A Homemade Fence Charger, Energizer Circuit Explained

The electric fence charger circuit presented here is basically a high voltage pulse generator. The super high voltage is derived from a commonly used automobile ignition coil. An astable multivibrator is used to generate the required frequency to drive the ignition coil. Another astable is used to control the pulses supplied to the fence.


If you have large agricultural fields and desperately need to protect the crops from uninvited guests like animals and possibly humans, then this electric fence charger device is just what you are looking for. Build and install it yourself.
An electric fence is an electrified high voltage barrier which produces painful shocks if physically touched or manipulated. Thus such fencing basically function as deterrents for animals as well as human intruders and stop them from crossing the restricted boundary.
The present circuit of an electric fence charger is designed and tested by me and has proved sufficiently powerful for the application. 
The fence charger circuit is able to produce voltage pulses up to 20,000 volts, needless to say about the fatality rate involved with it. However the pulses being intermittent, provides the subject with enough time to realize, recover and eject.
The generated pulse is so powerful that it can easily arc and fly-off between short distances of around a cm. so the fencing conductor needs to be separated adequately to avoid leakages through arcing and sparking. If not tackled, may drastically reduce the effectiveness of the unit.
Here the generation of high voltage is primarily carried out by an automobile ignition coil. 
The winding ratios of an ignition coil are specifically designed and intended for creating high voltage arc between a two closely spaced conductors inside the ignition chamber to initiate the ignition process in vehicles.
Basically it’s just a step-up transformer, which is able to step-up an input applied voltage at its primary winding to monstrous levels at its output or the secondary winding.

SOME POINTS OF THE CIRCUIT AND THE IGNITION COIL IS VERY DANGEROUS TO TOUCH WHEN POWERED. ESPECIALLY THE IGNITION COIL OUTPUT IS TOO LETHAL AND MAY EVEN CAUSE PARALYSIS.







Let’s diagnose the proposed electric fence charger circuit more deeply.

 Circuit Description

In the CIRCUIT DIAGRAM we see that the entire circuit is basically comprised of four stages.
A DC oscillator stage,
An intermediate 12 to 230 volts step-up stage,
The voltage collector and firing stage and the super high voltage-booster stage.
TR1 and TR2 are two normal step-down transformers whose secondary windings are connected through SCR2. TR1 input primary winding may be selected as per the country specification.
However, TR2 primary should be rated at 230 volts.
IC 555 along with the associated components forms a normal astable multivibrator stage. The supply voltage to the circuit is derived from the secondary of TR1 itself.
The output from the astable is used to trigger the triac BT136 and the whole system, at a particular fixed intermittent rate as per the settings of P1.
During the ON periods, the triac connects the 12 volt AC from TR1 to the secondary of TR2 so that a 230 volt potential instantly becomes available at the other end of TR2.
This voltage is fed to the voltage-firing stage consisting of the SCR1 as the main active component along with a few diodes, resistor and the capacitor C4.
The fired voltage from SCR1 is dumped into the primary winding of the ignition coil, where it is instantly pulled to a massive 20,000 volts at its secondary winding. This voltage may be suitably terminated into the fencing.
The high voltage generated by this electric fence charger will need to be carefully applied across the whole length of the fence. 
The two poles from the ignition coil connected to the fence wiring should be kept at least 2 inches apart. 
The pillars of the fence should be ideally made of plastic or similar non conducting material, never use metal and not even wood (wood tend to absorb moisture and may give path to leakages).

