Pump control over electric fence

[domwild]

Hi,

Slightly off-topic (my apologies!) but may be useful to control mills, etc. via electric fence lines.

Wish list:

Is there a circuit, which ignores the 4000V pulses as I wish to have the pump control connected to it at all times? I can switch off the fence energizer from 300m away and send a low powered control signal (24VAC or similar),which does not get ignored to switch the pump on. Another control signal to switch the pump off again and then I can activate the fence again. A latching relay to switch the pump on/off or a continuous 24VAC voltage to keep the pump relay on.

Fence consists of three active lines and two earthed lines.

I want to have all three lines active, otherwise I could use one circuit for the control and the other lines for the fence.

Any suggestions??  

[Flux]

I think it would be far easier to inject your control signal between the 2 ground wires. If they get connected together at several points you may have to inject between ground wires and true ground.

If the wires are not connected except at one end you could connect a low voltage transformer between them with a 1uf capacitor to keep them at the same potential to the pulse. A similar transformer at the other end would extract the signal.

If you can't do it this way then you may need audio signals and tone detectors, with small audio transformers. Still simple but only if you understand these things.

If you must send it via the HT circuit then think about car ignition coils as matching transformers with capacitors across the primaries, tuned to mid way between your tone frequencies. That will remove most of the pulse volts. May need a bit of extra LC filter.

Try to keep the ground wires separate and use the simple ac control ( or even dc with a small battery).

I think you can do it but much depends on the type of fence wire and how it is set up.

Flux

[wpowokal]

Dominic within Wester Power in the early days we had a telephone system that ran over the 330,000V power lines before the microwave system.

Why can this pump not be controlled by a pressure switch? Ok so its filling a tank, just put a two level float valve on the tank.

Allan need a few days on your plantation to help with these problems.

Allan down under

[domwild]

Thanks Flux and Allan for the suggestions. It was a big ask or tall order for a simple circuit to ignore 4000 V and to act on 24VAC as I do not have a black belt in electrickery. The ground wires are connected at every steel post and the active wires are all reconnected at the gates. The pump does not fill a tank and has to be switched manually.

I have 200m of telephone wire, which I have to lay over the property and let the kangaroos break the cable, rather than lay 300 meter's worth of cable around the property, where it would be safe from breakage.

*

[scottsAI]

I just posted a wireless solution:

http://www.fieldlines.com/comments/2006/10/5/21552/2063/1#1

Using directional antennas, 300m should not be a problem.

Skip the processor, using serial on both ends.

Remote car start, may be another option, range less than 200m.

Have fun,

Scott.

[maker of toys]

there are many ways to accomplish what you want to do.  Most of them involve quite a bit of (as you put it) 'Electrickery' . . . so if one of the radio remote options will work with turn-key parts, do that.  you may find that bringing both the transmit and recieve antennas close (5 cm?) and parallel to the fence wire will extend the radio's range.  (works best with low-frequency radios, but hey, it's easy to try. . .)

Otherwise, if you go to a 24VDC latching relay, and can gin up a couple of decent-sized inductors, you could conceivably run the pump control and the fence at the same time:  assuming that the fence pulses are inductive kicks, a suitable pair of inductors would protect the fence from shorting through the low voltage part of the circuit. I say 'assuming inductive kicks', because I have an old charger that puts 2.8kV at 60hz sinewave on the fence.  MAN, does it get your attention!  (we also had a horse that would get bored and lick that same fence, but that's a different story. . . .)  

Basically, put a big inductor in series between the fencewire and the relay, and another seriesed between the controls and the fencewire.  Make sure the charger does not connect to anything other than the fence wire itself. to activate pump, connect your 24VDC controls to the 'non-fencewire' side of the 'control end' inductor, (with a latching relay, hold the signal for a good few seconds) and off you go. the return side of the controls would use an earthed line. . .In my case, (and I recommend in yours, too) I'd disconnect the fence from the charger before using the control feature, for added  protection of equipment and operator.

Serveral hundred turns of magnet wire around a ferrite or steel rod is a good start on a home-made inductor.  1-2 cms is a good diameter for the rod. the more turns, the better.  Potting a home-made inductor in epoxy is probably a good plan, and try not to overlap any windings, lest that 4kV punch through the insulation on your magnet wire.

-Dan

[kell]

Right.  Use chokes.

[domwild]

Thanks, Dan, Kell and Scott for that. The wireless solution, I believe, is more for data transfer and possibly an overkill for a simple one-shot on/off situation. Have to digest the "choke" solution. It is no problem turning the fence energizer off and then sending an on/off signal.

This fence energizer would pulse once a sec or so, so it must be a "kicker".

[domwild]

Dan,

Am easily confused! How can I put several hundred turns round a large piece of round steel without overlapping the windings? That rod must then be very long.

By the way, I was talking of 24VAC as I have to turn on a three-phase motor via a contactor and most irrigation equipment, including contactors and valve solenoids respond to 24VAC. But if it has to be 24VDC for the latching relay, then I can handle that, too.