Stainless steel and garden slugs killing each other... - Page 1
Forum section: electronics / projects

author: Konkedout
author_rank: Frequent Contributor
timestamp: October 01, 2024, 05:36:30 am
content: I live in the area of Puget Sound Washington. Good for apples, other garden plants, and slugs. Slugs do a lot of damage in our garden.A few years ago, I learned that 9V would dissuade a slug. Experimenting with an old laptop power supply, I found that 18V would kill them right away with all of their mucus oozing out.So I designed a pulser which powers a pair of wires spaced about 1/2 inch (1.27 cm) apart like railroad tracks, laying on top of the garden soil. It delivers a pulse once every 15 seconds or so with a 1/8 duty cycle. The idea is to give the slug a chance to get completely across the pair of wires before zapping it. The pulser delivers 18V which is current limited by a series connected 82 ohm 0.5W carbon composition resistor. (I happened to have a bunch of those; it is good for the purpose.)I am powering all of this with a 40W solar panel, a charging module from Amazon, and a 12V 7 A-H sealed lead acid battery also from Amazon.I initially tried tinned copper AWG 20 hookup wire for the "railroad tracks". Those wires were corroding badly. Galvanized steel wire (same diameter) conducts well enough but was also corroding. So I tried Chinese-made 304 stainless steel also from Amazon. The DC resistance is acceptable. This all kills slugs and generally works, BUT.....Once in a while the stainless steel wire breaks for no apparent reason. Today my wife mentioned to me that it broke right where a slug died. I have googled the question of whether the slug mucus is corrosive but I cannot see that that is the case. The current is limited to (really much less than the calculated 220 mA.) First the resistance of those 82 ohm resistors tends to run closer to 100 ohms, and I have additional overcurrent protection which shuts it down when I short the wires for example. So a maximum current of 50 - 100 mA is more realistic.I would be happy to share my schematic and/or KiCad files for the pulser but that is not the issue.I wonder what the heck is causing my wire to break? I might try ordering some (American made but maybe not?) stainless steel wire from McMaster as maybe the Chinese stainless steel wire is low quality. I do not want to buy gold plated wire!!! Any ideas?

author: IanB
author_rank: Super Contributor
timestamp: October 01, 2024, 05:54:31 am
content: I think your problem is galvanic corrosion.DC current, metal, and damp environments will cause nearly all metals to corrode except for noble metals like platinum. Stainless steel will resist corrosion in electrically neutral circumstances, but it will not survive electric current.A possible solution is to use an AC supply instead of DC. The alternating current will repeatedly "do" and "undo" the corrosion, causing the effect to balance out. But now your electrical supply will become more complicated, and I do not know if it will affect the slugs in the same way. That is something you would have to find out.

author: Ian.M
author_rank: Super Contributor
timestamp: October 01, 2024, 06:05:19 am
content: +1 for IanB's explanation. Another approach to balancing the corrosion that wont reduce the slug-killing effectiveness would be to reverse the polarity after every pulse. This is likely to be less effective at reducing corrosion than using AC as the metal ions travel further from the wires.

author: JohanH
author_rank: Frequent Contributor
timestamp: October 01, 2024, 06:06:49 am
content: Get some hot-galvanized (zink) steel wire from farmer shops. There is specially made wire for electric fencing for cattle. It will last much longer, but will also eventually suffer because you have it on the ground.There is also some nylon varieties with a steel core. I don't know how it affects longevity.Btw, they use pulses 3 kV to 12 kV, with energy 1 to 12 J (just looked it up). Different for different animals. If I remember correctly from when I was a kid, the pulses were every few seconds or so. You could get really stunned if you had good ground contact. It could really kick you down. With rubber soles you could barely touch it, it still stung. Every kid learned you shouldn't pee on the wire!

