Electric fence remote control

I'm looking for ideas to switch my electric fence for my cattle on and off for short periods while I move tapes , connectors and posts.

I am up to 1 KM away from the power point controlling the fence zapper box. I wondered about something like a garage door opener but with an antenna extension or power boost maybe?

I use walkie talkies ATM which is ok but needs two people ,one standing around near the switch ( I try to make this me)

tytower said:

I'm looking for ideas to switch my electric fence for my cattle on and off for short periods while I move tapes , connectors and posts.

I am up to 1 KM away from the power point controlling the fence zapper box. I wondered about something like a garage door opener but with an antenna extension or power boost maybe?

I use walkie talkies ATM which is ok but needs two people ,one standing around near the switch ( I try to make this me)

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I don't know where you live, but remote control transmitters and receiver kits were (and probably still are) available in Australia.

I bought one from Oatley electronics. It has 4 channels. But you may need a preamp on the receiver for a 1 km range.

I'll look at some catalogues (after I post this) and do an edit later if I find anything useful.

I could not find anything in the catalogues, but I found this

**broken link removed**

However, do you really need such a high tech solution?

I have seen farms that have a timber frame over each gate that supports the electric fence wire so the gate can be opened and vehicles driven through without turning the power off.

Another possible option would be to make a tool from say PVC pipe that can open the fence with the power on. But keep it dry in wet weather!

Also, if you do make the radio switch, how would you know if the power is off? Radio transmission can have dead spots. I would want something to test if the fence is live, eg. you can buy screw drivers with a neon lamp inside that glows if held on a live wire.

Thanks Len , Im up on the Atherton Tablelands in the wet rain belt . Two to three meters each year rainfall.

My arrangement is a fixed central wire and I go off sideways to cut them a bit of paddock each day. Strip grazing . Moving the line involves 10 posts beng moved and the connection to the main wire has to be removed to do so . Another way for gates is to dig a channel under and bury the insulated line.

Plastic pipes are OK normally but my grass is up to my navel or better and wet so off is the best way . The tester is me . You can buy fence testers which tell you the power at that point but at $75 I havn't bothered.Id also like to make something simple myself.

I made a remote from Oatley about 7 years ago but range was the problem . You had to be within 50 feet for it to receive. The pre amp for TV's anyway is $70 odd bucks. I wondered about connecting a long wire type antenna to it and pointing the long wire in the direction I will be . Don't know if a 30 ft wire extension with a tuning capacitor at the connection point would work but I might pull it all out and try it.

You already have an electrical connection to the zapper box, why not just use that to transmit a signal to a circuit attached, kind of like X10 communication over power lines? I know the voltage is pretty high and have no idea of the frequency these fence's put out but there's no reason you shouldn't be able to superimpose a signal at any point in the fence that a receiver near the actual 'zapper box' can use to turn off the fence. The 'transmitter' could be as simple as a wire stuck into the ground attached to a short pole with a conductor on the tip to ground the fence in a coded series of tapped pulses that a voltage detector near the zapper box could decode to turn the fence on and off. The 'transmitter' is just a stick and a piece of wire basically, and the receiver would depend on the voltage and currents invovled when the fence is floating and when it's actually sourcing current.

tytower said:

Thanks Len , Im up on the Atherton Tablelands in the wet rain belt . Two to three meters each year rainfall.

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2 to 3 metres of rain! you'd better send some to Melbourne, we are on stage 3 water restrictions.

tytower said:

My arrangement is a fixed central wire and I go off sideways to cut them a bit of paddock each day. Strip grazing . Moving the line involves 10 posts beng moved and the connection to the main wire has to be removed to do so . Another way for gates is to dig a channel under and bury the insulated line.

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Understood.

tytower said:

I made a remote from Oatley about 7 years ago but range was the problem . You had to be within 50 feet for it to receive. The pre amp for TV's anyway is $70 odd bucks. I wondered about connecting a long wire type antenna to it and pointing the long wire in the direction I will be . Don't know if a 30 ft wire extension with a tuning capacitor at the connection point would work but I might pull it all out and try it.

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The aerial would have to be tuned to the frequency of the transmitter and, if you want it to be omnidirectional, it should be a vertical rod with a ground plane & as high as possible.

