In article ,
Matty F writes:
On Sep 28, 9:25 pm, larkim wrote:

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?

The resistor would be just to limit the current in case of a short,
e.g. a whole pile of dead slugs across the wires!. I already have a
fuse but I don't want that to blow or I could lose my garden
overnight. According to the OP, only a very small current is enough to
stop the slugs.

Yes. I didn't want to kill them, because a line of smoldering slugs
around your flower bed doesn't look good, and they are food for things
like hedgehogs.

Also, I have an LED to let me know if there's any current leakage,
and doubles up as a battery test. In the event of a slug arriving
with a crowbar, I need to limit the LED current to 20mA to avoid
damaging the LED. If you want to see if it's working, the LED flashes
when a slug actually gets a belt. I also used it to test the effect
of watering the area.

Also as I mentioned before, I want to limit ground currents, as I
don't know what effect it might have on other wild and domestic
animals which roam around, and I have no wish to harm. I do know
livestock is very seriously affected by leakage currents at levels
you can't even feel, which is why you have to be very careful with
earthing of electricity supplies on farms.

--
Andrew Gabriel
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