Introduction: Critter Counter With Makey Makey

As winter draws in each year in our ramshackle housing we get the same problem - mice looking for food and shelter raiding our kitchen. Now we've managed to secure most of the obvious holes in our walls and around pipes with expanding foam and wire wool, and we've stopped seeing them scurry away when we make a midnight trip to the kitchen, but a few tell tale signs are still there!

We've got a few humane traps down but can't tell where they're coming from and they're very good at avoiding these! The brutal solution would be to lay a load of traps all over the house, but we really don't want to hurt them, we just want to know the house is secure! At the same time, we're a bit sick of investigating every creak in the house thinking it's a mouse infestation!

So what we need is some way of knowing how many mice or other creatures are scurrying about each night!

Here's where the critter counter comes in! A portable solution that can be moved around the critter hotspots for a night at a time to check if they are active or not!


Tools & Equipment

  • Scissors or cardboard cutter
  • Makey Makey
  • 2 crocodile clips
  • Laptop/raspberry pi


  • Tinfoil
  • Electrical tape/masking tape
  • Cardboard - a size as wide as the space you're trying to mouse proof!

Step 1: Step 1 - Locate the Critter Entrance Point

So we know our critters come from behind the sink. We blocked up the holes behind the kitchen cupboards so the only way through the kitchen is straight across the open floor.

Find a piece (or stick together multiple pieces) of cardboard that covers the width of the area you think your critters are waltzing across like they own the place, and place it down.

Step 2: Step 2: Make the Contact Points

The idea is that when the critter moves across the floor it will complete a circuit, triggering scratch via the makey makey. Scratch will then log a number for each time this happens, and the next day we'll see if any critters have passed through!

So, we need to turn the cardboard base into a switch. we do this by wrapping either side with a sheet of tin foil.

Make sure there's a gap between them so they don't touch, but still small enough to be bridged by the average critter.

Step 3: Step 3: Secure the Tin Foil

Tape each side of the foil down - this is important as while the circuit would work without this step, the more the critters run all over the shop, the more they'll pull up the foil and eventually widen the gap, rendering the counter useless.

Step 4: Step 4: Connect Up Your Makey Makey

Now we've made the critter connection plate, we need to turn it into a switch!

Stick one crocodile clip on either side of the sheets of tinfoil.

With the other ends, one will go to the EARTH connection of your makey makey, the other can go to any switch you like.

Here I've used the SPACE button - if you use a different one just remember to swap the "space" command in my code for whichever button you use

Step 5: Step 5: Make Your Code!

plug your makey makey into your laptop and go to scratch! -

Here's my code you can use if you want but there are many ways of creating a counter -

Now every time a critter runs across your floor it will count on scratch for you!

Test it out by placing your palm across the tape so you touch both sides of the foil - the number next to CRITTERS COUNTED should go up by 1!

Step 6: Step 6: Complete!

Now all that's left is to go to sleep and see if any critters visit overnight!