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: October 01, 2024, 07:01:30 am
content: You should avoid the zink oxyde in a garden IMO, you should use a less toxic sacrificial anode.

author: voltsandjolts
author_rank: Unknown
timestamp: October 01, 2024, 08:29:59 am
content: Titanium isn't a noble metal but it has impressive galvanic corrosion resistance, and titanium wire is fairly cheap. If that doesn't work then, yeh, AC supply.

author: hanakp
author_rank: Regular Contributor
timestamp: October 01, 2024, 08:33:53 am
content: You could try cathodic protection:https://en.wikipedia.org/wiki/Cathodic_protectionPassive sacrifical anode would be easiest, since your device is solar/battery powered. It's a bit tricky connecting the metals together though, the joint must be waterproof, otherwise it will corrode first and it stops working. For active protection, you could add negative DC voltage to both rails in respect to ground (that's how analog telephone lines, pipelines etc. are protected).

author: ejeffrey
author_rank: Super Contributor
timestamp: October 01, 2024, 11:05:02 am
content: A sacrificial anode is only going to provide a about 1 volt of potential, depending on the metals used. That's enough to prevent corrosion from other electrochemical potentials but since you are applying 18V you have to make sure it's connected to the most positive point in the circuit such as the solar panel + terminal.

author: AndyC_772
author_rank: Super Contributor
timestamp: October 01, 2024, 11:18:15 am
content: Is a slug conductive enough that you could detect it by applying a much lower voltage, and only applying a high voltage when there's one across the wires? A low voltage, short duration 'detect' pulse wouldn't have nearly as strong a corrosion inducing effect.

author: magic
author_rank: Super Contributor
timestamp: October 01, 2024, 11:51:24 am
content: I must admit that I don't like slugs, and I like your ideaMaybe mount the wires on a vertical fence, so the corpses fall off faster. Having them laying on the wires cannot possibly do any good in the long run.

author: daniel444
author_rank: Regular Contributor
timestamp: October 01, 2024, 01:07:15 pm
content: i have been using a 0.9mm titanium wire to boil my daily water for a few years now , i bought it surplus , i got lots of it , i would go with 0.9 or 1mm titanium wireits 0.7 ohms per meter for the 0.9mm wire

author: BrokenYugo
author_rank: Super Contributor
timestamp: October 01, 2024, 01:30:41 pm
content: Quote from: Coordonnée_chromatique on October 01, 2024, 07:01:30 amNevermind the zinc, you can assume anything hot dip galvanized is lead containing if it doesn't say otherwise.This honestly sounds like a better way to put various metals in the garden than kill slugs, have you tried any sulfur based products? Nematodes? Permethrin or relatives thereof?

author: tszaboo
author_rank: Super Contributor
timestamp: October 01, 2024, 02:03:43 pm
content: I had a lot of slugs in my garden about 4 year ago. They lived under the wooden decking. Three years ago we renovated it, dug up the soil and since then its the fraction of the number. 1/20th is a good estimate.For your wires, reversing the polarity every 2nd cycle could lengthen the life time, maybe.

author: Randy222
author_rank: Frequent Contributor
timestamp: October 01, 2024, 02:13:08 pm
content: Maybe gold plated wire?I forget the site, but there's a good metallurgy site/forum where you can get all the info on metal and how they react with other environmentals. The slug carries a PH level and that's most likely 90% of the battle.

author: Konkedout
author_rank: Frequent Contributor
timestamp: October 01, 2024, 04:37:17 pm
content: Thank you all for the comments!One or two posts mentioned galvanic corrosion, and that is my best guess as to what is going on.The wires need to lay on the soil so that slugs might crawl across. Slugs are most likely to be marauding when the ground is wet, and there is (maybe a few mA?) flowing between the two wires through the wet soil even when no slugs are present. But that current flow is likely to be spread out. I still think there is something about the slug mucus....I think the problem happens when the dead slug has been laying there for hours.I googled titanium wire; it looks like it is roughly $2 per foot. I am probably using > 100 feet of SS wire right now. I don't think I want to try titanium or gold plated wire.As for chemical solutions; nah we do not use chemicals in the garden. And as science figures out more and more (such as the microplastics in our bodies) I am not eager to change that practice. I like to cook in cast iron rather than Teflon for the same reason.After posting, I was thinking that yeah; alternating the current flow might be what I need to do. Right now I have two of my circuit boards in different locations. One of them uses all four of its sequentially pulsed outputs. The other I think uses two of them. But for all of that, there is one sort of "common ground" which goes out to one wire of every pair of "railroad tracks." It is not so truly a common ground because I think the charging module regulates the negative side so that the negative terminal of the solar panel is not at the same potential as the negative terminal at the battery and at my slug wires or circuit boards. But this does not matter so long as I do not short those points.I am thinking to try a complete re-design to output AC instead of DC. This will be significantly more complicated....but that is life. I would like to use a frequency > 20 KHz so there is no chance of human-audible beeping, and also to reduce the size of coupling capacitors. But I would need to confirm that 18V or 20V peak 20 KHz will kill the slug. Maybe the DC current which causes galvanic corrosion is the same thing that kills the slug. But testing this will not be as easy as poking a slug with the 18V output of an old laptop power supply. I need to design, build, and test something - even if it is crude - just to see whether 20 KHz can kill a slug in the same way that DC does.Thanks everyone for your responses!!

