Handmade GPS Tracker Keeps An Eye On Adventurous Cats

A ginger cat, wearing a blue harness with a brass and wooden box on its back

One of the most convenient things about having cats is their independent lifestyle: most are happy to enjoy themselves outside all day, only coming back home when it’s time for dinner and a nap. What your cat gets up to during the day remains a mystery, unless you fit it with a GPS collar. When [Sahas Chitlange] went searching for a GPS tracker for his beloved Pumpkin, he found that none were exactly to his liking: too slow, too big, or simply unreliable. This led him to design and build his own, called Find My Cat.

The heart of the device is an A9G GSM/GPS board, based on the RDA8955 system-on-chip. [Sahas] combined this with a data SIM card, a 2600 mAh lithium battery and a charger module to make a completely self-contained GPS tracker capable of transmitting location information in real time. The system is housed in a hand-made brass box designed to be attached to a cat harness, where it sits safely on Pumpkin’s back.

A brass box with a GPS tracker inside, along with a wooden lid with antennas embedded insideIt took a bit of experimentation to find a workable antenna setup for this system, because the brass box works as a Faraday cage. [Sahas] therefore made the lid of the enclosure out of wood, and embedded two thin strips of brass within it to make a dipole antenna. Tests in his car confirmed that it got a reliable fix and was able to communicate through the GSM network.

On the software side, The A9G module came with a C/C++ based SDK that [Sahas] found so inconvenient to use that he decided to replace the whole thing with a MicroPython setup. He then programmed it with a simple routine that waits for an MQTT message to start tracking, and otherwise stays in sleep mode. Location data is sent to a Raspberry Pi running Traccar, an open-source GPS tracking server that provides a ready-to-use web interface. Finding Pumpkin’s location is now as simple as opening a web browser, navigating to the Pi’s IP address and looking at the map.

As in many wearables, the largest part of the system is the battery, which in this case provides a good twelve days of usage between recharge sessions. We’d assume that to be plenty, unless Pumpkin is one of those cats that like to go on multi-week expeditions. Limited battery life is a common problem for GPS pet trackers; perhaps switching to an ultra-low-power LoRa-based system might help.

27 thoughts on “Handmade GPS Tracker Keeps An Eye On Adventurous Cats

    1. 100% agree that pet cats should be kept indoors. From the article it sounds like the owner is actually doing that, and this project came about because the cat got away a couple of times during walks (note the harness in the pictures actually has a leash on it.)

  1. Given the amount of Time, Effort and Material required to make such a device, I think simply purchasing an “AirTag” for your wayward adventurous pet would be cheaper…

    1. Not if you don’t have any other iDevices and have to buy them. Also, airtags require other iDevices to be in proximity to upload the location. A cat isn’t going to stick to well populated areas.

      1. Depends. Here in the UK most would remain in range of (someone’s!) phone most of the time. Not going to work if you live out in the sticks, but for most suburban cat owners they’ll work perfectly.

        There are android alternatives I think…?

        1. AIRCable! An AIRCable can boost a Bluetooth signal up to 40-miles, depending on whatever obstructions are likely to block the signal. Cost is about $140 usd and available at some electronics stores…

  2. Does it work for dogs? Sometimes Pokey slipped away, and I wasn’t sure which way he went.

    The last time was three years ago. I fpund him up the street, his tail was wagging. I realized he wasn’t trying to get away, but wanted to get back to proper walks after my illness.

  3. I for one am glad for our neighborhood cats…for once (lol.) The squirrels here in Southern Indiana have over bred in treacherous numbers and they are a menace to society. My dog Otis only wishes he could help curtail their numbers. The cats in the neighborhood actually do. Think of it this way fellow HaD readers – if you have a healthy ammount of free-range kitties you won’t have a healthy ammount of vermin mice and rats. I’ll take the kitties despite being allergic.

  4. One of the ‘hood cats visits my place quite regularly and I can only guess where he has been by the different smells in his fur. I’d like to track him to see where he goes, but he’s not my cat. Maybe a discrete sub-cutaneous tracker would do the job?

  5. It is okay to build something like this. But there have been smaller GPS trackers – even especially for cats – on the market for several years. And they were not even expensive.

  6. Crap, the GPS tracker I bought for my kids car is about 2″ x 2″ and its cellular biased with live real time tracking. Lasts for 2 days. I feel sorry for that cat lugging around that huge box on it’s neck all because the owner is cheap. Better idea is just to keep the cat inside all the time.

  7. I was contemplating making a tracker for my cat as well. Using one of those Topin Z310 modules.

    However, when I started thinking about how to power it, I thought “LiPO!”.

    And then I started thinking about the fail cases. The battery being punctured and possibly even catching fire.

    And then the whole idea was beginning to look a great deal less great. Imagine your cat or dog running in circles with its head engulfed in flames… :X

    I think that any tracker for pets should have a system to immediately release the device from the collar as soon as it detects something wrong with the battery (could measure the temperature in the casing, for instance, or sudden unexpected drops in voltage). If the system is too zealous and releases too quickly, it wouldn’t matter at all. Because it’s a tracker device and you’ll always be able to retrieve it, if it fell off.

    I am amazed that nobody seems to have given this much thought.

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