13-03-2022, 13:01
Hi,
Yes a beautiful construction, but the use of Perspex (aka Acrylic Sheet or Plexiglass) might not be an optimum choice.
Certainly those particular PV panels do need some protection because surprisingly they do not appear to be satisfactory for long term external use.
However, an issue with any "transparent" panel is the reflection from both of its surfaces (about 10% in the graph below), which increases greatly at "glancing" angles (e.g. low elevation of the sun in winter). Also, the majority of Acrylic sheets block Ultra-Violet radiation, either by "accident" or by design, since they are often used to protect materials in Museums and Art Galleries against fading, etc.. Here's an example from This Web Link , and if I read another data sheet correctly, even a "UVI Transmissive" version (ACRYLITE OP-4) is only transparent to UVB in a thickness of less than 1 mm.
Personally, I would use a thin sheet of PTFE (aka Teflon) sheet, which is known for its excellent optical diffusing (and reflection) characteristics, for all wavelengths between about 200nm (UVC) through UVB, UVA and Visible light to the Near Infra Reds beyond 1000nm. It also has excellent chemical and mechanical resistance properties and its diffusing characteristics can give the required "Cosine" optical response. It actually reflects much of the light; Another Web Link indicates that a 1mm sheet will transmit (i.e. allow to pass through) only 10% of the light (and 2mm pass 5%), but this shouldn't be a problem: The PV panel can easily still deliver enough current and another interesting web link suggests that the "Guva-S12SD" UVI sensor (which I suspect might use the same chip) overloads in bright sunlight.
Not specifically relevant to this thread, but I'm very "suspicious" about the specification of the UVM-30A (and most others) as a "UV Index" sensor. I can't find any data sheet for the sensor itself (only for the complete PCB "module"), but the "Real UV Index" should strongly block wavelengths above 315 nm (i.e. UVA), whilst the sensor is said to cover UVA+UVB (200 - 370 nm). IMHO the "real" UV Index requires a specialist "Erythemal" Optical Filter (as used by Davis) or a true UVB sensor such as the VEML6075 (which has sadly got quite expensive now).
Cheers, Alan.
(06-03-2022, 19:41)SR123 Wrote: For the UV/Solar sensors ....... I will cover the sensors with a piece of 3mm Perspex.
Yes a beautiful construction, but the use of Perspex (aka Acrylic Sheet or Plexiglass) might not be an optimum choice.
Certainly those particular PV panels do need some protection because surprisingly they do not appear to be satisfactory for long term external use.
However, an issue with any "transparent" panel is the reflection from both of its surfaces (about 10% in the graph below), which increases greatly at "glancing" angles (e.g. low elevation of the sun in winter). Also, the majority of Acrylic sheets block Ultra-Violet radiation, either by "accident" or by design, since they are often used to protect materials in Museums and Art Galleries against fading, etc.. Here's an example from This Web Link , and if I read another data sheet correctly, even a "UVI Transmissive" version (ACRYLITE OP-4) is only transparent to UVB in a thickness of less than 1 mm.Personally, I would use a thin sheet of PTFE (aka Teflon) sheet, which is known for its excellent optical diffusing (and reflection) characteristics, for all wavelengths between about 200nm (UVC) through UVB, UVA and Visible light to the Near Infra Reds beyond 1000nm. It also has excellent chemical and mechanical resistance properties and its diffusing characteristics can give the required "Cosine" optical response. It actually reflects much of the light; Another Web Link indicates that a 1mm sheet will transmit (i.e. allow to pass through) only 10% of the light (and 2mm pass 5%), but this shouldn't be a problem: The PV panel can easily still deliver enough current and another interesting web link suggests that the "Guva-S12SD" UVI sensor (which I suspect might use the same chip) overloads in bright sunlight.
Not specifically relevant to this thread, but I'm very "suspicious" about the specification of the UVM-30A (and most others) as a "UV Index" sensor. I can't find any data sheet for the sensor itself (only for the complete PCB "module"), but the "Real UV Index" should strongly block wavelengths above 315 nm (i.e. UVA), whilst the sensor is said to cover UVA+UVB (200 - 370 nm). IMHO the "real" UV Index requires a specialist "Erythemal" Optical Filter (as used by Davis) or a true UVB sensor such as the VEML6075 (which has sadly got quite expensive now).
Cheers, Alan.