Parts List for the explained electric fence charger circuit using SCR

R4 = 1K, 1WATT,
R5 = 100 OHMS, 1WATT,
P1 = 27K PRESET
C4 = 105/400V PPC,
ALL DIODES ARE 1N4007,
IC = 555
TR1 = 0-12V/3Amp (120 or 230V)
TR2 = 0-12V/1Amp (120 or 230V)
THE SCR IS BT151,
THE TRIAC COULD BE ANY 1AMP/400V SUCH AS BT136

TWO WHEELER IGNITION COIL IS SHOWN IN FLUORESCENT BLUE COLOR


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Anonymous
March 15, 2012 at 10:56 PM delete

thanks for the info.its really help me in my assignment.i hope u allow me to copy all of these.hehe thank u

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Anonymous
March 24, 2012 at 12:50 AM delete

there are difference betwen schematic and material list. can you clear it?
Very good apport!!!!!!!
thanks

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March 24, 2012 at 9:19 AM delete

OK I'll correct it...Thanks!

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Anonymous
March 30, 2012 at 10:01 AM delete

Can we simply use a CDI unit of any motorcycle?

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March 30, 2012 at 10:43 AM delete

Very good suggestion , in fact you can do it, but you will have to first understand the outputs from the CDI and connect them correctly as per the above diagram.

Regards.

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Anonymous
March 31, 2012 at 2:13 AM delete

Hello swagatam: i´m trying to mount the circuit; in correction, you rotate scr2. ???
thanks.!!!

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March 31, 2012 at 8:35 AM delete

Hi,

Yes you are right, SCR2 is wrongly connected, just turn it round to make the connection right.

Thanks.

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Anonymous
April 12, 2012 at 7:24 AM delete

I´m building circuit, but output trafo is very low; what can i do?

thanks

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April 12, 2012 at 8:33 AM delete

which circuit did you build? I would suggest, you build the upper circuit first....

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Anonymous
April 14, 2012 at 1:13 AM delete

Hello swagataM:
I built upper circuit en work ok. I add temp (below circuit) and output TR2 is very low. ?????
Thanks

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April 14, 2012 at 8:29 AM delete

Hi,

Yes, it's because we have used an SCR, please replace the SCR C100 with triac BT136.

Thanks and Regards.

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Anonymous
April 15, 2012 at 7:02 AM delete

Hello suagatam:

I like very much your circuit but it is highly dangerous! In eleectric fences, time pulses must be less than 10 ms; freq, 1 Hz aprox. If you review TEMP 555, Tm is greater than 10 ms. I suggest review design because it es a good aport. Please, let me know if I am wrong.

tkanks

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April 15, 2012 at 8:43 AM delete

Hi,

I think you may be right, I would appreciate of you could do the necessary corrections so that I can correct the diagram accordingly.

Regards.

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Anonymous
April 16, 2012 at 2:45 AM delete

Do I replace both SCR 100?

thanks

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April 16, 2012 at 9:17 AM delete

Only the right hand side SCR needs to be replaced with a triac.....

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Anonymous
April 16, 2012 at 8:09 PM delete

Thanks you for your confidence. I´ll try to do it soon.

Regards

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Anonymous
May 4, 2012 at 12:23 AM delete

Hi Can I make this Energizer using just a 12v battery to keep horses in. Am I correct in thinking the circuit is intended for AC at 240 so if I leave the first transformer out and put 12v battery in will it still work as using direct current without other modifications ?
Regards Thanks

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May 4, 2012 at 8:51 AM delete

Hi,

If you leave out the first transformer, the second transformer would need a 12v AC for operating the energizer circuit.

Probably it's the second circuit which will function exactly as per your requirement, you may try it.

Regards.

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May 4, 2012 at 8:52 AM delete

Oh yes.... you may eliminate TR1, in case you employ the second circuit.

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Anonymous
May 4, 2012 at 7:59 PM delete

wats d use of d capacitor, the one which is in parallel with IN4007?

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May 4, 2012 at 8:16 PM delete

for switching high voltage to the coil....

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May 21, 2012 at 9:36 PM delete

hello sir...
this is really nice... but how we can apply this to the fencing sir..?? i mean this circuit should be attached to normal fencing??

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May 21, 2012 at 9:55 PM delete

Hello Siree,

Since this circuit involves high voltages, requires utmost care while applying to the fences, which must be accurately laid down as per the instructions.

