How to electronicly detect a pest trap has been triggered. - Page 1
Forum section: electronics / projects

author: mrpackethead
author_rank: Super Contributor
timestamp: September 20, 2017, 01:46:33 am
content: I am wanting to electronically detect if a pest trap has been triggered. It does'tn have to be detected in real time, it can be done periodically. ( ie, check once every x hours ).. I'm wondering what kind of sensor system might be useful for this.Its got to be low powered as well.. ( needs to run off batterys.. ). I'll have a low power microprocessor and radio to process the message..Anyone got some great ideas.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 20, 2017, 02:05:38 am
content: That thing is going to make a seriously loud noise when it trips, so how about a microphone?Dedicated "mute" ICs used to be available which were used in radios, so if you can get one which just presents a logic level change at its output, you are halfway there.If you have to fart around setting levels & stuff with a PIC or whatever, it is a bit more messy, but still do-able.

author: Unknown
author_rank: Unknown
timestamp: September 20, 2017, 03:09:25 am
content: Those are usually fixed in a box/tunnel - why not just use a waterproof microswitch or a car interior light door switch (with rubber boot), mounted on the side of the box & held operated by the hammer when set, as the sensor?

author: ez24
author_rank: Super Contributor
timestamp: September 20, 2017, 03:17:18 am
content: Is the trap for kangaroos ? Never seen it before.Seems a micro switch would work.

author: GigaJoe
author_rank: Frequent Contributor
timestamp: September 20, 2017, 03:34:42 am
content: simple pulse light sensor working on reflection from the part when it off. of course this parts shouldn't be there when armed.Option 2, a hair like coil wire torn when it moving.

author: Teledog
author_rank: Regular Contributor
timestamp: September 20, 2017, 03:40:28 am
content: Radio? VHF/UHF/WIFI?Lots of information out there for go/no-go signalling with the ESP8266 (WIFI)..they're pretty cool!Just got a pile of RCWL0516 sensors in..THEYare some nifty & cheap units!!! Use a logic level latch for trigger indication, as the reset is just a few seconds.Might want to check the RF/Ham radio forum/section (or ARRL handbook ) for more VHF/UHF signalling questions?..perhaps "strike anywhere" matches attached to the trip/bail....when you see smoke in the woods!!!.. (joking!)Edit: More interesting stuff here;http://andicelabs.com/2013/07/the-tale-of-a-rat-zapper-part-2/

author: tpowell1830
author_rank: Frequent Contributor
timestamp: September 20, 2017, 04:52:39 am
content: As EZ said, use a simple micro switch. When the trap is set, the switch interrupts the power to the micro, then when the trap is triggered the power comes on and your software controls the time on and off as you wish to broadcast. Use the frame to mount the switch.

author: DTJ
author_rank: Super Contributor
timestamp: September 20, 2017, 07:59:45 am
content: Huge trap!What are you catching? Possums or stoats?

author: oldway
author_rank: Super Contributor
timestamp: September 20, 2017, 11:32:31 am
content: Place a microphone to catch the cries of the animal when it has the paw broken by the trap ...It's cruelty to animals ... Permitted in Australia?

author: mrpackethead
author_rank: Super Contributor
timestamp: September 20, 2017, 11:38:30 am
content: Quote from: DTJ on September 20, 2017, 07:59:45 amStoats, Rats.. mostly.. Yes, these are normally set up in a 'tunnel' so that non target species ( domestic cats mostly ) or birdlife ( which is why we are trapping ) can't get in.For possums we use somethign similar in operation, called a tims trap. Quite a bit bigger set up though.

author: DTJ
author_rank: Super Contributor
timestamp: September 20, 2017, 11:42:10 am
content: Quote from: oldway on September 20, 2017, 11:32:31 amPretty sure the OP is Kiwi.Similar flags but different tastes in livestock to us Aussies.

author: mrpackethead
author_rank: Super Contributor
timestamp: September 20, 2017, 11:56:46 am
content: The traps have been tested and approved to be humane. A stoat is dead before it knows what has happend. Its instant.

author: DaJMasta
author_rank: Super Contributor
timestamp: September 20, 2017, 04:33:49 pm
content: It's sort of too bad the trap is all metal, if you got the right mix of materials used in the base and support structure, you could just wire a sense line on the trigger and the arm and when the sense line goes open, your trap is sprung.

