For a new project (actually a add-on for an old one -> link) I'm building a PAR meter. The difference between measuring PAR and Lumen, for example is the spectrum being analysed is different. Since PAR sensors are quite expensive I've found a way to do it with led's using 'Mims discovery/effect'... There's also a book called 'Atmospheric Monitoring With Arduino' where one can build a simple photometer with some LED's and use this to measure the PAR spectrum (400nm - 700nm), but I don't know if I'm allowed to post the schematic and/or code from this project here...correct me if I'm wrong ;)
When I attach a led to my multimeter and set this to measure mV it measures about 80mV when I turn on a light, so the LED is producing a voltage...Yeah... Thank you Forrest!! :) When connected to the arduino the output starts to swing going from 230 to 0 and then back up...I think it has something to do with the amount of mV the arduino can register --> 5V/1023 = 0.004887586V = 4mV per step. So I've read some threads on this forum and others and started thinking about it. First I have to step up the voltage with a linear rail-to-rail op-amp and second stabelise the reading by using a capacitor. Now my electronic skill set isn't much to write home about and this is why I need some help... I've found several diagrams which would do the trick, but none of them tell me which kind of op-amp and capacitor I should use...
What do you guys/galls think?
With kind reagards,
p.s. If I forgot to mention some information I sincerely apologise ;)