Solar Powered Electric Fence from electric fly swatter and garden lights

[Claptrap]

Hey everyone, I'm working on a little project but circuit design isn't my area of expertise. I want to build a little electric fence to put around some potted plants and keep the squirrels away. There isn't an electrical outlet nearby, so I want to rely on solar power.

I bought an electric fly swatter from Harbor Freight and two solar garden lights. The fly swatter runs on 3 volts, and each garden light has a 1.5 volt battery. I want to wire the batteries in series, but if I'm not mistaken, won't that mess with the charge controller circuits on the garden lights? How can I accomplish this?

 

[audioguru]

A solar garden light operates on a low current but the fly swatter needs much more current. The battery in a solar garden light is 1.2V, not 1.5V.
If you use a much larger 3V solar panel and two 2500mAh AA Ni-MH cells (2.4V total) then I doubt the cells can operate the fly swatter circuit all day on one charge. Also the circuit in the fly swatter will probably overheat when running all the time anyway. It is designed to operate for only a few seconds at a time.

Design a circuit to detect that a squirrel is there and it turns on the fly swatter for a few seconds. It does not matter that two solar garden lights are connected in series together.

 

[Claptrap]

The flyswatter circuit is basically a transformer to step up the voltage and a capacitor to store the high voltage on the other side. There was a resistor in parallel with the capacitor to bleed off the charge, but I removed that. Will the circuit continue to draw power while it is activated? Will the constant charge damage the capacitor?

 

[audioguru]

The fly swatter is powered from DC, not AC. A transformer does not work with DC, it needs AC. So there is an oscillator that uses battery power to feed the transformer. The oscillator uses much more current than a solar garden light can supply.
The capacitor is fine with a continuous charge but you will not have one because of the mismatch between the high power fly swatter and the low power solar garden light.

 

[Claptrap]

Let's say I have two 1.2v AA batteries, wired in parallel. I have already determined that this is capable of charging a shock. If the unit charges up the capacitor but nothing contacts the wires to discharge it, how much drain will this have on the batteries throughout the day?

 

[audioguru]

I have never measured a fly swatter. If its oscillator is running then it is draining the batteries and maybe making the oscillator transistor so hot that it fails. A solar garden light solar panel is too small. It cannot charge two AA cells in parallel in one day, maybe in a few sunny days. Then the zapper will work for part of one day and rest for a few days while the batteries are charging.

 

[Claptrap]

I was going to try to wire two garden lights in parallel by having jumper wires attached to the battery terminals in parallel and then running that to the flyswatter unit. However, I'm measuring the amperage and it doesn't seem to be doubling it, so I don't know what I'm doing wrong. Harbor Freight sells a solar fence charger with a solar panel that's about the same size as just one of my units, and they claim it will charge 3 miles of fencing, so I suspect there's a way to do this. Maybe it would be better to just consolidate the panel and battery from the second light onto the first to make it more powerful, instead of trying to wire two complete units together?

I don't know what the effect will be on the flyswatter unit, having it on 24/7, but someone on youtube made a video charging a fence with a similar unit, and the device is only $3, so if I burn it out then I'm okay with the learning experience.

 

[audioguru]

A Cheap Chinese solar garden light operates the LED at a dim low current. If the battery is AAA size then it is 300mAh (that is printed on it but it is actually 200mAh). A Duracell AAA Ni-MH battery has 4.25 times more capacity at 850mAh.
If the cell is AA size then it is 600mAh (actually 500mAh). A Duracell AA size Ni-MH cell has 5 times more capacity at 2500mAh.
Likewise, the solar panel size is 1/4 to 1/5th it should be.

 

[tcmtech]

Harbor Freight sells a solar fence charger with a solar panel that's about the same size as just one of my units, and they claim it will charge 3 miles of fencing, so I suspect there's a way to do this.

Yes, They don't continuously power the fence with high voltage but rather give it short pulses every second or two.

Depending on your skill sets and availability of parts you can make a similar circuit from an old ignition coil or old CRT screen type computer monitor or TV flyback coil and a few other components. Getting it to run off of bare minimal voltage and power like you want may be a bit more challenging though.

 

[large_ghostman]

Dont underestimate squirrels, one day you will look out the window and see one with wire cutters and a multi meter taking your device apart....