author: magic
author_rank: Super Contributor
timestamp: October 01, 2024, 04:49:00 pm
content: 18V AC into grounded 80Ω load is something that any audio amp can drive with ease. Good enough for a prototype

author: Randy222
author_rank: Frequent Contributor
timestamp: October 01, 2024, 05:14:54 pm
content: Quote from: magic on October 01, 2024, 04:49:00 pmWould be neat to learn if any specific frequency frys the slug better than another, using an audio amp and bare wires. Another test might just be using insulated speaker wire with a dummy load at the end, and then change the amp input frequency along with output power to see how that affects the slugs.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: October 01, 2024, 05:27:42 pm
content: I would not use an audio amplifier, far to complicated, Also note you would need a stereo audio amplifier, to get a nice symmetrical waveform at the output.The simplest solution is probably some kind of motor driver H-bridge IC, combined with an oscillator (Maybe a NE555). You could build it with a few NE555's and drive the wires with that too, but you would be limited to it's maximum voltage (Which also happens to be 18V (I thought it was only 15V)).It's important to make it symmetrical to avoid galvanic corrosion as much as you can. Preferably you also put a capacitor in each line so no DC can pass at all.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 01, 2024, 05:38:00 pm
content: Quote from: voltsandjolts on October 01, 2024, 08:29:59 amTitanium doesn't usually corrode anodically, but it anodizes instead. This may make it difficult (non repeatable?) to maintain function.Under the correct conditions, it is indeed attacked; bromide is such a case, at least in my experience, though I'm not sure what else. (Usually it's pretty inert, and is regularly used in electrochemical plating baths for this reason, meanwhile a metal part can still make contact with it somehow.)The only thing that works here is AC (which will cook rather than chemically melt a slug), or inert anodes like platinum ($$$), MMO (pool chlorinator anode), lead dioxide (good luck forging a ceramic into wire), and a few other less effective and harder to use materials.Tim

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 01, 2024, 05:51:33 pm
content: Quote from: Doctorandus_P on October 01, 2024, 05:27:42 pmUh--??(To unpack that:1. A linear audio amplifier is already symmetrical. A "half bridge" or "totem pole" design is typical, so, there's a positive swing and a negative swing. If one were missing,it wouldn't be linear.2. Switching (class D) amplifiers are quite popular, highly efficient, and readily available these days; with a filter network provided, they are electrically equivalent to (1).3. If the output were DC biased (offset), it would cook speakers just as quickly as it would corrode the wires here. Even if the amplifier is such a bad (or archaic) design that a coupling capacitor is required to use it... I mean there you go, coupled and done. Such designs haven't been in use since the 1960s, and who knows if this is what the above had in mind?4. A stereo amp does nothing here. Where is the other channel going?5. If both channels go to each wire, then, that's not stereo, they'd be driven equal and opposite, there's nothing stereo about it, it's mono by definition. The word commonly used for this is "bridged". The resulting H-bridge topology doubles the voltage output from a given supply voltage, which can be handy.6. The whole thing is floating, battery and solar, no ground connection required -- only the wires laying on the ground provides any earth reference, by way of leakage to it. It's SELV, it's not mains powered, no isolation required. Even if a strongly-offset amplifier were used, the offset can simply be subtracted out, say with a battery (or again, dropped passively with a coupling capacitor), and any offset between the device and earth is simply determined by the resistor divider (sort of) between wires and earth.As a rule, I try to avoid (ignore) posts that aren't contributing  to a thread; but this one seems so exceptional, in how irrelevant it is to the present thread, and, seemingly, out-and-out mistaken, that I feel it necessary to point out the disconnects, and misinformation.)Tim

