Active or Passive Cooling for P2?

[hedwards]

aluminum would have safety issues in terms of insulation.

Safety of what? The user or the electronics?

Devices like this are normally double insulated because they won't have a grounding pin.

As long as the item is just running on battery power, it shouldn't be an issue, but if something in the power brick breaks, then there's a slight risk.

In practice though, I'd imagine that the electronics would be more likely to be damaged than the user. Primarily because the device is a low voltage device, it shouldn't ever have enough juice to kill somebody. That being said, I think the investigation into that iPhone that allegedly shorted out killing somebody hasn't been completed, or if it has, I don't recall hearing the results.

People tend to underestimate the amount of juice it takes to stop the heart. A landline in a bathtub is sufficient to do the job, which is why one should never use any electronics in the water that isn't specifically engineered for use under water.

 

[Binky]

^ overestimate, surely?

 

[hedwards]

^ overestimate, surely?

Nope, underestimate. Few people are aware that the low voltage things like telephones are sufficient to kill a person. Which is why it happens relatively frequently. Relative to how frequently it would happen if people just kept the telephone out of the bath.

That being said, this is a theoretical risk that's likely outweighed by practical considerations.

 

[_wb_]

So you meant they overestimate the voltage needed to kill a person.

 

[Binky]

Thinking it takes 1kV to kill a person is an overestimation.

Thinking you can get a nasty shock from a 1.5V  button cell is an underestimation.

 

[Klumpen]

1.21 GW

 

[slaeshjag]

It completely depends on how the power supply breaks.

It is illegal to sell power supplies in the EU that doesn't have a secondary elecrically isolated from the primary. Which means that even if the power supply breaks and outputs 2 kV at an amp, it is of no risk as long there is no return path for the current. So for a power supply failure to be dangerous, it has to be a failure in the isolation. That's only to expect from cheap chinese ones. As long as it isn't subjected to stuff like a lightning strike, that is.

And when it comes to killing someone with power, it's all about the energy of the shock. Although the voltage needs to be over a certian threshold for that enegry to be deliverable.

EU regulations have a limit on double-insulated case/other protective means when there's voltages above 50 vAC or 75 vDC.

 

[WizardStan]

A 9 volt battery provides enough current to kill someone when used "properly", and provide a very nasty shock even when used "improperly". Whenever playing with electricity never assume it's not enough to do you harm.

*for definitions of "properly" and "improperly" meaning that you're intentionally trying to kill someone with them.

 

[hedwards]

Thinking it takes 1kV to kill a person is an overestimation.

Thinking you can get a nasty shock from a 1.5V  button cell is an underestimation.

 I see what you mean there. I really should have completely rewritten that sentence as you're right. Sometimes it's annoying trying to read what you've written knowing what you meant. I meant to say underestimate the risk from low voltages, but apparently, I wrote half of both ways of saying it, rather than either one.

It completely depends on how the power supply breaks.

It is illegal to sell power supplies in the EU that doesn't have a secondary elecrically isolated from the primary. Which means that even if the power supply breaks and outputs 2 kV at an amp, it is of no risk as long there is no return path for the current. So for a power supply failure to be dangerous, it has to be a failure in the isolation. That's only to expect from cheap chinese ones. As long as it isn't subjected to stuff like a lightning strike, that is.

And when it comes to killing someone with power, it's all about the energy of the shock. Although the voltage needs to be over a certian threshold for that enegry to be deliverable.

EU regulations have a limit on double-insulated case/other protective means when there's voltages above 50 vAC or 75 vDC.

The rule around here is double insulated or grounded. Generally if you've got that third pin, the double insulation shouldn't be necessary. And when unplugged, there shouldn't be sufficient juice to cause that sort of a problem.

At any rate, it's moot seeing as the wifi and cost considerations would ensure that the unit wasn't built purely of metal.

As for the lightning, always unplug your electonics from the wall during a lightning storm. The surge protectors aren't generally sufficient to provide that level of protection.

 

[slaeshjag]

^ I think you're thinking of different kinds of isolation here. When I say electrically isolated, I mean that no wires on the "safe" low-voltage side of the power supply is in any way connected to mains.