The ptSolar is the newest version of Project: Traveler's series of APRS trackers. The ptSolar has been designed and optimized for low-power operation, especially when using a solar panel.
3D rendering of the ptSolar circuit board.
Under the hood, the ptSolar runs on the same Microchip ATMega328p microcontroller that the other trackers have been using for years, although this board runs at a lower 3.3 volt level, and a slower 8MHz clock speed.
A 2m VHF transmitter is provided by the SA818S-V transmitter-on-a-chip system, which means it's frequency agile and can be used throughout the world.
The GPS receiver is utilizes the ATGM336H GPS engine which has a light-weight footprint while being a cost-effective solution. The ATGM336H is capable of position reports in excess of 60,000', making it a suitable solution for high altitude (latex) balloons traveling to over 100,000'.
The circuit board is designed in Kicad and features a 4-layer design with castellated solder points for the attached solar panels.
The ptSolar is currently in the prototyping stages. Version 1.0.0 of the PCB was the initial design that was first built in early 2025, and includes the ATMega328p microcontroller, an ATGM336H GPS receiver, and the SA818S-V VHF transmitter. VHF signal filtering is provided by a 3-pole pi filter, reducing spurious harmonic output to well within Part 97 specifications.
An optional BME280 temperature and barometric pressure sensor, as well as an option Sparkful Qwiic I2C header port can be installed to give additional flexibility to the tracked payload.
In the Arduino IDE and go to File → Preferences. In the Additional Boards Manager URLs field, add the URL to the Project: Traveler website .json file:
https://www.projecttraveler.org/downloads/package_projecttraveler_index.json
Note that if there's already something in that field, you can click the small icon to the right of the text field where you are allowed to enter multiple entries on multiple lines.
Setting the custom download URL for the Boards Manager.
Click OK to close the preferences dialog. Then go to Tools → Boards → Boards Manager.
When the Boards Manager opens, select "Contributed" from the Type drop-down. In the resulting list, you should find the Project Traveler Boards by Project Traveler option. Click the Install button in the lower-right corner.
Using the Boards Manager in Arduino IDE.
Close out of the Boards Manager dialog, and the back under Tools → Board, you should see "ptSolar Tracker (Arduino as ISP)" near the bottom of the list.
If this is a brand new ptSolar board that has never been programmed before, there are several commands that must be run from a DOS command prompt. If the ptSolar was purchased as an assembled and tested kit, you can skip these steps.
Open a command prompt on the PC.
C:\> cd \Program Files (x86)\Arduino\hardware\tools\avr\bin
C:\Program Files (x86)\Arduino\hardware\tools\avr\bin> avrdude.exe -p m328p -b 19200 -c avrisp -C ..\etc\avrdude.conf -P comX* -U hfuse:w:0xD6:m -U lfuse:w:0xFF:m -U efuse:w:0x05:m
This will write the fuses to the new processor. To verify that the fuses have been written, run these commands:
C:\Program Files (x86)\Arduino\hardware\tools\avr\bin> avrdude.exe -p m328p -b 19200 -c avrisp -C ..\etc\avrdude.conf -P comX* -U hfuse:r:highfuse:h -U lfuse:r:lowfuse:h -U efuse:r:exfuse:h
C:\Program Files (x86)\Arduino\hardware\tools\avr\bin> cat highfuse
C:\Program Files (x86)\Arduino\hardware\tools\avr\bin> cat lowfuse
C:\Program Files (x86)\Arduino\hardware\tools\avr\bin> cat exfuse
* Replace "comX" with whatever Com port your ArduinoISP is enumerating on.
To program the ptSolar, open the firmware Sketch in this GitHub Repository in the Arduino IDE.
Go to the Tools → Board menu, select the "ptSolar Tracker (Arduino as ISP)" from the list of targets.
The ptSolar boards are automatically configured to use the Arduino as ISP programmer to load the firmware onto the tracker boards, so no further configuration is necessary. Click the Upload button which will cause the Sketch to compile and will program to the ATmega328 processor similarly to how a normal Arduino board is programmed.
Sometimes it is necessary to apply external power to the ptSolar Tracker, depending on how much current the Programmer board is capable of sourcing.