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: October 01, 2024, 07:39:34 pm
content: Quote from: Konkedout on October 01, 2024, 04:37:17 pmI'm not a slug expert, but I know that frequencies above 20kHz have limited effects on the human body. That's why you can touch a Tesla coil and not get an electrical shock because the frequency is so high your nervous system doesn't react to it. I don't know if a slug's nervous system is faster or slower than the human nervous system.So what I think would work fine is just using an H bridge inverter to make a low frequency switching at say 5Hz so it's not very audible, but can still stop a slug. The H-bridge will also allow high currents to flow if needed.

author: daniel444
author_rank: Regular Contributor
timestamp: October 02, 2024, 02:13:02 am
content: stainless is vulnerable to pitting corrosion , where it gets corrosion all in one little spot rather than evenly

author: duak
author_rank: Super Contributor
timestamp: October 02, 2024, 03:39:10 am
content: I also live in the Pacific Northwest and like the idea of dealing with slugs electrically - electrocide? Co-incidentally, I use electrolysis to remove rust from tools and car parts and picked up a few bits and bobs.The sacrificial anode (positive) electrode is oxidized by the reaction with water. Usually, a sheet of mild steel is used because it's cheap but it dissolves far faster than the rust on the cathode. A graphite anode isn't affected but I've never seen flexible carbon rods. (Carbon fiber?)Since most metals will be oxidized, I would be concerned about introducing metallic or organo-metallic compounds into the soil. eg., copper and zinc are considered anti-microbial. Note that they also kill moss. Lead is used as an anode in the acidic anodization of aluminum but I wouldn't try it here.I found that a stainless steel sacrificial anode corrodes almost as fast as one of mild steel. This is important!--> It also releases Hexavalent Chromium which is a hazardous compound, especially if it ends up in a garden. The Nickel is probably bad also.Aluminum and titanium form a very tough oxide layer that eventually gets thick enough to become an insulator. BTW, with titanium, you could also get some nifty colors.AC is probably the easiest and safest way to minimize the corrosion problem. I should give it a try myself.Cheers,

author: Ian.M
author_rank: Super Contributor
timestamp: October 02, 2024, 04:19:38 am
content: I suspect a large thick section scrap aluminum casting would be satisfactory as a sacrificial anode for quite a few years e.g. a gearbox housing or aluminum cylinder head or engine block. It needs to be totally free from paint, oil or grease, and any baked on dark residue should be removed abrasively. Aluminum is a normal component of many soils and is only problematic in acid soils - seehttps://agsource.com/wp-content/uploads/2024/04/F-6278509012-Agro-Soil-Aluminum-Tech-Bulletin_HR-2.pdfso if you have acid soil, pack round the aluminum with plenty of crushed chalk or limestone to keep it safe for nearby plants.Drill and tap or through bolt using zinc plated hardware to attach a heavy gauge insulated wire, preferably 7 strand 10 AWG or similar, with a preferably crimped on ring terminal. Use a light smear of Noalox on the inside of the crimp and the ring terminal when assembling the connection. Clean up all excess Noalox, abrade and degrease the aluminium round the connection and coat with a thick layer of hot tar or polyurethane sealant or marine sealant for min. 1" round the fastener, over the ring terminal and up the wire so no dissimilar metals are exposed to avoid local corrosion.Bury below the frost line - about a foot down should do in the Puget sound area unless in a notably exposed location or at altitude.

author: Konkedout
author_rank: Frequent Contributor
timestamp: October 02, 2024, 05:53:48 am
content: I think I need to build something in order to run a test. Fortunately if I build this I ought to be able to bring a slug (on a small wood plank?) to my lab and not vice versa.If I make this comparator oscillator run at about 20 KHz, Q1 and Q2 should produce a ~ 0-40V square wave with a 40V supply. Then AC coupling through C8 = a 1 uF or larger capacitor of some sort ought to give me a 20V peak square wave with negligible DC current.This design is preliminary/based upon the through hole parts which I have in my lab. Most of the parts I have are SMT but those are too difficult to use without a pcb, and I don't want to get a pcb for one 1-minute test. This schematic is sort of rough; I can adjust values somewhat on the bench to get it to work as I want....

