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Are there any electronics geeks who can tell me why the f*k PAR meters are so expensive? The standard models don't even have a logging function FFS, and start at around AUD $300 PAR ( Photosynthetically Active Radiation ) meters measure light based on that part of the spectrum which is used for photosynthesis by plants. https://en.wikipedia.org/wiki/Photosynthetically_active_radiation Dead handy little buggers those meters. Our human irises open and close to adjust the amount of light they let in, but plants don't have this light-adjusting capacity the same way. So a plant can be getting much less useful light than we realise til we test it. Plants in tissue culture photosynthesise way less than outdoor plants because they use the sugars ( or other carbon sources ) in the media for energy. It's why we get away with using fluro tubes and get good growth. But fluro tubes lose a large proportion of their photosynthetically useful light after 3 months and need replacing- the light at those wavelengths isn't differentiated by our eyeballs, but the plants notice, believe me. I've been told that other indoor lights- metal halides for example- also lose some of their PAR strength after a period of time, but I have no experience with this. And I've seen people swear blind their plants are sick, when after careful checking their plants aren't getting enough light because they're shaded for the parts of the day when there's no-one around. This is more pronounced in winter when the days are shorter and the sun's angle of attack is different I bought plans to make a unit with an Arduino using LEDs, but it's a world of hurt for me and the tek ( to my n00b eye ) seems to be primitive and possibly inaccurate. It'll have to wait until I have some geek mates in-house for a weekend with soldering irons and whisky and those weekends never turn out the way they're planned anyhow :D Fuck it, I want a network of the little buggers with temp and PH, two sensors it's easy to build loggers with. Then I can really see what my plants are up to. Plus it could save me some $$ replacing fluros all year. And maybe save some planty lives if there are dodgy tubes in the rack Anyone know of a cheap chip that's up to the job?