Not killing mouse trap [140011-I]
Published in Elektor Magazine, July & August 2014 edition (UK: page 36)
Published in Elektor Magazine, July & August 2014 edition (UK: page 36)
Two years ago a mouse in a usual mouse trap was not battered to death. Because of a bad strike she was living and dithered half dead. So I had to kill her with an axe myself. The poor mouse! I promised to build a trap not killing a mouse anymore. And here it is: This is a project of a "not killing mouse trap" (I hope the mouse will not be died for hunger because of no one uncaging her). For all friends of mice and other animals. Cost: about 20,-€. You should not count the hours. But a hobbyist and home constructor should never count hours.
A metal basket bought in a Aldi store was the beginning of the adventure. I everted the box upside down, greatened an entrance door and built a trap door with a hinge out of a piece of PCB. The door is held from a needle. Moving the needle with a magnetic coil (electric bell system) the door falls down and closes the entrance. The mouse inside the cage can´t open it anymore and has to wait until anyone is rescueing her.
Perhaps there may be better magnetic coil systems. Mine is from a electric bell system and is operating well.
The history:
A short period after constructing the trap she showed her ability once and a few months later a mouse family with six members of beautiful small mice was cought one at a time with this trap (look picture)
All mice were put to a part of the wood with rocks and holes outside our piece of land. So the mouse trap project was finished and we can proudly claim that our work was worth the effort.
http://members.vol.at/michaelh/
Discussie (2 opmerking(en))
ClemensValens 11 jaar geleden
Built and tested this project in the lab. I modified the circuit a little bit:
I designed a PCB for the circuit, Eagle files are attached. Note that the original project schematic has a few errors, notably around T1. Also pin 2 and 3 of the MCU are swapped. The schematic attached to this post is correct.
A note on doorbells. It turns out that you cannot buy them as easily as before. All you have today are ding-dongs and MP3 bells (wireless or not). This may depend on the country you live in. I found a Friedland Underdome D792 for about 12 euros. This bell has a diode inside and therefore has a polarity. It works fine with this circuit, but the mechanics are different. The solenoid has a DC resistance of 3 ohms.
There is room for improvement in the software to make it consume less power when the trap is armed. I measured 625uA in armed mode and 24uA after closing the trap. In armed mode the MCU polls at 10 Hz and could sleep the rest of the time, but it doesn't. Correcting this would certainly improve consumption.
Make sure to allign the phototransistor and the IR LED properly. The angle seems to be quite narrow and I have not succeeded with a mirror. If you have an oscilloscope, you should see good active-low pulses on pin 7 of the MCU. In clear daylight the circuit will not work and the red LED will blink erratically. This is normal behaviour. When all is well and armed the LED will flash briefly every 2 seconds or so.
The photos do not show the 4700uF caps, because I did not try them. I have only put them on the PCB.
Regards,
Clemens
Schematic as PDF (35kb)
Eagle files + BOM (107kb)
140011-59.jpg (943kb)
140011-56.jpg (931kb)
ClemensValens 11 jaar geleden
How about using an old toaster? The ones that have more than one toast option usually are electronic and use a magnetic circuit to keep the bread down while toasting. When the toasting time is up, the power is cut and the magnetic circuit is broken, ejecting the bread. The ejection mechanism is spring loaded so if you put it upside down it can close the trap even quicker.
The inconvenience is of course that it has to be powered to work, but you can scavenge everything from the toaster, including parts for the cage (and the smell of burnt bread).
(Then you connect it to a Raspeberry Pi and make it send a Tweet or post a photo of the mouse on Facebook.)
Regards,
Clemens