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Anonymous
May 27, 2012 at 9:30 AM delete

Can you post a new Diagram for the wrongly connected SCR2 Circuit?

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Anonymous
May 27, 2012 at 9:40 AM delete

Hi Anonymous;
What IC do you think should be used in place of the 555 IC ?

Thanks

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May 27, 2012 at 5:51 PM delete

I've corrected it, kindly check it.

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May 29, 2012 at 11:36 AM delete

Hello ! I have some rodents digging new holes almost on daily basis in my home lawn. I have tried my best to fill the holes with even broken glass bits, broken brick bits but they manage to dig new holes. The holes are about 2 inch wide and go deep in the ground. I tried simple mousetrap as well but failed.

And dogs getting the smell of the rodents also dig my lawn.

They all have created a mess.

I want to make an electric fencing used a 12 V power source + a motorcycle CDI unit and a motorcycle ignition coil.

I want to put this small 2 inch high fencing along the holes that rodents have made so that while going in and out they can get electrocuted.

Help me with circuit diagram please.

kaps163 AT gmail DOT com

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May 29, 2012 at 2:37 PM delete

You may build the circuit shown in the second diagram, it will work for you.

By the way we don't want to electrocute the animals, just drive them off.

The shown circuit is actually a motorcycle cdi unit.

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Anonymous
June 16, 2012 at 7:50 PM delete

Hi Swagatam
I'm From Sri lanka.Our villages are facing life threaten problem because of elephant. in night people couldn't go out because elephants are hanging here and there. once a week a human die b'couse of elephant attack. What i really begging you give me a high voltage dc fence energizer circuit diagram to use each house . Must be low budget because our villages are very farmers.In my area we don't have ac power.We are using 12v battery power. Please give me a good solution.

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June 16, 2012 at 9:47 PM delete

The circuit explained in this article can be used for guarding houses, however i am sure whether it will be enough for stopping an elephant's might....not sure.

You may try it though, it uses low cost auto ignition coil and some ordinary electronic parts.

Regards.

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July 15, 2012 at 1:46 AM delete

A simple high voltage unit can be made by cutting off the bottom inch or so of the coil.Connect negative as normal fasten coil in upright position on door post and run high voltage across the door. Knock nail into doorpost about half inch below the square iron core of the coil ,bend a strip of iron round nail and connect nail to battery positive. Let the iron strip rest on any fixed piece of metal with a wire going to the coil positive. It works thus, the positive current flows through the loose iron flap, which is resting on the metal connected to the coil positive. This energises the coil making tthe core magnetic and attracting the loose iron strip. this breaks the circuit and the loose iron strip rests on the metal connected to the coil and the circuit repeats itself. To improve it make the loose iron flap a weak spring and the system becomes portable

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Anonymous
July 17, 2012 at 9:03 AM delete

Dear squire,

Please post a circuit diagram

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August 25, 2012 at 11:48 PM delete

wher did you get the capacitor C4 from ???

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August 26, 2012 at 8:07 AM delete

C4 is an ordinary high voltage polypropylene capacitor.

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December 25, 2012 at 10:37 AM delete

Please sir can send me a book in pdf or ppt from which i could from basics to higher level about electronics . I love electronics . Plese send it to vaibhavdhiman10@gmail.com
thankyou

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December 25, 2012 at 2:42 PM delete

Hi, Vaibhav,

Presently I do not have any such suitable book for the beginners, if I find one will surely inform you regarding it.

Regards.

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Anonymous
December 29, 2012 at 11:25 PM delete

HI
the circuit works great but please tell me the exact capacitor spec to be used to get the output

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December 30, 2012 at 8:32 AM delete

Hi,

C4 is 105/400V or 1uF/400V, metallized PP capacitor.

0.01 is ordinary disc ceramic,

1uF and 1000uF are ordinary electrolytic type.

