The idea
Light sets your body clock. The advice is simple: lots of light by day, very little in the evening, none at night. The trouble is that your eyes are bad at judging brightness because they adapt. A well lit library and an overcast day outside both feel bright, yet the sky is 30 times brighter.
This clip measures it for you and reports where you fell short, in minutes.
Why it could matter
Two studies each followed nearly 90,000 people who wore a light sensor for a week. People with the brightest days had lower death rates over the next eight years, and people with the brightest nights had higher ones. A sister study found the same pattern for depression. These studies show a link, not proof, and nobody has yet tested whether giving people this feedback changes anything.
What exists
Research labs can buy devices like this by asking for a quote. Smart watches offer a rough “minutes outdoors” number that stops working under a sleeve. Nothing a normal person can buy measures light at the eye against the day, evening and night targets.
Build plan
- A 10 channel light sensor (AS7341, about A$32)
- ESP32-C3 board, small battery, a diffuser dome and a printed clip
- A phone app with the three part daily score
The hard part
Calibration. Each unit has to be compared once against a laboratory instrument, and the sensor has to cope with everything from a dark bedroom to direct sun.