Transformer help

[Disco]

Ok I have a fairly complex problem, with a very limited number of options.

I need to be able to get electricity inside a roof cavity or on an industrial site, somewhere in the order of 12v at about 300mA for extended periods of time. But I need to be able to do it without disrupting, or attaching to the 240v mains power.

In certain areas the mains wires will be separated, so I was hoping for a design of a transformer arrangement that could be clipped over the mains wire/s or place along the mains to produce this kind of power?

Before anyone mentions it SOLAR is not an option and BATTERIES dont last long enough.

I would just like some advice if this is possible? my understanding is that it is possible but highly impractical, this does not concern me as I am willing to try anything, I just need some assistance.

Thanks for you time, hopefully someone can help.

 

[Nigel Goodwin]

Sounds like you need magic! - try looking for a witchcraft forum!

 

[Hero999]

How long does it need to last for?

A 7Ah lead acid battery will last for 23 hours and 20 miniutes.

If you charge it from the mains then I don't see the problem.

 

[ericgibbs]

I need to be able to get electricity inside a roof cavity or on an industrial site, somewhere in the order of 12v at about 300mA for extended periods of time. But I need to be able to do it without disrupting, or attaching to the 240v mains power..

Can you tell us why, you cannot make a normal connection to the mains wiring??..
It sounds like some covert, iffy application.

 

[jpanhalt]

If a large storage battery (>50 Ah) won't last long enough, there is always thermal conversion using plutonium as the heat source, like was used on some US spacecraft. Of course, such a source has disadvantages too.

If an inductance-based system would work at that power level, it should be as easily detected as a direct tap into the mains. Nothing is free. John

 

[Optikon]

Clipping onto mains with a transformer is illegal. Use batteries. You dont have much choice. Or how about a hand crank generator?

 

[grim]

you could pass one of the leads through the middle of a toroidal, to make a current transformer that would generate a voltage and current, but his only works if you know the lead you are going onto will always be carrying the same current.

like everyone else, I am fascinated why you cannot connect to the supply direcly.

 

[Hero999]

Stuck a wind turbine up there and it might be able to keep the charge in a battery if it's windy enough.

 

[Disco]

Firstly, thanks Nigel, yes I am looking for magic, its called electricity and the witchcraft is mutual inductance. lol.

I probably should have explained it a bit better as everyones imagination is going crazy, no I don't work for the CIA and I'm not trying to steal electricity for a crop of herb.

I need to power remote monitoring equipment that gets installed at water treatment sites, often underground so solar and wind are no good.

There is always power at the sites but rarely power outlets. I'm not an electrician so I cannot connet an outlet myself, legally. (and no I can't get an electrician out there.)

Currently I'm using batteries and can get upto 2 weeks, but some remote installations require longer deployments. unfortunately some of the sites are upto 4hrs from civilization so battery changes are time consuming and expensive.

It is a private power grid so connecting a transformer on the line is not an issue, and definitely not illegal.

The method described by GRIM sounds perfect now I just need to know how to do it? if I can purchase/make a system that will work?

Thanks again

 

[Nigel Goodwin]

Firstly, thanks Nigel, yes I am looking for magic, its called electricity and the witchcraft is mutual inductance. lol.

I probably should have explained it a bit better as everyones imagination is going crazy, no I don't work for the CIA and I'm not trying to steal electricity for a crop of herb.

I need to power remote monitoring equipment that gets installed at water treatment sites, often underground so solar and wind are no good.

There is always power at the sites but rarely power outlets. I'm not an electrician so I cannot connet an outlet myself, legally. (and no I can't get an electrician out there.)

Currently I'm using batteries and can get upto 2 weeks, but some remote installations require longer deployments. unfortunately some of the sites are upto 4hrs from civilization so battery changes are time consuming and expensive.

It is a private power grid so connecting a transformer on the line is not an issue, and definitely not illegal.

The method described by GRIM sounds perfect now I just need to know how to do it? if I can purchase/make a system that will work?

You're still left with the same installation problem, it would be as easy to connect directly across the power as do this. There's also the problem that the power produced is VERY small, and dependent upon the current passing through the conductor.

Sounds more like you need better monitoring systems, two weeks battery life sounds pretty pathetic?. A ex-workmate of mine works for a company who makes PIC based water monitors, and I seem rto recall they have much longer battery life.

 

[grim]

trouble is, to pass a wire through the toroid, you need to break into the circuit.

and as Nigel says it wont make huge amounts of power - if you are killing a battery in a couple of weeks, it's doubtfull this would extend that much

 

[Hero999]

Go on a training course so you can bread in to the circuit and connect you monitoring device.

I agree with Nigel, you need a better monitoring device which doesn't use as much power, I can't see any reason why it can't last for years running from a lithium pack, providing it doesn't take measurements too frequently.

 

[blueroomelectronics]

Might look into kinetic generators, they should work almost anywhere and some can run on the small vibrations on the ground.
https://www.gizmag.com/go/7584/
**broken link removed**

 

[Hero999]

A good idea but I doubt it'll be able to produce 3.6W, although if a system that only uses a few mW could be designed it would be perfect.

There are lots of ways to use the small amounts of energy in the surrounding environment, for example changes in ampmospheric pressure or temperature can also be used to generate small amounts of energy to power things like clocks and data loggers.

 

[ericgibbs]

hi,
I once saw a mains 'terminal' block that used the IDC technique.

If you can split the outer pvc insulation that covers the cable and separate the line and neutral wires
you could make up and IDC clip on/screw into connector.

If you use the toroid as 'grim' suggests, you will still need to separate the line and neutral wires.

Get a 25Watt ferrite transformer core, the circular type that splits into two identical halves [double 'E' type], wind say 24 turns of 22swg enamelled copper wire onto one half, wrap about 4 turns of the mains line wire around the other half and bolt the two halves together.

Measure what Vac is on the 24 turns winding, you may have to adjust the number of turns to get the output you want, as you don't know the average current flowing in the line wire. [ to the external load].

 

[Hero999]

I don't like the mains idea, suppose you calibreate it to 9VAC, then the current tripples, you'll have 36VAC which would blow components and is high enough to shock you.

The only sensible way is to either improve your current battery system or reduce the power consumption of the monitoring device.