Calculate Day Light Integral DLI using a Photosynthetically Active Radiation PAR sensor (also known as a PAR or Quantum Meter)

[Peter]

@ben

A new method to evaluate PAR values is with the Photone app for a phone. It uses an existing sensor within a phone to get PAR readings without using an expensive PAR sensor, and it is available on both Android and iOS.

After hearing about this, I decided to compare it to our PAR sensor, which we know to be very accurate. This was done with both inside a GBE FG.V3 box, using a setup posted below:

I was working with @Jamira as part of his Supervised Agricultural Experience (SAE) and I had recommended he use the Photone app.

A few observations about our experiences with Photone

1. **As Ben noted above, THE ‘MODE’ IN THE PHOTONE APP SIGNIFICANTLY IMPACTS ITS ABILITY TO MEASURE THE DIFFERENT LED CHANNELS.

• Never trust the Photone app to correctly measure umol in the blue channel.**
  • For this reason, I recommend not using that channel of LEDs at all.
• Use the ‘LED Red/Blue’ mode to measure umol for the red channel
• Use the ‘LED Full Spectrum’ to measure umol for the white and green channels.
• Do not use Photone to measure the ‘combined’ umol for multiple channels of LED - because of the need to use different modes.
  • This requires that the 4 Amps of power from the power supply be distributed across the LED channels - with room to spare.
  • A good rule of thumb would be to not exceed a ‘knob setting’ of 150 for any of the four channels.

2. They have a $6.99 paywall (not sure what features require it, @Jamira may have more insight here)
3. They recommend related products (LED diffuser to improve sensor readings) for their software

• When @jamira mentioned that the app was recommending he buy a ‘diffuser’ I jumped to the incorrect conclusion that the wrong conclusion that it essentially meant a lamp shade. Instead, what they’re recommending you purchasing is an attachment for your phone to improve the sensors accuracy.

Regardless of the ‘Mode’, Photone fails to measure the blue channel of LEDs

@ben

Photone Mode	Knob Controller Setting	PAR Meter	Photone
LED Blue/White	Blue 255	371	32
LED Blue/White	Blue 175 White 175	483	327
LED Blue/White	Blue 125 White 125	282	198
LED Red/Blue	Blue 255	372	53
LED Red/Blue	Red 150 Blue 150	416	299

How Photone can be used to compare photoperiods.

Steps 1-2 of this process only apply to the ‘manual knob LED controller’ (shown below) that is used in models FG.V1-V4. @Jamira Upload screenshots from the Photone app as you do this - please! Unfortunately, MARSfarm is no longer an authorized distributor for that product line - so skip to step #3 if you don’t already have one to learn how you can automate these light settings using the software ‘recipe’ that runs on a MARSfarm Version 1!

1. Settings for 12 hour photoperiod (12 DLI) using white and red LEDs.

• start by turning red to 100 umol (the number in the photone app, not the # on the controller)
  • write the # on the controller down - this is your ‘Knob Controller Setting’ for red.
• now turn white up until it reaches 200 umol in the app.
  • write the # on the controller down - this is your ‘Knob Controller Setting’ for white.
• these become the light settings for your 12 hour photoperiod experiment (set timer accordingly)
  - 300 umol * 60 seconds * 60 minutes = 1.08 mol per hour * 12 hours = 12.96 DLI

2. Settings for 12 hour photoperiod (12 DLI) using white and red LEDs.

• start by turning red to 50 umol (the number in the photone app, not the # on the controller)
  • write the # on the controller down - this is your ‘Knob Controller Setting’ for red.
• now turn white up until it reaches 100 umol in the app.
  • write the # on the controller down - this is your ‘Knob Controller Setting’ for white.
• these become the light settings for your 12 hour photoperiod experiment (set timer accordingly)
  - 100 umol * 60 seconds * 60 minutes = 1.08 mol per hour * 24 hours = 12.96 DLI

3. Use the settings for recipe #16 and #17 on this calculator to determine what the equivalent MV1 settings would be.
   • Download/modify the PWM values in an existing recipe like DLI: 30 (240ML).

Your measurements of FG.V1-V4 using Photone should be similar to these

@ben

Photone Mode	Knob Controller Setting	PAR Meter	Photone
LED Full Spectrum	White 255	640	684
LED Full Spectrum	White 175	354	379
LED Full Spectrum	White 125	190	205
LED Full Spectrum	Green 255	112	128
LED Red/Blue	Red 255	504	550

Evaluating the Photone app quality and its value to this community

I found a ‘Plant Light Database’ on the Photone website - the measurements line up with normal recommendations I’ve seen elsewhere but this is one (if not the most) comprehensive databases of lighting recommendations I’ve found. They seem to be pretty open and motivated by getting views/afilliate ad money - I’ll be reaching out to see about collaborations but want to do a bit more digging first. Here’s a few places I plan to reference in the future:

• Plant Light Database
• Photone - Grow Light Meter
• Calibrating a Photone using a known LED source or PAR meter
• What is a diffuser and how does it help Photone work better?

@jeremy.hall @wxazygy it would be helpful to have another ‘expert’ or two collect comparable data here. Since there are ~1,200 FG-V1-V4 models in schools right now - creating a calculator (similar to the MV1) for those models of hardware would be a valuable addition to this community.

@hmw Would you be willing to take a few minutes to look into what/anything you can find about who makes Photone and how it works? I’m interested in better understanding the hardware it uses and any variations we should be aware of in terms of hardware (Samsung vs LG, etc.) - do the sensors vary at all? Any guesses on why blue stinks? Does it use the camera or the ambient light sensor? What changes based on the ‘mode’ setting? How could we create a similar ‘mode’ using an ambient light sensor that would convert the white light from an MV1 into umol?