They asked us to make an electric fence. I googled, there are a lot of diagrams, but nothing really caught my eye. Circuits powered by 220 volts are out of the question: stupid and dangerous. The common circuit on three 555 timers surprised with its redundancy; an electric chair based on the PWM ignition coil principle will not give a sufficient spark length and is just as dangerous.
What is an electric sheath? In the simplest case, it is a plot of land fenced with a wire or special tape under voltage.
So what happened:
The circuit operates from 10 to 14 volts. The primary converter charges C4+C5 to 400 volts, after which they are discharged to the ignition coil. The discharge frequency is regulated by R2 and limited by R3; these resistors are responsible for the duty cycle of the primary converter pulses. The converter itself is powered by the common SG3525 microcircuit, which in this connection requires a minimum of wiring. The frequency of the converter (C1 and R1) is selected depending on the transformer, in my case ~66kHz. In my case, the maximum duty cycle is limited by resistor R3 at ~18%, and the maximum current consumption from a 12-volt source is ~250mA. If the power is not limited, you may need a snubber and replacing the transistor with something more powerful, such as IRF3205.
C2 at 25 volts. Transformer T1 on the RM8 N87 AL=250 core is redundant, but no smaller cores were found. Calculate the turns in the Old Man program, in the secondary winding there are ~250 turns, this is enough with a margin on almost any core, and since This is a flyback, I highly recommend layer-by-layer insulation to avoid breakdown.
Next come two diodes and a current-limiting resistor R5, which uselessly consumes power, heats up and helps to lock the thyristor in this connection. It is better to make it a composite of two parallel or series resistors with a power of 2 watts of suitable ratings. Capacitors C4 and C5 at 630 volts. C3 can be taken at 50 volts. Ratings of the dinistor and thyristor in the diagram.
Resistor R6 regulates the response voltage of the threshold unit, I set it to 400 volts, which seems to me excessive, the spark is too powerful, all this will be adjusted during the experiments.
T2 – ignition coil, the primary winding is shunted by 3 serial HER208 diodes.
I don’t like the threshold node because of R5, it will be redone, but for experiments it will do just fine.
At the moment, the discharge frequency at maximum (R2) power is about 4Hz, it seems to me that more is not needed, but most likely less, if you leave this frequency and reduce the operating voltage of the threshold unit to 100-200 volts, the consumption will be about 50-100 milliamps, respectively, from a car battery this circuit will live forever.
For safety, it is planned to connect the HV output of the ignition coil to the fence through a 5 megaohm composite resistor, which will allow limiting the current that offends animals to a safe level.
Upd: The electric shepherd was tested, here is the video:
The voltage on the capacitors is reduced from 400 to about 150-200 volts, the spark is about two centimeters, maybe a little more.
Please enable JavaScript to view theA device such as an electric shepherd (a mobile electric fence on a pasture site) allows grazing of various types of farm animals or poultry without direct human intervention. Cattle grazing freely inside a fenced area do not suffer as much from blood-sucking insects as they do when tied. The electrical wire protects the livestock from attacks by predators. Electric fences are also used to protect crop areas or hay reserves from damage. You can also protect dangerous areas of the landscape (ditches, ravines) with a similar fence.
An industrial electric shepherd is quite expensive equipment. But if you want to save money, you can make it yourself at home.
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An electric shepherd is a device that is a generator operating from a 220 volt network (or from a 10-12 volt battery) and transmitting current pulses to a bare wire stretched over the insulators of the support posts. The wire fences off the area within which animals graze.
When you touch it, a current discharge passes through the animal’s body and goes into the soil to the grounding part of the device. A low-power discharge is not capable of causing harm to the body, but causes discomfort in the animal. The reflex to avoid the wire is developed very quickly.
Making an electric shepherd for animals (cattle, pigs, sheep, goats) with your own hands is a task that even a novice radio amateur can handle.
Most of the components necessary for this can be found on the farm. What you can't find will have to be purchased.
