Is the Si1145 reliable or is it a piece of crap

Currently working on a project that includes the Si1145 lightsensor.
The Si1145 measures visible light and infrared light and then calculates the UVI from that, without measuring actual UVA or UVB levels.
According to Adafruit it is very reliable.
When i used it however, it seemed the visible and infrared readings always hung around 625 or were 0, while the UVI was always 0.
Now ofcourse I could have a faulty sensor, but some browsing on the internet showed that this was a common occurrence.
When I put the (adafruit) library next to the datasheet, at first glance I couldn’t help but get the impression the library had some shortcomingins that might well explain the erratic behavior.

After some searching I found a latched library that worked better……but even then, in total darkness the ambient light and IR light hung around 600, but at least in daylight I would get different values and even a UVI reading.

The latter though proved totally inaccurate, easily going up to 7 in overcast weather.

I will do some further digging in the code but for now I would not recommend this sensor

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4 thoughts on “Is the Si1145 reliable or is it a piece of crap”

    1. Yes they do. I wouldn’t expect them to put down a sensor they are selling. The sensor is in fact made for mobile phones and in spite what they say an UVIlike 15 is just not possible in overcast weather. Also, the visible light and infrared still give values (usually 260) in total darkness

  1. Its datasheet shows that from a large database of sunlight spectra, a real UVI of 5 is reported by the sensor’s emulation algorithm ranging from about 2 to 8. This must be the first time I have seen what I can best describe as mass-market deception designed into a semiconductor device (by a reputable manufacturer, well, except FTDI and Prolific but at least that behaviour was in response to a threat). I could ask “what is happening to this world”, but I already know…

    1. Definitely true Antony. Mine at least also goes haywire after a while, showing UVI far above what is ever measured.

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