Lux to PPFD Converter App | PPFD Meter

groweee

groweee

Active Member
Wow thanks, guys for providing nice feedback.

@Moflow seems like the app is pretty accurate on a single spectrum as you say 3500k.
Also, a good suggestion to freeze reading, I will put this if the user presses volume buttons I can freeze the screen until the next press.

@Wizzlebiz good luck on your next setup, I am using Bava 240W with Samsung chips, I always put 660 +IR on, and from time to time especially late flower I use UV on. The dim is always around %50 + 60cm in height. I guess it's more than enough for 2x4 tent.

@cobshopgrow Couple of things could be gone wrong with your measurements. But 220 vs 360 is a huge gap. First, I see some fingerprints on your top part of the screen :bigjoint:. I previously see that dust grease effect readings at some percent. Also, ambient light sensors can only read direct light with a fairly small area surface. You have to be sure the phone sensor is looking directly at the light source.
If all good at this point, I am curious if the phone itself measures lux correctly, maybe you can do this with another phone by using the lux meter on the app. That is the raw output what the phone sensor gives. So, at this point, if the phone reads correctly this means I need to add another rate factor for the source that has 660nm leds.

@rkymtnman I have checked vipar it has many different LEDs, I guess all these conversions are based on one single research and there they only used what is written. LUX has a very narrow band when compared with PAR, so when I check the numbers I see red&blue highly elevated since most of the light is not detected by the phone sensor. in your case, those white LEDs mislead the conversion.
 
cobshopgrow

cobshopgrow

Well-Known Member
i dont think there went so much wrong with the measurement to explain the gap.
can not tell what a apogee would tell compared to a spectromaster as i have only the c7000, i guess it should be about the same.
as far i read apogee are calibrated with a spectrometer and bugbee himself saying that basically a spectrometer is the way to go.
would suspect the sensor/algo from my phone so far simply dont give the right lux value and moflow give better values.
the 360 to 220 comparsion was under plain 3000k, no 660nm reds involved.
maybe my spectromaster is broken, but i have reproducable readings since i have it (its not old, stored in case always), it self calibrate on every startup etc.
the math seconic is using is probably right, the whole par range is measured and ppfd are calculated accordingly.
if you compare what the sekonic measures to what a converter say you also see a difference always, havent found one calcualtor showing the same lux to ppfd ratio as the spectromaster is showing when converting the c7000 lux readings.
so i somehow doubt the c7000 is so off, i mean you pay basically most of its price for having a solid reference and calibration.
as you say there is a lot guesswork involved taking the lux reading (basically the green peak) as the base.
 
cobshopgrow

cobshopgrow

Well-Known Member
oh forgot, i have no other android at hand when there is a chance i may compare with a another one, maybe post covid.
 
rkymtnman

rkymtnman

Well-Known Member
groweee said:
I have checked vipar it has many different LEDs, I guess all these conversions are based on one single research and there they only used what is written. LUX has a very narrow band when compared with PAR, so when I check the numbers I see red&blue highly elevated since most of the light is not detected by the phone sensor. in your case, those white LEDs mislead the conversion.
Click to expand...
i agree.
i just set the Vipar at the same distance i was getting my 12K lux with the 4k QB
 
groweee

groweee

Active Member
@Moflow I have just posted an update to Play Store possibly in a day or so update will be available. Now you can use volume buttons to pause/play measurements. Thanks again for feedback!

@cobshopgrow I had gathered some devices and did some lux measuring with my app and others I found online.
There is no magic including iOS, all apps just output what the system reads.

Mi Pad 4 results in the lowest reading where iPhone 6 is in the middle and Huawei P20 Pro has top readings.
The difference is quite high between devices, Mi Pad 4 reads almost half of Huawei so this affects PPFD readings directly.

Indeed this sensor is just for dimming the brightness of the phone, does not need to precisely measure LUX however it should be consistent on changes so as long as I add calibration app will perform good.

So, I end up buying a real lux meter on amazon :bigjoint: I would like to see which device is reading correctly.
I guess eventually I will add a calibration factor to LUX readings, so the user can calibrate this per device once...

Also saw such product with a strange price tag, could be useful indeed.
 
cobshopgrow

cobshopgrow

Well-Known Member
thanks for the test.
thats what i feared that all sensors give some different values.

are the phones using dedicated ambient light sensors or simply using the front camera for it?

i used some ambient light sensors and their readings where pretty much all over the place.

my cheap luxmeter shows way lower readings then my spectrometer.
was considering getting the here famous dr.meter to see if its as wrong as my cheapo.
could imagine they also only use cheap ambient light sensors often.
 
groweee

groweee

Active Member
My LUX meter delivered and did some test & research with the devices I have.

So, my Bava 240W has 2700k, 4000k, 660nm, UV + IR
First of all, I see that UV and IR do not make much difference on the LUX meter so these are not measurable. But 660nm makes the difference.
This is actually what I was expecting and makes sense why conversions do not have these ranges.

When I first check the readings on Huawei P20 Pro, Huawei P9 Plus, and Xiaomi Mi Pad 4 they all off calibration but between 0-4k lux they were consistent. When lux level goes beyond 10k only Huawei P20 kept its consistency. Beyond 50k Mi Pad just stops even giving continuous output.