Also, the transmitter and receiver would have to be matched to the antenae for maximum power transfer.

I'm not an RF expert, but someone else may be able help.

The idea in the post by Sceadwian above is good, but you would need the probe to be well insulated and the systems would have be be able to withstand the pulse. My recollection is that the pulses are spaced at about 2 seconds. Is that true? And the voltage is several thousand volt.

Another idea would be to use a CB radio and modulate the audio with a tone (or a pair of tones) when you want to turn the fence off. Then send a different tone combination to turn it on.

Another way to confirm whether the fence is off would be to mount a flashing light (like on police cars) on a high point. It could be arranged to flash when the fence is off. Not much good in NQ rain though.

You MAY still be able to use the Oatley remote.

I don't know if this will work as I don't know how far a radio signal will propagate along an electric fence. But, if you still have the remote, it won't cost you anything to experiment except some time.

Turn the fence off, loosely wrap the aerial wire of the receiver around the fence wire.

Ask someone to monitor the receiver and walk down the fence with the transmitter.

Stop at a modest distance and loosely wrap the aerial wire of the transmitter around the fence wire.

Press the button and see if it is received.

If not, then move the transmitter aerial about 35 cm one way or the other along the fence wire and try again.

The reason for this is that the transmitter will set up a standing wave on the fence wire.

If you had a signal strength meter and measured the signal emanating from the fence at various points, you would notice that the strength varies from a maximum to a minimum about every 70 cm. (From memory, the Oatley transmitter transmits 433 MHz)

So the wavelength is 300/433 = 70 cm approx. (the speed of light is 300 Mm/second approx.)

Keep walking along the fence and test occasionally to see how far it will work.

Let me know whether it works at 1 km or not.

If so, I'll post a diagram of how you could make a more practical arrangement.

If not, you will have to try a lower frequency. I'll explain how - if necessary.

OK Len I'll be a few days getting the remote out and I think I can find the circuit without much trouble . Be at least next Wednesday before I'll get a chance to play with it . The pulse is 1 sec approx and I think its about 3,000 volts.at best but I will check that with the specs. My useage is mostly in one direction from the house and power ,thats why the long wire would suite. You put a variable capacitor to ground on the feed point and tune it to resonance.

Sceadwian said:

The 'transmitter' could be as simple as a wire stuck into the ground attached to a short pole with a conductor on the tip to ground the fence in a coded series of tapped pulses that a voltage detector near the zapper box could decode to turn the fence on and off. The 'transmitter' is just a stick and a piece of wire basically, and the receiver would depend on the voltage and currents invovled when the fence is floating and when it's actually sourcing current.

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I'll have to study this and work on it , like a morse key when I want to turn it off , dit dit dah dit ,thanks

Another thought. Could you simply drive in an earth stake and short the fence to gnd?

I assume that the 3000 Volt is current limited, in fact I suspect it would be a current source, so grounding it should not do any harm.

Do you have a circuit of the fence pulser?

Exactly like morse code, and of course the fence is current limited, it's a reminder for livestock not to go near it, it doesn't cook them =) a simple voltage detector hooked up to a relay or other power control device to the fence controller itself would work fairly well, when the fence is disabled you can either do a 5 minute timer and have it turn back on automatically, or figure out some other way to send a signal when the fence itself wasn't active. A simple 5 minutes timer to get through the fence should work fine, for your intentions. Though I wouldn't rely on it if you were going to be spending a lot of intimate time with the fence. Anyone ever seen Jurasic park when the fence turns on before timmy can climb back down? =) Granted these fences generally don't kill, under the right cicumstances they will stop your heart.

Sceadwian, do you actually know that the fence is current limited?

It is possible that they simply rely on the length of the pulse to prevent electrocution of stock.

tytower, I think Sceadwian's idea is a good one.
The receiver would need several high voltage capacitors (Dick Smith sells them) connected as a voltage divider in order to provide a managable voltage at the input to the electronics. The "Morse Code" could be done by holding the "transmitter" on the wire for a count of say 3 for a dit and 6 for a dah. Then, once the fence pulses stop, connect the wire permanently to gnd.

When the receiver detected the "Morse" it could switch off the fence pulser and apply a low voltage in order to detect the S/C to gnd.

