Simplest Way 13 KV To Charge A 9 KV

[abk111]

Simplest way to use a 13 KV, 1 / sec discharge to produce a 9 KV, 5 / sec discharge when engaged?
Guessing this would involve charging a capacitor (or battery) that will then be able to prodice the 9 KV.
Ideally would like to sustain this 9 KV for 10 sec on, 20 sec off, cycle for 3 minutes, then disconnect from the 13KV source.
Thanks

 

[hevans1944]

Where are you getting the 13 kV from? This sounds dangerous. What is your application? What load does the 9 kV discharge into? Will any animals be harmed?

 

[davenn]

please answer with all project info
else I will close the thread

 

[abk111]

I put up an electric fence after about $10,000 dollars in damage and 5 years of chasing deer out of my orchard / garden. DNR encouraged me to have hunters come in and harvest them, but am trying to be as humane as possible.

Also have a problem with rats and there is a product called the Rat Zapper that is supposed to be the most humane control of rats. Rat Zappers are about $50 and a set of D batteries about $20 (plus shipping). I am trying to make similar that uses the electric fence as a power source. Will be enclosed and safe, and too small for cats to enter.

I would never want to harm harmless creatures.
Not sure what the load would be.
Thanks

 

[hevans1944]

It is far from humane to allow a deer population to grow to such numbers that the deer seek food from men. Here is Ohio, such misguided attempts in the past have resulted in deer devastating crops, even entering and destroying green houses, because of their large numbers. Controlled hunting is a way to "thin the herd" to manageable numbers. Deer are naturally shy creatures and will stay out of sight if there is sufficient natural habitat to support their population. Unfortunately, natural habitats as well as predators are disappearing, leaving the deer to procreate prolifically and (as you have discovered) destructively. So, invite a few hunters to shoot Bambi and perhaps his mother too. The meat that is harvested will not likely go to waste.

An electric fence may or may not deter deer. Deer are pretty good at jumping fences, except maybe barbed-wire fences... I have seen dead deer who attempted to jump a barbed-wire fence, got caught in the barbs, and died there of exposure. In any case, commercial electric fences are relatively safe for humans, unless you try to urinate on one. The fence is designed to deliver a pulsating, high-voltage, low-current discharge that is extremely uncomfortable for cattle and horses, but not lethal. The same is not necessarily true for whatever contraption you build that can deliver 9 kV for ten seconds. Depending on the current available, this could easily be lethal. I doubt you can, or should even try, to use your electric fence "buzz box" for this purpose.

As for rats... I hate rats. The last one I encountered was about forty years ago in the basement of a rental property my brother was living in. I stomped it to death after cornering it with a broom. Back then, there were no Rat Zappers available. You either called a professional exterminator who trapped or poisoned the rat(s) or found a way to do it yourself. The Rat Zapper does appear to be a humane way to lure and electrocute mice and rats. There are no electrically exposed parts, and you just slide the dead animal out the end. I would go with the commercial product and forget about any "do it yourself" scheme.

 

[abk111]

The fence is working. I used a combination of the leaning and 3-wire designs.
The Rat Zapper product is an expensive way to go and I would have to build something for each one anyway to protect from weather. Would like to make at least 4 of them.

The below description for the Rat Zapper is what led me to my original plan (to slightly exceed those numbers):
"delivers a quick, humane 8,000 volt shock. Since rats have the ability to restart their hearts, the shock is applied for 2 minutes ensuring a high kill rate."

 

[hevans1944]

It could be beneficial to obtain a Rat Zapper and "reverse engineer" it to allow you to construct three more. I would be particularly interested in how the voltage is applied to electrocute the rat. Perhaps a gridded conductive floor? Alternating conductive metal strips? Or perhaps the bait container could serve as one electrode and a conductive floor the second?

... the shock is applied for 2 minutes ensuring a high kill rate."

This would help explain why these puppies go through $20 worth of D-cells in a few days.