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Anonymous
February 13, 2013 at 10:42 AM delete

swagatam,
excellent work with the electronic diagram. I am impressed with your patients toward others that are less fortunate, with meager resources and limited knowledge. It is easy to be impatient with others if a you can't understand the context of the writer and their immediate situation. In this world of profit and money, the poor who are the planets majority really need easy, cheap solutions to their problems. can you imagine having your sister killed by WILD ELEPHANTS while peeing in a dirt hole at 2am because "rich people" wouldn't explain a simple electrical schematic?
thank you from all of those that can't say it.

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February 13, 2013 at 5:03 PM delete

Thanks very much, I highly appreciate your feelings!

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Anonymous
March 1, 2013 at 11:22 PM delete

hey, i want to make one for my field fence i have unwanted horses in and i want them out, anyway. i have no idea what your talking about as i am not a technition haha and i am totally confused but really need to build one to get the eletric flowing. out of all the thing i have looked at yours seems to be the most explained. but i have no idea what any of them things are or where to get them i have a soilder iron and soilder ready haha.
Thankyou

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March 2, 2013 at 8:01 PM delete

If you are so very new in the field, and confused, I wouldn't recommend you this circuit, it's strictly not for the newbies.

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March 7, 2013 at 11:37 AM delete

Can you please explain the connections to the fence wiring. You said:The two poles from the ignition coil connected to the fence wiring should be kept at least 2 inches apart.I did not get that part.

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March 8, 2013 at 8:02 AM delete

the fence barb wires must be stretched through rigid non conductive pillars positioned close to one another in order to keep the wires tightly held.

all the barb wires must run parallel at a distance of about 6 inches from each other (not 2 inches actually).

The current from the above circuit must be fed to the alternate wires such that when an intruder touches any of the two barbs, the voltage gets a path through its body, and provides the required shock.

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May 28, 2013 at 9:38 AM delete

1. Sir what will be the output voltage of this circuit?

2. I want to use this circuit as a protection from rats in farms of villages, so the wires will be laid on the ground meshing throught the field. I want only the rats to be driven off and not cause much damage to humans in case the come in contact with it.

3. What other changes should I be making in order to use this circuit for this purpose. Should i use the first circuit or the second one.

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May 28, 2013 at 2:26 PM delete

around 20000V

use a lower rated transformer for tr1 and tr2, for lowering the power of this fence charger.

no changes would be required.

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Anonymous
June 29, 2013 at 8:06 PM delete

how exactly does the circuit of tr2 secondary work.. i mean what is the need of those diodes

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Anonymous
July 15, 2013 at 4:02 PM delete

Please, can you tell me how to connect normal car coil only two terminals feeds one positive one negative?
It's a pain that coil isn't electronic circuit.
And i suppose i'll not have to buy another type of coil.
Grateful for your response.

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July 15, 2013 at 9:38 PM delete

the negative terminal is the ground point.

the positive terminal goes to C4.

the central top cap is the high tension terminal.

you may refer to this diagram

http://static.ddmcdn.com/gif/ignition-system-coil.gif

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Anonymous
July 16, 2013 at 3:39 AM delete

Ok! thanks
Now i know positive terminal goes to C4.
I know the coil is autotransformer type.
I built all, the exiter with pwm, i have the 220 v pulses controlled
but how my interest is only for electronics experiments i would appreciate if you know where i can found some electronic explanation about the last section 220v - scr -diodes - cap and ht.
I experienced previously with only 110 v scr pulses but dont work and if now work will be some of magic circuit with the diodes ....
I suppose the pulse have to be of square quality and the capacitor is fundamental.

well grateful for your circuit i've kept pretty building it


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July 16, 2013 at 12:20 PM delete

The capacitor accepts and stores the 220V input, and in the process when the firing limit of the SCr is crossed, the SCR fires and shorts the capacitor leads across the connected winding of the coil discharging the cap voltage into the coil. This discharge is stepped-up by the coil to the specified levels at the high tension output....so this is how it works.