author: ez24
author_rank: Super Contributor
timestamp: September 20, 2017, 04:45:27 pm
content: Quote from: mrpackethead on September 20, 2017, 11:56:46 amSounds like stoat is something you order when you go to a bar, "hey bartender, give me a tall cold stoat".https://en.wikipedia.org/wiki/StoatQuestion - do birds eat sand flies (the most evil thing in the world)?Example of a micro switchhttps://www.amazon.com/URBESTAC-Momentary-Hinge-Roller-Switches/dp/B00MFRMFS6/ref=sr_1_3?ie=UTF8&qid=1505925717&sr=8-3&keywords=micro+switch

author: mrpackethead
author_rank: Super Contributor
timestamp: September 20, 2017, 08:30:48 pm
content: Quote from: vk6zgo on September 20, 2017, 02:05:38 amThis is very true. And this gives me an idea. When they go off, they really do go off. Its a very strong spring and it really accelerates very fast. When it hits the base, it really hits. At least for the said 'victim' the end is quick.A peizeo electric transducer would certainly pick up the hit.The problem i have with microswitches ( which would be the easiest way by a long time ) is that these traps are in ugly places, with mud, and rain. A peizo could be sealed up and attached to the side of the box.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 21, 2017, 12:21:09 am
content: Quote from: ez24 on September 20, 2017, 04:45:27 pm"What is the difference between a Stoat & a Weasel?""A Weasel is weasely distinguished, as a Stoat is stoatally different!"

author: Unknown
author_rank: Unknown
timestamp: September 21, 2017, 01:58:19 am
content: Quote from: oldway on September 20, 2017, 11:32:31 amWhen set up properly, in the box with baffles & all, they're (a) pretty impervious to larger animals sticking a random paw in & getting it smooshed, and (b) fairly humane in that they're designed to kill animals of the target size instantly.Here's a NZ DoC brochure showing the usual setup. (pdf)Quote from: mrpackethead on September 20, 2017, 08:30:48 pmFWIW I've seen car interior light switches used on live cage traps to trigger a transmitter in cases where you don't want the animal to be trapped & vulnerable for too long (e.g. where there lots of predators, like dingoes, that can trash a small trap). They're pretty well sealed to start with, and a bit of silicone sealant or 'blackshit' (self amalgamating tape) works well enough on the terminals / connectors / entry holes. No problems in coastal Australian bush/forests/swamps, though admittedly it's probably drier than most NZ bushland.

author: zeqing
author_rank: Regular Contributor
timestamp: September 21, 2017, 03:02:40 am
content: firstly thought about a button used on the 3D printer... or IR detector to detect the trap location(trapped or not):

author: mrpackethead
author_rank: Super Contributor
timestamp: September 21, 2017, 03:56:01 am
content: Quote from: Tac Eht Xilef on September 21, 2017, 01:58:19 amThe animal is well dead almost instantly. the reason for the notification is so you can go and reset the trap, to catch the next one.

author: hendorog
author_rank: Super Contributor
timestamp: September 21, 2017, 04:21:19 am
content: Quote from: oldway on September 20, 2017, 11:32:31 amAnd that right there is an example of why we shoulda changed the flag....

author: Someone
author_rank: Super Contributor
timestamp: September 21, 2017, 04:37:34 am
content: Quote from: mrpackethead on September 20, 2017, 08:30:48 pmWhy not stick with the agricultural mindset and have a small transmitter that is enabled when its switched on, the trick being that switch is one that is turned on by pulling a pin (pin flag switch style) out of it with a string attached to the closing jaw. There are ways to get enough travel/leverage on the trap its self and make a solution which doesnt require any constraints on the placement within a box/tree trunk/etc. Or if you're concerned about the weatherproofness of typical limit switches there are Automotive switches for checking if doors/bonnets/hatches are open that are available and some of those might fit the required shape already, held open by the jaw until it closes then enabling the transmitter.

author: Habropoda
author_rank: Regular Contributor
timestamp: September 21, 2017, 05:36:32 am
content: Probably the simplest and most robust solution is a vibration sensor switch like this:https://www.adafruit.com/product/2384There are a few variations on this; a spring around a rod, a ball or rod rolling amongst multiple contacts. Set up a pin change interrupt to wake up a sleeping microcontroller or trigger a comparator, super low standby current. Plenty of examples once you get the right search phrase.They are very cheap on ebay and you can encapsulate them as needed for conditions. If you epoxied one to the base of that trap it would trigger for sure, it would not need to go on the killer arm.I use one with a Moteino to protect a wildlife camera. Works great.

