Mixed LV ans ELV is it safe?

[bernardgreen]

If it is fluctuating it is not DC. It is DC with added AC.

Battery--- switch--- lamp

Switching the switch on and off creates AC ? , I do not think so,

 

[Harry Bloomfield]

Battery--- switch--- lamp

Switching the switch on and off creates AC ? , I do not think so,

It does create a matching pulse in anything conductive near enough to it, it will radiate on switching.

 

[SUNRAY]

A steady magnetic field, such as a steady DC current and a cable carrying an AC current within the DC field will potentially vibrate, if currents are high enough the vibration may be audible.

Additionally other metalic items within the fields may be similarly affected.

 

[Harry Bloomfield]

if currents are high enough the vibration may be audible.

Quite, as in a transformer, but the OP is discussing fairly normal levels of domestic current.

Normally, there should be no eddy currents induced, because of counter windings - a live will be matched with a neutral, or a phase with another phase(s) so they cancel out, just as they would if a transformer were to be would with a counter winding.

 

[SUNRAY]

Quite, as in a transformer, but the OP is discussing fairly normal levels of domestic current.

Normally, there should be no eddy currents induced, because of counter windings - a live will be matched with a neutral, or a phase with another phase(s) so they cancel out, just as they would if a transformer were to be would with a counter winding.

I can't fault your comments and yes I wholeheartedly agree.
However I have the T-shirts.

Something that nobody has mentioned yet, what is the liklyhood of these 2 cables being used at the same time?
In my experience of camping the chances of batterypower being used when mains is available is pretty slim.

Being me I'd probably be aiming for some sort of automatic changeover.

 

[plugwash]

Battery--- switch--- lamp

Switching the switch on and off creates AC ? , I do not think so,

The fundamental issue here is there are two different worldviews of AC and DC.

One worldview, is that we look at the total current, if it flows in only one direction that's DC, if it alternates direction that is AC.

The other worldview is that a signal is made up of a series of components at different frequencies, including DC. In this worldview, switching stuff on and off absoloutely does create AC components in the current.

A DC current being repeatedly switched on and off is equivilent to a superposition of a DC current and a square wave. An ideal square wave has an infinite series of frequency components, though each component is weaker than the last and in reality no squarewave is idea.

 

[bernardgreen]

switching stuff on and off absoloutely does create AC components in the current.

There can only be an AC component if the direction of electron flow reverses

 

[DetlefSchmitz]

There can only be an AC component if the direction of electron flow reverses

I think you've forgotten what the word 'component' means.

 

[john4703]

Something that nobody has mentioned yet, what is the liklyhood of these 2 cables being used at the same time?
In my experience of camping the chances of batterypower being used when mains is available is pretty slim.

Probably the simplest method for me is to remove the 230v stuff and just use 12v. It will work anywhere and if I am on a mains hook up the battery will be getting charged.

 

[Harry Bloomfield]

Probably the simplest method for me is to remove the 230v stuff and just use 12v. It will work anywhere and if I am on a mains hook up the battery will be getting charged.

Most these days do not even need the battery at all, you can consider the charger as a charger/power supply. The battery is only needed when off EHU, or to use the mover.