First you need to decide which area around the perimeter needs to be fenced. The maximum distance between two support posts should not exceed ten meters (if the animals are large and active, then even less).
To find out how many support posts you will need, you should divide the perimeter of the site by the distance between them. A homemade electric shepherd can have support posts made from:
Metal posts (pins sharpened at one end) are heavy, but easy to drive into the ground. Those cut from wood will be cheap, but fixing them in the ground will not be easy; you will have to dig them in. Ready-made posts made of polymer materials, purchased in a store, are an expensive pleasure.
The height of the support posts is selected depending on the type of animal for which the electronic shepherd is being made.
Each support post must have an insulator to which the wire will be attached. Industrially produced insulators sometimes appear on sale. It would be good if they were ceramic.
You can make insulators with your own hands. A good insulator can be made from a plastic bottle without a bottom. It is put on a post, and several turns of wire are made around the neck.
The wire must be resistant to adverse environmental factors. Iron will quickly rust. Galvanized with a diameter of 2 mm is suitable.
The bare wire itself is hard to see for animals, so it is worth using it in combination with brightly colored ribbons. A warning message for people is also necessary.
You can purchase a ready-made electronic fence pulse generator, but with some experience it is not difficult to assemble one yourself from an ignition coil and three 555 timers.
If an experienced radio amateur gets down to business, this diagram can be somewhat simplified or supplemented.
It is convenient to use an iron rod (one or more) with a length of at least 120 cm as grounding. The grounding goes 1 m deep into the soil. In dry weather, for better electrical conductivity, the soil around the grounding must be shed generously with water.
To protect your plot of land from animals (and not only) you can use an electric fence, which is made of wire or metal mesh stretched on insulating posts; it does not come into contact with the ground, but is connected to a grounded source of high-voltage pulses. In relation to the life of animals or people, this does not pose a danger, but it gives a rather unpleasant and frightening feeling.
In order for the electric fence to perform only a repellent function, it is necessary to apply short high-voltage pulses to it, which are repeated at a certain interval.
You can make a pulse generator according to the circuit shown in Fig. 1. The generator is based on a ready-made high-voltage transformer; its role can be played by an ignition coil taken from a passenger car. The ignition coil is a transformer with a low-resistance primary and high-resistance secondary coils. When current ripples in the primary, high voltage pulses are formed on the secondary. In a car they go to the spark plugs, but here they go to the fence.
For the circuit to operate, a pulse voltage must be applied to the primary, which consists of intermittent trains of audio frequency pulses; they are repeated after a certain period of time. The circuit for recreating these pulses is made using three 555 integrated timers.
Generators of infrasound and sound vibrations, respectively, were made based on timers A1 and AZ. Based on timer A2 - one-shot.
The current to the primary of the ignition coil T1 goes through the switch on the field-effect transistor LG 1. In order for a high voltage to form in the secondary T1, the current must pulsate in the primary. A sound pulse generator is made based on the AZ timer. When it works, audio frequency pulses from its output (pin 3) go to the gate of the transistor. As a result, a pulsating current is formed on the primary T1, which induces a high alternating voltage on the secondary.
The sound pulse generator is controlled by the level at pin 4 AZ. In order for the generator to operate at this pin, a logic one voltage is needed. At logical zero, the generator is blocked and its output is set to logical zero.
An infrasound generator is made based on the A1 timer; it generates pulses. The frequency of these pulses can be adjusted using variable resistor K1. The frequency of supplying high-voltage pulses to your fence depends on this generator. Pulses from pin 3 of A1 go to pin 2 of A2.
A one-shot circuit is made based on timer A2. Upon arrival of each pulse at pin 2, it forms one pulse of a given duration, which can be adjusted using variable resistor K4. This pulse signal goes through resistor B10 to the gate of the powerful key field-effect transistor UT1A, in its drain circuit the primary of the standard automobile ignition coil T1 is connected. Almost any ignition coil can be used. It is better to use a coil from cars with a “contact” ignition system. For example, from Zhiguli VAZ - 2101 or 2106, from Moskvich 412 or 2140.