I did find an ancient thread on another forum dating back to 2008 that discusses one man's attempt to solve his "rat problem" in Florida using all manner of creative and inventive schemes, including the purchase of two Rat Zappers which worked well but ate up batteries. Neither this guy nor the responders to his posts appeared to be particularly gifted in the art of electronics, or electricity for that matter. There is a picture of a Rat Zapper with a dead rat inside, uploaded from one of his posts. I would post it here, but that might violate someone's copyright. Go visit the site and take a look. It looks like there is a large metal plate with a visible wire attached at the entrance, and another plate further in towards the bait. Applying 8 kV between the two for two minutes should be effective. The walls appear to be metal plates too, perhaps also connected to the entrance plate. No indication of how the presence of a rat is detected to discharge the zap that kills them. There are many ways to detect rat presence but only a few ways to deliver the lethal jolt of electricity. Perhaps a relay contact would be sufficient.

I am not sure that "How to construct a Rat Zapper" is an appropriate topic for this site, but I will let the moderators decide that. If I had a rat problem I would surely give it a try, but then I do know a thing or two about 'lectricty. This is not a project for an amateur..

 

[abk111]

The plates / switches / relays are not a problem.
The challenge for me is making use of a power source that is already where I need it.
IOW, how to capture that 13 KV (1 pulse /sec) and utilize that to power the rest. I'm not familiar enough with the different capacitor / ultra-capacitor technologies to know what is possible.

I could not find a patent for the Rat Zapper. Nor info on the exact timing involved.
It may be that the Rat Zapper's 8 KV is applied 1 pulse /sec and thus a "direct" connect to the fence is more than enough.
Guess I could get one RZ and measure what it actually does.
Of course then I would need help with a circuit to measure this 8-13 KV without frying my multimeters ;-).

 

[hevans1944]

It is fairly easy to build a high voltage probe for a multimeter, at least for measuring DC and low-frequency AC. You just solder together a series string of high-value resistors and place them inside a small PVC tube of appropriate length. I happen to have a bunch of surplus 100+ megohm resistors that I often jury-rig as a temporary high-voltage divider. You can also purchase high voltage probes for multimeters at fairly reasonable prices. Tektronix has a high-voltage probe for oscilloscopes, but it is a bit pricy.

So, I can see why you would want to "steal" a little power from your electric fence to run a Rat Zapper. That does sound like it would be doable, but I don't know what kind of voltage the electric fence provides... is it in the form of high-frequency AC pulses? I do know the fence voltage must be current-limited by design, but some research is necessary to determine how that is done and how it would affect your ability to "charge up" a Rat Zapper.

IMO it would take a significant amount of energy to effectively electrocute a rat. One pulse per second from the electric fence is not going to do the job. You would have to store that energy in a capacitor and then wait to discharge it through the rat. It may take several minutes to accumulate enough charge from the fence to do the job, so it would have to be a "one-shot" discharge of sufficient amplitude and duration, perhaps as long as two minutes, before it could "fire" again. Of course if it kills the rat in two minutes there is no need to recharge that particular trap until you dispose of the rat. There is also the minor problem of automagically disconnecting it from the fence after it kills a rat and before you empty the trap. That might be necessary to allow multiple devices to operate at the same time from the fence wire. I would also add a little LED to indicate the device was on and had NOT been triggered. LED off: dead rat inside.

Do you have any information on the electric fence you are using, such as model number, length of wire it is designed to energize, etc? It is likely that you will need some high-voltage rectifiers as well as largeish capacitors to obtain and store power from the fence. This stored power would possibly have to be increased in voltage with a DC-to-DC converter to provide sufficient voltage and current to electrocute a rat, so we are getting into a more expensive design area. It might make more economic sense to buy a commercial Rat Zapper and then figure out a way to power it from your electric fence rather than the batteries it was designed to use. I am sure there would be a commercial market for such a "power converter" device, so that is the first thing I would consider building. Just set your RZ on the ground and clip the "power converter" wire to your electric fence. A few minutes of "charging" and it is good to go.

If I haven't made it clear yet, the electric fence doesn't provide enough power to electrocute a rat. This is by design. You need to take power from the fence at whatever rate it will provide and save it up in a capacitor (or a re-chargeable battery, but I would avoid that) until the stored energy is delivered to the rat in sufficient quantity and duration to ensure the rat is killed. We can probably help you with that here.