Saturday, 7 June 2008

Electric slug fence

This spring, full of the enthusiasm of novice gardeners, we spent many hours digging up and taming the wilderness that was our new garden.

Then countless further hours carefully raising and nurturing tiny plants from seed through a fragile adolescence indoors on a windowsill before finally planting them out into their new home in the garden.Then the first damp evening: death by slug-horde.

Now. I have nothing personal against slugs and snails: in fact I rather like snails, but when they treat the fruits of our labour so casually it is hard to feel so kindly towards them. So what's a novice vegetable-grower, keen to avoid slug pellets and other chemicals to do?

Well I guess the answer to that question depends upon how handy you are with a soldering iron - and your views on the application of animal rights to slugs and snails.

Personally I would recommend making an electric slug fence, and soothing your conscience (and laziness) by keeping it charged from a solar cell.

Here's one I made earlier:

(In situ powered by a 1.6Ah lead-acid battery)

Connected to the fence itself (available from ebay)

And showing a bit more of the fence in place

(And connected to the solar cell)

It took three goes to get a practical version up and running: the first didn't work at all. The second worked extremely well: turning large snails around in their tracks and (perhaps slightly unfortunately) killing small slugs outright.

However it only offered a couple of nights protection but then drained the battery flat. After several modifications (replacing a power-hungry NE556 timer with a lower power CMOS equivalent, and changing the mark-space ratio of both the driving oscillator and the timing oscillator: longer spaces, shorter marks) this final version should consume about one tenth of the power and be able to run continuously throughout the summer.


* One lower-power dual timer chip (7556)
* One maplin miniature audio transformer (32 ohm : 12 k ohm)
* One BD235 NPN power transistor
* Four 1N4003 diodes
* Various resistors and capacitors


La Ferme de Sourrou said...

Brilliant Alex - I'll share this with my pals in my blog !!

I hope your garden blooms this summer.

Jan said...

I am thinking of building one.

What voltage levels and pule widths did you settle on?

Great job.

Jan said...

It looks like you are using copper strips. How often do have to clean them? Do they tarnish quickly?