Decided to make an electric slug fence yesterday, after my new autumn crocus shoots got eaten for the second night in a row.
PP3 (9V) battery, in series with a 470 ohm resistor and a high efficiency LED (plus the earth rod resistance). The LED lights to tell you there's some leakage current (high efficiency one means you can see even fraction of a milliamp leakage at night). It flashes quite brightly when a slug touches the contact. Given the dramatic effect on a couple of slugs and a snail which I saw approch it last night, I suspect a much lower voltage would work fine too. It's probably not safe to use such a scheme if you have livestock nearby, due to their vulnerability to very low earth leakages.
Construction is 25mm PVC conduit with 12mm galvamised capping screwed to the top. The profile of the capping is perfect for rain water shedding from the top. I tried a deluge from a watering can rose, and even that didn't cause the LED to light. Just touching the rail whilst kneeling on the ground generates enough current to light the LED though. Water droplets bead on the surface of the PVC, so it won't conduct. It might be that it needs lifting and wiping clean occasionally to maintain this, but I haven't had it deployed for long enough to know yet. Ground needs to be very level. I filled in a couple of dips under the fence with some old building sand. A couple of tiny slugs appeared inside the area, presumably sleeping inside the fence when it was positioned. After removal, no more were seen inside. I'll keep an eye out over the next few nights. Can easily test the battery just by touching the rail and ground with a hand. Operation probably requires that the area stays damp, but a) that's needed for the plants anyway, and b) slugs don't tend come out when the ground is very dry.
Hehehehe how are you powering it, can't quite tell from the pics
Brilliant!
Until the animal rights activists (mollusc protection section) get to know about it.
Andrew Gabriel wibbled on Sunday 27 September 2009 11:03
Wow - I was looking at the jar trying to see the 10kV inverter circuit you made...
But I suppose slimy slugs have a pretty low resistance so I can see how 9V really gives them a spike (cf: anyone else, try licking the terminals of a PP3).
You should market that - it's simple and, powered by a pp3 at 9V, pretty idiot proof.
Fantsastic! I've taken the liberty of cross-posting from uk.d-i-y to uk.rec.gardening where I'm a long-term lurker, they'll be interested.
This looks like a good one for the wiki. Would you mind the pic being posted there?
NT
Darwin says to wait for the evolution of slugs with jumper leads.
Tony
Or that adapt their tentacles for burrowing.
you might even be able to do this without a battery! remember the earth clock that uses a copper tic and a zinc covered steel nail. Each copper nail and tack make a cell of about 1 volt of Lecky.
I wonder if they where small enough to crawl fully up onto the PVC then across the capping without touching "ground" at the same time? I guess their slim trail would be conductive enough assuming it was contiguious.
or develop high resistance slime; if the resistance is adjustable they'll be gastropots.
I'm aghast.
Bill
Are there lots of electric slugs in your area? :-)
Can slugs swim? Wondering if a moat around the garden would achieve the same end but maybe have less maintenance requirements (given need for watering plants anyway)?
I was going to make a slug/snail electric fence for my new garden. I already have a 12 volt DC supply nearby so I was intending to run two bare copper wires about a quarter of an inch apart on the timber around the garden. After reading this I will put a resistor in the supply line!
You need a good expense account for moats.
I'm plauged with cats, crapping on the lawn. Any designs for electric cat fences? Prolly need 25v or more to give enough across the cojones to warn them off.
The orange DIY shed(warehouse variety) sells a device that is PIR mounted below a sprinkler. Leave connected to the hose and when an animal walks in front of the sensor it gives a 5 second burst of water as well as making a clicking sound. There is an adjustment for the range of the PIR. Costs around =A325. It does work well and if you keep moving the device around the garden they will avoid the entire place.
You can also buy a device called ssscat which works well(search on youtube to see examples). Shame the refills are only good for 150 sprays unless someone can recommend a safe way of repressurising an air duster can.
Dave
Just occurred to me that I never see slugs on the fence, and potted plants stood on a length of wooden gravel board don't seem to be attacked. It's either the preservative or the surface texture they don't like. Maybe a case for decking after all.
an excellent idea! IMHO tis indeed the littlest b*ggers that do the most eating - anychance AG can do some controlled testing with assorted sized slugs with a tasty hosta/petunia/dahlia/delphinium salad as bait?
cheers JimK
You do all know that slugs won't cross a copper wire even if it is not connected to a PSU.
My wife will be interested in this. But please explain to me what the resistor is for? I'm sure my physics GCSE (grade B, 1988) will stretch to me actually understanding it, but I can't bring enough pre- existing knowledge to understand it on my own!! Also, why the LED?
Perhaps a full "how to build an electric slug fence" guide is required?
THanks
Matt
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