Once you have finished moving the fence, remove the S/C and the receiver then re-starts the fence pulser.

The receiver wouldn't need any high voltage capacitors, just a few dozen turns of wire around the fence wire's primary outgoing line. The sudden start and stop of currents/voltages would cause inductive spikes on the wrapped wire. Easily enough to trigger 5 volt cmos logic.

Sceadwian said:

The receiver wouldn't need any high voltage capacitors, just a few dozen turns of wire around the fence wire's primary outgoing line. The sudden start and stop of currents/voltages would cause inductive spikes on the wrapped wire. Easily enough to trigger 5 volt cmos logic.

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That is essentially what I started to type, but then it occurred to me that if the fence pulser is a current source, the same current will pass through the wire regardless of whether there is a S/C or not since there will be capacitance and some leakage resistance to gnd under normal circumstances.

I've been thinking about this issue while doing other more mundane work.

I don't think we need to monitor the high voltage side at all. Bear with me while I waffle.

Its a long time since I've seen a fence unit with the cover off, but my vague recollection is that it is similar to a car's ignition system. It has a transformer with a low V primary & a high V secondary driven by an oscillator that delivers short current pulses to the primary.

When the pulse is switched off, any poor fool who is touching the wire receives the benefit of the di/dt from the secondary.

I expect that there is a resistor in series with a capacitor across the primary in order to limit di/dt so that the secondary voltage only rises to around 3000V (using tytower's figure).

Normally, the load on the high V side would be only the capacitance & any leakage resistance to gnd.

The leakage resistance would be a function of the quality & design of the insulators. I don't know what would happen during a NQ rain storm. It would depend upon the purity of the rain water & the insulators.

The old style telephone insulators (& mains power insulators) had a skirt to allow the water to flow off & thus keep the under side dry & therefore maximise the insulation resistance during rain. Some years ago, my boss at work had a telephone insulator that he had found in Spain & it had small lumps around the circumference of the skirt - presumably to form the water into streams & thus flow off better.

So it would appear that the fence unit is a voltage limited current source, since by Lenz's law, the inductance wants to keep the magnetic flux constant, ie. the minimise d phi/dt. In order to do this (& neglecting the primary circuit for the moment), the inductor tries to keep the same current flowing after the pulse turns off as was flowing while the pulse was on.

Hence, given that the impedance of the load is fairly high, the voltage must rise to a high enough level in order to maintain the current at the same level that was flowing at the moment the pulse was switched off. So it is essentially a current source.

Now, the thought that struck me is that there is no need to do the "Morse Code" - just apply the S/C to gnd & leave it connected until you have finished moving the fence. Thus the time constant (L/R) will change significantly. Normally, L/R will be small since (neglecting C) R is high. But when the S/C is applied, R becomes small and so L/R becomes high (& C would be swamped by R).

So I feel that all we need to do, in essence, is to connect a wire to the primary of the transformer and design a circuit to measure the pulse length. When it detects that the PL has increased, it operates a relay to disconnect the power to the fence unit and connect a low V DC monitor circuit to detect when the S/C is removed.

So it could be done quite simply, either with a PIC to do the control and timing or, if "tytower" is not comfortable with PICs, a simple hardware circuit.

What do you think?

Sounds more than reasonable to me. Any animal that runs into it isn't going to stay there long enough to trigger the disabling circuit.

Sceadwian said:

Sounds more than reasonable to me. Any animal that runs into it isn't going to stay there long enough to trigger the disabling circuit.

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One point I forgot to mention is that I would count several pulses (say 6 for example) before deciding that it is a disable signal. This should prevent invalid disables.

Electric Fence Energisers and Testers

ljcox said:

...........
Its a long time since I've seen a fence unit with the cover off, but my vague recollection is that it is similar to a car's ignition system. It has a transformer with a low V primary & a high V secondary driven by an oscillator that delivers short current pulses to the primary.

When the pulse is switched off, any poor fool who is touching the wire receives the benefit of the di/dt from the secondary.
...........................
So it would appear that the fence unit is a voltage limited current source, since by Lenz's law, the inductance wants to keep the magnetic flux constant, ie. the minimise d phi/dt. In order to do this (& neglecting the primary circuit for the moment), the inductor tries to keep the same current flowing after the pulse turns off as was flowing while the pulse was on.

