"Rodent Control Device" Teardown - Page 1
Forum section: electronics / projects

author: Chet T16
author_rank: Frequent Contributor
timestamp: May 18, 2012, 09:39:51 am
content: Bit of an odd one this, plug it into a socket and it scares mice/rats etc away. From the patent it works by "generating a pulsating and interrupted magnetic field offensive to rodents in buildings"Patent linkThis is a JML branded product bought in a retail store somewhere here (ireland) but is clearly the usual china tat, the board is marked Lucky Good Industrial Ltd - make your own jokes!No marking on the 8 pin dip, to the left is an X0405MF SCR.Google brings up lots of people saying they work, any idea on the science behind it?

author: G7PSK
author_rank: Super Contributor
timestamp: May 18, 2012, 11:57:53 am
content: As I live in the country surrounded by fields every time they harvest I get inundated with rodents and insects looking for a new home for the winter. I have tried those things and they do not work.

author: SeanB
author_rank: Super Contributor
timestamp: May 18, 2012, 03:36:58 pm
content: ultrasonic ones work better, but do not deter all rodents equally. The deaf ones and the hungry will still come in, but at least it keeps them away somewhat.

author: saturation
author_rank: Super Contributor
timestamp: May 18, 2012, 03:46:13 pm
content: You can test it yourself by going to a pet store that sells mice or similar. See how they react to it.Some years ago, I tested the mosquito repellant circuit by going to a mosquito riddled island. I wore a mosquito suit and they swarmed me with or without the unit on. First and last trial. I then used just the suit and OFF [ they still managed to sneak in the suits gaps] and all was well.

author: SeanB
author_rank: Super Contributor
timestamp: May 18, 2012, 04:21:24 pm
content: For mosquito's all I use is a local plant, which repels them all. Grows all over, but is a little smelly, but works a treat. Even works on fleas.

author: nukie
author_rank: Frequent Contributor
timestamp: May 19, 2012, 01:54:08 am
content: Snakes and Cats works well for the first issue because when mice are gone the snakes will go after the cats. Once the cats are gone, you can go after the snakesRegarding the mosquito, we have CO2 emitting units with UV light source which attracts and trap them. This method has proven to work quite well in countries like Taiwan, Malaysia, China, India, Queensland Australia and some other parts of the world. Malaysia is researching an additional method which attracts mossie by smell. I don't know if it works it's still experimental.

author: amyk
author_rank: Super Contributor
timestamp: May 19, 2012, 11:38:27 am
content: I think this should be a pretty accurate schematic. The claims that it produces a magnetic field are true, but I doubt it can do anything to mice.The power supply pins on the IC suggest it might be something like a PIC12 running with internal oscillator and MCLR disabled. Anyone have any other guesses?Notice the switch appears to do nothing other than control an LED.

author: Rerouter
author_rank: Super Contributor
timestamp: May 19, 2012, 12:04:20 pm
content: ok, now i truely cannot see how it could repel rats, unless somehow that inductor is working as a HF speaker (unlikely, but only thing that makes sense) if that was the case you would probably measure with an oscillascope about a 50Khz to 70Khz signal, that would still piss off some cats, but no other pets, and it would also overlap with the hearing range of mice,providing all of that holds up, it would probably work similar to mosquito tone generators used on kids and teenagers, its a loud noise only selected animals can hear and as such the rats dont want to hang around there unless its for a very good reason, probably a similar contruction to a low frequency light dimmer (not a speaker but the inductor sings at a high frequency)

author: SeanB
author_rank: Super Contributor
timestamp: May 19, 2012, 12:40:30 pm
content: Looking at it it basically is placing a DC load across the mains, something that actually caused damage years ago, when Phillips made the first generation SMPS TV sets. The original ones used a thyristor to provide a 110V main rail, with it taking a 11A current pulse every 2nd mains cycle or so. These caused a few problems for power suppliers, as the nett DC current caused by dozens of these sets turned on for long periods at night drove distribution transformers into saturation, causing a few substations to fail for no apparent reason. This was redesigned later to use 2, with another 2 diodes in a bridge, so as to reduce the DC draw.All this may do is cause the wiring to flex in the conduit or in the wall, which may not be good for long term reliability, and with UK ring mains this may lead to excessive heating in the ring.

author: Zero999
author_rank: Super Contributor
timestamp: May 19, 2012, 11:02:06 pm
content: Quote from: SeanB on May 19, 2012, 12:40:30 pmIt would've been far cheaper to just make half with one polarity and the other half with the opposite so they cancel each other out.

author: SeanB
author_rank: Super Contributor
timestamp: May 20, 2012, 10:50:48 am
content: They wanted a chassis close to neutral, to reduce the stress on the antenna's coupling capacitors and the rislk of shock during servicing. Naturally this resulted in all having the same DC current pulse..........

author: Zero999
author_rank: Super Contributor
timestamp: May 20, 2012, 09:25:27 pm
content: Quote from: SeanB on May 20, 2012, 10:50:48 amThat's bad design. The device should be designed to be safe in the event of a live neutral reversal or broken neutral.

author: SeanB
author_rank: Super Contributor
timestamp: May 21, 2012, 04:29:43 pm
content: This was designed in the 1970's, not an IC in sight, all transistors. Later models got IC IF and signal stages.

author: FJV
author_rank: Regular Contributor
timestamp: May 21, 2012, 05:05:51 pm
content: I've heard diesel fuel will repel mosquito's.

author: SeanB
author_rank: Super Contributor
timestamp: May 21, 2012, 06:41:06 pm
content: Only if you light it.

author: muvideo
author_rank: Frequent Contributor
timestamp: May 21, 2012, 09:26:39 pm
content: Quote from: nukie on May 19, 2012, 01:54:08 amJust be careful not to swap the rolesQuote from: nukie on May 19, 2012, 01:54:08 amHere I've only seen around the zappers with UV light and high voltage that just explodes the poor insects.

author: MikeK
author_rank: Super Contributor
timestamp: May 21, 2012, 09:58:48 pm
content: I would think the magnetic field would be almost nil at the distance the rodents would be from the device.

author: Chet T16
author_rank: Frequent Contributor
timestamp: May 21, 2012, 10:06:23 pm
content: Quote from: MikeK on May 21, 2012, 09:58:48 pmAccording to the blurb the magnetic field is changed aroundallyour wiring. They mention something like one unit being enough for a 2000 square foot house. I also read somewhere that if the rodents aren't nearing wiring you can run an extension lead in loops around the area close to them!

author: Rerouter
author_rank: Super Contributor
timestamp: May 22, 2012, 07:55:56 am
content: so it injects noise into your mains eh? still doesnt quite add up, rats like us dont quite give a damn about the frequency of a magnetic feild, until you get up to serious flux densities,

author: amyk
author_rank: Super Contributor
timestamp: May 22, 2012, 08:30:48 am
content: It would be interesting to see what kind of current waveform it draws, because there's a capacitive dropper and a coil in parallel to it.