Hello, I’m a new member would be greatful for some help with this circuit diagram for an electric fence energiser. What is the gap above the top HER108 diode, is it some sort of spark gap. Also can anyone make out or deduce the value of what I assume is a potentiometer, labelled “freq”

 

From what I can tell, and I very well could be wrong on this, the gap above HER108 might be a spark gap. They're usually noted as such in schematics, but the fact that the two seemingly-floating wires still exists in the schematic suggests it's intentional.

The element marked "FREQ" appears to be a jumper or pin header (1x2 pin header), where some device (likely a potentiometer) would connect externally. I had to download the Eagle files to figure it out (Radu Motisan, based on some of his other schematics as well, seems to be a little...messy with his schematics at times, especially with labels), but I did confirm: that jumper connects to a 1M potentiometer. The "DURATION" jumper also connects to a potentiometer (10k).

The original schematics and designs can be found here. He has some videos, files, and alternative designs as well.

 

Also looking at his demonstration pictures, he shows the spark gap sparking (by a surprisingly length, too - about 2-3cm based on semi-fuzzy images), so it is, indeed, a spark gap.

 

Old fence chargers used spark gaps.

 

High there! I hope you are doing well...
The circuit runs on 12V (batteries), making this a very portable fence energizer solution. It uses 2x 555 timers, one runs in astable mode and is used to generate the frequency interval, while the second one controls the pulse length and so the output voltage. A calculator for the 555 timers can be found here The updated circuit diagram for this version of the circuit is oavailable:


Here are the Eagle files, with both the SCH and the PCB layout: fence-4.3-orig
alternatives, such as the double timer 556, we can shrink this circuit even further, without making any compromises. Here is an improved version that I’ve just designed and tested with excellent results


The eagle files: fence-4.2
Both the designs can operate on battery and have low power consumption. https://www.pocketmagic.net/electric-fence-circuit-for-perimeter-protection/

 

From what I can tell, and I very well could be wrong on this, the gap above HER108 might be a spark gap. They're usually noted as such in schematics, but the fact that the two seemingly-floating wires still exists in the schematic suggests it's intentional.

The element marked "FREQ" appears to be a jumper or pin header (1x2 pin header), where some device (likely a potentiometer) would connect externally. I had to download the Eagle files to figure it out (Radu Motisan, based on some of his other schematics as well, seems to be a little...messy with his schematics at times, especially with labels), but I did confirm: that jumper connects to a 1M potentiometer. The "DURATION" jumper also connects to a potentiometer (10k).

The original schematics and designs can be found here. He has some videos, files, and alternative designs as well.

Thanks Z that’s very helpful

 

Thanks Z that’s very helpful

Just a quick one, so how would I create a spark gap please or is there a device you can buy?

 

hi Dp,
Depending on the breakdown voltage you require, I have used an old vehicle spark plug with the gap opened up to suit the fence.
E

 

The updated circuit diagram for this version of the circuit is oavailable:

The LEDs are the wrong way round.

 

This won't work for more than 10 feet of fence. Very high impedence.

 

hi Dp,
Depending on the breakdown voltage you require, I have used an old vehicle spark plug with the gap opened up to suit the fence.
E

Thanks Eric

 

This won't work for more than 10 feet of fence. Very high impedence.

How would I modify it please so it would work?

 

hi Dp,
Interested to know which part of the circuit @Hamlet is referring too.?

What are the details of the induction coil.

E

 

How would I modify it please so it would work?

If this uses an automotive ignition coil, the impedence is too high, it can't push enough amps.

 

hi Hamlet,
I have in operation on our farm a number of home designed Fence Energisers, using old 12V vehicle ignition coils, they work well over a 100mtrs of fencing.
Its important that the pole insulators that carry the wire are a good quality and the energiser is well Grounded.

A typical Ignition coil with its ballast resistor draws about 4Amps pulse current from 12V car battery, believe me if you touch the fence wire you will get a good jolt.
E

 

hi Hamlet,
I have in operation on our farm a number of home designed Fence Energisers, using old 12V vehicle ignition coils, they work well over a 100mtrs of fencing.
Its important that the pole insulators that carry the wire are a good quality and the energiser is well Grounded.

A typical Ignition coil with its ballast resistor draws about 4Amps pulse current from 12V car battery, believe me if you touch the fence wire you will get a good jolt.
E

Great, that's really interesting. I've built several different types of ignition coil fencers, and never found the performance
worth a darn, especially in the rain, as the insulators soak up most of the current. The one idea I haven't tried is a
capacitive discharge style into an ignition coil... Looks good on the bench, with a 30mm spark, but I haven't wrapped one
up and actually hung it on a fence to test, which is the ultimate test.

What design are you using? Schematic?

 

hi Hamlet,
This is the version we use, the Ballast, Ign coil and Cx are from car scrap yard vehicles.
The pulse is a nominal one second interval.

As you say, good all weather insulators are a must.
One extra feature we sometimes add, is an uninsulated wire connected to Ground at the energiser, the wire is run about 12 inches below on the same poles as the hot wire [ no insulators].
The animal usually tries to poke its head between the two wires.!
Also tie Red marker ribbons to the hot wire about 2 - 3 mtrs apart, the animals soon learn its hot and keep away.
E

What animals are you corralling.?

 

That relay doesn't look connected right, I would expect it to be between ign and ground.

 

hi. K
Dont forget the transformer is an 'auto transformer', ie primary CB to Ign and the secondary Ign to EHT... A step up transformer.
E

 

hi Hamlet,
This is the version we use, the Ballast, Ign coil and Cx are from car scrap yard vehicles.
The pulse is a nominal one second interval.

As you say, good all weather insulators are a must.
One extra feature we sometimes add, is an uninsulated wire connected to Ground at the energiser, the wire is run about 12 inches below on the same poles as the hot wire [ no insulators].
The animal usually tries to poke its head between the two wires.!
Also tie Red marker ribbons to the hot wire about 2 - 3 mtrs apart, the animals soon learn its hot and keep away.
E

What animals are you corralling.?

Interesting circuit, I haven't seen that one. You have alternating +/- wire, which works better with ign. coils. I use
multi-wire earth grounded systems. In summer, the earth is too dry for high impedance solutions, and in winter
with rain/snow, I have too many insulators which drain the mA away.

I don't keep livestock in, but varmints out, as mule deer, raccoons, & elk want into my garden, and bears want into the garbage and bee hives. Attached is a picture of a corner-post (foreground) and the enemy...