author: Zero999
author_rank: Super Contributor
timestamp: October 02, 2024, 09:04:24 am
content: Why 20kHz?I don't know about slugs, but data from humans and other mammals shows that high frequencies are less likely to be lethal than mains frequencies and DC, because the nerves typically don't respond to higher frequencies. 20kHz just causes heating due to I2R losses, which might be enough to cook a slug, but are probably less likely to electrocute it, as DC does.In humans, mains frequencies are typically the most lethal, compared to much higher frequencies or DC. Again, with slugs it's probably different, but I doubt 20kHz is the way to go.If mains isn't available (obviously use a step down isolation transformer if it is: 12V will probably do), then DC with an inverter will do.Why not use an H-bridge, that way a low supply voltage can be used? An H-bridge can be made to self-oscillate by adding RC circuits.This circuit oscillates at about 50Hz. It's a basic astable multivibrator, but with extra transistors added to pull the output up.https://en.wikipedia.org/wiki/Multivibrator?useskin=vector#Astable

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 02, 2024, 09:15:33 am
content: Quote from: duak on October 02, 2024, 03:39:10 amCorroded aluminum is pretty non-toxic, in and of itself, though various alloys do contain a little copper, zinc, iron... The majority is Al, Si and Mg though, all pretty innocuous.Probably worth noting that most all of these metal oxides are insoluble, and tend to remain in place in the soil. So, even if Cu, Zn, Ni, etc. are present in toxic levels, with respect to one or another thing in the soil, it's not like the whole area will be contaminated, in just a few months, or decades hence. Plenty of things grow in or around galvanized metal, lead cladding, copper sheet, what have you. Not that their heavy metal content in turn might be something you'd want to eat, but at least to say it's not fatal for the direct things growing there.QuoteDoubtful, though I don't know offhand if the amount will be actually zero, or at what rate if not. If there's metal to corrode, that has the lower oxidation potential than Cr(III) to (VI) does, and Cr(OH)3 is pretty damn insoluble/nonconductive so makes a poor target for further oxidation. Cr(VI) can likewise be reduced by free metal. To reduce, chromate has to be in solution; precipitated chromate could persist, but then, it's likely not too soluble in general, making it less of a hazard (lead chromate is surprisingly not very hazardous, despite what it's made from... not that I would bathe in the stuff..!).Alas, I never tried the experiment, back when I had chemicals and a place to do it... Dissolved stainless, yes, but not anode-ized it, in a neutral pH.Believe I've electrolyzed with it in alkaline, with no yellowing of the solution seen.Anyway, the resulting crud, predominantly (hydrated or as hydroxides) Fe2O3 and Cr2O3, extraordinarily insoluble, neutral, more or less inert in soil; and NiO, also quite insoluble, but a known toxin you don't want huge amounts of. (I mean, nickel occurs in soils all over, if not very much; its mere presence isn't a problem, it's the amount that matters. It is toxic in large amounts, except to a few extreme species -- New Caledonia has some *wild* plants on it, evolved to its ultramafic soils rich in heavy metals.)But yeah, also just to make this clear: Cr(III) is essentially inert in the environment, it's present in various rocks, it acts much like Fe(III) and Al(III), indeed their ions substitute in various minerals, and reactions. Even Cr(III) salts have shockingly low toxicity (comparable to table salt IIRC), not that I would recommend spreading it on your food... It's specifically when it's been oxidized to Cr(VI) that it's carcinogenic, and rather devious at that, when it gets into groundwater say. There are ions that can sequester it (like PbCrO4 being very insoluble), but it's not held around by clays for example (those trap positive ions like K+, not negative ions like CrO4(2-)), which is why it can be a groundwater hazard.QuoteNot necessarily. Titanium I think does just anodize at most pHs? Aluminum may just corrode. The anodize process specifically uses acid, though I'm not sure offhand how much that's a matter of just getting good conductivity (could sodium sulfate or nitrate be used instead?), or to optimize the deposit (is it less strong, more flaky, or not as porous, in other conditions?). Aluminum definitely corrodes in strong acidand base-- it's amphoteric, and most stable (insoluble) at neutral pH. But that's not to say, non-corrodable: it may powder up and flake off: "rust", instead of forming a tight protective oxide.Depends on alloy too; some are particularly corrosion prone, 2000 series (copper alloyed) for example. The most common ones (say, 5000, 6000, 300 serieses) use Mg and Si for strength, which are pretty well-behaved with respect to corrosion.The main thing is, with voltage applied constantly, there's a pressure towards acid and base at the anode and cathode respectively, perhaps causing anodization (but then no current flows to the snail either) but also dissolution/corrosion, including at the cathode. So I wouldn't use aluminum here.Also not to mention, flesh-goop left on the wires will tend to give off all sorts of things -- acids as proteins and sugars and various other things are broken down and oxidized, bases like amines as amino acids break down and putrefaction occurs (if it stays moist long enough for bacteria to move in, I guess?). Hard to be inert to all those things, without simply insulating the wire in the process!For my part, I'd suggest trying a low voltage, and AC (at modest frequency, 10s to 100s Hz say; should still be tingling to most nervous systems), more as a discouragement than a fatal punishment. But I don't have any data to suggest how effective or reliable that would be; you'd have to try it and see. And maybe you'd prefer the culling effect of executioner over a mere deterrent.Tim

