled interactively by the user's remote handset allowing him to align video and audio for perfect lip-sync without disturbing his LCD, DLP, or plasma image. It is therefore ON waiting for an IR command from the remote handset "all the time". When OFF, the only difference is that it turns off its 3 digit numeric display which is an insignificant difference in power consumption. It continuously performs coax to optical and optical to coax conversion which needs to be powered as long as any audio is routed through this switch even if lip-sync correction is not being used. Most of our customers therefore leave them active all the time and 58 cents a year is a small price to pay for that convenience but all 36 preset delays as well as the last delay used on each input are stored in non-volatile memory so the unit can be switched off via power strip if desired and that would save the 58 cents but 730 manual switch operations are definitely not without a cost. My long winded point is that low cost products such as ours (<$250) which use an incredibly small amount of energy (maybe 6 Kw hours per year in 24X7 operation) are now maligned by the preposterous misinformation put forth by technicallly unqualified authors whose garbage in print is taken as gospel by our similiarly technically deprived legislators who have passed laws "requiring" more efficient wall warts while ignoring the tremendous inefficiency in HVAC units, water heaters, etc. which waste many "orders of magnitude" more energy. Can you believe it is still legal in this country to sell commercial HVAC units with an EER of 10? Home HVAC units have required 13 for quite awhile. There is absolutely no excuse for this. Our next production run of DD740's will have to have a more efficient wall wart to meet California requiemnets and all we are talking about saving is a few milli-watts! I'm not suggesting a higher efficiency power adapter is a bad idea even in a <2 watt device like ours. I think it should be our goal to continuously improve efficiency in everything we design but as engineers "we" are more qualified than our legislators in making the trade offs to accomplish that. Not that this would happen but as an example we "could" meet California requirements with a new design that consumed 100 times the power of our present product as long at the % efficiency of the new higher poweered wall wart met the increased efficiency specs. Would that eally be a ggod idea?

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re: Black & Decker Power Monitor audits the digital home
Engineer1   11/19/2008 5:04:29 PM
Some random thoughts... "vampire power" is really only a problem in Summer - you have to pay for it first and then again to pump the heat out with low efficiency (Coeff. of Perf.) A/C! In Winter it's only a matter of the differential cost of electricity and gas/oil heat - not so bad. We tell people to unplug various wallwart chargers when not in use but none of mine get warm when plugged and not charging so they're not pulling power, nor even significant VA's. However, I'll admit I don't know what my TV, PC, display and printer comsume on standby (the last two have automatic power saver modes.) Again, really only an issue in Summer here in the North East NA. So, I'd say: "pick the low hanging fruit first", i.e. go after more efficient transportation and space heating.

EE Times Senior Technical Editor Martin Rowe will interview EMC engineer Kenneth Wyatt.
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