PPFD Meter Phone App - Crowd Sourcing Lux Readings

newbie2323

Well-Known Member
Hi Growers -

I'm hoping you can help me and your fellow growers out.

I built an android app that uses the light meter in your smartphone to convert the LUX reading to PPFD.

The app will be completely free once it's ready for the app store.


2019-09-13 16_50_21-PPFD.png

The conversion factor used to go from LUX to PPFD depends on the selected light source.

I was able to get these conversion factors from a few manufacturers, but the accuracy of the light meter in the various smart phones is something I'm hoping this community can help me figure out and account for in the app.

Here's the problem...A Samsung S7 will likely have a different Lux reading than a Pixel 3 XL. Without knowing the exact Lux reading of a particular light, at a specific distance, and for the users exact brand and model of smart phone, the readings won't be as accurate as they would be otherwise.

If you're willing to help a brotha out, please install a lux light meter on your smart phone and answer the questions below...

1. Phone brand and model?
2. Light source? - please be specific
3. Total Watts it's pulling from the wall?
4. Lux reading at exactly 12 inches
5. Lux reading at exactly 18 inches

Some lux meters in the app store:

https://play.google.com/store/apps/details?id=com.doggoapps.luxlight&hl=en_US
https://play.google.com/store/apps/details?id=crunchybytebox.lightmeter&hl=en_US
https://play.google.com/store/apps/details?id=kr.sira.luxmeter&hl=en_US

Thanks and happy growing!
 

TrippleDip

Well-Known Member
1) you can estimate your lux to ppfd conversion factor from the colour temperature or spectrum. There's at least two threads here detailing how to do so.

2) you don't have to worry about the cameras response, see https://www.researchgate.net/publication/317596937_Smartphones_as_a_Light_Measurement_Tool_Case_of_Study

3) maybe add a hold button to your app. This was the big problem with other apps (you have to put your finger over the sensor move it into position then remove your finger to take a reading then put it back over the sensor to take it out of the tent.
 

newbie2323

Well-Known Member
3) maybe add a hold button to your app. This was the big problem with other apps (you have to put your finger over the sensor move it into position then remove your finger to take a reading then put it back over the sensor to take it out of the tent.
Great point. Yep, I've had the same issue.
 

Star Dog

Well-Known Member
Light lux meter... app was fairly consistent when tested with a £2000 lux/umol meter.
The quality of the light sensor gets a mention.
Screenshot_20200922-011104.png
 
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