You can buy fairly cheap electric fence energizers that are run off 12V sealed lead acid batteries and solar charged. We use a mains powered one because of the fence length, but for what you want one of the small solar unit ones would work, be careful using flybacks etc. Its a short distance from pain to death when messing with those.

Pulse is around 600ms on and 1.2 seconds off for a fence one, you could stretch that to two seconds off and 500ms on. But dont be surprised if they get around it somehow, in Devon we had a constant battle with squirrels, smart beggers and always got the upper hand.

 

[dr pepper]

You can get a nasty crack of a Tv flyback even with 1.5v, there are vids on youtube of people building them.

 

[Claptrap]

So, progress thus far. I have wired the battery (rated 1500 mAh) and solar panel with one of the lights in parallel with the solar panel and battery of the other. With this power supply, I charged the modified flyswatter device. After an hour, I detected that the unit was about 1 degree Fahrenheit warmer than the surrounding surface, and all components were room temp to the touch. I left the device turned on for 11 hours straight, and the device was still able to produce sparks when the contact wires were touched. I still need to see if having it hooked up to an actual wire fence will cause more static discharge, but I think this system is actually going to be viable.

 

[large_ghostman]

So, progress thus far. I have wired the battery (rated 1500 mAh) and solar panel with one of the lights in parallel with the solar panel and battery of the other. With this power supply, I charged the modified flyswatter device. After an hour, I detected that the unit was about 1 degree Fahrenheit warmer than the surrounding surface, and all components were room temp to the touch. I left the device turned on for 11 hours straight, and the device was still able to produce sparks when the contact wires were touched. I still need to see if having it hooked up to an actual wire fence will cause more static discharge, but I think this system is actually going to be viable.

Now the bad news no one has mentioned.....

Keep the line absolutely free of vegetation!! It will drain the battery quickly or overheat your unit. Our mains fencer is designed for cattle, i totally forget its rating but its enough on high to throw a grown man onto the floor if your near a earth point, the low setting is 4kV but i think the high setting is 10-12kV (really dont remember now). When we had the farm we had miles of fence wire to run, here we run maybe 2-3 miles off it, so its well under spec for load. If grass or weeds grow up and touch the bottom wire the unit gets hot if enough veg grounds it.

Actually its my fault, it has two fence lines and a ground, i mixed up the lines as the one i have at the top is designed to go at the bottom. That wire is there to detect vegetation, grass touches it and the unit ramps up a bit and gives faster pulses until the veg dies!! Only now we will get 5 foot weeds until it kills them .

Seriously though a fly swatter isnt designed for this, £30 buys you a unit designed for the job and part solar powered. Go careful with it, first time i grabbed the cattle line isnt something i will forget. BTW i hope its grey squirrels?

 

[audioguru]

Does rain also kill the high voltage circuit?

 

[large_ghostman]

Does rain also kill the high voltage circuit?

Dsont hurt the real systems, I live in Scotland so i can categorically state state rain does not kill electric fence energizers! No idea how they fair in the sunshine........ If we get any i will report back . Rain does however make them hurt more if your wearing fishing waders, which is really messed up if you think about it.

grabbing the fence with both hands dosnt seem to hurt as much but that is highly subjective, might just be its harder to throw you a distance when you got it by two hands . Snow makes them warm if they short out against a post or whatever, BTW most use stand offs from the main fence line. Few people attaches the wire directly to a post, well few with sense.

 

[audioguru]

Rain causes cheap Chinese solar garden lights to rust away in a couple of months because they are poorly sealed.
Sunshine causes the cheap plastic covered solar panels to get sunburned and stop within a few months, but new ones have a glass cover that lasts for years.

 

[large_ghostman]

Rain causes cheap Chinese solar garden lights to rust away in a couple of months because they are poorly sealed.
Sunshine causes the cheap plastic covered solar panels to get sunburned and stop within a few months, but new ones have a glass cover that lasts for years.

Rust away in a few Scottish weeks then lol, sun is not a problem here. I did see it once but was so quick i am still not sure it wasnt just a orange coloured tennis ball in the sky

 

[alec_t]

Rain causes cheap Chinese solar garden lights to rust away in a couple of months because they are poorly sealed.

They last a good bit longer if, before first use, you smother everything except the internal switch with a clear varnish.

 

[large_ghostman]

They last a good bit longer if, before first use, you smother everything except the internal switch with a clear varnish.

Now and then just before summer, local cheapo shops do them 6 for £1. Used to be my favorite source of cheapo solar panels.