First thing, I have added a calibration option to the app, and when I calibrated P20 Pro it started to be as consistent as the LUX meter!
However, it still misses calibration when the range changes hugely. Ex: when I calibrate it on 1k lux, it is accurate around 0-30k but starts to be off between 30k-70k. When I do the calibration at 40k it reads 30k-70k accurate but not around 1k. By accurate I mean almost %2 percent error.

I try to do the calibration P9 Plus and it's totally a different story.
First of all, I couldn't find an accurate spot for calibration when the range is beyond 30k. The sweet spot seems like calibrating at the highest this was 66k at the center when Bava is on %100. By not accurate I mean %10 percent error.
Also, I saw a strange behavior only with P9 when I changed the angel 90 z-axis, readings muted %10 percent... I guess on P9 sensor cover is polarized so reading is changing hugely since Bava is rectangular :)
This means for P9 you should always preserve the angel on which you calibrated. Also, it will not be accurate/trustable when it starts to be off the center.

Xiaomi Mi Pad 4 (great device but) is just rubbish at this point since its sensor just does not work beyond 20k or so.

At this point, I decided to check what sensors are these devices use and that explained everything.

P20 has an advanced ambient light sensor. Supports 5 different ranges (I guess this explains why it is accurate in some sort of a window) and able to measure up to 65k (this is where it is claimed to be accurate and it is still capable of output more)

P9 has an average sensor, max claimed range is 10k, and it's more like a light detector rather than a LUX meter, also explains why not that accurate when LUX goes beyond 30k

Mi Pad has a simple sensor, max claimed range is 4k...

Also when you check the screens of these phones P20 is the one that is still readable under 60k LUX, I guess designers just choose a capable sensor that can level the LCD, so more complex the screen sensor gets better, but they are never calibrated as matching LUX since I think they just measure the change when they are functioning...

I feel lucky that I have a good sensor on my P20, once it is calibrated -%42 percent then the actual :) I can really use it as a PPFD meter.
For P9 it will be still ok but P9 can not replace a lux meter...

@cobshopgrow I have checked S8 it uses TMD4903 but I can not find its datasheet. However, it looks as good as the P20 sensor. I will post when I am done with this calibration update.
 
groweee

groweee

Active Member
Guys big day!

Just pushed the new version to Play Store, now under LUX Meter, now there is an option for calibration which is persistent and will be applied to PPFD readings.

My Huawei P20 Pro needs -42% just for reference when lux is 30k+
Please post your device sweet spot maybe we can build up some sort of a DB.

@Moflow I guess this is now the only app that has a calibration option for LUX and from my experience, this is a must...

@Green Refuge I have checked them, found an iPhone to test, most of the app is bullshit IMO, they claimed to use a front camera on reading but this is far impossible for the hardware. You can use EXIF data but still does not make sense... On biz side, you need to purchase conversions to use I guess this is greedy. But I liked their UI.
 
Skyhound

Skyhound

Well-Known Member
groweee said:
Guys big day!

Just pushed the new version to Play Store, now under LUX Meter, now there is an option for calibration which is persistent and will be applied to PPFD readings.

My Huawei P20 Pro needs -42% just for reference when lux is 30k+
Please post your device sweet spot maybe we can build up some sort of a DB.

@Moflow I guess this is now the only app that has a calibration option for LUX and from my experience, this is a must...

@Green Refuge I have checked them, found an iPhone to test, most of the app is bullshit IMO, they claimed to use a front camera on reading but this is far impossible for the hardware. You can use EXIF data but still does not make sense... On biz side, you need to purchase conversions to use I guess this is greedy. But I liked their UI.
Click to expand...
Hi there Groweeee , thanks for for ure app .

Do u think i will get a precise measuring using a Samsung A50 ?

Thanks for all
 
groweee

groweee

Active Member
Hey @Skyhound
I tried to check this for you. I guess many Samsung device uses integrated special sensors, both color + proximity + lux sensor are together. It's hard to find what exact chip they are using. Here is the datasheet but it does not mention about lux range. However, most recent Samsung devices have really good sensors.

I guess this related to how good the screen is, if it's bright enough you should use a good sensor.

One other news is I have ordered some sensor modules and many tinny controllers for USB OTG!
I will try to build a relatively cheap external sensor. If I will succeed, as home growers we can definitely ditch expensive PPFD sensors and have crisp readings no matter what device you are on!
 
Skyhound

Skyhound

Well-Known Member
groweee said:
Hey @Skyhound
I tried to check this for you. I guess many Samsung device uses integrated special sensors, both color + proximity + lux sensor are together. It's hard to find what exact chip they are using. Here is the datasheet but it does not mention about lux range. However, most recent Samsung devices have really good sensors.

I guess this related to how good the screen is, if it's bright enough you should use a good sensor.

One other news is I have ordered some sensor modules and many tinny controllers for USB OTG!
I will try to build a relatively cheap external sensor. If I will succeed, as home growers we can definitely ditch expensive PPFD sensors and have crisp readings no matter what device you are on!
Click to expand...
ty so much , i tried it but i dont know how to calibrate , it does seems to shoot good numbers but right at the center of the canopy hes unstable(the sensor i guess ) so i get 1200 ppfd but sometimes it just shoots to + then 2000
 
Skyhound

Skyhound

Well-Known Member
hi groweee , just to inform u , that with my leds , the readings are precise , at least they are the same as the manufactures publishes , ty very much for the app =)
 
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