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July 20, 2013 at 9:58 AM delete

dear sir sir how measure 20,000 v
thanks

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Anonymous
August 21, 2013 at 11:01 PM delete

Mr majoomdar i m a farmer can i use it for our crop protection .will it be not dengerous for elephant dear tiger. Is it not making much voltase for wild animal.can v reduse it and how

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August 23, 2013 at 11:04 AM delete

it's current that may be lethal, not voltage, it will depend on the transformer current rating.

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August 31, 2013 at 3:16 PM delete

hai......this circuit is very use full to my home...for wild elephants...please correct diagram send to me..my email address is - madushankagamage445@gmail.com -

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Anonymous
November 23, 2013 at 7:17 PM delete

circuit is running off 50hz power supply.

power supply for Capacitive Discharge part of circuit is therefore at 50hz also.

the 555 is running from rectified source.

1 cycle at 50hz is 20 ms. 60hz a bit less.

the cdi only charges/discharges and fires on one half cycle.

that is 10 ms.

if the 555 is only on for 10ms, which allows the triac to conduct for only one half cycle...whats the problem?

the actual pulse from the coil is only around 50 MICROseconds long... a typical cdi spark duration.


and you would only have to change the CR(R) circuit on the 555 to alter the duty cycle. not really a major re design if required. which it isnt.

heres the problem. with ONLY 10ms long pulses...the triac may conduct on the wrong half cycle.

i personally would lengthen the pulse to 20-25 ms, just to ensure that at least one cycle of the correct waveform charges the capacitor in the CDI section, as there is apparently no synchronisation in this circuit.

if you removed the 555 and triac, the circuit would produce one 50 microsecond pulse, 50 times a second. (at 50hz)

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November 23, 2013 at 9:04 PM delete

a simpler solution is to pulse TR2 directly with the IC555 via a transistor or a mosfet and eliminate TR1 entirely from the CDI circuit.

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February 3, 2014 at 9:59 PM delete

how can i measure the ampere from tranformer?

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February 5, 2014 at 12:19 PM delete

connect meter prods directly across the secondary output wires, in the AC Amp range

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February 18, 2014 at 6:27 PM delete

Hi Swagatam

1) According to the circuit description, the right transfo should be labelled TR2 and the the left one as TR1.

2) What is the purpose of the diode in the lower right corner, next to the capacitor?

3) Is it important to connect one lead of the primary to one lead of the secondary, of the 2nd transformer?

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February 19, 2014 at 10:34 AM delete

Hi Abu-Hafs,
2)the diode is for grounding the negative spikes.
3) yes it's very important for providing the ground to the scr with reference to its gate voltage.

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February 21, 2014 at 2:05 AM delete

Hi Swagatam

For my CDI bench test, I want to switch off the traic whenever there is trigger pulse. Please check if following configuration is OK:

https://dl.dropboxusercontent.com/u/20969135/Traic.gif

I haven't used traic before so please suggest me suitable values for the resistors and how much collector current would be enough to operate BT136?

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February 21, 2014 at 7:55 PM delete

Hi Abu-Hafss,

It's correct, the resistor can be any value between 2k and 10k as the triac would require just 15mA or even less to trigger fully.

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March 2, 2014 at 8:43 PM delete

dear sir
i want to make solar fence enegiser. i m from chemical field so don't have technical info.so plz guide me for the same. can we have ready made circuit for energiser?

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March 3, 2014 at 11:49 AM delete

Dear Ramesh,
I think the following circuit will be perfect for your applications:

http://homemadecircuitsandschematics.blogspot.in/2012/05/make-this-solar-powered-fence-charger.html

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June 11, 2014 at 5:17 PM delete

Hy Swagatam

i like your ckt but have some questions

there is some difference in the part list and fig -2 also some parts from fig 1 also differ from fig-2
so which is completely write part list or fig-1 or fig2

thanks

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June 12, 2014 at 10:21 AM delete

Hi Samaj,

I'll do the necessary corrections soon. thanks

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December 5, 2014 at 4:16 PM delete

hello sir
any idea about make alarm circuit when fence wire is short.
please give me circuit.