author: ez24
author_rank: Super Contributor
timestamp: September 21, 2017, 05:48:32 am
content: After reading the docs on the trap, my guess is a sound solution is best. I think you could come up with a small box that could be placed near the trap therefore no work would have to be done on the trap.

author: mrpackethead
author_rank: Super Contributor
timestamp: September 21, 2017, 07:20:26 am
content: Quote from: Habropoda on September 21, 2017, 05:36:32 amThats a great idea. I'm goign to give this one a try. thats really simple. and i suspect it will work nicely.

author: mrpackethead
author_rank: Super Contributor
timestamp: September 21, 2017, 09:01:29 am
content: Found those sensors on aliexpress for just 0.05c each! ( including postage ) so orederd some of the various grades.. Just search on that part number.https://www.aliexpress.com/item/50PCS-SW-18020P-Electronic-Shaking-Vibration-Sensor-Switch-Black-hot/32788166427.html?spm=a2g0s.9042311.0.0.IgBpxt

author: Croadie
author_rank: Newbie
timestamp: June 20, 2019, 03:59:14 am
content: Mr Packetheadhow did you get on with this - I'm really interested inthe same thing - inthe middle of setting up a predator free program in Hawke's BayMany thanksRichard

author: Circlotron
author_rank: Super Contributor
timestamp: June 20, 2019, 04:48:43 am
content: A magnet on the moving part and a reed switch or Hall Effect sensor on the stationary bar?

author: tautech
author_rank: Super Contributor
timestamp: June 20, 2019, 05:22:49 am
content: The pic shows the kill trap in the tripped position when the kill bar is on the trigger pad.When the kill bar is cocked and loaded it’s vertical and perfect to have a micro switch mounted on the rear frame for the kill bar to contact against.Then all you need is the comms device.

author: Marco
author_rank: Super Contributor
timestamp: June 20, 2019, 08:34:55 pm
content: There seems to be some room beneath the "treadle" which will move down when the trap springs. You should be able to measure the increased proximity of the treadle. Inductive, capacitive or even optic could work ... but optical would be more sensitive to fouling. Distance too short for ultrasonic.For the rest it depends on how available networks are. If there is good mobile phone coverage a phone modem is always an option. Otherwise LoraWAN or setting up your own 433 MHz narrowband network.

author: Circlotron
author_rank: Super Contributor
timestamp: June 20, 2019, 09:49:40 pm
content: Think like it’s 1890.Tie a string around the top of the bar. The other end of the string connects to a U shaped link that gets pulled out of a socket when the trap goes off.

author: johnkenyon
author_rank: Regular Contributor
timestamp: June 21, 2019, 09:57:10 am
content: The KISS principle applies here - the thing has a moving part which moves at least an inch from its armed position.Connect two wires to the trap, and create a "normally closed" switch.One wire connects to the trap itself.The other wire is mechanically attached to the frame at the top, and is hooked over the arm which falls when the trap is triggered, with no slack.When the trap is set, the wire is hooked onto the arm, circuit made.When the trap is triggered the arm loses the wire - circuit opens, trigger detected.When the "switch" fails, or someone nicks the trap, or the trap gets lost, all you have lost is the cost of the switch - less than 2 cents/pence/whatever's worth of wire.

author: soldar
author_rank: Super Contributor
timestamp: June 21, 2019, 04:06:21 pm
content: That trap looks mean. I'd keep my fingers well clear of it.The same as stepping on the trap releases a spring which actuates the kill bar, it should not be difficult to set a (mechanical) trigger that raises or lowers a flag or sign when the trap is triggered. No need for electricity. That would be fun.OTOH,Shawn Woods has a YouTube channelwhere he has tested hundreds of different traps, some of them with remote radio notification.

author: Marco
author_rank: Super Contributor
timestamp: June 21, 2019, 04:33:55 pm
content: Quote from: johnkenyon on June 21, 2019, 09:57:10 amJust don't mix up the S's.Adding an extra step for resetting the trap, which might mechanically interfere with its operation and which relies on predictably unreliable electrical contact ... I don't think whomever has to reset the trap would consider it simple. Whereas something under the treadle would be completely invisible, irrelevant during normal maintenance and could be made highly reliable with non contact sensing.

