vampires and power usage

Good question. Not only the ones with wall warts, those black "adaptor" boxes that plug into the wall with a cord coming out of them, but many radios etc. with the transformers inside, have no switch in the primary of the power transformer, and they are ON all the time.

For electronic reasons I don't well understand, when there is no current in the secondary of a transformer, there is higher impedance in the primary of the transformer, so less current flows even through the primary. The heat one can feel, that you feel, the waste heat would be iiac the same percentage of energy used, as when the device is running and there is current through the secondary.

From your touch, it sounds like the current is a lot lower, but otoh, it's on all the time if the thing is plugged in, even for things that are only used an hour a year.

Does anyone know what the percentage is, or how much these things use when off?

xposted to sci.electronics.repair

Well, there's been a lot of discussion on this. Essentially, when there's no load on the phone charger or other appliance, it's like having an inductance across the power line of your house. There will be some very small current flow, but only because it's not a perfect inductance. All of the energy used in these wall transformers when they're just idling is dissipated in the form of heat in their black plastic case, so you can get an idea of how much power they're using by just feeling them. It's not really very much. Note that you'll have a tough time measuring the power drain with a multimeter, because both current and voltage will show rather high readings. But since they're almost 1/4 cycle out of phase, there's almost no power being dissipated, and only a good power meter will take this into account. (This problem is the basis for a lot of free energy claims, you'll be happy to note.)

In general, wall transformers aren't a big deal.

M Kinsler

You can pick up a gadget called a Kill A Watt and other similar devices for under 30 bucks. It's a pretty impressive power analyzer, the wonders of modern technology. Pick up one of those and you can find out how much power anything in the house draws, as well as the power factor, cumulative consumption, etc. I have one and love it.

Is vampire some in-joke conflation of V(olt) + amp that I'm out of the inductive loop with (sorry Mr Churchill)

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

on

I believe that it has to do with the idea that a vampire is something of a parasite, living as he or she does on the blood or electric current of the host. It's one of those imprecise terms up with which we all must put.

M Kinsler

okay, _you_ try to match wits with Winston Spencer C.

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So is Vampire = Wall Wart another term to add to my USA/UK (2 nations divided by a common language) file ?

If anyone, reading this, is aware of any other tool/technical terms in US or UK, my real email address is spelt out on the URL below

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

From my understanding of the term, a vampire device is any one that continues to draw power even when in the 'off' state. This would include devices powered by a 'wall-wart', devices with a built-in clock, devices that are powered on/off by a remote control (the circuit that receives from the remote needs power all the time), etc.

So they would include most microwave ovens (the clock), TVs, VCRs, DVD players/recorders, DVRs, personal computers, etc.

It's a term used mostly by the solar/wind guys running houses off-grid. It refers to any device which draws power even in the off state, regardless of the sort of power supply.

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of

There does not seem to be an equivalent recognised UK term for this, any limies/pomms know any different ?

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

In message , N Cook writes

I'd never heard it until it appeared here (about a week ago?). If you have to have a term to describe such power supplies, it's quite a good one. However, it's just one more step down the road where words don't actually mean what they say (most of which seem to originate in the USA). Ian.

Hi,

On some of these smaller power supplies there is no transformer at all! I.E. no primary and secondary. They do have an inductor that is used to step down the power and rely on a Thysistor (aka. electronic switch) to turn on an off very fast. Usually 60 times a second (ac mains frequency). The voltage regulation is dependent on the amount of time the switch is on during the power cycle.

One nice thing about this is that they can adapt to many mains voltages and mains frequency. Hence for laptop computers you only need one "International" power brik like supply.

Warmest regards, Mike.

I had not heard of this usage regarding power consumption until this thread, however 'vampire tap' in electronic parlance refers to a piercing type of cable connector, most often a coaxial connector used in Ethernet 10base5 wiring.

...hmmm, I never cease to be amazed by the Brits' continual misuse of case in referring to companies (in usenet postings) in the plural instead of the singular, e.g. "Hewlett Packard have a new line of servers" instead of "Hewlett Packard has a new line of servers".

Regards,

Michael

Hey! You are right about the 'vampire tap'.

I'm in the CATV industry, and I've just remembered that, many years ago, I did see reference to 'vampire taps' as being the latest and greatest for coaxial ethernet. That took me back to the early 1960s, when similar tap devices were manufactured in the UK (by Thorn, I think). I may still have one somewhere. Nasty things!

Re the British incorrect use of plurals when referring to companies (or, indeed, any group), yes, this is very common, eg the 'government are', 'the team are' etc. However, being grammatically correct does sometimes grate a little. Maybe the Americans are not totally to blame for this sad world we live in. But, of course, we always (correctly) say 'maths' (for mathematics).

Ian.

instead

I never hear the royal "we" but I'm often forced to hear reference to the football "we" all the time. As in "we were robbed" mouthed by people who haven't kicked a ball since they were kids.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

In message , N Cook writes

Nah. You've got it wrong. It's usually 'We WAS robbed!' Ian.

And don't forget, in winter you don't mind a little heat radiating, so there really is no waste, unless you have them plugged in the attic or something.

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"A vampire is a-a cell deal you can plug in th' wall to charge your cell phone."

-George Bush, Denver, Aug. 14, 2001

am, "N Cook" wrote:

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Could the vampire thing relating to cable piercing connectors originally have come from festoon lighting lamp holders as used on fairgrounds etc. where two sharp spikes (fangs) pierce the insulation of flat twin cable to provide power to the lamp holder?

RonUK

They were real low grade shit. They were replaced by backmatched taps when systems were extended past the original 12 channel systems in the US. They caused mismatch problems, and wasted a lot of the signal on the trunklines or feeders. They worked, more or less on systems with just a few channels, and very few customers, but them, those people were already used to ghosting and snow. They had all been pulled from the 17 systems around Ft Rucker by 1972, including a couple short haul feeds that only had a couple channels.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida