Hi all!
A month ago @Markw84 and me had a conversation about UVB sensors here: https://tortoiseforum.org/threads/meet-Áfonya-lift-and-mormota.165538/
As a summary: I am on a quest of finding a UVB sensor that is suitable for our purposes, and build a meter around it. Both the software and the hardware will be open source, so if successful, anybody with a bit of soldering skills could build their own. I think it's important to say that I'm not doing this because I don't want to spend money on the Solarmeter (I will anyways, because I need the baseline for the experiments); I just like to build stuff and experiment. That said, if successful, maybe a cheaper option could result in more torts getting adequate UVB light. Yeah, me and my world-changing plans
The plan is to find a sensor that has a close enough spectral response to the Solarmeter 6.5, and see if a regression equation could be devised that would calculate the Solarmeter 6.5 value from the output of my meter. This is not something unheard of: the study that resulted in the Ferguson zones (Voluntary Exposure of Some Western-Hemisphere Snake and Lizard Species to Ultraviolet-B Radiation in the Field: How Much Ultraviolet-B Should a Lizard or Snake Receive in Captivity?) used three types of meters (Solarmeter 6.2, Solarmeter 6.4 and Gigahertz-Optik UVB meter), and they too converted them to match the Solarmeter 6.5 UVI reading.
I have found a UVB sensor family (GUVB-xxxx) that has a very similar spectral response to the Solarmeter 6.2 (not the 6.5 sadly, but they are quite close to each other). The following picture shows the spectral responses of those sensors, the Solarmeter 6.2 and 6.5, and the vitamin D3 action spectrum:
The data on this picture came from digitizing graphs from the datasheets and from the Solarmeter website. The raw data and the Python script used to create the graph is on GitHub (https://github.com/sghctoma/uvb-sensor-graphs), and the interactive graph is accessible here: http://sghctoma.com:8060/
As you can see, the GUVB-T11GD and GUVB-S11SD are really similar to the Solarmeter 6.2, which gave me hope that this whole thing could work. There are of course a lot of factors that could ruin it. Just to name a few:
I am currently waiting on the OLED order, but my PCBs arrived yesterday, and everything else is here. The displays are not an essential part, so I can finally start soldering A picture of the sensors and PCBs (from left to right: S11SD, T11GD, and the last one is not a UVB sensor, but an MLX90614 IR thermometer to measure basking spot temperature):
As I have said earlier, this whole thing will be open source. In fact, it already is: the PCB designs are on my GitHub (https://github.com/sghctoma/terrapi-boards) as KiCAD projects, and released under the MIT licence. I am not an electrical engineer, so it is quite possible that these are not optimal, but I believe they will work.
Let me know what you think of this project, or if you have any questions or suggestions! I will document my progress and the whole experiment in this topic, so you will experience my success of failure at first hand
A month ago @Markw84 and me had a conversation about UVB sensors here: https://tortoiseforum.org/threads/meet-Áfonya-lift-and-mormota.165538/
As a summary: I am on a quest of finding a UVB sensor that is suitable for our purposes, and build a meter around it. Both the software and the hardware will be open source, so if successful, anybody with a bit of soldering skills could build their own. I think it's important to say that I'm not doing this because I don't want to spend money on the Solarmeter (I will anyways, because I need the baseline for the experiments); I just like to build stuff and experiment. That said, if successful, maybe a cheaper option could result in more torts getting adequate UVB light. Yeah, me and my world-changing plans
The plan is to find a sensor that has a close enough spectral response to the Solarmeter 6.5, and see if a regression equation could be devised that would calculate the Solarmeter 6.5 value from the output of my meter. This is not something unheard of: the study that resulted in the Ferguson zones (Voluntary Exposure of Some Western-Hemisphere Snake and Lizard Species to Ultraviolet-B Radiation in the Field: How Much Ultraviolet-B Should a Lizard or Snake Receive in Captivity?) used three types of meters (Solarmeter 6.2, Solarmeter 6.4 and Gigahertz-Optik UVB meter), and they too converted them to match the Solarmeter 6.5 UVI reading.
I have found a UVB sensor family (GUVB-xxxx) that has a very similar spectral response to the Solarmeter 6.2 (not the 6.5 sadly, but they are quite close to each other). The following picture shows the spectral responses of those sensors, the Solarmeter 6.2 and 6.5, and the vitamin D3 action spectrum:
The data on this picture came from digitizing graphs from the datasheets and from the Solarmeter website. The raw data and the Python script used to create the graph is on GitHub (https://github.com/sghctoma/uvb-sensor-graphs), and the interactive graph is accessible here: http://sghctoma.com:8060/
As you can see, the GUVB-T11GD and GUVB-S11SD are really similar to the Solarmeter 6.2, which gave me hope that this whole thing could work. There are of course a lot of factors that could ruin it. Just to name a few:
- I don't have any data on how precise the sensors themselves are. It is quite possible that sensors of the same type give different reading under the same conditions.
- A lot could depend on how precise the surrounding electronics (resistors, operational amplifiers, ADCs, etc.) are. I have tried to pick quality components, but we will see.
- My biggest concern at this point: the spectrum of various bulbs vary a lot (even between individual pieces of the same type at the same age!), and this may prevent me from devising a universal regression function (remember, the Ferguson study had to deal only with the spectrum of the Sun - albeit that is not exact either).
I am currently waiting on the OLED order, but my PCBs arrived yesterday, and everything else is here. The displays are not an essential part, so I can finally start soldering A picture of the sensors and PCBs (from left to right: S11SD, T11GD, and the last one is not a UVB sensor, but an MLX90614 IR thermometer to measure basking spot temperature):
As I have said earlier, this whole thing will be open source. In fact, it already is: the PCB designs are on my GitHub (https://github.com/sghctoma/terrapi-boards) as KiCAD projects, and released under the MIT licence. I am not an electrical engineer, so it is quite possible that these are not optimal, but I believe they will work.
Let me know what you think of this project, or if you have any questions or suggestions! I will document my progress and the whole experiment in this topic, so you will experience my success of failure at first hand