If you have an outdoor cat or dog, you’ve probably wondered where it goes during the day. Do they just hang around outside the house, or do they go on long adventures exploring the neighborhood? To snoop on my cat Conley, I made a GPS cat-tracking collar that would log his location during the day, then let me download the data to a computer when he gets back home.

At the core of this collar is a TinyDuino microcontroller and a few of the expansion TinyShields that are available for this platform. The TinyDuino works just like the Arduino Uno and can run the exact same sketches, yet it’s only the size of a quarter. You can easily add capabilities just by plugging TinyShields into it — I used the GPS TinyShield to get the position data and the microSD Card TinyShield to log the data.


To power the system, you need a small and light battery with the capacity to run the system long enough to get useful data. The GPS and SD card writes are fairly power-hungry, so I use a small lithium-ion rechargeable battery that provides up to 6 hours of logging capability. A larger battery can also be used to get much longer logging times.

To make the electronics box for the collar, I used a Tic Tac container cut down to the exact size, with a small slot cut in it to let the cat collar slide through. This lets the GPS module sit on the back of Conley’s neck during his adventures strolling around, and provides the best GPS antenna reception.

The software used to program the system is very simple: an Arduino sketch runs on the TinyDuino, which captures the raw data from the GPS module and writes it to a text file on the microSD card. Pop out the microSD, put it in your computer, and you can open up the file in a program like Google Earth and see exactly where your cat was during the day, complete with timestamps.