author: Konkedout
author_rank: Frequent Contributor
timestamp: October 02, 2024, 04:15:38 pm
content: Some time after posting the above...I realized that (to test it on a captured test subject) I need only to assemble the output stage with the two complementary BJTs, diodes, capacitors and resistors, and drive it with my (mal)function generator.This will make a lot more sense for a "One and done" test.

author: Zero999
author_rank: Super Contributor
timestamp: October 02, 2024, 05:51:32 pm
content: Quote from: Konkedout on October 02, 2024, 04:15:38 pmIndeed, your signal generator will probably drive Q1 & Q2 via the capacitors, which will need to be made larger if you're going to test lower frequencies.

author: peter-h
author_rank: Super Contributor
timestamp: October 02, 2024, 09:34:03 pm
content: I use this producthttps://www.amazon.co.uk/gp/product/B0BYSB6K7Mwhich works very wellIt does suffer from corrosion where some organism ended up on it but with a 9V PP3 supply it is ok. Snails and slugs don't get across unless they are very small

author: IanB
author_rank: Super Contributor
timestamp: October 02, 2024, 09:46:34 pm
content: Quote from: peter-h on October 02, 2024, 09:34:03 pmThickness is one of the ways of mitigating corrosion. In engineering, it is common to estimate corrosion rates over the lifetime of a component, and then add sufficient extra thickness to compensate.

author: 5U4GB
author_rank: Super Contributor
timestamp: October 03, 2024, 04:52:38 am
content: For a non-electronic solution (sorry :-), to protect trees and bushes you can rub a band of vaseline around the trunk which makes it unclimbable by most crawling things, for example it'll also keep ants out of electronic gear mounted on poles. The vaseline seems to last more or less forever and is pretty much invisible to the eye. You just need to make sure there are no bridges providing access, e.g. branches that droop onto the ground.

author: bson
author_rank: Unknown
timestamp: October 03, 2024, 09:53:55 pm
content: Quote from: JohanH on October 01, 2024, 06:06:49 am+1 on cattle fence wireWe also used to poke livestock fences with a straw of grass... got you a much reduced jolt. But yeah, just grabbing it felt like someone kicked you to the ground from behind! With good rubber soles you could barely feel it, and you could then poke your friends! Good times.I was going to suggest switching on 15-20V AC for a few seconds twice a minute or so.

author: JohanH
author_rank: Frequent Contributor
timestamp: October 04, 2024, 06:19:28 am
content: Quote from: bson on October 03, 2024, 09:53:55 pmI didn't think on the aspect that zinc oxide could poison your vegetables, etc. Maybe if keeping the wire a fair distance away. It will eventually corrode as well due to ground contact. Maybe the nylon wrapped wires they use could work better in that aspect.

author: Ice-Tea
author_rank: Super Contributor
timestamp: October 04, 2024, 06:26:46 am
content: On a somewhat related note, putting a tray with beer in it in your garden will cause them to commit mass suicide ;-)

author: coppercone2
author_rank: Super Contributor
timestamp: October 04, 2024, 06:34:18 am
content: maybe you should call it even, you saw what happened in jurassic park with the electric fence

author: peter-h
author_rank: Super Contributor
timestamp: October 04, 2024, 07:42:52 am
content: QuoteIt doesn't work. The copper tape also doesn't work - the video above, IIRC, shows that 50% of snails don't mind copper.

