Projects and Fun Stuff! | Electronic
Slug Buster Project
Posted by Beech nut on May 30 2006, (popular)
Disgusting Project Alert - Read at your own risk!
A few years ago, we planted a nice organic vegetable garden. Soon we noticed that some of the shoots were getting eaten up almost as fast as they were growing. We didn't see any bugs but we did see a lot of mucus trails. So at night we went out with flashlights and found nearly one hundred snails. Yecch! By the way, during the day they hide under things in the garden and in the compost bin. We got rid of all the snails. Problem solved, we were so smart!
Wrong! So we went out at night and looked closer... there were slugs... lots of them, up to 4 cm long. So we used long nose pliers and miscellaneous tools to pick them off the plants. It was really difficult to pick them up or squash them. If you squash them in one part, they just get bigger in another. Double yecch! What to do 
!
There was no way we were going to use snail bait (arsenic) and contaminate the soil forever, along with risking our dog's health. So I made a little slug zapper. It's no more disgusting than putting salt on a slug, and a lot easier to use on the baby slugs (4 mm) that occur in the spring around here. We also tried the another supposedly "humane" method, to sink a small saucer of beer in the garden. The slugs sniff it out and drown. It works...sort of... if you're willing to clean out the bloated slugs and snails 
every day.
If you're easily grossed out, stop here. Oops, probably should have stopped earlier. On the other hand, if there's a bit of a 5 year old boy in you, well, maybe this will fascinate you.
The slug buster generates a small current which passes through the slug. I thought that would kill the slug. I was wrong 
. It instantly extracts fluid out of the slug! So sometimes the now much smaller slug slithers off covered by a big glob of mucus. Sometimes the slug will die, and after a couple days in the sun, the carcass will be hard like a little stick. But, get this, here's the gross part... usually other slugs will swarm the dead one and eat it.
The slug buster I will present has a larger capacitor to help kill the slug. But it's not really the whole solution, as what I found is that once the slug mucus comes out it covers the electrodes and shorts them out. The output voltage of the slug buster goes down to near zero, because the inverter has a high output impedance. Even changing to a more powerful inverter is not a good solution... the coductive mucus will just cause most of the energy to be dissipated in the inverter, and your batteries will die quickly. I think a second generation slug buster would be a constant power output device. After the initial high voltage pulse, it wuld produce a low voltage at higher current capability. In DC-DC converter terms I think that would be a buck-boost converter, or maybe a dual output supply would work too.
I did notice that if you hold the button down. and poke the slug two or three times, the electrodes don't get covered in mucus and the slug always dies. Sometimes some guts come squirting out of the slug. Yuuuuck! 
Slugbuster.png
TrackbackBeech nut Associate 83 posts registered on May 18 2006 |
OK, here's the overall design. There is no resistor where D1 is because I used a cheap inverter which was basically a single transistor oscillator coupled through an audio transformer for voltage boost. The output resistance of the transformer is enough to protect the circuitry. You can get DC-DC converters like this (which are meant to power EL panels) from places like: 213/ELECTROLUMINESCENCE_KIT_.html I would suggest replacing the AAA batteries with something beefier, or better yet, finding an inverter with a 6V or 12V input. Don't forget to check out Safety Discussion Board. R2 is there to slowly discharge the capacitor when the unit is switched off. 100K and 330uF give a time constant of 33 seconds, so after about a minute or so, the voltage on the cap should be safe. The neon bulb is there as a warning that the cap is still pretty highly charged. After the neon bulbs goes out, I would wait for another 30 seconds or so for the cap to discharge to a safe level. If the neon bulb doesn't go out for more than two minutes after power off, I would guess R2 is not connected or the wrong value. The electrodes I used were just two small nails, approx 4mm apart, to get the little slugs. You'll probably have to wipe off the tip of the ground frequently to get rid of mucus. The mucus also shorts out the output, so you might as well release the button then. The short is indicated by the neon bulb going out, and usually you can hear the whine of the transformer sweep to a frequency too low to be heard. |
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