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Cat Tracker

2 years ago 668
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The goal of the project is to help cat owners to locate their lost cat. The construction is based on S76G chip (SEMTECH SX1276, STM32L073x & SONY CXD5603G GPS). The device will wake up from the deep sleep each hour, get GPS/LORA (approx. traingulation) coordinates and send them over LORA to the server. Android application can than display the cat route on the map. I assume power supply by three Zinc-Air 675 batteries (11.6x5.4mm 620 mAh), need to add the second LDO to 3.3V, with expected battery life about 3 months.

The PCB 6, see picture, is working (SWD FW Upload, UART RX/TX Commands) and I can send mannualy LORA test messages to server. The problem is I can't get GPS coordines on wire antenna even at the top of the hill.



Tracker PCB 0

Tracker PCB

Tracker PCB 2

Tracker PCB 3

Tracker PCB 4

Tracker PCB 5

Tracker PCB 4 fence

Tracker PCB 4 vias

Tracker PCB 6

Tracker PCB 7

Tracker PCB 8

Tracker PCB 9


ID Name Designator Footprint Quantity
1 15nF C15 C0201 1
2 100nF C1,C5 C0201 2
3 10pF C7,C6 C0201 2
4 33pF C8 C0201 1
5 NC C9,C10 C0201 2
7 TI LDO 3.3V U3 DQN0004A 1
8 TI LDO 1.8V U2 DQN0004A 1
9 8.2nH L1 L0201 1
10 NC C13,C12 C0201 2
11 47pF C11 C0201 1
12 S76G U1 S76G 1
13 32.768KHz X1 OSC-SMD_4P-L2.0-W1.2-L 1
14 NT2016SA-26M X2 NT2016SA-32M 1
15 1uF C14,C3,C4,C2 C0201 4
17 47K R2,R1 R0201 2
18 10K R3 R0201 1
19 PAD_Oval_1x2.3mm P7,P5,P8,P6 PAD_OVAL_2X5MM 4
20 + P1 PAD_OVAL_2X5MM 1
21 - P2 PAD_OVAL_2X5MM 1
22 LoRa P4 PAD_OVAL_2X5MM 1




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Comments (4)

raaden89 Reply

Hi caster,

I'm looking at your cat tracker and it looks amazing! I want to do same thing for my dog. Did you ever tested it? i'll try to get a quotation, but it's not possible to get the SMD Assembly because pcb it's to small. Did you assembly yourself? Did you solve problems about GPS?


Caster Reply

In the meantime I did some test programs in Atmel Studio to test ATSAMR34 how to work with the SPI  attached u-Blox GPS receiver e.g. set it to UBX commands only, send command to get GPS data within 60 seconds etc. I mainly use interrupts trigerred by pins on ZOE-M8Q to know if (TIMEPULSE) and when the GPS data are ready.

I am also working on a new PCB design with the dimensions about 8 x 35 mm.

The tracker will also measure the battery voltage each hour and will have a small LED which you can activate from your Android program to let it flashing in the night temporary to help you find your cat.

I woul like to power the tracker by three Energizer 675 Zinc Air cells which should last about three months with GPS/LoRa tracking each hour.


Caster Reply

The major problem was that I was unable to order the S76G chip again. You read for sure about the chips shortage.

That's why I fas forced to swich to plan "B" and design the cat tracker around ATSAMR34 and u-Blox ZOE-M8Q GPS Receiver.

I have also  let manufactured the test PCB with two Infineon GPS LNA's and SAW filters to test the boosting the passive GPS wire dipole antenna by 39.2 dB.  I am using the smallest components available so now a proffesional company is soldering them to the board. When I get the assabled PCB back I will test it.

Some time ago I also bought the NanoVNA so I fine tuned the dipole antennas for GPS and LoRa by cutting wires, measured the VSWR charts and antenna impedance (real & imaginary) and let automatically calculate the matching impedance components (induktance) to achieve 50 Ohms by SimSmith program.

Caster Reply

Hi Andrea,

Yes I tested it. I was able to program the chip over SWD and the program run. I also sucesfully send LoRa messages. The problem was that I was unable to get the GPS signal with the passive dipole antenna. Another problem was that I didn't need to program the chip but just send a few AT commands to let the chip know what to do. Unfortunatelly I had a problem as the command to read GPS don't have a option to send a dummy text message when the GPS signal is not available within set timeframe e.g. 60 seconds, which would allow to find out approximate positon by LoRa triangulation.

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