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December 6, 2014 at 8:20 AM delete

hello vikas, it could be implemented using a current sensor stage.....if possible I'll try to update it in the above article.

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January 2, 2015 at 10:41 PM delete

sir can y guide me whats the exact purpose of first circuit which make a alternate voltage and how its operate

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January 2, 2015 at 10:42 PM delete

and what is 1M pot is it a variable resistor which adjust the frequency

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January 3, 2015 at 12:09 PM delete

the first circuit is explained here:

http://homemadecircuitsandschematics.blogspot.in/2011/12/how-to-make-capacitive-discharge.html

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January 3, 2015 at 12:10 PM delete

yes it's for adjusting the 555 IC frequency

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Anonymous
April 3, 2015 at 11:35 AM delete

Hi swagtam your work is amazing !! .... I'm bulding this circuit as fence charger for Monkeys . So please suggest which one is better .Also in Second one some components values are missing .so what will be appropriate values of these components for monkey repellent fence.

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April 3, 2015 at 5:20 PM delete

Thanks anonymous,

According to me the first circuit is easier and recommended for your purpose, although it could be a bit bulky, but can be built with minimum hassles.

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January 16, 2016 at 8:39 AM delete

hi Swagatam
i made this fence circuit but its working fine for 1 minutes
after 1 minutes traic BT136 getting hot and spark stops
whats cause for that ?

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January 17, 2016 at 11:17 AM delete

Hi mukpti, you can connect a heatsink with the triac or use a 10ohm/5 watt resistor in series with its supply leads

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January 18, 2016 at 10:33 PM delete

thanks for reply
now am changing from 230 ac to 12 dc power supply options
for that i am going to replace bt136 with tip122 and 1k resistor with 100 Ohms that connects to tip122 Base
but i not sure with 3 legs of tip122
1st leg of tip122 connect with output from timer 555
2nd leg with TR2 and 3rd with ground wire
is that correct ?

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January 19, 2016 at 9:43 AM delete

I can specify the leg orientation here, but it would be better if you check it through an image.

just type and search TIP122 datasheet and you'll be able to get the complete info regarding the device, or you can click the "images" option in Google search for getting an instant view of the same

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January 19, 2016 at 11:34 AM delete

Thanks a lot
i made it working but still tip222 getting hot

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January 19, 2016 at 4:44 PM delete

it will get hot, you will need to add a heatsink to it.....also try increasing its base resistance from 1K to may be 22k or even higher.

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January 20, 2016 at 12:05 AM delete

can tip122 replace with MOSFET irfz44 in 12v dc model or BT136 replace with MOSFET irfz44 in AC230 model to solve hitting problem ?
thanks

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January 20, 2016 at 8:14 AM delete

mosfet cannot be replaced with BT136....it can be replaced with TIP122 in the DC model

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January 29, 2016 at 11:37 PM delete

Hi will this work on a colourbond roof? I'm desperate to stop intruders, thank you

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January 30, 2016 at 10:38 AM delete

the wiring will need to be done as done for fences, if you just connect it to the roof it won't work

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February 6, 2016 at 3:56 PM delete

can we remove TR2 and use direct 230 ac ?
if removed tr2 and trigger SCr from 555 will work ?
please see this
https://drive.google.com/file/d/0BzbroLfbdv4haE53eWxvc0Vmdk0/view?usp=sharing

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February 7, 2016 at 7:49 PM delete

In your drawing the SCR will instantly burn, since it's directly connected across the mains...and anyway it looks dangerous.

instead, you can try one of the designs shown in the following article:

http://www.homemade-circuits.com/2013/01/make-this-enhanced-capacitive-discharge.html

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