author: icharters
author_rank: Contributor
timestamp: June 22, 2019, 12:42:50 am
content: Use a commercial surface mount security alarm contacts. They come with plastic shims to keep the magnet and reed switch away from the metal. They also screw into the trap so it violently closing isn't going to dislodge them. You can get them in NC, NO, NO+NC types.Honeywell 7939WG ->https://www.security.honeywell.com/product-repository/7939wg

author: Dubbie
author_rank: Unknown
timestamp: June 22, 2019, 01:09:25 am
content: I think you are 100% on the right track with the vibration sensor.Means your unit can be completely sealed and just velcroed to the top of the tunnel or something. No wires or other complicated mounting.I'm interested to hear what you are planning for the Radio also. I looked at something for an almost identical use case. However I couldn't figure out a radio scheme that would handle the distances required, considering it would be on the floor of dense bush.

author: digsys
author_rank: Unknown
timestamp: June 22, 2019, 01:47:27 am
content: 100 yrs ago (feels like), I lived in a hippie household in Glebe Sydney, right by the water. We had a huuge problem with rats and all sorts of vermin.All the "floaties" (dead animals etc) that choked the waterways attracted them. Rats the size of cats, the size of dogs. They'd eat through heavy storerooms doorsat night, and small 22 rifles would just annoy them. So, we made up a HV HE trapdoor. It was mounted high up and when the rat walked to the center, they werehit with a vh energy pulse. We used various grids / cloth covered plates. The trap door opened and it'd fall into a 44 gal drum of water, making sure it drownedif not dead. For the first few weeks, we filled the drum each night !! A "one off" approach was pointless. They bred faster than we'd be able to kill them.Soon after, Sydney had a massive clean-up of the waterways and life went back to normal.Maybe a similar system would be better. Doesn't need to be HV electric, but something that doesn't require resetting, and "dumps" the body.

author: Zero999
author_rank: Super Contributor
timestamp: June 22, 2019, 05:11:38 pm
content: Quote from: digsys on June 22, 2019, 01:47:27 amWhat would be cool if you had a similar system, with a shredder, next to a sewage drain: first the vermin is trapped, tghen humanely killed, minced and flushed down the toilet!

author: digsys
author_rank: Unknown
timestamp: June 22, 2019, 11:56:26 pm
content: ok, that's a bit severe :-) and environmentally unfriendlyWhat I was alluding to was - IF you have a greater # than just 1 or 2 pests, doing them 1 at a time then going back every day or 2 may be a losing battle.A simple setup we started with was an old car battery, old style ignition coil and a trigger device. If the vermin is too big though, the coil will only stun them,is why we needed a 2nd "process".

author: Chris Wilson
author_rank: Super Contributor
timestamp: June 26, 2019, 03:25:00 pm
content: Large sheet of Veroboard with tracks paralleled, suitably spaced for no arc over and connected to ground and the HV probe of a tube / vac variable HV tester. Put corn on another board so the rat walks across the charged Verobaord to get to it. The Veroboard board is hinged on a balance spring so the dead rat drops into a container, works well, and if you have a power point indoors where the HV tester can be left safely and locked ON you can run car ignition cable to the trap. Has dispatched dozens of the blighters...As someone said a car electronic ignition system with a simple circuit to keep firing the coil will also work, and from a car battery... The less "feeling" would just let the rat drop into the container and die without killing it, not sure if the squeaking would deter others though

author: floobydust
author_rank: Super Contributor
timestamp: June 26, 2019, 04:59:41 pm
content: OP I would use a magnet and reed switch. Vibration sensor may not work as the soft squishy rat will dampen the trap's closing, and its weight is on the trap too.It rain outdoors so anything else I think will fail from dirt and water.There's several electric mouse/rat trap videos on youtube. Once the HV is on they jump up off the electrodes and run/bounce away, unless you have a cage cover or something complicated to navigate which keeps them there long enough.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 28, 2019, 02:28:41 pm
content: This trap looks like it goes off violently.I would probably not trust a reed switch in this setup, the're too fragile, but a HALL sensor would work, or even a simple Microswitch that is activated when the trap is in the armed position.

author: fcb
author_rank: Super Contributor
timestamp: June 28, 2019, 02:58:23 pm
content: I think I would use audio - that trap is going to make a sharp sound when it goes off - so use a microphone in the equivalent of a PIR sensor circuit. Could be made with very low idle current, easy to adjust and test. The output would drive a pulse stretcher (comparator) which goes to whatever you need to drive.