Need help with electric fence charger

crutschow

Joined Mar 14, 2008
34,285
The energy stored in an inductance is ½LI², so you would need about 20A of primary current to store 1J of energy in the typical 5mH inductance of the ignition coil primary.
Unfortunately, the coil will likely saturate before you reach that current level.

Alternately a capacitive discharge into the primary would require a 200μF cap charged to 100V to achieve 1J of stored energy.
 
Last edited:

Thread Starter

lukimaister

Joined Sep 18, 2020
25
The energy stored in an inductance is ½LI², so you would need about 20A of primary current to store 1J of energy in the typical 5mH inductance of the ignition coil primary.
Unfortunately, the coil will likely saturate before you reach that current level.

Alternately a capacitive discharge into the primary would require a 200μF cap charged to 100V to achieve 1J of stored energy.
So it's basically impossible, to get 1J. Then how do the others get it?
 
Last edited:

crutschow

Joined Mar 14, 2008
34,285
If you can operate from the mains, and really need 1J of spark energy, then I suggest a capacitive discharge approach.
You could do that with a 220V-to-110V isolation transformer (not an un-isolated travel adapter), a diode bridge, a charging resistor, an SCR, a PUT (Programmable Unijunction transistor) or 555 to trigger the SCR, a 100μF 200V capacitor, and an ignition coil.
 
Last edited:

Thread Starter

lukimaister

Joined Sep 18, 2020
25
If you can operate from the mains, and really need 1J of spark energy, then I suggest a capacitive discharge approach.
You could do that with a 220V-to-110V isolation transformer (not an un-isolated travel adapter), a diode bridge, a charging resistor, an SCR, a PUT (Programmable Unijunction transistor) or 555 to trigger the SCR, a 100μF 200V capacitor, and an ignition coil.
Yeah I'll be making mains one (230V), as its easier.
I've come up with some block scheme. What do you think, could that work, is it too complicated?

EDIT:
The second picture is problably the easiest circuit, I just need to calculate the values for components.
 

Attachments

Last edited:

crutschow

Joined Mar 14, 2008
34,285
That circuit should work but you don't show an isolation transformer, which you must have.

You will need a higher current diode than a 1N4148 to charge the capacitor.
 

ericgibbs

Joined Jan 29, 2010
18,766
hi luki,
When you started this Thread you said it was school project.
You said that some of the earlier proposed circuits created a too higher voltage.

It appears now that you are proposing a non isolated mains powered electric fence for 1000 mtrs, with at least 1 Joule.

Is this a school project.??

E
 

Thread Starter

lukimaister

Joined Sep 18, 2020
25
hi luki,
When you started this Thread you said it was school project.
You said that some of the earlier proposed circuits created a too higher voltage.

It appears now that you are proposing a non isolated mains powered electric fence for 1000 mtrs, with at least 1 Joule.

Is this a school project.??

E
It's my last year in High school and we had to choose what we'll make for our 4th subject final exam. I chose an electric fence energizer, because it could be useful at home. At first I wanted to make one with 12V battery and add solar, because we have some fence that is far away from any el. socket/supply. But then after your help, I realized that 12V is not enough to get at least 1J out of it. I know that 12V ones can provide high energy, but their circuits are far too complicated for a beginner like me.
 

Thread Starter

lukimaister

Joined Sep 18, 2020
25
Yeah I'll be making mains one (230V), as its easier.
I've come up with some block scheme. What do you think, could that work, is it too complicated?

EDIT:
The second picture is problably the easiest circuit, I just need to calculate the values for components.
As for isolation transformer, you mean I should have one at beginning for protection. Could I just use a fuse, or do I need both.
 

shortbus

Joined Sep 30, 2009
10,045
Those circuits use a car coil, and that likely can't achieve the 1J energy he wanted.
Even if that is his goal, it isn't needed. I have my doubts if even a store bought one does it. Chemlec if you read all he wrote explains a lot about what is needed to charge a fence, and his were and are in use in many places world wide.
 

crutschow

Joined Mar 14, 2008
34,285
As for isolation transformer, you mean I should have one at beginning for protection. Could I just use a fuse, or do I need both.
You need an isolation transformer to protect against the electrocution danger of the mains voltage to ground in your circuit.
The transformer isolates the voltage from ground.
A fuse does not provide isolation.
 
Last edited:

Thread Starter

lukimaister

Joined Sep 18, 2020
25
Hi,

I've been trying to calculate the resistances, and I don't quite get the timing of circuit.
So C1 should recharge in less than a second (in 1s pulses), which is controlled by R1-2. But the discharge should be coule of mS, which is determined by cap value and load resistance (which should be low).
C2 chargetime depends on R3-4, which constrols the rate of pulses. So does C2 need to be charged only to 32V if the breakover voltage of DIAC is 32? C2 would also have to discharge faster than C1, so the charging can begin at 0V, right?
But then how can C2 discharge faster than C1?
 

Attachments

Thread Starter

lukimaister

Joined Sep 18, 2020
25
Hi,

Looks like it works.
But isn't the (vc2) like 80V, wouldn't the DIAC conduct constantly. I guess I'm looking at it wrong.
Also why is there R1k for transformer? If possible I'll be using ignition coil, because its cheap and easy to get, otherwise I'll try to get some microwave transformer. I think I'll also need a series resistor for it.
The pulse time is a little too short, lower R4 will fix that.
 
Top