This Instructable will demonstrate how to build a system for detecting cat presence and providing light/ventilation for their litter box experience. The circuit includes a timer to prevent wasted electricity and uses no microcontrollers.

This system consists of two distinct components: a cat-sensing pressure mat and a circuit to power the lights and fans. I'll show you how to build both.

Note: The mat can be used as a simple switch to activate any circuit. Likewise, the circuit can be activated by other means. Today's your lucky day - this is like 3 Instructables in one!

    Cat Mat:
        Aluminum Foil
        2x Posterboard/foamboard*
        Spray adhesive
        Craft foam
        Hot glue
        Wire and connectors (male | female)

    Power/control Circuit:
        Breadboard or protoboard or PCB
        1x 12v AC/DC Adapter
        2x 12v PC fans
        12v Lights**
        1x 12v relay
        1x 555 Timer IC
        1x 10nF Capacitor
        1x 0.47μF Capacitor
        1x 470μF Capacitor***
        1x 10kΩ Resistor
        1x 350kΩ Resistor***
        1x Diode
        Assorted wires

Of course, the most important ingredient is love.

*I originally selected posterboard because of it's small profile. Unfortunately, the top layer turned out to be a little too flimsy/unreliable/inconsistent, so it was replaced with foamboard.
**For the lighting, I used 12 LED's from a reel I purchased online. I bought these specifically because they only required a 12v power supply, which matched the PC fans I was using. You may find something more suitable for your needs.
***The values of these components affects the timing of the circuit. For more information, see step 7.

Step 1: Cat Mat: Functional Overview

The idea behind the mat is simple, although there are some caveats to it's construction.

Basically, two pieces of aluminum foil are physically separated by foam. When weight is applied, the foil layers come together to make contact. When weight is removed, the foam lifts and separates the two foil layers.
<p>Will try to make something similar (sans fans) for a shelf in our wardrobe where my cat seems to like to perch.</p>

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More by domstyle:Prepping images for Lumi Inkodye using Free (and Open Source) Software (GIMP) Low-power, Low-cost, Cat-sensing, Litter Box Lighting and Ventilation 
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