author: RoGeorge
author_rank: Super Contributor
timestamp: October 04, 2024, 07:47:21 am
content: I would rather harvest themhttps://en.wikipedia.org/wiki/Snails_as_food

author: Ice-Tea
author_rank: Super Contributor
timestamp: October 04, 2024, 10:25:48 am
content: Quote from: peter-h on October 04, 2024, 07:42:52 amDid you use Heineken? Because Ididsay beer

author: Ian.M
author_rank: Super Contributor
timestamp: October 04, 2024, 10:58:17 am
content: https://barrypopik.com/blog/cheap_beer_is_like_having_sex_in_a_canoe

author: Konkedout
author_rank: Frequent Contributor
timestamp: October 05, 2024, 03:03:07 am
content: Well I am more than pleased that this thread got a lot of responses. I HAVE SOME HOT NEWSAnyone who hypothesized that high frequency would not work....was apparently correct. Within the last hour I subjected a test subject to a 20V peak 20 KHz AC square wave. The slug did NOT CARE!!Well I wish this had fried the slug, but hey....this is why I ran the test so I am glad that I tried it. See my other threadhttps://www.eevblog.com/forum/projects/lets-get-down-to-brass-tacks/Where I eventually post a lousy photo of my test circuit. I brought the victim to the test circuit and nothing much happened until (experimental control) I hit it with DC after the 20 KHz AC did not work.I wanted to use 20 KHz because it is easily coupled through small value capacitors, and it will not be audible to humans, even if something (??) acts as a transducer. Understand that each of my two similar boards has four output rails which are sequenced with a counter and 3 to 8 decoder. Each of the four outputs has a 1/8 duty cycle and it cycles in about 15 seconds. This gives the slug enough time to get across the rails before being electrocuted.Anyway I think now what I need to do is (a bit more complexity) use DC but reverse the polarity of each pulse to a given output. I think I want to use +/- 20V to each output so I can keep a common ground for one of the rails. If I were to use differential outputs then that would increase the output wiring. So I would probably use a complementary pair such as MMBTA06 and MMBTA56 given that each will see 40V when the other one is on. Right now I am using MMBT4403s for 18V and those have been running for 2-3 seasons with no failures. So that is enough "beef" in the output drive, helped by having 82 ohm resistor in series with each BJT output collector. The present (DC only) is a 38 x 100 mm board 4 layers from JLCPCB. The 100 mm dimension keeps the price down, and the 38 mm dimension allows it to fit inside a pill bottle in my old rural mailbox. The mailbox also contains the charging module and a 12V 7VA SLA battery. The mailbox hangs on a post under my 40W solar panel.

author: robert.rozee
author_rank: Frequent Contributor
timestamp: October 05, 2024, 11:55:45 am
content: Quote from: Konkedout on October 05, 2024, 03:03:07 amthis may in fact be agoodthing... you now know that you can safely pass a 20kHz signal into the two rails and use the presence of a current flow to detect when your 'subject' is in place across the rails and unable to make a quick retreat. once the current flow at 20kHz increases beyond a predetermined point, just turn off the oscillator and let the DC current do its magic.next, you need to design an automatic reset - this could be as simple as a carefully positioned windscreen wiper motor that is activated 30 seconds after the DC is applied!cheers,rob :-)

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 05, 2024, 12:23:17 pm
content: Quote from: robert.rozee on October 05, 2024, 11:55:45 amOr keep it at 20kHz but greatly increase the voltage.

author: Seekonk
author_rank: Super Contributor
timestamp: October 05, 2024, 04:21:30 pm
content: Quote from: Zero999 on October 02, 2024, 09:04:24 amAny cheap $15 MSW inverter will work. I use these for lots of things. Just frrd any voltage over 12V into the high voltage capacitors and just supply 12V on the non powered side of the on off switch to power the electronics. The boost inverter section is not powered.

author: DavidAlfa
author_rank: Super Contributor
timestamp: October 05, 2024, 04:23:49 pm
content: Try carbon/graphite coating.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 05, 2024, 04:49:24 pm
content: Quote from: DavidAlfa on October 05, 2024, 04:23:49 pmor just graphite - pencil leads perhaps

author: DavidAlfa
author_rank: Super Contributor
timestamp: October 05, 2024, 04:52:34 pm
content: Sure, but not easy to work with...But you can solder / screw on / bend any metal tape, then apply the coating on top.

