Mains to 12 volt supply needed, but what type?

[fizzy]

If it was connected to an 11kV line (How did he connect it there in the first place?) then its verrrrry unlikely you would be here typing this now....and I'd also be surprised there was any fence wire left if it was down to earth anywhere

That is what the Police told us anyway. Didn't see it myself - miles from where his connection was. Apparently he had been stealing electricity for 20 years.
Plenty of our power lines around here are in a bad state as well - running through trees and down on the ground in places.
Phone lines just as bad.

 

[daleyd]

That is what the Police told us anyway. Didn't see it myself - miles from where his connection was. Apparently he had been stealing electricity for 20 years.
Plenty of our power lines around here are in a bad state as well - running through trees and down on the ground in places.
Phone lines just as bad.
View attachment 338133

Mains (240V) , maybe

11kV - not a chance....if you've never seen pictures/videos of when that kind of voltage goes wrong, I'd advise you not to.

 

[fizzy]

Mains (240V) , maybe

11kV - not a chance....if you've never seen pictures/videos of when that kind of voltage goes wrong, I'd advise you not to.

I have seen it and also find it unlikely - now I know a lot more about electricity than I did then I would guess maybe he used a tapping off the 3 phase - they said he had an "industrial supply". Totally reckless whatever he did. Luckily we were in our late teens and very fit. Even though we had thick rubber soled boots on we had quite a jolt - mind you we were soaking wet at the time.
Inductance can have funny effects as well. I remember walking under some 475000 volt pylons in wet weather and we started buzzing loudly Didn't feel a thing though but didn't hang around long.

 

[Matrixx]

A car induction coil will only work with an alternating voltage for use as an electric fence. in a car the DC is pulsed .

normally you would use a diode capacitor arrangement to step up the voltage. but it still needs an AC source. typical fence voltage is 8kV but very low current (mA)

UK OHL voltage is no more than 400kV.

China has some 1.1 million V DC lines.

 

[oddbob]

Just a greased pole should suffice...

https://imgur.com/LXCrLDE

Or a slinky hanging around the pole ...I reckon that could be attached to your zapper to make doubly sure!

 

[mart]

A car induction coil will only work with an alternating voltage for use as an electric fence. in a car the DC is pulsed .

normally you would use a diode capacitor arrangement to step up the voltage. but it still needs an AC source. typical fence voltage is 8kV but very low current (mA)

UK OHL voltage is no more than 400kV.

China has some 1.1 million V DC lines.

When you say an AC source I'm unsure in which context you mean. Re- the transformer I have is AC 240 in, but is transformed down to 12v Dc output to the coil.

Potentially with a 555 timer chip, and probably a very small resistor, plus a capacitor to step up the output that leaves the coil. All theory in my case. Has not been put to the test as yet.

 

[Matrixx]

A transformer only works with an alternating voltage, a constant voltage will only give a spike then nothing, you cannot get dc from a transformer direct. I think you are talking about something like below?

 

[mart]

Hi Matrix,
I have a 240AC transformer and the supply to my circuit will be 12v DC.

I can understand simple circuits when I see the actual components in place such as on breadboard. I cannot understand the standard disgram circuits as you have provoided, but thank you.

I am teaching myself about electronics, and hopefully I will find a tutorial to help me follow the circuit diagrams.

 

[pitmole]

I used to sell/ repair/ modify electric fencers years ago Hotline and Gallagher 2 manufacturers that spring to mind. they would take dcv from a battery, use that to charge a capacitor, then once that had reached saturation voltage, discharge through a transformer, repeat. No timer needed, by controlling the charge rate of the capacitor it controlled the pulse rate of the fencer, hence when the battery ran down the fencer would still operate near full power, just at a wider pulse rate.
Want more joules? then add another capacitor, twice the time to charge but a big big shock! perfect for fencing on an ostrich farm where the guests are very well insulated with tiny brains!

 

[mart]

I used to sell/ repair/ modify electric fencers years ago Hotline and Gallagher 2 manufacturers that spring to mind. they would take dcv from a battery, use that to charge a capacitor, then once that had reached saturation voltage, discharge through a transformer, repeat. No timer needed, by controlling the charge rate of the capacitor it controlled the pulse rate of the fencer, hence when the battery ran down the fencer would still operate near full power, just at a wider pulse rate.

I'm no expert but in post No47 Matrixx above, says "A transformer only works with an alternating voltage"

I don't know

 

[mart]

By the way, I understand that it is not only timers and tramsformers. Apparently relays can be used too.

 

[Bravheart]

Interesting but you guys are all over engineering the problem surely. Most ag. suppliers as mentioned above should be able to sell a mains fencer unit or heres a link to one

Mains Energisers - UK Countrystore

www.ukcountrystore.co.uk

 

[Matrixx]

I'm no expert but in post No47 Matrixx above, says "A transformer only works with an alternating voltage"

I don't know

Alternating i.e. on / off /on etc AC 50hz does it 50 times a second. (well +/- 240 V AC).

If you have 240V AC to 12 V DC I would call it a power supply ( transformer/rectifier)

You can buy the parts ready made , but its nice to be able to make something your self.

 

[eddie49]

I'm no expert but in post No47 Matrixx above, says "A transformer only works with an alternating voltage"

I don't know

Usually, yes. Alternating as in reversing polarity, plus to minus and back to plus. E.g. UK mains does this 50 times per second.

However, an ignition coil is also a kind of transformer. It has a primary, and a secondary. The secondary delivers 25,000 volts. The primary runs on 12 volts, from the car battery or the dynamo/alternator. However, that is DC.....

So can a "transformer" run on DC? Yes, if the voltage in the primary is made to vary, e.g. from 0 to 12 volts and back to zero. Then the magnetic field produced will vary, and a voltage will be induced in the secondary. It helps if this happens quickly, and that is the job of the contact breaker and the capacitor ( aka condenser ). The primary voltage does not alternate, or reverse polarity, but it does change.

 

[mart]

On the subject of condensers (old name for capacitor) does anyone know what the capacitance of the the condensers in cars from the 70s & 80s was.