The basis of the article is taken from the magazine "RADIO CONSTRUCTION"
An electric shepherd or electric fence is a kind of device that is used for various purposes. It helps protect animals or protect against animals. The design of the ignition coil device is quite simple, so you can create it yourself. Strictly speaking, an electric shepherd is a generator that transmits current through a wire. Voltage helps scare away large animals, protect crops, or protect livestock from attacks by wild animals.
The device of the electric shepherd is simple. The live wire does not allow the animal to leave the pen or go beyond its boundaries. If cattle are grazing in a certain place, the electric shepherd will not allow them to leave the pasture area. But you can see what a factory device for cows looks like.
Circuit and software component of the electric shepherd.
If cows graze freely, which is suitable for, then the fence will help protect crops, haystacks, flowers and other decorative plants from them.
On the video - why an electric shepherd is needed:
On some farms, such a fence is used to protect the feeders of other animals from pigs.
Electric shepherds are also used to protect their own plot of land from “encroachments and raids” by various animals. The fence is installed around the perimeter.
Do not be afraid that the current will harm a person or animal. The impulses will not cause harm and are not life-threatening. Contact with a fence is fraught with the occurrence of inconspicuous sensations and severe discomfort, which will scare away the animal, but will not cause significant harm to its health. Provided that all safety rules are followed. It may also be useful for you to know what this problem looks like and what can be done about it.
On the video - how to make equipment with your own hands:
Among the advantages of a fence it is worth highlighting:
If you construct a fence yourself, problems may arise:
It is advisable to have certain design skills; this will help to avoid mistakes when creating an electric shepherd. But what the symptoms of mastitis in cows may be will help you understand.
You will need an ignition coil. It will act as a voltage source and as a device that converts voltage into impulse. In order for the fence to only scare away livestock and not kill them, it is necessary to focus on the transmission of short impulses. They will be repeated at a certain frequency (interval). It is not difficult to make a generator if you take a completely finished transistor, which will transmit impulses or directly to the ignition coil from a passenger car. But what breeds of dairy cows there are and how to raise them correctly are indicated.
The ignition coil plays the role of a transformer; it is a device that performs 2 functions. The coil “generates” voltage and converts it into impulses.
High voltage pulses in the car are transmitted to the spark plugs, and in the electric shepherd they are sent to the fence. What to do with mesh or wire, as well as poles, is very clear. After the structure is installed, it should be connected to the generator. You may also be interested in learning about what it looks like and what conditions exist for its maintenance.
Step-by-step analysis of creating a generator:
If we take the A2 timer circuit as a basis, we can create a one-shot circuit. When voltage is applied to pin 2, it will form a certain pulse, the duration of which can be selected independently using resistor number K4. This signal is in the nature of a pulse and will be sent to resistor B10. It goes to the gate of the switching, field-effect and fairly powerful transistor UT1. In its stock circuit there will be a connection to the “primary” of a standard ignition coil from a T1 passenger car. You may also be interested in information about how to increase your milk yield.
It is worth noting that any ignition coil is suitable for creating a fence, but it is better to give preference to a car coil with a contact ignition system, such as the following cars:
But you can find other suitable cars with a contact ignition coil, which is suitable for creating an electric shepherd. But you can read how much hay a cow needs for the winter and what feed is the most effective.
It is advisable to choose a scheme with a short pulse, because if the pulse is long and quite powerful, the animal will not be able to leave the dangerous place. The unpredictable behavior of the animal (this rule applies to horses to a greater extent) is caused by muscle spasms. The spasm occurs due to too long and powerful an impulse. And if the animal does not leave the dangerous place, then a second impulse will follow and as a result of such an impact it may die.
Different animal species require different characteristics. Therefore, before starting to manufacture an electric fence, you should familiarize yourself with the related information.
Disadvantages of such a generator:
