g4s
FreeDSM (Free Dark Sky Meter)
This DIY photometer is part of the project Gaia4sustainability, funded by the Spanish Ministry of Science MCIN / AEI / 10.13039 / 501100011033 and the European Union Next Generation programme EU/PRTR through the coordinated grant PDC2021-121059-C21/C22.
The FreeDSM allows you to measure the quality of the sky background during your night observations. It is a photometric instrument that incorporates the Osram TSL2591 sensor, with two diodes: one will make a measurement in the infrared range and the other in the full spectrum. From the data proviced by those diodes, it calculates the mpsas measurements every minute (its range is 12-23 mpsas) but algo temperature and humidity (sensor AHT2x).
You can build your own FreeDSM with the information contained here, by assembling low cost and easily available components and some small parts for the chassis that you can create on any 3D printer. It resists weather, is small and incorporates a battery, which allows us to use it in a portable way, although you can also install it permanently, even ignoring the installation of the battery inside and its charge regulator. The software is based on Tasmota, making it easy to integrate data across a multitude of environments and to include hundreds of additional sensors. The license of the firmware is GPL 3.0 and additional proccesing in Berry code run by FreeDSM.
This device is part of the Gaia4sustainability project and can provide measurement data to our open platform. We say can because FreeDSM allows the sending of data via MQTT messages to your own home automation platform (for example, Home Assistant), it can also save them in the memory of the device itself and, if you allow it, also send the data to our platform, where You can have your own profile and see your FreeDSM data in it.
We hope you enjoy it as much as we have designing and programming it. We also thank the community for their support during its development, and for them it is the result.
WARNING: This is a non-commercial development. Use the information on this page at your own risk, it may contain errors. The hardware uses low voltage electronic components but can still potentially compromise the integrity of your body and/or home if not done correctly.
Description of the components and Do-It-Yourself process
Firmware releases
Here you will find the latest FreeDSM firmware and Berry script.
IMPORTANT: The firmware and berry script must match the first two digits. If you are performing an initial flash, the file includes firmware and script but the update by hte web interface DOES NOT update the berry script, it is mandatory to update it manually (in the web interface, select "Console" -> "File system upload")
- Latest Firmware v2.4 initial flashing (firmware.factory.bin, initial flashing by command line, includes firmware and script)
- Latest Firmware v2.4 web update (firmware.bin, flashing using the Tasmota web interface, it ONLY updates firmware)
- Berry script v2.4.7 web update (autoexec.bec, to upload in the Tasmota filesystem)
Source code
FreeDSM v2.4 is based on Tasmota 13.1, license GPL 3.0. The modification introduced is a specific driver xdrv_111_freedsm_id.ino to generate the FreeDSM id (name) and an xsns_111_freedsm.ino, based on the original tsl2591 files, but allowing an integration time of 6 seconds (without interfering with the sensor reading cycles of Tasmota) and debug commands. More details can be found in README.md. Click to download the source code.