author: Perkele
author_rank: Regular Contributor
timestamp: October 05, 2024, 06:19:07 pm
content: Get a pair of ducks.

author: Konkedout
author_rank: Frequent Contributor
timestamp: October 06, 2024, 06:24:45 am
content: Quote from: Perkele on October 05, 2024, 06:19:07 pmYou are quacking me up!! :-)There is a paradox somewhere in your idea, but I cannot quite nail it down....

author: Zero999
author_rank: Super Contributor
timestamp: October 06, 2024, 06:34:45 pm
content: Quote from: Konkedout on October 05, 2024, 03:03:07 amThat looks far too complicated.Why not use low frequency AC? If you don't want to use a self-oscillating bridge, like the one in myprevious post, then how about an H-bridge IC and an oscillator or microcontroller? The old L293 will work at up to 36V and is available cheaply off ebay.I doubt reversing the pulses (which really is AC) and such a low frequency would have much of an anti-corrosive effect.I suggest doing more experiments at lower frequencies, with your original test circuit. The capacitors would have to be bigger, but hundreds of µF isn't that big.

author: DavidAlfa
author_rank: Super Contributor
timestamp: October 06, 2024, 07:04:36 pm
content: Gets the ducks... Then opens a new thread asking advice to stop them from eating the entire garden!Train some corvids instead!

author: Terry Bites
author_rank: Super Contributor
timestamp: October 07, 2024, 04:48:57 pm
content: The only reliable remedy for the slug is the chicken.Chickens eat them, chickens crap under the trees, you eat the chicken. Win-win-win!Try not to think about it too much while you tuck in.

author: IanB
author_rank: Super Contributor
timestamp: October 07, 2024, 05:48:35 pm
content: Quote from: Terry Bites on October 07, 2024, 04:48:57 pmI've never kept chickens, but I rather think that if you let chickens loose in your vegetable garden, you won't have much of a vegetable garden left after the chickens have finished with it.

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: October 07, 2024, 06:39:44 pm
content: The chickens will eat your vegetables and let the slugs in peace.

author: Konkedout
author_rank: Frequent Contributor
timestamp: November 02, 2024, 04:48:19 am
content: Quote from: Zero999 on October 06, 2024, 06:34:45 pmI guess the question is how low a frequency would be low enough. My original pcb is not so complicated and fits into a pcb (37 x 100 mm) inside a pill bottle which is inside an old classic American rural mailbox. My DC pulses are maybe a bit under two seconds long. But anyway that all needs a new pcb if I want to reverse polarity at any frequency. That may be OK. Thanks for the tip about the L293; was not familiar with that one. But microcontrollers are completely outside of my "wheelhouse"...I do power converters but not programming. Anyway a comparator makes an easy oscillator. But I am thinking that my next move might be to buy some better stainless steel wire. What I bought previously was from Amazon and probably from China. The one pound of wire looks like it was hand wound onto the spool. So if I buy more wire I will probably go to McMaster which is an old American distributor; a bit like Digikey but for mechanical fasteners and materials.https://www.mcmaster.com/

author: Konkedout
author_rank: Frequent Contributor
timestamp: November 02, 2024, 05:38:07 am
content: Quote from: Terry Bites on October 07, 2024, 04:48:57 pmMy wife and I have discussed having chickens. I do not know if I have it in me to slaughter one. And....how do you go on vacation when you have chickens. We also have coyotes here. Chickens might be eaten by the coyotes if bird flu does not get them first.

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 02, 2024, 09:23:04 am
content: Get a donkey, they have truly bad manners when molested. Will grab the coyote's head and bash the fc*er against the floor or perform a ballistic launch with him.

author: Zero999
author_rank: Super Contributor
timestamp: November 02, 2024, 04:30:49 pm
content: Quote from: Konkedout on November 02, 2024, 05:38:07 amDon't eat the chickens, eat the eggs.Don't you have neighbours who can look after them when you go away? They'll appreciate the eggs as payment.Your next project can be a higher powered electric fence to deal with the coyotes.Quote from: Konkedout on November 02, 2024, 04:48:19 amI don't know what the minium frequency is required to prevent corrosion, but does it matter? It makes more sense to optimal frequency for electrocution of slugs.