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We keep livestock...
All our energisers (half a dozen) have more in common with electronic flash guns than car ignitions; a high frequency oscillator drives a transformer to charge a capacitor to several hundred volts - you can hear the characteristic 'whistle', rising in pitch - then, about once a second, this is discharged into a second transformer to produce about 8kv or 10kv. this HT pulse is around 10ns in duration and LEGALLY has to be controlled to make it non-lethal, your energiser will state how many joules it puts out - ours vary up to 3 joules.
The output voltage is rated with NO LOAD- wet grass or poor insulators will significantly reduce it, Gallagher print a table of reccommended voltages for various animals, pigs need very little while sheep need some 2 or 3kv (as measured on the wires).
It is quite safe to short the fence out.

For a simple tester, see this thread - near the bottom
https://www.electro-tech-online.com...-tester.3451/?highlight=electric+fence+tester

One of the energiser manufacturers produce a system that uses the wire as a control line to switch the energiser on and off, so this is possible - a small 'probe' is touched to the line to signal to the energiser.
I wouldn't short the wire to ground for a signal as this would be too prone to false signals from vegitation or animals touching the wire, I would rather stand on the wire to short it out and stay there until the work is done.

Actually, we sometimes strip-graze and we just use crocodile leads to disconnect the fence we are moving, leaving everything else live !

mechie said:

We keep livestock...
It is quite safe to short the fence out.

For a simple tester, see this thread - near the bottom
https://www.electro-tech-online.com...-tester.3451/?highlight=electric+fence+tester

One of the energiser manufacturers produce a system that uses the wire as a control line to switch the energiser on and off, so this is possible - a small 'probe' is touched to the line to signal to the energiser.
I wouldn't short the wire to ground for a signal as this would be too prone to false signals from vegitation or animals touching the wire, I would rather stand on the wire to short it out and stay there until the work is done.

Actually, we sometimes strip-graze and we just use crocodile leads to disconnect the fence we are moving, leaving everything else live !

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Good stuff - I like the foot on the fence bit ,funny how you don't think of the obvious. I tie the side tapes to the main line so getting them untied is taking the time and giving the boot. I have to tie the knot pretty tight cause if the join sparks it burns out the fine stainless threads that run through the Gallagher white tape

Wondered why two resistors in series on your circuit -could be a 10 KOhm by the looks of it. Will try this . My unit is a Thunderbird M100 made in Australia. Supposed to power up to 10 KM. Appreciates the posts fellas.

tytower said:

Good stuff - I like the foot on the fence bit ,funny how you don't think of the obvious. I tie the side tapes to the main line so getting them untied is taking the time and giving the boot. I have to tie the knot pretty tight cause if the join sparks it burns out the fine stainless threads that run through the Gallagher white tape.

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This may be OK in the wet season, but it may be painful in the dry season since the earth won't be as conductive.

I suggest you make up a "wand" that has an earth stake at one end and a crocodile type clip (remotely operated via some nylon fishing line to make sure you are not zapped) on the other.
Drive the stake into the gnd and then clip the croc clip onto the wire.

In the dry season you may have to drive the stake in a bit, pull it out and then pour some water in.

tytower said:

Wondered why two resistors in series on your circuit -could be a 10 KOhm by the looks of it. Will try this . My unit is a Thunderbird M100 made in Australia. Supposed to power up to 10 KM. Appreciates the posts fellas.

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I expect he used 2 resistors in series since the voltage is so high.

A single 10 k may be zapped by the voltage.

In fact I would be inclined to use three 3.3 k resistors in series to give you more margin.

My electric fence tester consists of a front door type key held firmly between thumb and first finger touched lightly on the fence. The large contact area between key and body and the loose connection from key to fence reduce the shock to a tingle. FYI, I normally have boots on and never do it in the wet. I once got zapped while standing bear foot in very wet mud - boy did that hurt.

BTW, the way I join the white tape is with a strip (12mm * 50mm) of soft drink can. I fold it around the two pieces of tape and crimp it with a pair of mole grips.

To disable it, I'd short it. Do you not run a separate earth that you could utilise?

Mike.