Building A Dead Mouse’s Switch


[Ned] had a mouse problem in a very uncomfortable place.

No, not like the back of a Volkswagen, in his ceiling. He wanted to put a mouse trap up there to take care of the critter, but knowing how nasty a tripped trap can be after a few days, he was hesitant. He recalled a project he saw online where a mouse trap was wired like a dead man’s switch and he got to work putting together a trap of his own.

He scavenged some parts from around the house and wired up the mouse trap so that a pair of LEDs were lit so long as the trap had not been sprung on an unsuspecting mouse. Once a mouse is caught in the trap, his circuit is broken, and the LEDs go off, letting [Ned] know it’s time to poke his head back up into the ceiling and clean things up.

While his trap is decidedly low-tech, we always enjoy seeing a cheap and easy solution to annoying, everyday problems.

40 thoughts on “Building A Dead Mouse’s Switch

    1. No, it would not. You would need to create a contact that makes o ce the mouse is caught. The only possibility i see for that is that you would need the kill-bar make contact with some metal once it has sprung. That’s a bit hard as the mouse’s neck is a bit unpredictable.
      Is it possible? Yes. Is it ‘just as easy’? No

  1. I agree with the thing about batterylife.. And if could not have designed it in another way I would at least wire up a transistor to invert “the signal” so the led only was on then the trap had been activated. Just for the looks of it…

    Anyway cool project, and even trough people might kill me, the thing about twittering mouse trap would be kind a cool… And you can always hope for the mouse to pee on the arduino or something.

  2. @Wiregeek I don’t know if you have all day or something, but someone is actually just skimming what hackaday haves to say about the project, and then moves on. This article actually sums it up pretty good, so no need for actually visiting the site.

    Anyway, why use more power than needed?

  3. “…so no need for actually visiting the site.”

    Unless you want to look like an idiot who can’t read.

    A nice hack! No need to invert the signal since it would make the project about 5x more complex and it wouldn’t really function any better.

    I probably would have soldered one wire to the back-breaking wire (whatever that things called) then twisted some stranded wire around it to complete the circuit. When the trap closed it would yank out of the stranded wire breaking the connection. (One less awkward solder joint. But I’m lazy.)

  4. Cool. Looks like I need to get my traps out and wire them up. I have a similar problem in my attic. And since I follow the K.I.S.S. principle, I’ll go the battery/off till tripped mode.
    Otherwise I’d have to make it trip something to turn something on, to broadcast it to my ethernet (the router of which is in the attic), to my web platform, to send me a text message to my phone. Which wouldn’t do any good, since I am at work all day.
    So K.I.S.S. it is.

  5. @Henrik Pedersen, Should I double space my comments in the future or type slowly, perhaps use large font?

    @Bob D, You could push even lazier by securing one stranded wire to the kill bar and the other to the top of the trap, and when the trap is triggered, it pulls the two apart. No soldering at all, for higher values of ‘lazy’.

  6. Reminder time:

    It does not cost a thing to omit the disrespect. Adding the disrespect subtracts from the enjoyment of all. Call that one- my attempt at “Social Hacking” and “Leading By Example.

    Which example shall any of us be? Tech Hacking’s a wonderful thing. Social Hacking’s what makes, and keeps our world a nicer one. That bumper sticker about Random Acts Of Kindness will never be a bad meme to follow. If you want to flame? redirect flames to dev/null. Please?

  7. @Kuhltwo

    I’m curious as to the basic design you’re looking at here. I cannot successfully envision a simple, reliable way to use a mousetrap to complete a circuit, given the presence of a large, furry, nonconductive obstacle under the killbar.

    1. You know how switches work ? There are hundreds of ways to do it. A contact point on one corner that would be spring loaded and go down when hit or even just have an extended arm like some micro switches have. That would avoid direct impact on the switch.

  8. When the trap is open, it holds a switch open too. This switch closes, goes through a serial interface to a Mac Classic, then through a 14.4k modem to the mouse’s Facebook page, posts “blargh i ded” and sends an alert to its followers.

  9. Actually, Jim makes me think of a very simply idea to solve the power wasting concern. Use a normally closed momentary push-button switch, and install it under the SET BAR of the trap, or the KILL BAR. When the trap is set, the switch is pushed down and the circuit is OPEN. You could also wire up a self-oscillating buzzer to this switch and power for a nice 2am wake up alarm ;-)

  10. if you’re really concerned about using more power than needed, manually (no electric drill) drill a hole, run a fishing line down through the ceiling and attach it to the swinging end of the mousetrap (either the killing end or the trigger bar) glue (no hot glue) the mousetrap in place, go downstairs, get a ladder, mark the string with sharpie.. DUDE IT’S A COUPLE LED’S!
    solar panel, windmill, charging batteries to run 2 LED’s. the point of having the LED’s always on is that if the lights are off, either something’s wrong with the electronics, or the trap has been triggered. either way, somebody needs to go upstairs and fix the problem.
    anyway, to maximize efficiency, you should sharpen the kill-bar to minimize drag. just watch your fingers! (Disclaimer: Mini-Guillotine mousetraps will have PETA going nuts, so keep it a secret!)

  11. Cellphone charger, resistor, and led. Wired thru hook and bait tripper. Some traps have plastic bait trips! or
    Ir led beam broken sets off HV on surface grid then emails user.
    Hacking a better mousetrap. Invented in 1890’s in Illinois, what a hack!

  12. Close a circuit? The OH seems to me an excellent use of an NC configuration. The “no solder, just twist” follow up by Wiregeek merits Simplication Cred.

    There’s a likely pre-LED even joke about a “Ball Bearing Mouse Catcher” being an unfixed Tomcat. Where’s my book of Robert Burns poems when I need it?

  13. Attaching a switch to the trap, for closed circuit when sprung misses the whole point of this neat design: using the no cost switch built into the trap. Plus, the normally closed circuit lets you verify that no wiring is broken…the same way burglar alarms are wired and for the same reason.

  14. Just for fun, rig it up to an mp3 playback module so when the trap is triggered it plays that clip from Ghostbusters when the secretary shouts:

    “WE GOT ONE!!!!!!!!!!” and she triggers the alarm

  15. @Wiregeek: “…given the presence of a large, furry, nonconductive obstacle under the killbar.”

    Critters are conductive, the mouse will act like a resistor. Then you can use the resistance to determine just how big it is, and hook up an Arduino and a GSM shield to SMS the size of the caught mouse to a Facebook update!

  16. Some time ago I saw a website devoted to mouse traps. The best trap was made by a guy or girl who was troubled by a lot of mice (Hundreds of them littel creatures).

    He made a trap from a little bait, an optical switch and a vacuum cleaner…

  17. Well, I had the same sort of issue living on the edge of teh woods. I installed an IP camera and LED light on a Universal Devices EISY (Insteon) 2450 module. I put two traps side by side and wired them in series. When a mouse gets caught it open the circuit and send me a notification immediately. The camera gets triggered and the LED light comes on and send me a picture 5 seconds later. They are stored on my NAS Just to upset PETA people It send out an email to certain people with the image and the time of death. All of them are accessable remotely. I succesfully have killed 16 mice over the last year. I did not see anything for months but caught two in the last week. I amy buy some extra mice and let them lose in my house to speed up the testing process. Enineering is a fabulous occupation. Mice as other mamels cannot see infra red and thus will swap my camera for a IR model, and a small IR illuminator to record video from 10 seconds before to 10 seconds after the event.

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