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> the USB ports only draw power when something is physically connected to the port. Am I mistaken that this is a physically impossible claim?
by asciilifeform 17y ago
> the USB ports only draw power when something is physically connected to the port.
Am I mistaken that this is a physically impossible claim?
- aaronblohowiak 17y agoHow do you figure?
- tb 17y agoThe wall-plate most probably has a AC-DC converter in it, and you're correct in thinking that these draw a small amount of power even under no load. However it would be almost trivial to completely turn this off when there is nothing physically plugged into the port using an electromechanical switch, and it makes sense to do this to avoid wasting power when the port is unused, so I suspect this is exactly what they have done.
- electromagnetic 17y agoTechnically speaking yes it will draw power, all wiring draws power (the wires develop capacitance, but there's also electrostatic leakages around the bare connectors, but at 110/240V it's negligible, this is a concern around 10,000V+, with DC it likely has no electrostatic leakage, and very little drain due to capacitance. However, what I believe you're thinking about is the transformer required to turn 110V->5V and yes you're correct. An old school transformer would drain a few watts when inactive, however the current types of transformers used in Wall->USB devices provide virtually no drain, perhaps less than a watt, so will have no noticeable effect on your electricity bill. Simply put, changing say 20 wall sockets in your house to one of these USB devices will likely have less effect on your electricity bill than plugging in a 7W night light and leaving it in.
- bhousel 17y agoNot necessarily. They could have designed a physical switch into the receptacle, so that the DC to AC conversion only happens when something is plugged in.