Humane mouse trap | The MagPi #108

Safely catching mice is a better way of fixing a problem, and using Raspberry Pi means it needs less supervision. In the new issue of The MagPi magazine, Rob Zwetsloot takes a look with the maker, Andrew Taylor.

With some IoT projects, it’s the little things that help. For example, take Andrew Taylor, who did the good thing of setting up a humane mousetrap. However, checking it to see if any mice had been caught in it, while necessary, was getting a little boring.

There’s one major component to the setup, which is the PIR sensor

“If a mouse had gone in and I did not check it, the mouse would quickly run out of food and water!” Andrew tells us. “Having been interested in Raspberry Pi for a couple of years and having recently begun learning Python using the Enviro+ environment sensors, I figured a Raspberry Pi with a motion sensor would be an ideal way to check.”

It’s a fairly simple setup, one commonly used in CCTV builds and some fun ‘parent detectors’ on the Raspberry Pi Foundation’s projects site.

An old coffee tub is used as a case for the sensor, a good way to recycle

Mouse motion

“I came across a couple of automated mousetraps that people had made from scratch, but wanting to keep it simple and cheap,” Andrew explains. “I wanted to use off-the-shelf parts where possible and keep costs down. The Pi Hut had a tutorial for a DIY burglar alarm utilising a PIR sensor, IFTTT, and Pushbullet, which seemed like an ideal starting point.”

A Raspberry Pi Zero is used to check the motion sensor and send data if it’s activated

IFTTT – If This Then That – is an online service popular with IoT folks. It’s great for small things like cross-posting images on social media services, or sending a push notification when motion is detected in a mousetrap.

“I have only had one mouse since, but it worked!” Andrew says. “I was averaging about 800 detections a day and suddenly got well over a 1000. Sure enough, there was a mouse in the trap which I released shortly afterwards. I do tend to notice that the values fluctuate a bit, so it is always worth checking over the previous day’s results to see if it is notably higher.”

Wiring up the PIR to Raspberry Pi is quite simple, and means the project is easy to maintain

You might think that 800 push notifications a day is far worse than just occasionally checking your garage, and you’d be right, so Andrew tweaked the code a bit: “The code examples I found sent a notification for each movement detection – which I knew would be rather annoying, considering how randomly PIR sensors sometimes seem to trigger. My script instead logs any hits at a max of 1 per 30 seconds and then triggers a notification once every 24 hours, meaning I just get one notification a day.”

It’s a simple design, and was kept simple to keep to a small budget

Beat a path

There’s always room for improvement, as Andrew explains: “I intend to improve the code so that it can record running averages and give an indication as to whether it believes there has been a significant spike that might necessitate me checking it out.”

The first successful capture was released back outside the garage

Whilst the aim of the project was to keep costs down, Andrew is tempted to experiment by adding a camera, and possibly a light, so he can have a peek remotely when there has been a spike in the readings and to see if it is a false alarm. Which, as he admits, is “a new height in laziness!”

The MagPi #108 out NOW!

You can grab the brand-new issue right now from the Raspberry Pi Press store, or via our app on Android or iOS. You can also pick it up from supermarkets and newsagents. There’s also a free PDF you can download.


W. H. Heydt avatar

Build a better mousetrap….and Nature will build a better mouse.

Andrew Taylor avatar

A nice surprise to see it in my feed! There’s a technical write-up as well source code available on GitHub here:

Harry Hardjono avatar

Link goes to MagPi #107?

thuan phuoc avatar

haha. This article is so sweet!

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