DIY electric fence energizer using battery, capacitor, pwm oscillator, dc-ac buck converter and ignition coil

Thread Starter

arnoldelsur

Joined Jul 4, 2022
4
has anyone built an electric fence energizer using battery in parallel with a capacitor, pwm oscillator, dc-ac buck converter and ignition coil?
 

MaxHeadRoom

Joined Jul 18, 2013
25,469
The one i just put together uses a 8 pin pic, outputs a single pulse every second to an automotive waste-spark ignition coil.
 

Thread Starter

arnoldelsur

Joined Jul 4, 2022
4
The copy I had on a thumb-drive appears to have been wiped, but it is very simple a 12f628, 78L05, 5v gate drive Mosfet, and a waste spark coil.
The primary was driven with a couple of 10ms pulses every 1 second.
I have no idea how to build using those. Hope you can find it but thanks anyway!
 

crutschow

Joined Mar 14, 2008
30,116
Designed this version a few years ago for our farm in RSA, works OK.
For better reliability I would eliminate the relay and change U1 to a higher voltage/current MOSFET with a high voltage Zener drain-gate for protection, to directly drive the coil.
Operating @ 1 pulse/sec I would think there's a good possibility the relay could fail after a few years operation.
 

ericgibbs

Joined Jan 29, 2010
15,726
hi Carl,
The fence is in RSA, in a high electrical storm area, we have found that strong induced electric fields into the fencing can take out semiconductor drivers.
The fence has been running since about 2008 with minimal problems.

When you consider a 1/sec rate and the coil/contacts/cap are from a motor vehicle, where the distributor is running at a few thousand sparks/min, they last a few years in the vehicle.

Eric
 

crutschow

Joined Mar 14, 2008
30,116
When you consider a 1/sec rate and the coil/contacts/cap are from a motor vehicle, where the distributor is running at a few thousand sparks/min, they last a few years in the vehicle.
I was more concerned about mechanical failure of the relay, not contact failure, as mechanical relays have a rated operational lifetime, typically in the neighborhood of a million cycles or so.

If yours has been operating since 2008, it's amazing to me since that's about 400 million cycles.
Must be a very durable relay.
 

ericgibbs

Joined Jan 29, 2010
15,726
hi C,
You are obviously not a small stock farmer, the fences are not run 24/7, they are only energised to keep our livestock off certain areas of ground, or straying during daylight hours.
During the night, the animals are housed in their respective safe lock up buildings.

It's not rocket science.;)
E
 

crutschow

Joined Mar 14, 2008
30,116
You are obviously not a small stock farmer, the fences are not run 24/7, they are only energised to keep our livestock off certain areas of ground, or straying during daylight hours.
During the night, the animals are housed in their respective safe lock up buildings.
No not now, but where I grew up on a dairy farm in Wisconsin the cattle were free to roam in the pasture day and night.
It's not rocket science.
Never thought the number of operations a relay can make before failure was. :rolleyes:
And even if it's only active during daylight hours, that still would be in the neighborhood of over a 100 million cycles.
 
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MaxHeadRoom

Joined Jul 18, 2013
25,469
I just needed mine to keep the deer off of the garden plants, I use a timer to operate it during hrs of darkness.
'I don't have a fence, as such, just a #12 g strand of galvanized iron wire, strung about Deer 'nose' height' :cool:
So far the night camera has proved it works well.
 
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